U.S. patent application number 11/641125 was filed with the patent office on 2008-05-01 for compositions including polymers aligned via interchain interactions.
This patent application is currently assigned to Massachusetts Institute of Technology. Invention is credited to Johan T.V. Hoogboom, Timothy M. Swager.
Application Number | 20080102386 11/641125 |
Document ID | / |
Family ID | 39330611 |
Filed Date | 2008-05-01 |
United States Patent
Application |
20080102386 |
Kind Code |
A1 |
Swager; Timothy M. ; et
al. |
May 1, 2008 |
Compositions including polymers aligned via interchain
interactions
Abstract
The present invention provides compositions, devices and methods
related to the alignment of materials including polymers. In some
cases, the present invention comprises the assembly of molecules
(e.g., polymers) via intermolecular interactions to produce
extended networks, which may have enhanced properties relative to
the individual molecules. Such networks may be advantageous for use
in electronics, photovoltaics, sensor applications, and the like.
In some embodiments, the present invention may enhance the
performance of certain optical devices, such as liquid crystal
displays (e.g., color liquid crystal displays) by providing
enhanced contrast ratio, faster response times, and/or lower
operating voltage.
Inventors: |
Swager; Timothy M.; (Newton,
MA) ; Hoogboom; Johan T.V.; (Nijmegen, NL) |
Correspondence
Address: |
WOLF GREENFIELD & SACKS, P.C.
600 ATLANTIC AVENUE
BOSTON
MA
02210-2206
US
|
Assignee: |
Massachusetts Institute of
Technology
Cambridge
MA
|
Family ID: |
39330611 |
Appl. No.: |
11/641125 |
Filed: |
December 18, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60855966 |
Nov 1, 2006 |
|
|
|
Current U.S.
Class: |
430/20 ;
430/270.1; 520/1; 526/348; 526/348.3 |
Current CPC
Class: |
C09K 19/542 20130101;
C08L 101/12 20130101; C08G 2261/148 20130101; C08L 65/00 20130101;
C08G 81/00 20130101; G02F 1/13345 20210101; C08G 2261/3422
20130101 |
Class at
Publication: |
430/20 ;
430/270.1; 520/1; 526/348; 526/348.3 |
International
Class: |
G03C 1/00 20060101
G03C001/00; C08F 210/00 20060101 C08F210/00; C08F 210/14 20060101
C08F210/14; G02F 1/03 20060101 G02F001/03 |
Goverment Interests
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] This invention was sponsored by the National Science
Foundation under Grant Number DMR-0314421. The government has
certain rights in the invention.
Claims
1. A composition, comprising: a polymeric network comprising the
assembly of a plurality of polymer molecules, wherein each polymer
molecule comprises at least one intermolecular interacting group at
or near a terminal end of the polymer molecule, wherein at least
50% of the polymer molecules are connected to an adjacent polymer
molecule via the at least one interacting group, wherein the
polymeric network has a greater dichroic ratio than a dichroic
ratio of a polymer molecule essentially identical, but lacking the
interacting group, under essentially identical conditions.
2. A composition as in claim 1, wherein the polymer molecules are
connected to an adjacent polymer molecule via a non-covalent
bond.
3. A composition as in claim 2, wherein the non-covalent bond is a
hydrogen bond, ionic bond, dative bond, or Van der Waals
interaction.
4. A composition as in claim 2, wherein the non-covalent bond is a
hydrogen bond.
5. A composition as in claim 1, wherein the polymer molecules are
connected to an adjacent polymer molecule via a covalent bond.
6. A composition as in claim 1, wherein the polymer molecule is a
polymer having a substantially rigid polymer backbone.
7. A composition as in claim 1, wherein the polymer molecule is a
poly(arylene), poly(arylenevinylene), poly(aryleneethylnylene), or
substituted derivatives thereof.
8. A composition as in claim 1, wherein the polymer molecule is
poly(aryleneethylnylene).
9. A composition as in claim 1, wherein the polymer molecule has
the structure, ##STR00008## wherein n is at least 1, A and C are
optionally substituted aromatic groups; B and D are absent, alkene,
alkyne, heteroalkene, or heteroalkyne; and E.sup.1 and E.sup.2 can
the be the same or different and are interacting groups.
10. A composition as in claim 9, wherein E.sup.1 and E.sup.2 are
groups capable of forming hydrogen bonds with an adjacent polymer
molecule.
11. A composition as in claim 9, wherein the polymer has the
structure, ##STR00009## wherein R.sup.1 and R.sup.2 can be the same
or different and are alkyl, heteroalkyl, aryl, heteroaryl, or
substituted derivatives thereof.
12. A composition as in claim 9, wherein the polymer has the
structure, ##STR00010## wherein R.sup.1 and R.sup.2 are
2-ethylhexyl, and R.sup.3 is butyl.
13. A composition as in claim 1, wherein at least 60% of the
polymer molecules are connected to an adjacent polymer molecule via
the at least one interacting group.
14. A composition as in claim 1, wherein at least 70% of the
polymer molecules are connected to an adjacent polymer molecule via
the at least one interacting group.
15. A composition as in claim 1, wherein at least 80% of the
polymer molecules are connected to an adjacent polymer molecule via
the at least one interacting group.
16. A composition as in claim 1, wherein at least 90% of the
polymer molecules are connected to an adjacent polymer molecule via
the at least one interacting group.
17. A composition as in claim 1, further comprising a host material
with which the polymer network is mixed.
18. A composition as in claim 17, wherein the host material
comprises a liquid crystal.
19. A composition as in claim 1, wherein the wherein the dichroic
ratio of the polymeric network is at least 10% greater than the
dichroic ratio of a polymer molecule essentially identical, but
lacking the interacting group, under essentially identical
conditions.
20. A composition as in claim 1, wherein the wherein the dichroic
ratio of the polymeric network is at least 20% greater than the
dichroic ratio of a polymer molecule essentially identical, but
lacking the interacting group, under essentially identical
conditions.
21. A composition as in claim 1, wherein the wherein the dichroic
ratio of the polymeric network is at least 30% greater than the
dichroic ratio of a polymer molecule essentially identical, but
lacking the interacting group, under essentially identical
conditions.
22. A composition as in claim 1, wherein the wherein the dichroic
ratio of the polymeric network is at least 40% greater than the
dichroic ratio of a polymer molecule essentially identical, but
lacking the interacting group, under essentially identical
conditions.
23. A composition as in claim 1, wherein the wherein the dichroic
ratio of the polymeric network is at least 50% greater than the
dichroic ratio of a polymer molecule essentially identical, but
lacking the interacting group, under essentially identical
conditions.
24. A composition as in claim 1, wherein the wherein the dichroic
ratio of the polymeric network is at least 60% greater than the
dichroic ratio of a polymer molecule essentially identical, but
lacking the interacting group, under essentially identical
conditions.
25. A composition as in claim 1, wherein the wherein the dichroic
ratio of the polymeric network is at least 70% greater than the
dichroic ratio of a polymer molecule essentially identical, but
lacking the interacting group, under essentially identical
conditions.
26. A composition, comprising: a polymer having a substantially
rigid polymer backbone, and at least one intermolecular interacting
group attached at or near a terminal end of the polymer.
27. A composition as in claim 26, wherein the interacting group is
capable of forming a non-covalent bond with an adjacent
polymer.
28. A composition as in claim 27, wherein the non-covalent bond is
a hydrogen bond, ionic bond, dative bond, or Van der Waals
interaction.
29. A composition as in claim 27, wherein the non-covalent bond is
a hydrogen bond.
30. A composition as in claim 26, wherein the interacting group is
capable of forming a covalent bond with an adjacent polymer.
31. A composition as in claim 26, wherein the polymer is a
poly(arylene), poly(arylenevinylene), poly(aryleneethylnylene), or
substituted derivatives thereof.
32. A composition as in claim 26, wherein the polymer is
poly(aryleneethylnylene).
33. A composition as in claim 26, wherein the polymer has the
structure, ##STR00011## wherein n is at least 1, A and C are
optionally substituted aromatic groups; B and D are absent, alkene,
alkyne, heteroalkene, or heteroalkyne; and E.sup.1 and E.sup.2 can
the be the same or different and are interacting groups.
34. A composition as in claim 33, wherein the polymer has the
structure, ##STR00012## wherein R.sup.1 and R.sup.2 can be the same
or different and are alkyl, heteroalkyl, aryl, heteroaryl, or
substituted derivatives thereof.
35. A composition as in claim 34, wherein the polymer has the
structure, ##STR00013## wherein R.sup.1 and R.sup.2 are
2-ethylhexyl, and R.sup.3 is butyl.
36. A method for increasing the dichroic ratio of a polymer
molecule, comprising: providing a host material and a plurality of
polymer molecules with which the host material is mixed, wherein
each polymer molecule comprises at least one intermolecular
interacting group attached at or near a terminal end of the polymer
molecule; and allowing the at least one interacting group to
interact with an adjacent polymer molecule to form a polymeric
network, wherein the polymeric network has a greater dichroic ratio
than the dichroic ratio of a polymer molecule essentially
identical, but lacking the interacting group, under essentially
identical conditions.
37. A method as in claim 36, wherein the host material comprises a
liquid crystal.
38. A method as in claim 36, wherein the at least one interacting
group interacts with an adjacent polymer molecule to form a
non-covalent bond therebetween.
39. A method as in claim 38, wherein the non-covalent bond is a
hydrogen bond, ionic bond, dative bond, or Van der Waals
interaction.
40. A method as in claim 38, wherein the non-covalent bond is a
hydrogen bond.
41. A method as in claim 36, wherein the at least one interacting
group interacts with an adjacent polymer molecule to form a
covalent bond therebetween.
42. A method as in claim 36, wherein the polymer molecule has a
substantially rigid polymer backbone.
43. A method as in claim 36, wherein the polymer molecule is a
poly(arylene), poly(arylenevinylene), poly(aryleneethylnylene), or
substituted derivatives thereof.
44. A method as in claim 36, wherein the polymer molecule is
poly(aryleneethylnylene).
45. A method as in claim 36, wherein the polymer molecule has the
structure, ##STR00014## wherein n is at least 1, A and C are
optionally substituted aromatic groups; B and D are absent, alkene,
alkyne, heteroalkene, or heteroalkyne; and E.sup.1 and E.sup.2 can
the be the same or different and are interacting groups.
46. A method as in claim 45, wherein E.sup.1 and E.sup.2 are groups
capable of forming hydrogen bonds with an adjacent polymer
molecule.
47. A method as in claim 45, wherein the polymer molecule has the
structure, ##STR00015## wherein R.sup.1 and R.sup.2 can be the same
or different and are alkyl, heteroalkyl, aryl, heteroaryl, or
substituted derivatives thereof.
48. A method as in claim 45, wherein the polymer has the structure,
##STR00016## wherein R.sup.1 and R.sup.2 are 2-ethylhexyl, and
R.sup.3 is butyl.
49. A method as in claim 36, wherein at least 50% of the polymer
molecules are connected to an adjacent polymer molecule via the at
least one interacting group.
50. A method as in claim 36, wherein at least 60% of the polymer
molecules are connected to an adjacent polymer molecule via the at
least one interacting group.
51. A method as in claim 36, wherein at least 70% of the polymer
molecules are connected to an adjacent polymer molecule via the at
least one interacting group.
52. A method as in claim 36, wherein at least 80% of the polymer
molecules are connected to an adjacent polymer molecule via the at
least one interacting group.
53. A method as in claim 36, wherein at least 90% of the polymer
molecules are connected to an adjacent polymer molecule via the at
least one interacting group.
54. A method as in claim 36, wherein the wherein the dichroic ratio
of the polymeric network is at least 10% greater than the dichroic
ratio of a polymer molecule essentially identical, but lacking the
interacting group, under essentially identical conditions.
55. A method as in claim 36, wherein the wherein the dichroic ratio
of the polymeric network is at least 20% greater than the dichroic
ratio of a polymer molecule essentially identical, but lacking the
interacting group, under essentially identical conditions.
56. A method as in claim 36, wherein the wherein the dichroic ratio
of the polymeric network is at least 30% greater than the dichroic
ratio of a polymer molecule essentially identical, but lacking the
interacting group, under essentially identical conditions.
57. A method as in claim 36, wherein the wherein the dichroic ratio
of the polymeric network is at least 40% greater than the dichroic
ratio of a polymer molecule essentially identical, but lacking the
interacting group, under essentially identical conditions.
58. A method as in claim 36, wherein the wherein the dichroic ratio
of the polymeric network is at least 50% greater than the dichroic
ratio of a polymer molecule essentially identical, but lacking the
interacting group, under essentially identical conditions.
59. A method as in claim 36, wherein the wherein the dichroic ratio
of the polymeric network is at least 60% greater than the dichroic
ratio of a polymer molecule essentially identical, but lacking the
interacting group, under essentially identical conditions.
60. A method as in claim 36, wherein the wherein the dichroic ratio
of the polymeric network is at least 70% greater than the dichroic
ratio of a polymer molecule essentially identical, but lacking the
interacting group, under essentially identical conditions.
61. A composition as in claim 9, wherein the polymer molecule
comprises a group having the structure, ##STR00017## wherein G, H,
I, and J are aromatic groups, d=1, 2, and d.sup.1=0, 1, such that
when d.sup.1=0, d.sup.2=0 and when d.sup.1=1, d.sup.2=0, 1.
62. A composition as in claim 61, wherein G and H can be the same
or different and are: ##STR00018## optionally substituted, I and J
may be the same or different and are: ##STR00019## optionally
substituted, wherein each Z.sup.1 can be the same or different and
Z.sup.1 is O, S or NR, wherein R is hydrogen, alkyl, heteroalkyl,
aryl, or heteroaryl, optionally substituted, and each Z.sup.2 can
be the same or different and Z.sup.2 is halide, alkyl, heteroalkyl,
aryl, or heteroaryl, optionally substituted.
63. A composition as in claim 9, wherein the polymer molecule
comprises a group having the following structure, ##STR00020##
optionally substituted.
Description
RELATED APPLICATIONS
[0001] This application claims priority under 35 U.S.C. .sctn.
119(e) to co-pending U.S. Provisional Application Ser. No.
60/855,966, filed Nov. 1, 2006, the contents of which are
incorporated herein by reference.
FIELD OF THE INVENTION
[0003] The present invention generally relates to composition,
devices, and methods involving the alignment of polymers.
BACKGROUND OF THE INVENTION
[0004] Liquid crystals are often employed in devices, such as
liquid crystal displays (LCDs), which utilize the different optical
properties of liquid crystalline molecules in either the presence
or absence of, for example, an electric field. In one example, the
liquid crystal material may be oriented in one liquid crystal phase
in the absence of an electric field, wherein light is transmitted
through the device and reflected back to the observer such that the
device appears clear. The liquid crystal material may be reoriented
in a different liquid crystal phase in the presence of an electric
field, wherein light is no longer transmitted through the device
such that the device appears dark. Thus, an electric field may be
applied to switch the liquid crystal material between clear and
dark (e.g., "on" and "off" states). In LCDs, images may be created
using a plurality of individual picture elements or "pixels,"
wherein each pixel may contain a liquid crystal material which may
be switched to form the image. In color LCDs, color filters or
chromophores such as dyes may be incorporated within the device to
generate the appearance of color within each pixel.
[0005] In many present day LCDs, the alignment of the liquid
crystal material in the absence of an electric field may be
determined by a surface in contact with the liquid crystal. The
surface may be rubbed or otherwise treated such that the surface
can orient the liquid crystal material in the absence of the
electric field. In the presence of an electric field, the liquid
crystal material may be switched to one state (e.g., "turn-on"
event), and, upon subsequent removal of the electric field, the
liquid crystal material may relax or decay to its original state
(e.g., "turn-off" event). In such cases, the "turn-on" event may be
fast because the switching of the liquid crystal is actively driven
by an electric field. However, the "turn-off" event may be slow
because the realignment of the liquid crystal by the treated
surface often begins at the surface and must propagate into the
bulk of the liquid crystal material. Additionally, many LCDs
require an active electric field to keep the liquid crystal
material in one of the two states (e.g., "on" or "off"), resulting
in the need for a constant source of external energy.
[0006] Accordingly, improved devices and methods are needed.
SUMMARY OF THE INVENTION
[0007] The present invention relates to compositions comprising a
polymeric network comprising the assembly of a plurality of polymer
molecules, wherein each polymer molecule comprises at least one
intermolecular interacting group at or near a terminal end of the
polymer molecule, wherein at least 50% of the polymer molecules are
connected to an adjacent polymer molecule via the at least one
interacting group, wherein the polymeric network has a greater
dichroic ratio than a dichroic ratio of a polymer molecule
essentially identical, but lacking the interacting group, under
essentially identical conditions.
[0008] The present invention also relates to compositions
comprising a polymer having a substantially rigid polymer backbone,
and at least one intermolecular interacting group attached at or
near a terminal end of the polymer.
[0009] The present invention also provides methods for increasing
the dichroic ratio of a polymer molecule comprising providing a
host material and a plurality of polymer molecules with which the
host material is mixed, wherein each polymer molecule comprises at
least one intermolecular interacting group attached at or near a
terminal end of the polymer molecule; and allowing the at least one
interacting group to interact with an adjacent polymer molecule to
form a polymeric network, wherein the polymeric network has a
greater dichroic ratio than the dichroic ratio of a polymer
molecule essentially identical, but lacking the interacting group,
under essentially identical conditions.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 shows a schematic representation of the formation of
a polymeric network from a plurality of polymer molecules.
[0011] FIG. 2 shows a schematic representation of the disruption of
a polymeric network by adding an excess of a species containing a
single interacting group.
[0012] FIG. 3A shows a schematic representation of the alignment of
a nematic liquid crystal host material by a polymeric network.
[0013] FIG. 3B shows a schematic representation of a polymer
comprising a shape-persistent group combined with a nematic liquid
crystal host material.
[0014] FIG. 4 shows the synthesis of a ureidopyrimidinone endgroup
precursor, according to one embodiment of the invention.
[0015] FIG. 5A shows the synthesis of poly(phenylene ethynylene)
comprising ureidopyrimidinone endgroups, according to one
embodiment of the invention.
[0016] FIG. 6 shows the plot of log K.sub.dim of compound 1 as a
function of solvent composition for CDCl.sub.3 mixtures of (a) MeOD
and (b) DMSO-d.sub.6.
[0017] FIG. 7 shows the (a) normalized absorption spectra of
polymer P2b in chloroform solution, and the polarized absorption of
polymer P2b in a liquid crystal cell with (b) parallel and (c)
perpendicular polarizer, with respect to the liquid crystal
director.
[0018] FIG. 8 shows the dichroic ratio of compounds P1b and P2b as
a function of time upon the addition of (a) 4.4 mM polymer P1b, (b)
9.6 mM polymer P1b, (c) 19.2 mM polymer, P1b, (d) 3.8 mM polymer
P2b, and (e) 16.2 mM polymer P2b.
DETAILED DESCRIPTION
[0019] The present invention generally relates to composition,
devices, and methods involving the alignment of materials,
including polymers.
[0020] In some embodiments, the present invention provides
compositions and devices comprising the assembly of molecules via
intermolecular interactions to produce extended networks. In some
cases, the extended networks may have enhanced properties relative
to the individual molecules. For example, embodiments of the
present invention may comprise the assembly of polymer molecules
via interchain interactions (e.g., hydrogen bonds) to produce
chain-extended polymeric networks, wherein the polymer network may
exhibit enhanced alignment properties, optical properties,
transport properties, or the like, when compared to an essentially
identical, individual polymer. Such polymeric networks may be
advantageous for use in electronics, photovoltaics, sensor
applications, and the like. In some embodiments, the present
invention may enhance the performance of certain optical devices,
such as liquid crystal displays (e.g., color liquid crystal
displays) by providing enhanced contrast ratio, faster response
times, and/or lower operating voltage.
[0021] In some embodiments, the present invention may
advantageously facilitate alignment of polymers. In some cases, the
alignment may be intermolecular alignment, wherein a plurality of
polymers may be assembled via functional groups positioned at or
near a terminal end of the polymer and capable of interacting with
an adjacent polymer. This may result in the formation of
chain-extended polymer networks exhibiting high order parameters
(e.g., high dichroic ratio), which may be determined from the
polarized absorption of the polymeric network. In some cases, the
alignment may be intramolecular alignment, wherein increased
alignment may occur within an individual polymer chain. For
example, a conjugated polymer molecule may, upon formation of a
chain-extended polymer network and/or when combined with a host
material, adopt a more planar conformation, which may produce
improved charge transport properties.
[0022] Some embodiments of the present invention may also be useful
as stabilizing elements or "molecular cytoskeletons" in the
alignment of materials. For example, when combined with materials
such as liquid crystals, polymeric networks as described herein may
stabilize and/or accelerate the alignment of one or more liquid
crystal phases. That is, the polymeric networks may serve as a
structural reinforcing group to stabilize, for example, liquid
crystals in a desired orientation, tilt angle, or mesophase, in
some cases, without need for an external source of energy. This may
be useful in the fabrication of bistable devices, such as
electronic paper, which may require materials to maintain a
particular orientation in the absence of an external energy source.
Another advantage of the present invention may be the ability to
accelerate and/or enhance the switching events in devices, such as
liquid crystal devices. For example, many liquid crystal devices
involve the heterogeneous alignment of a liquid crystal, wherein,
in the absence of an external source of energy, the alignment of a
liquid crystal sample in a particular orientation may begin at the
interface between the liquid crystal and at least one surface
(e.g., rubbed or treated surface), wherein the surface interacts
with (e.g., orients) the liquid crystal at the surface, followed by
propagation of the alignment through the bulk of the sample. In
some cases, heterogeneous alignment may occur on a timescale that
may be slow, relative to the desired rate of switching. In
contrast, polymeric networks of the invention may be present
throughout the bulk of the material and may facilitate homogeneous
alignment of a liquid crystal, i.e., from a first orientation to a
second orientation, which may occur more rapidly than heterogeneous
alignment. Thus, devices of the invention may switch between
different liquid crystal states with greater speed and uniformity,
resulting in devices having faster response times and enhanced
performance.
[0023] In some embodiments, the present invention provides
compositions comprising polymeric networks comprising the assembly
of a plurality of polymer molecules, wherein each polymer molecule
comprises at least one intermolecular interacting group at or near
a terminal end of the polymer molecule. The polymer molecules may
be connected to an adjacent polymer molecule via the interacting
group, wherein the interacting group forms a bond with an adjacent
polymer. The bond may be non-covalent bond or a covalent bond. In
some cases, the bond is a non-covalent bond such as a hydrogen
bond, ionic bond, dative bond, or Van der Waals interaction. In
some embodiments, the polymer molecules may be connected to an
adjacent polymer molecule via a hydrogen bond. In some embodiments,
the polymer molecules may be connected to an adjacent polymer
molecule via a covalent bond. The polymer molecules may assemble
via the interacting groups to form a polymeric network having a
greater chain length than an individual polymer molecule
[0024] As shown schematically in FIG. 1, polymer molecule 10 may
comprise interacting groups 20 attached to the terminal ends of
polymer 20. Polymer molecule 10 may then form a bond, such as a
hydrogen-bond, for example, with an adjacent polymer molecule to
form polymeric network 40. The polymer molecule may comprise
interacting groups positioned at or near both terminal ends of the
polymer molecule, allowing formation of a polymeric network that
may extend throughout the bulk of a given volume and may have
essentially infinite length within the volume. In some embodiments,
at least 50% of the polymer molecules are connected to an adjacent
polymer molecule via the at least one interacting group. In other
embodiments, at least 60%, at least 70%, at least 80%, or, at least
90% of the polymer molecules are connected to an adjacent polymer
molecule via the at least one interacting group. In some cases,
formation of the polymeric network may be reversible. As shown
schematically in FIG. 2, addition of an excess of a species 50
comprising a single interacting group may disrupt the polymeric
network, wherein the individual polymer molecules interact with the
species 50 rather than with an adjacent polymer molecule.
[0025] The polymeric network comprising the assembly of a plurality
of polymer molecules may advantageously have a greater dichroic
ratio than a dichroic ratio of an individual polymer molecule that
is essentially identical to an individual polymer molecule of the
polymeric network, but lacking the interacting group, under
essentially identical conditions. As used herein, the term
"dichroic ratio" is given its ordinary meaning in the art and
refers to the ratio of the polarized absorption of a species along
two different axes of the species. The dichroic ratio may be
defined by the formula,
DR=(A.sub..parallel.-A.sub..perp.)/(A.sub..parallel.+A.sub..perp.),
wherein A.sub..parallel. is the absorption measured along a
direction that is parallel to an expected alignment of a species,
while A.sub..perp. is the polarized absorption along a direction
that is perpendicular to the expected alignment of the species. In
some cases, A.sub..parallel. refers to the alignment of a species
along the long axis of the species. The dichroic ratio of a
material generally indicates the extent to which the material may
be aligned along a particular direction, wherein a large dichroic
ratio may indicate a high degree of alignment. In some embodiments,
the dichroic ratio of the polymeric network is at least 10%, at
least 20%, at least 30% at least 40%, at least 50%, at least 60%,
or, at least 70% greater than the dichroic ratio of a polymer
molecule that is essentially identical to an individual polymer
molecule of the polymer network, but lacking the interacting group,
under essentially identical conditions. In some cases, the dichroic
ratio may be increased by 80%, 90%, or even greater.
[0026] As used herein, a first species may be exposed to a set of
"essentially identical conditions" as a second species by
subjecting the first species and second species to a similar or
substantially identical set of environmental parameters, such as
temperature, pressure, pH, solvent, concentration, chemical
reagent, atmosphere (e.g., nitrogen, argon, oxygen, etc.), electric
field, electromagnetic radiation, other source of external energy,
or the like, for a similar or identical period of time.
[0027] In some cases, compositions of the invention may further
comprise a host material with which the polymeric network is mixed.
For example, the host material may be a solvent, polymer, gel,
liquid crystal, other materials capable of forming anisotropic
phases, or materials that are miscible with the polymeric network.
In some embodiments, the host material comprises a liquid crystal.
In some cases, the polymeric network may be molecularly dissolved
in the host material. As used herein, a "molecularly dissolved"
polymeric network refers to a polymeric network that may be soluble
within (e.g., does not phase-separate from) a host material while
remaining an intact, polymeric network. That is, while the polymer
network may be soluble within the host material at the molecular
level, there may be little or no disruption in the assembly of the
individual polymer molecules. In some cases, upon switching of the
host material and polymer network between different orientations,
the polymer network may remain intact. In some cases, upon
switching of the host material and polymer network between
different orientations, the polymer network may undergo slight
disruption but may then rapidly re-assemble such that the alignment
of the host material is essentially unaffected by the slight
disruption. Compositions comprising polymeric network mixed with
and/or molecularly dissolved in host materials may have use in a
wide variety of applications, as described more fully below.
[0028] The present invention also provides methods for increasing
the dichroic ratio of a polymer molecule. In some cases, the
formation of a polymeric network as described herein may increase
the dichroic ratio of a polymer molecule. For example, the method
may comprise providing a host material and a plurality of polymer
molecules with which the host material is mixed, wherein each
polymer molecule comprises at least one intermolecular interacting
group attached at or near a terminal end of the polymer molecule.
The at least one interacting group(s) may then be allowed to
interact with an adjacent polymer molecule, i.e., via an
interacting group of the adjacent polymer molecule, to form a
polymeric network. The interaction between adjacent polymer
molecule may comprise the formation of a bond, as described herein.
In some cases, the formation of the extended polymer network may
cause an individual polymer molecule to adopt a chain-extended
confirmation which may be aligned with the host material, thereby
increasing the dichroic ratio of the polymer molecule. For example,
the host material may be a liquid crystal, wherein the liquid
crystal and the polymeric network are oriented such that the
polymer backbones of the individual polymer molecules may be
oriented substantially parallel to the liquid crystal director.
[0029] In some cases, formation of the extended polymer network may
cause an individual polymer molecule to adopt a planar conformation
along the polymer backbone. For example, conjugated polymer
molecules comprising interacting groups may assemble to form
polymeric networks as described herein, which may result in
increased conjugation lengths along the polymer backbone and
enhanced optical properties (e.g., luminescence emission). In some
cases, the polymer may comprise a shape-persistent molecule which
may facilitate alignment in and/or compatibility with the host
material.
[0030] The interaction between individual polymer molecules may
increase the dichroic ratio of the polymer molecules, since the
polymeric network may have a greater dichroic ratio than the
dichroic ratio of a polymer molecule that is essentially identical,
but lacking the interacting group, under essentially identical
conditions. The presence of polymeric networks as described herein
may also influence (e.g., increase) the alignment of the host
material. For example, as shown in FIG. 3A, a polymer molecule 60
comprising a shape-persistent moiety 70, when mixed with a liquid
crystal material 90, may adopt an extended structure wherein the
polymer backbone aligns in the direction 100 of the liquid crystal
director. However, as shown in FIG. 3B, a polymeric network 110 may
be formed by the assembly of individual polymer molecules 62, each
comprising a shape-persistent moiety 72 and interacting groups 74
positioned at or near the terminal ends of a polymer molecule 62.
Each polymer molecule 62 may adopt an extended structure such that,
when mixed with the liquid crystal material 90, the polymeric
network aligns in the direction 100 of the liquid crystal director.
In some embodiments, polymeric network 110 may have a greater
dichroic ratio than the dichroic ratio of polymer molecule 60 under
essentially identical conditions, wherein polymer 60 is essentially
identical to the individual polymer molecules 62 of polymeric
network 110, except that polymer 60 lacks interacting group. That
is, the interaction between adjacent polymer molecules to form an
extended polymeric network may increase the dichroic ratio of the
polymer molecules.
[0031] The present invention also relates to devices wherein
increased alignment (e.g., increased dichroic ratio) may improve
the performance of the devices. Devices of the invention may
comprise polymeric networks as described herein, alone or in
combination with a host material, to facilitate alignment of at
least one component of the device, such as a liquid crystalline
component. For example, the device may comprise a polymeric network
and a host material with which the polymeric network is mixed,
wherein the polymeric network is capable of orienting the host
material. In some cases, the host material comprises a liquid
crystal material, and the polymeric network may serve as a
directing element or "molecular cytoskeleton" for facilitating
alignment of the individual liquid crystalline species. That is,
the liquid crystal and the polymeric network may be aligned in the
same orientation, wherein the polymer backbones of the individual
polymer molecules are oriented substantially parallel to the liquid
crystal director. The polymeric network may increase, stabilize,
accelerate, or otherwise improve the alignment of the host
material. In some cases, the polymeric network may allow the host
material to adopt a particular orientation that may not be stable
in the absence of the polymeric network. For example, the polymeric
network may stabilize the host material in an orientation having
relatively high energy.
[0032] In the illustrative embodiment shown in FIG. 3B, polymeric
network 110 may have an axis 120 along the assembly of the
plurality of polymer molecules, i.e., along the long axes of the
polymer molecules 62, and the host material may comprise a
plurality of liquid crystalline species 90, each having a primary
axis aligned so as to together define an average axis 92 of the
liquid crystalline species primary axes (e.g., the liquid crystal
director). The polymeric network 110 may interact with the host
material 90 to direct the individual liquid crystalline species to
align substantially parallel to the axis 120 of the polymeric
network.
[0033] The devices may comprise additional components capable of
orienting the host material in one or more orientations. In some
cases, the device may comprise at least one surface in contact with
at least a portion of the host material, wherein the surface is
capable of orienting the host material. The surface may be a rubbed
surface, wherein the host material may align along grooves formed
by the rubbing direction. In some embodiments, an inorganic
material (e.g., silicon oxide, and the like) may be evaporated onto
a surface such that the treated surface may then align a host
material. In some cases, one or more surfaces may contact the host
material at different locations. For example, a liquid crystal may
be placed between a first rubbed surface having a rubbing direction
and a second rubbed surface having a rubbing direction, wherein the
surfaces are arranged such that the rubbing directions of the two
surfaces are positioned perpendicular (e.g., 90.degree.) with
respect to one another. This may result in the formation of a
twisted nematic phase, wherein the liquid crystal director rotates
90.degree. from the first rubbed surface to the second rubbed
surface. Examples of surfaces that may be used as alignment layers
for liquid crystals include polymer surfaces, including polyimide,
and the like. Other examples of surfaces that may align host
materials are described in, for example, Thermotropic Liquid
Crystals, G. W. Gray, Ed., John Wiley & Sons, 1987, and a
review by J. Cognard, Mol. Cryst. Liq. Cryst. 78, Supplement 1
(1981), pages 1 77.
[0034] In some cases, the devices may comprise more than one
polymeric network. For example, the device may comprise a first
polymeric network and a second polymeric network, both mixed with
the host material, wherein the first polymeric network is capable
of orienting the host material in one orientation and the second
polymeric network is capable of orienting the host material in a
different orientation.
[0035] Devices of the invention may further comprise electrodes,
polarizing filters, sources of external energy, and the like, in
combination with the components described herein.
[0036] In some embodiments, the present invention advantageously
provides devices and methods for orienting a host material. In some
cases, the device may be capable of rapidly orienting and/or
re-orienting a host material such that the device has an
accelerated response time. As used herein, the "response time" of a
device may be measured by the amount of time required to reorient
or switch the host material between two orientations. For example,
the response time may relate to the amount of time it takes to
switch the "on" and "off" states of a liquid crystal device.
Devices having faster response times may generally have improved
performance. For example, in some cases, display devices with rapid
response times may exhibit fewer visible image artifacts.
[0037] Accordingly, in some embodiments, methods of the invention
may comprise providing a device comprising a polymeric network and
a host material with which the polymeric network is mixed, wherein
the host material has a first orientation. Exposure of the device
to a source of external energy may cause at least some of the host
material to move from the first orientation to a second
orientation, wherein the second orientation is different than the
first orientation. Subsequent removal of the source of external
energy may then cause the host material moved from the first to the
second orientation to move or relax from the second orientation to
the first orientation, wherein the host material moves from the
second orientation to the first orientation more rapidly than in a
device that is essentially identical, but lacks the polymeric
network, under essentially identical conditions. That is, the
presence of the polymeric network may accelerate reorganization of
the host material from the second orientation to the first
orientation by serving as a directing or aligning element
positioned throughout the bulk of the host material, resulting in
faster switching speeds and improved device performance. Methods
described herein may be advantageous over devices which lack the
polymeric network, such as, for example, devices where realignment
of the host material often depends on interaction of the host
material with a rubbed or otherwise treated surface, followed by
propagation of the alignment into the bulk of the host material,
which can limit the response time.
[0038] Another advantage of the present invention may be the
ability to provide methods and devices comprising a polymeric
network and host material as described herein, wherein the host
material (e.g., liquid crystal) is capable of substantially
maintaining more than one orientation (e.g., liquid crystal phase,
tilt angle, other orientation, etc.) in the absence of an external
source of energy. For example, methods of the invention may
comprise providing a device comprising a polymeric network and a
host material with which the polymeric network is mixed, wherein
the host material has a first orientation, and exposing the device
to a first source of energy to cause at least some of the host
material to move from the first orientation to a second
orientation. Upon removal of the source of energy, the host
material that was moved from the first to the second orientation
may remain substantially in the second orientation for a period of
time. Subsequent exposure of the device to a second source of
energy may then cause the host material moved from the first to the
second orientation to return to the first orientation. In some
cases, the polymeric network may orient and/or maintain the host
material in the second orientation for a longer period of time
than, for example, in a device that is essentially identical, but
lacks the polymeric network, under essentially identical
conditions.
[0039] In some cases, the device may require application of a
source of external energy in order to switch the host material from
one orientation to another, but the source of external energy may
not be required substantially retain the host material in an
orientation for a period of time. In some cases, the host material
may substantially retain a higher energy state (e.g., orientation)
in the absence of a source of external energy. That is, the host
material may be oriented to a relatively high energy state upon
exposure to a source of energy, and, upon removal of the source of
energy, the host material may slightly relax or decay from the high
energy state, but may substantially retain the orientation of the
high energy state. For example, a liquid crystal host material may
have a first orientation in a low energy state. Upon exposure to an
electric field, the liquid crystal may be oriented by the electric
field and may adopt a second orientation in a relatively high
energy state. When the electric field is removed, the liquid
crystal may undergo slight decay or relaxation to a metastable
state, which may be stabilized by the presence of a polymeric
network, wherein the liquid crystal substantially retains the
orientation of the relatively high energy state (e.g., the second
orientation). The liquid crystal may then be triggered, upon
exposure to an electric field, to relax to the low energy, first
orientation. As described herein, the device may comprise
additional components that may aid in the stabilization of a
particular host material orientation. For example, the devices may
comprise a surface in contact with at least a portion of the host
material, wherein the surface is capable of orienting the host
material, or the devices may comprise more than one polymeric
network, wherein each polymeric network is capable of orienting the
host material in a different orientation.
[0040] In an illustrative embodiment, a polymeric network as
described herein may be mixed with a nematic liquid crystal host
material, wherein the polymeric network and liquid crystal are
oriented in a direction that is parallel to, for example, the
grooves of a rubbed surface in contact with the polymeric
network/liquid crystal mixture. Upon application of an electric
field, the polymeric network/liquid crystal mixture maybe oriented
in a direction that is perpendicular to the rubbed surface, i.e.,
the liquid crystal molecules and polymeric network are moved
90.degree. relative to their original orientation, which may be a
relatively higher energy orientation relative to the original
orientation. Upon removal of the electric field, the liquid
crystal/polymeric network may relax or decay to an orientation
where the liquid crystal/polymeric network may be positioned less
than 90.degree. relative to the original orientation but
substantially retains the orientation of the relatively high energy
state.
[0041] In some embodiments, the device may be a bistable device,
such as a bistable liquid crystal device. As used herein, a
"bistable liquid crystal" refers to a liquid crystal which can
substantially maintain two different orientations (e.g., liquid
crystal orientations) for an amount of time without need for an
external source of energy to stabilize the orientations. In some
cases, the amount of time may be longer than in devices which lack
polymeric networks as described herein.
[0042] Devices and methods of the present invention may be used in
a wide variety of applications. For example, the device may be
constructed and arranged to display a particular type of behavior
upon application of a source of energy to the device, removal of a
source of energy from the device, and/or orientation/reorientation
of the host material, including a change in color, a change in
luminescence, a change in transmission of an optical signal (e.g.,
hologram, diffraction pattern, reflection pattern, or the like), or
other signal recognizable by a human. In some cases, application of
a source of energy to the device causes switching in a liquid
crystal display.
[0043] The present invention also relates to polymer compositions
comprising a polymer having a substantially rigid polymer backbone
and at least one intermolecular interacting group attached at or
near a terminal end of the polymer, as described herein. As used
herein, a "substantially rigid" polymer backbone refers to a
polymer backbone having sufficient rigidity such that it may adopt
a chain-extended structure within a host material, such as a liquid
crystal. In some cases, at least a portion of the polymer backbone
is rigid. In some cases, the polymer backbone is rigid along the
essentially the entire length of the polymer backbone. As used
herein, a "rigid" portion of a polymer backbone refers to a portion
wherein the spatial relationship (e.g., angle, distance, etc.)
between adjacent monomeric moieties cannot change, outside of
normal molecule-scale changes in temperature, etc., without
breaking at least one bond. For example, a portion of a polymer
including sp.sup.3-hybridized carbon atoms may not be rigid (e.g.,
alkyl chains, heteroalkyl chains, and the like), while
sp.sup.2-hybridized or sp-hybridized carbon atoms may impart a
higher degree of rigidity (e.g., aryl groups, alkynyl groups).
However, portions of a polymer including sp.sup.3-hybridized carbon
atoms, wherein the sp.sup.3-hybridized carbon atoms, for example,
form bridgeheads between fused rings in a bicyclic or polycyclic
structure or otherwise form a shape-persistent moiety may be
considered to form a rigid structure. In some embodiments, a
polymer or portion thereof may comprise a metal atom, wherein the
metal atom, when bound to or otherwise attached to the polymer,
imparts a degree of rigidity to the polymer.
[0044] In some cases, the polymer may include rigid portions and
one or more non-rigid portions, so long as the combination of rigid
and non-rigid portions allows the polymer to adopt a chain-extended
structure within a host material. In some cases, adjacent monomeric
units which are joined by a single bond may rotate around the
single bond, but may be considered rigid with respect to one
another within the polymer backbone. In some cases, the spatial
relationship between pendant side groups on adjacent monomers, or
between a pendant side group of one monomer and an adjacent
monomer, may change but the polymer backbone may be considered
rigid. In some embodiments, the polymer may have a substantially
rigid polymer backbone and pendant side groups which may or may not
be rigid.
[0045] In some cases, the polymer may be a conjugated polymer
(e.g., pi-conjugated, sigma-conjugated, or the like), such as a
poly(arylene), poly(arylenevinylene), poly(arylene-ethynylene), or
a substituted derivative thereof. In a particular embodiment, the
polymer may be poly(aryleneethynylene). In some cases, the polymer
may comprise portions which are not conjugated, but may be rigid,
such as fused, bicyclic and fused, polycyclic structures. For
example, a polymer backbone may comprise an iptycene moieties,
wherein adjacent monomeric units are attached via the bridgehead
atoms of the iptycene moiety.
[0046] Polymers of the invention may also comprise shape-persistent
molecules. As used herein, a "shape-persistent" molecule refers to
a molecule or portion of a molecule having a significantly rigid
structure, wherein no portion of the shape-persistent molecule
having a combined molecular weight of at least 15 g/mol may move
relative to other portions of the shape-persistent molecule moiety
having a molecular weight of greater than 25, 50, or 100 g/mol can
move relative to other portions of the shape-persistent molecule
via rotation about a single bond. Rigid structures may be provided,
for example, by aromatic structures, polycyclic structures
including non-planar polycyclic structures, and the like. Examples
of shape-persistent molecules include polycyclic aromatic groups
(e.g., naphthalene, anthracene, etc.), bridged polycyclic
structures (e.g., iptycenes, norbornanes, adamantanes, etc.),
ladder polymers, and the like. In some cases, the shape-persistent
molecule may be located within the polymer backbone. In some cases,
the shape-persistent molecule may be located within a group that is
pendant to the polymer backbone.
[0047] In some cases, the shape-persistent molecule may
advantageously facilitate alignment of species within a host
material or may facilitate alignment of the host material itself.
For example, a shape-persistent molecule may be covalently attached
to a species and, when combined with a host material, may
facilitate alignment of the species within the host material. In
some embodiments, the shape-persistent molecule may have a
three-dimensional structure having a sufficient degree of free
volume to create void spaces. When mixed with a host material such
as a liquid crystal, for example, the host material may fill in the
void spaces. Other species, including small molecules,
macromolecules, polymers, etc., may also occupy the void spaces. In
some cases, the shape-persistent molecule may advantageously have
minimal affect on the alignment of the host material, i.e., does
not change the director of the host liquid crystal. In some cases,
such as, for example, when the shape-persistent molecule is
included in an extended polymeric network as described herein, the
shape-persistent molecule may facilitate alignment of the host
material in a particular orientation.
[0048] In some embodiments, the polymer molecule may be
appropriately functionalized to impart desired characteristics
(e.g., surface properties) to the polymer. For example, the polymer
may be functionalized or derivatized to include compounds,
functional groups, atoms, or other species that can alter or
improve properties of the polymer. In some embodiments, the polymer
may include compounds, atoms, or materials that can alter or
improve properties such as compatibility (e.g., solubility,
stability) with a host material. In some cases, the polymer may
comprise functional groups selected to possess an affinity for a
surface. Other properties of the polymers may be tailored based on
substitution of the polymer backbone, such as a particular band gap
or a specific emission wavelength or color emission. For example, a
conjugated polymer may be substituted with electron-poor groups,
such as acyl, carboxyl, cyano, nitro, sulfonate, or the like, or
the polymer may install electron-poor aryl groups in the backbone
of the conjugated polymer, such that the conjugated polymer
exhibits an emission (e.g., luminescence emission, color emission)
at shorter wavelengths. In other embodiments, the conjugated
polymer may be substituted with electron-rich groups, such as
amino, hydroxy, alkoxy, acylamino, acyloxy, alkyl, halide, and the
like, or the monomers may install electron-rich aryl groups in the
backbone of the conjugated polymer, such that the conjugated
polymer exhibits emission at longer wavelengths. In some
embodiments, the polymer may tailored to advantageously have a
large Stokes shift, wherein the fluorescence spectrum is observed
at a substantially longer wavelength than the excitation
spectrum.
[0049] In some embodiments, the polymer may have the structure,
##STR00001##
wherein n is at least 1, A and C are optionally substituted
aromatic groups; B and D are absent, alkene, alkyne, heteroalkene,
or heteroalkyne; and E.sup.1 and E.sup.2 can the be the same or
different and are interacting groups. In some cases, E.sup.1 and
E.sup.2 are groups capable of forming hydrogen bonds with an
adjacent polymer molecule. In some cases, A and/or C may comprise a
shape-persistent moiety, such as an iptycene or triptycene
moiety.
[0050] In some cases, the polymer molecule may comprise a group
having the following structure,
##STR00002##
wherein G, H, I, and J are aromatic groups, d=1, 2, and d.sup.1=0,
1, such that when d.sup.1=0, d.sup.2=0 and when d.sup.1=1,
d.sup.2=0, 1. In some embodiments, G and H can be the same or
different and are:
##STR00003##
optionally substituted, I and J may be the same or different and
are:
##STR00004##
optionally substituted, wherein each Z.sup.1 can be the same or
different and Z.sup.1 is O, S or NR, wherein R is hydrogen, alkyl,
heteroalkyl, aryl, or heteroaryl, optionally substituted, and each
Z.sup.2 can be the same or different and Z.sup.2 is halide, alkyl,
heteroalkyl, aryl, or heteroaryl, optionally substituted. In some
cases, the polymer molecule comprises a group having the following
structure,
##STR00005##
optionally substituted.
[0051] For example, the polymer may have the structure,
##STR00006##
wherein R.sup.1 and R.sup.2 can be the same or different and are
alkyl, heteroalkyl, aryl, heteroaryl, or substituted derivatives
thereof.
[0052] In a particular embodiment, the polymer has the
structure,
##STR00007##
wherein R.sup.1 and R.sup.2 are 2-ethylhexyl, and R.sup.3 is
butyl.
[0053] As used herein, the term "polymer" or "polymer molecule" is
given its ordinary meaning in the art and generally refers to
extended molecular structures comprising polymer backbones and,
optionally, pendant side groups. As used herein, the term "polymer
backbone" refers to a linear chain of atoms within the polymer
molecule by which other chains may be regarded as being pendant. In
some cases, the backbone may be the longest chain of atoms within
the polymer. The term "polymer" may be used to describe both
polymers and oligomers. As used herein, an "oligomer" may refer to
a polymer as described herein having 2-20 monomeric units. For
example, an oligomer may refer to a dimer, a trimer, a tetramer,
and the like. In some cases, the polymer is a conjugated polymer.
The term "conjugated polymer" refers to a polymer in which electron
density or electronic charge can be conducted along at least a
portion of the polymer. Conjugated polymers comprise atoms capable
of participating in delocalized bonding, such as pi-bonding or
sigma-bonding. In some embodiments, a substantial length of the
backbone (e.g., the entire backbone) may be conjugated.
[0054] Polymers of the invention may generate an emission signal.
In some cases, the emission signal may be generated upon exposure
to electromagnetic radiation, an electric field, a chemical
reagent, or the like. As used herein, an emitted radiation or
"emission" may be luminescence emission, in which "luminescence" is
defined as an emission of ultraviolet or visible radiation.
Specific types of luminescence include fluorescence,
phosphorescence, chemiluminescence, electrochemiluminescence, and
the like. In some cases, polymer of the invention may emit a signal
which is visible by sight (e.g., color).
[0055] As described herein, the polymer molecule may comprise at
least one interacting group at or near a terminal end of the
polymer molecule, such that the polymer molecule may be connected
to an adjacent polymer molecule via the at least one interacting
group. As used herein, "connected to an adjacent polymer molecule
via the at least one interacting group" can be defined as follows,
and involves definitions of both the interacting groups and the
connectivity which they provide. Interacting groups can be selected
readily, by those of ordinary skill in the art, based upon the
description herein as their function, examples of such groups, and
knowledge herein and in the art as to simple techniques for
identifying suitable groups. Interacting groups are groups which,
in the context of polymer molecules used herein, can connect those
molecules to each other to form networks serving functions
described herein. The term "connect" encompasses any type of
interaction which allows networks to be formed, as described herein
and includes, without limitation, covalent bonds, ionic
interactions, Van der Waals interactions, hydrogen bonds, and the
like.
[0056] The interacting group may be any moiety capable of
intermolecularly associating with another species, for example, an
interacting group of another polymer molecule. The interaction
between the two polymer molecules may comprise formation of a bond,
such that the polymer molecules are connected to an adjacent
polymer molecule via the bond (e.g., non-covalent bond, covalent
bond). Accordingly, the interacting group may comprise functional
groups capable of forming such bonds. The functional group or
groups may be positioned at or near the terminal end of a polymer
molecule, such that the functional groups may undergo
intermolecular reaction(s) with adjacent polymer molecules, rather
than intramolecular reactions, to form the polymeric network. In
some cases, the interacting group may form a covalent bond with an
adjacent polymer molecule via, for example, a Diels Alder reaction
between a diene and a dienophile, a Michael addition between a
nucleophile and an alpha-beta-unsaturated ketone, an addition
reaction between a thiol and an alkene (e.g., a maleimide), a
cycloaddition reaction, or a radical reaction between two species
capable of forming radicals. It should be understood that covalent
bonds between two polymer molecules, i.e., via the interacting
groups, may be formed by other types of reactions, as known to
those of ordinary skill in the art, using interacting groups
comprising the appropriate functional groups to undergo such
reactions.
[0057] The interacting groups may be positioned and/or
functionalized such that they may interact intramolecularly, i.e.,
with adjacent polymer molecules, rather than intermolecularly, in
order to form the polymeric network. In an illustrative embodiment,
a polymer molecule may comprise a diene as a first interacting
group at one terminal end of the polymer molecule and a dienophile
as a second interacting group at the other terminal end of the same
polymer molecule, wherein the polymer molecule is sufficiently
rigid, i.e., has a substantially rigid polymer backbone, such that
the diene does not undergo and intramolecular Diels-Alder reaction
with the dienophile. Thus, the diene of one polymer molecule may
form a covalent bond with the dienophile of another, adjacent
polymer molecule, to form the polymeric network.
[0058] In some cases, the interacting group may form a non-covalent
bond with an adjacent polymer molecule via, for example,
hydrogen-bonds, ionic bonds, dative bonds, Van der Waals
interactions, or the like. In some embodiments, the interacting
group forms a hydrogen-bond with an adjacent polymer molecule.
Interacting groups capable of forming hydrogen-bonds include
hydrogen-bond donors and acceptors. Those of ordinary skill in the
art would be able to identify hydrogen-bond donors and acceptors
suitable for use in the present invention. For example, a
hydrogen-bond donor may comprise at least one hydrogen atom capable
of interacting with a pair of electrons on a hydrogen-bond acceptor
to form the hydrogen bond. In some cases, the hydrogen atom may be
positioned adjacent to an electron-poor group, such as fluorine,
nitro, acyl, cyano, sulfonate, or the like, to increase the acidity
of the hydrogen atom and, thus, the ability of the hydrogen atom to
form a hydrogen bond. In some cases, the interacting groups may
comprise one or more hydrogen-bond donor/acceptor moieties. In an
illustrative embodiment, the interacting group may be a
ureidopyrimidinone group, which exhibits self-association constants
of about 10.sup.7 in organic solvents. Other examples of
interacting groups which may form hydrogen bonds include carbonyl
groups, amines, hydroxyls, and the like.
[0059] In some cases, the interacting groups may comprise an
electron-rich or electron-poor moiety, wherein interaction between
interacting groups of adjacent polymer molecules comprises an
electrostatic interaction.
[0060] In some embodiments, the interacting groups of adjacent
polymer molecules may interact via a biological binding event, i.e.
between complementary pairs of biological molecules. For example,
an interacting group may comprise an entity such as biotin that
specifically binds to a complementary entity, such as avidin or
streptavidin, on an adjacent polymer molecule. Other examples of
interactions that occur between pairs of biological molecules
including proteins, nucleic acids, glycoproteins, carbohydrates,
hormones, and the like. Specific examples include an
antibody/peptide pair, an antibody/antigen pair, an antibody
fragment/antigen pair, an antibody/antigen fragment pair, an
antibody fragment/antigen fragment pair, an antibody/hapten pair,
an enzyme/substrate pair, an enzyme/inhibitor pair, an
enzyme/cofactor pair, a protein/substrate pair, a nucleic
acid/nucleic acid pair, a protein/nucleic acid pair, a
peptide/peptide pair, a protein/protein pair, a small
molecule/protein pair, a glutathione/GST pair, an anti-GFP/GFP
fusion protein pair, a Myc/Max pair, a maltose/maltose binding
protein pair, a carbohydrate/protein pair, a carbohydrate
derivative/protein pair, a metal binding tag/metal/chelate, a
peptide tag/metal ion-metal chelate pair, a peptide/NTA pair, a
lectin/carbohydrate pair, a receptor/hormone pair, a
receptor/effector pair, a complementary nucleic acid/nucleic acid
pair, a ligand/cell surface receptor pair, a virus/ligand pair, a
Protein A/antibody pair, a Protein G/antibody pair, a Protein
L/antibody pair, an Fc receptor/antibody pair, a biotin/avidin
pair, a biotin/streptavidin pair, a drug/target pair, a zinc
finger/nucleic acid pair, a small molecule/peptide pair, a small
molecule/protein pair, a small molecule/target pair, a
carbohydrate/protein pair such as maltose/MBP (maltose binding
protein), a small molecule/target pair, or a metal ion/chelating
agent pair.
[0061] Materials suitable for use as a host material include, for
example, solvents, polymers, liquid crystals, or other anisotropic
materials capable of being aligned by methods as described herein,
e.g., when mixed with polymeric networks, when in contact with a
rubbed surface, upon application of an external source of energy,
etc. In some cases, the polymeric network is molecularly dissolved
in the host material. In one set of embodiments, the host material
comprises a liquid crystal. As used herein, the term "liquid
crystal" is given its ordinary meaning in the art and refers to
organic or organometallic materials having certain physical
properties of both liquids and solids. For example, a liquid
crystal phase may have the fluidity of a liquid, but may exhibit
molecular ordering and anisotropic interactions with light, as in
solids. In some cases, liquid crystals suitable for use in the
invention include those which are capable of forming nematic
phases, chiral nematic phases, or other liquid crystal phases
useful in devices involving alignment and/or switching. Examples of
common liquid crystals include as cyano-biphenyls, bicyclohexyls,
cyclohexylphenyls, other nematic or chiral nematic liquid crystals,
and the like. A liquid crystal may comprise a plurality of liquid
crystalline species, each having a primary axis aligned so as to
together define a "liquid crystal director," i.e., an average axis
of liquid crystalline species primary axes.
[0062] Devices, and related methods, of the invention may comprise
at least one external source of energy applicable to the polymer
network/host material. In some cases, the source of external
energy, when applied to the polymer network/host material, may
cause a change in orientation of the polymer network/host material.
The source of external energy may be an electric, magnetic,
optical, acoustic, electromagnetic, or mechanical field. In some
embodiments, the source of external energy is an electric field.
The source of external energy can be provided in combination with
the device in a variety of ways, such as being integrally and/or
functionally connected to the polymer network/host material (for
example, by providing a compartment or other assembly supporting
both the polymer network/host material and the energy source), or
in combination such that the polymer network/host material and
energy source can be used together (e.g., packaged together, or
otherwise provided together and with the ability to arrange each,
with respect to the other, for use as described herein).
[0063] As used herein, the term "alkyl" is given its ordinary
meaning in the art and may include saturated aliphatic groups,
including straight-chain alkyl groups, branched-chain alkyl groups,
cycloalkyl (alicyclic) groups, alkyl substituted cycloalkyl groups,
and cycloalkyl substituted alkyl groups. In some embodiments, a
straight chain or branched chain alkyl may have about 30 or fewer
carbon atoms in its backbone (e.g., C.sub.1-C.sub.30 for straight
chain, C.sub.3-C.sub.30 for branched chain), and alternatively,
about 20 or fewer. Likewise, cycloalkyls may have from about 3 to
about 10 carbon atoms in their ring structure, and alternatively
about 5, 6 or 7 carbons in the ring structure. The term
"heteroalkyl" is given its ordinary meaning in the art and refers
to alkyl groups as described herein in which one or more atoms is a
heteroatom (e.g., oxygen, nitrogen, sulfur, and the like).
[0064] The term "aryl" is given its ordinary meaning in the art and
refers to aromatic groups such as, for example, 5-, 6- and
7-membered single-ring aromatic groups. The term "heteroaryl"
refers to aryl groups which comprise at least one heteroatom as a
ring atom, with the remainder of the ring atoms being carbon atoms.
Suitable heteroatoms include oxygen, sulfur, nitrogen, phosphorus,
and the like. Examples of aryl and heteroaryl groups include, but
are not limited to, benzene, furan, thiophene, pyridine, pyrrole,
pyrimidine, pyrazine, pyridazine, imidazole, indole, oxazole,
thiazole, triazole, pyrazole, and the like, all optionally
substituted.
[0065] The term "polycyclic group" or "polycyclic structure" refers
to structures with two or more rings (e.g., cycloalkyls,
cycloalkenyls, cycloalkynyls, aryls, heteroaryls, heterocyclyls,
etc.) in which two or more atoms are common to two adjoining rings,
e.g., the rings are "fused rings." For example, a "bicyclic" group
contains two adjoining rings. In some cases, two rings share two
common atoms which are adjacent to one another. Rings that are
joined through non-adjacent atoms, e.g., three or more atoms are
common to both rings, are "bridged" rings. The term "polycyclic
aromatic group" refers to a polycyclic group as described herein
containing at least one aromatic group. Examples of polycyclic
aromatic groups include naphthalene, anthracene, phenanthrene,
pyrene, and the like.
[0066] As used herein, the term "substituted" is contemplated to
include all permissible substituents of organic compounds,
"permissible" being in the context of the chemical rules of valence
known to those of ordinary skill in the art. In some cases,
"substituted" may generally refer to replacement of a hydrogen with
a substituent as described herein. However, "substituted," as used
herein, does not encompass replacement and/or alteration of a key
functional group by which a molecule is identified, e.g., such that
the "substituted" functional group becomes, through substitution, a
different functional group. For example, a "substituted benzene"
must still comprise the benzene moiety and can not be modified by
substitution, in this definition, to become, e.g., a pyridine
group. In a broad aspect, the permissible substituents include
acyclic and cyclic, branched and unbranched, carbocyclic and
heterocyclic, aromatic and nonaromatic substituents of organic
compounds. Illustrative substituents include, for example, those
described herein. The permissible substituents can be one or more
and the same or different for appropriate organic compounds. For
purposes of this invention, the heteroatoms such as nitrogen may
have hydrogen substituents and/or any permissible substituents of
organic compounds described herein which satisfy the valencies of
the heteroatoms. This invention is not intended to be limited in
any manner by the permissible substituents of organic
compounds.
[0067] Examples of substituents include, but are not limited to,
lower alkyl, lower aryl, lower aralkyl, lower cyclic alkyl, lower
heterocycloalkyl, hydroxy, lower alkoxy, lower aryloxy,
perhaloalkoxy, aralkoxy, lower heteroaryl, lower heteroaryloxy,
lower heteroarylalkyl, lower heteroaralkoxy, azido, amino, halogen,
lower alkylthio, oxo, lower acylalkyl, lower carboxy esters,
carboxyl, -carboxamido, nitro, lower acyloxy, lower aminoalkyl,
lower alkylaminoaryl, lower alkylaryl, lower alkylaminoalkyl, lower
alkoxyaryl, lower arylamino, lower aralkylamino, lower
alkylsulfonyl, lower-carboxamidoalkylaryl, lower-carboxamidoaryl,
lower hydroxyalkyl, lower haloalkyl, lower alkylaminoalkylcarboxy-,
lower aminocarboxamidoalkyl-, cyano, lower alkoxyalkyl, lower
perhaloalkyl, lower arylalkyloxyalkyl, and the like.
EXAMPLES
Example 1
[0068] To investigate the affect of the formation of extended
polymeric networks on the alignment of polymers, a series of
polymers were synthesized. Polymers containing interacting groups
at the terminal ends of the polymer and essentially identical
polymers lacking the interacting groups were synthesized, for
suitable comparison. Compound 2 was synthesized as an endcapping,
hydrogen-bonding, interacting group in a 4-step reaction adapted
from literature procedures, in 39% isolated yield, as shown in FIG.
4 (see Hirschberg, J. H. K. K.; Beijer, F. H.; Van Aert, H. A.;
Magusin, P. C. M. M.; Sijbesma, R. P.; Meijer, E. W. Macromolecules
1999, 32, 2696, for example). The triptycene compounds were
synthesized according to procedures described in, for example, Zhu,
Z. Z.; Swager, T. M. J. Am. Chem. Soc. 2002, 124, 9670.
[0069] As shown in FIG. 5, endcapped polymers were synthesized by
first reacting diethynyltriptycene (1 eq) and
di-2,5-(2-ethylhexyl)-1,6-diiodobenzene (1 eq) under
palladium-catalyzed Sonogashira conditions for a reaction time, t,
upon which half of the reaction mixture was removed and isolated to
serve as a "blank" (e.g., a polymer lacking the endcapping groups).
Next, 0.05 eq of compound 2 was added to the remaining reaction
mixture and allowed to react for 2 more hours to yield endcapped
polymers. As shown in Table 1, polymer P1a was allowed to
polymerize for 18 hrs, while polymer P2a was reacted for 4 hrs, to
yield polymer "blanks." Polymer P1b was allowed to polymerize for
18 hrs and then was further reacted to form an endcapped polymer.
Polymer P2b was reacted for 4 hrs and then was further reacted to
form an endcapped polymer. The variations in the reaction times
allowed for polymer growth before the addition of the endcapping
moiety (Table 1), with longer reaction times (e.g., >4 hrs)
giving higher molecular weight polymers with a relatively low
percentage of hydrogen bonding units, which were isolated as
powders that formed gels in common solvents. Shorter reaction times
(e.g., <4 hrs) provided lower molecular weight polymers with a
relatively higher percentage of hydrogen bonding units. These gave
materials formed elastomers and gels.
TABLE-US-00001 TABLE 1 Physical and spectral data of polymers P1
and P2.sup.a a denotes the blank; b is endcapped with 2. M.sub.n
dichroic Polymer (KDa) PDI .lamda..sub.max sol (nm) .lamda..sub.max
LC (nm) ratio P1a (no endcap) 15 2.5 385 405 8.7 P1b (with endcap)
18 2.6 385 405 13.2 P2a (no endcap) 3 2.0 385 407 8.5 P2b (with
endcap) 3 2.0 385 407 14.2
Example 2
[0070] The dimerization of compound 1 was studied with NMR
spectroscopy. The monomer and dimer were observed to exchanged
slowly on the NMR timescale, and distinct signals were observed for
both species, thereby allowing a dimerization constant to be
determined by integration. In pure chloroform, the monomer
concentration remained below the NMR detection limit. However, by
employing hydrogen bonding co-solvent mixture (e.g., CDCl.sub.3
with DMSO-d.sub.6 or MeOD), the dimerization constants could be
measured and K.sub.dim could be estimated by extrapolation to 0%
co-solvent. FIG. 6 shows the plot of log K.sub.dim of compound 1 as
a function of solvent composition for CDCl.sub.3 mixtures of (a)
MeOD and (b) DMSO-d.sub.6. The results indicated that the lower
limit for the dimerization constant is about 10.sup.6.
Example 3
[0071] The optical properties of polymer P2b was then studied.
Polymer P2b, which contains endcapping moieties, was dissolved in
either chloroform or a mixed with 5-cyanobiphenyl (5CB) in a liquid
crystal cell, and the optical characteristics of the polymer were
observed. FIG. 7 shows the (a) normalized absorption spectra of
polymer P2b in chloroform solution, and the polarized absorption of
polymer P2b in the liquid crystal cell with (b) parallel and (c)
perpendicular polarizer, with respect to the liquid crystal
director. The absorption spectra exhibited a characteristic peak at
385 nm for chloroform solutions of the polymers. Upon combining the
polymer with 5CB and transferring the mixture to a parallel rubbed
liquid crystal cell, the absorption maximum of the polymer shifted
to 407 nm, indicating an increased conjugation length of the
polymer.
Example 4
[0072] The alignment properties of the polymers containing the
interacting groups (e.g., P1b, P2b) were studied. The dichroic
ratios of the polymers P1b and P2b were measured by determining the
polarized absorption of the endcapped polymers in liquid crystal
solutions in parallel aligned test cells. FIG. 7B shows the
polarized absorption of polymer P2b in the liquid crystal cell when
positioned parallel to the liquid crystal director, while FIG. 7B
shows the polarized absorption of polymer P2b in the liquid crystal
cell when positioned perpendicular to the liquid crystal director.
The decrease in the absorption spectrum observed upon moving the
cell from a position parallel to the liquid crystal director to a
position perpendicular to the liquid crystal director indicates the
high degree of alignment of polymer P2b with the liquid crystal
director. As shown by the polarized absorption data in Table 1, the
polymers endcapped with compound 2 displayed higher dichroic ratios
than their non-functionalized counterparts, suggesting that
endcapping the polymers with compound 2 dramatically increases the
polymer ordering, even at the low concentration of polymers used in
these experiments (0.6 w % P1 and 0.78 w % P2).
Example 5
[0073] To further investigate the effect of the hydrogen-bonded
polymeric network on dichroic ratio, control experiments were
conducted wherein an excess of a species containing a single
hydrogen-bonding group was added to disrupt the polymeric network.
An excess of compound 1 was added to either polymer to P1b or
polymer P2b, and the dichroic ratio of each mixture was measured.
FIG. 8 shows the dichroic ratio of compounds P1b and P2b as a
function of time upon the addition of (a) 4.4 mM polymer P1b, (b)
9.6 mM polymer P1b, (c) 19.2 mM polymer, P1b, (d) 3.8 mM polymer
P2b, and (e) 16.2 mM polymer P2b. As shown in FIG. 8, the dichroic
ratio was observed to decreased in time and leveled off around the
dichroic ratio values obtained for polymer P1a and polymer P2a,
i.e., the polymers without hydrogen-bonding groups. Control
experiments were also conducted with polymer P1a and polymer P2a
and found no change in dichroic ratio upon addition of similar
amounts of compound 1, indicating that extended, polymers networks,
created by intermolecular hydrogen bonding, have increased ordering
and that the materials are still able to equilibrate with other
hydrogen bonding donors.
[0074] While several embodiments of the present invention have been
described and illustrated herein, those of ordinary skill in the
art will readily envision a variety of other means and/or
structures for performing the functions and/or obtaining the
results and/or one or more of the advantages described herein, and
each of such variations and/or modifications is deemed to be within
the scope of the present invention. More generally, those skilled
in the art will readily appreciate that all parameters, dimensions,
materials, and configurations described herein are meant to be
exemplary and that the actual parameters, dimensions, materials,
and/or configurations will depend upon the specific application or
applications for which the teachings of the present invention
is/are used. Those skilled in the art will recognize, or be able to
ascertain using no more than routine experimentation, many
equivalents to the specific embodiments of the invention described
herein. It is, therefore, to be understood that the foregoing
embodiments are presented by way of example only and that, within
the scope of the appended claims and equivalents thereto, the
invention may be practiced otherwise than as specifically described
and claimed. The present invention is directed to each individual
feature, system, article, material, kit, and/or method described
herein. In addition, any combination of two or more such features,
systems, articles, materials, kits, and/or methods, if such
features, systems, articles, materials, kits, and/or methods are
not mutually inconsistent, is included within the scope of the
present invention.
[0075] The indefinite articles "a" and "an," as used herein in the
specification and in the claims, unless clearly indicated to the
contrary, should be understood to mean "at least one."
[0076] The phrase "and/or," as used herein in the specification and
in the claims, should be understood to mean "either or both" of the
elements so conjoined, i.e., elements that are conjunctively
present in some cases and disjunctively present in other cases.
Other elements may optionally be present other than the elements
specifically identified by the "and/or" clause, whether related or
unrelated to those elements specifically identified unless clearly
indicated to the contrary. Thus, as a non-limiting example, a
reference to "A and/or B," when used in conjunction with open-ended
language such as "comprising" can refer, in one embodiment, to A
without B (optionally including elements other than B); in another
embodiment, to B without A (optionally including elements other
than A); in yet another embodiment, to both A and B (optionally
including other elements); etc.
[0077] As used herein in the specification and in the claims, "or"
should be understood to have the same meaning as "and/or" as
defined above. For example, when separating items in a list, "or"
or "and/or" shall be interpreted as being inclusive, i.e., the
inclusion of at least one, but also including more than one, of a
number or list of elements, and, optionally, additional unlisted
items. Only terms clearly indicated to the contrary, such as "only
one of" or "exactly one of," or, when used in the claims,
"consisting of," will refer to the inclusion of exactly one element
of a number or list of elements. In general, the term "or" as used
herein shall only be interpreted as indicating exclusive
alternatives (i.e. "one or the other but not both") when preceded
by terms of exclusivity, such as "either," "one of," "only one of,"
or "exactly one of." "Consisting essentially of," when used in the
claims, shall have its ordinary meaning as used in the field of
patent law.
[0078] As used herein in the specification and in the claims, the
phrase "at least one," in reference to a list of one or more
elements, should be understood to mean at least one element
selected from any one or more of the elements in the list of
elements, but not necessarily including at least one of each and
every element specifically listed within the list of elements and
not excluding any combinations of elements in the list of elements.
This definition also allows that elements may optionally be present
other than the elements specifically identified within the list of
elements to which the phrase "at least one" refers, whether related
or unrelated to those elements specifically identified. Thus, as a
non-limiting example, "at least one of A and B" (or, equivalently,
"at least one of A or B," or, equivalently "at least one of A
and/or B") can refer, in one embodiment, to at least one,
optionally including more than one, A, with no B present (and
optionally including elements other than B); in another embodiment,
to at least one, optionally including more than one, B, with no A
present (and optionally including elements other than A); in yet
another embodiment, to at least one, optionally including more than
one, A, and at least one, optionally including more than one, B
(and optionally including other elements); etc.
[0079] In the claims, as well as in the specification above, all
transitional phrases such as "comprising," "including," "carrying,"
"having," "containing," "involving," "holding," and the like are to
be understood to be open-ended, i.e., to mean including but not
limited to. Only the transitional phrases "consisting of" and
"consisting essentially of" shall be closed or semi-closed
transitional phrases, respectively, as set forth in the United
States Patent Office Manual of Patent Examining Procedures, Section
2111.03.
* * * * *