U.S. patent application number 14/698365 was filed with the patent office on 2015-08-27 for surface treatments for alignment of block copolymers.
This patent application is currently assigned to Board of Regents, The University of Texas System. The applicant listed for this patent is Board of Regents, The University of Texas System. Invention is credited to Christopher M. Bates, Christopher J. Ellison, Jeffrey Strahan, Carlton Grant Willson.
Application Number | 20150240110 14/698365 |
Document ID | / |
Family ID | 44649607 |
Filed Date | 2015-08-27 |
United States Patent
Application |
20150240110 |
Kind Code |
A1 |
Willson; Carlton Grant ; et
al. |
August 27, 2015 |
Surface Treatments for Alignment of Block Copolymers
Abstract
The present invention relates to a method the synthesis and
utilization of random, cross-linked, substituted polystyrene
copolymers as polymeric cross-linked surface treatments (PXSTs) to
control the orientation of physical features of a block copolymer
deposited over the first copolymer. Such methods have many uses
including multiple applications in the semi-conductor industry
including production of templates for nanoimprint lithography.
Inventors: |
Willson; Carlton Grant;
(Austin, TX) ; Bates; Christopher M.; (Austin,
TX) ; Strahan; Jeffrey; (Austin, TX) ;
Ellison; Christopher J.; (Austin, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Board of Regents, The University of Texas System |
Austin |
TX |
US |
|
|
Assignee: |
Board of Regents, The University of
Texas System
|
Family ID: |
44649607 |
Appl. No.: |
14/698365 |
Filed: |
April 28, 2015 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
13583518 |
Oct 4, 2012 |
|
|
|
PCT/US2011/028858 |
Mar 17, 2011 |
|
|
|
14698365 |
|
|
|
|
61315278 |
Mar 18, 2010 |
|
|
|
Current U.S.
Class: |
428/141 ;
428/336; 428/522 |
Current CPC
Class: |
Y10T 428/31935 20150401;
C09D 153/00 20130101; Y10T 428/31938 20150401; B81C 1/00031
20130101; G03F 7/0002 20130101; Y10T 428/265 20150115; B81C
2201/0149 20130101; Y10T 428/24355 20150115; G03F 7/265 20130101;
B05D 1/005 20130101 |
International
Class: |
C09D 153/00 20060101
C09D153/00 |
Claims
1-13. (canceled)
14. A composition, comprising a second polymer film coated on a
first polymer film, said first polymer film comprising first and
second monomers, said second polymer film comprising third and
fourth monomers, wherein said third and fourth monomers are
chemically different from said first and second monomers.
15. The composition of claim 14, wherein said second film comprises
nanostructures, said structures controlled by the chemical nature
of said first film.
16. The composition of claim 15, wherein said nanostructures
comprise cylindrical nanostructures, said cylindrical
nanostructures being substantially vertically aligned with respect
to the plane of the first film.
17. The composition of claim 14, wherein said second film comprises
a polystyrene-block-poly(methyl methacrylate) copolymer.
18. The composition of claim 14, wherein said first polymer film is
coated on a surface.
19. The composition of claim 14, wherein said first polymer film is
crosslinked.
20. The composition of claim 14, wherein the thickness of said
first film is between 10 and 30 nm.
21. The composition of claim 20, wherein said thickness of said
first film is between 15 and 20 nm.
22. The composition of claim 14, wherein the thickness of said
second film is between 10 and 100 nm.
23. The composition of claim 22, wherein said thickness of said
second film is between 20 and 70 nm.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a method for the synthesis
and utilization of cross-linked substituted polystyrene copolymers
as surface treatments (PXSTs) for control of the orientation of the
physical features of a block copolymer deposited over the first
copolymer. Such methods have many uses including multiple
applications in the semiconductor industry including production of
templates for nanoimprint lithography.
BACKGROUND OF THE INVENTION
[0002] Appropriately structured block copolymers (BCs)
self-assemble into regular patterns with features that are less
than 100 nm [1] and can be exploited in nanomanufacturing
applications such as microelectronics, solar cells, and membranes.
Hexagonally packed cylinders aligned perpendicular to the substrate
surface are one of the more useful nanostructures for these
applications. Multiple surface treatment techniques have been
reported that enable this orientation including surface treatment
with alkyl chlorosilanes [2, 3], chemical patterning [4-6], and
polymer "brushes" [7-10]. However, control over feature size and
orientation is still lacking. What is needed is a method which
provides a large process latitude in the necessary control over
feature orientation.
SUMMARY OF THE INVENTION
[0003] The present invention relates to a method for the synthesis
and utilization of random cross-linked substituted polystyrene
copolymers as surface treatments (PXSTs) for control of the
orientation of the physical features of a block copolymer deposited
over the first copolymer. Such methods have many uses including
multiple applications in the semiconductor industry including
production of templates for nanoimprint lithography. A wide range
of surface energies can be obtained from these materials, and the
results show the PXSTs need not be constituted from the identical
two monomers in the block copolymer (BC) to obtain a wide process
latitude for perpendicular orientation.
[0004] In one embodiment, the invention relates to a method,
comprising: a) providing: i) a crosslinkable polymer comprising
first and second monomers, ii) a block copolymer comprising third
and fourth monomers, wherein said third and fourth monomers are
chemically different from said first and second monomers; b)
coating a surface with said crosslinkable polymer to create a first
film; c) treating said first film under conditions such that
crosslinkable polymer is crosslinked; d) coating said first film
with said block copolymer to create a second film, and e) treating
said second film under conditions such that nanostructures form,
wherein the shape (and/or orientation) of the nanostructures is
controlled (at least in part) by the chemical nature of said first
film (and in some embodiments, it is also controlled in part by
film thickness). In one embodiment, the block copolymer forms
cylindrical nanostructures, said cylindrical nanostructures being
substantially vertically aligned with respect to the plane of the
first film. In one embodiment, said coating of step b) comprises
spin coating. In one embodiment, the thickness of said first film
is greater than 5.5 nm and less than 30 nm. In one embodiment, the
thickness of said first film is between 10 and 30 nm. In one
embodiment, said thickness of said first film is between 15 and 20
nm. In one embodiment, said crosslinkable polymer comprises an
azido group on said first or second monomer (although other
crosslinkable groups are used in other embodiments). In one
embodiment, the PXST can contain one or several comonomers, the
comonomers need not be those that are used to produce the block
copolymer. In one embodiment, said treating of said first film in
step c) comprises heating. Alternatively said treating comprises
treating with light. Furthermore, in one embodiment said treating
comprises light and heat. In one embodiment, said third monomer is
styrene and said block copolymer comprises polystyrene. In one
embodiment, said block copolymer is a polystyrene-block-poly(methyl
methacrylate) copolymer. In one embodiment, said coating of said
first film in step d) comprises spin coating. In one embodiment,
wherein the thickness of said second film is between 10 and 100 nm.
In one embodiment, said thickness of said second film is between 20
and 70 nm. In one embodiment, the treating of step e) comprises
heating (e.g. under vacuum) so that the film is annealed. In one
embodiment, the nanostructures are less than 100 nm in height.
[0005] In further embodiments, the invention relates to a
composition, comprising a second polymer film coated on a first
polymer film, said first polymer film comprising first and second
monomers, said second polymer film comprising third and fourth
monomers, wherein said third and fourth monomers are chemically
different from said first and second monomers. In one embodiment,
said second film comprises physical structures on a nanometer scale
or "nano structures", said physical structures controlled by the
chemical nature of said first film. In one embodiment, said second
film comprises cylindrical nanostructures, said cylindrical
nanostructures being substantially vertically aligned with respect
to the plane of the first film. In one embodiment, the
nanostructures are less than 100 nm in height (and more typically
between 20 nm and 70 nm in height).
[0006] In one embodiment, said second film comprises a
polystyrene-block-poly(methyl methacrylate) copolymer. In one
embodiment, said first polymer film is coated on a surface. In one
embodiment, said first polymer film is crosslinked. In one
embodiment of the composition, the thickness of said first film is
between 10 and 30 nm. In other embodiments, said thickness of said
first film is between 15 and 20 nm. In one embodiment, the
thickness of said second film is between 10 and 100 nm. In other
embodiments, said thickness of said second film is between 20 and
70 nm.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] For a more complete understanding of the features and
advantages of the present invention, reference is now made to the
detailed description of the invention along with the accompanying
figures.
[0008] FIG. 1 shows the synthesis of poly(styrene-b-methyl
methacrylate) (PS-b-PMMA). PS-b-PMMA was anionically synthesized
via standard Schlenk line techniques [11, 12].
[0009] FIG. 2 shows the Refractive Index detector response from a
Gel Permeation Chromatography (RI GPC) of PS-b-PMMA.
[0010] FIG. 3 shows the of a family of polymers with different
surface energies made by polymerization of monomers having a
variety of different substituents. The characterization of
P(SR)-r-P(SBnAz) and the impact of the various substituents are
shown in Table 1.
[0011] FIG. 4 shows the surface energies of PXSTs where R=tBu, Cl,
Me, H, and Br (blue), homopolymers (red), and wafer (grey).
[0012] FIG. 5 shows an atomic force microscopy (AMF) phase image of
PS-b-PMMA on PXST where (R=Br).
[0013] Table 1 shows the characterization of P(SR)-r-P(SBnAz)
(shown in FIG. 3) with different substituents at the R
position.
[0014] FIG. 6 is a schematic which shows the difference between
homopolymers, random polymers and block polymers.
DEFINITIONS
[0015] To facilitate the understanding of this invention, a number
of terms are defined below. Terms defined herein have meanings as
commonly understood by a person of ordinary skill in the areas
relevant to the present invention. Terms such as "a", "an" and
"the" are not intended to refer to only a singular entity, but
include the general class of which a specific example may be used
for illustration. The terminology herein is used to describe
specific embodiments of the invention, but their usage does not
delimit the invention, except as outlined in the claims.
[0016] The present invention also contemplates styrene
"derivatives" where the basic styrene structure is modified, e.g.
by adding substituents to the ring (but preferably maintaining the
vinyl group for polymerization). Derivatives can be, for example,
hydroxy-derivatives, oxo-derivatives or halo-derivatives. As used
herein, "hydrogen" means --H; "hydroxy" means --OH; "oxo" means
.dbd.O; "halo" means independently --F, --Cl, --Br or --I.
[0017] In addition, atoms making up the compounds of the present
invention are intended to include all isotopic forms of such atoms.
Isotopes, as used herein, include those atoms having the same
atomic number but different mass numbers. By way of general example
and without limitation, isotopes of hydrogen include tritium and
deuterium, and isotopes of carbon include .sup.13C and .sup.14C.
Similarly, it is contemplated that one or more carbon atom(s) of a
compound of the present invention may be replaced by a silicon
atom(s). Furthermore, it is contemplated that one or more oxygen
atom(s) of a compound of the present invention may be replaced by a
sulfur or selenium atom(s).
[0018] Styrene is represented by the following structure:
##STR00001##
[0019] 1-(chloromethyl)-4-vinylbenzene is represented by the
following structure:
##STR00002##
[0020] P-methylstyrene is an example of a styrene derivative and is
represented by the following structure:
##STR00003##
[0021] P-chlorostyrene is another example of a styrene
haloderivative and is represented by the following structure:
##STR00004##
[0022] It is desired that the second film deposited over the first
film develop "physical features on a nanometer scale,"
"nanofeatures" or "nanostructures" with controlled orientation.
These physical features have shapes and thicknesses. For example,
various structures can be formed by components of a block
copolymer, such as vertical lamellae, in-plane cylinders, and
vertical cylinders, and may depend on surface energies and film
thickness. In a preferred embodiment, the second film develops
cylindrical nanostructures, said cylindrical structures being
substantially vertically aligned with respect to the plane of the
first film. Orientation of structures in regions or domains at the
nanometer level (i.e. "microdomains" or "nanodomains") may be
controlled to be approximately uniform. The methods described
herein can generate structures with the desired size, shape,
orientation, and periodicity. Thereafter, in one embodiment, these
nanostructures may be etched or otherwise further treated.
DETAILED DESCRIPTION OF THE INVENTION
Surface Energies of PXSTs
[0023] In the course of our efforts to employ non-traditional
monomers for BCs, we became interested in the effect of surface
energy on BC orientation. Films thicker than 15 nm of polymer 3
(FIG. 3) were spin-coated, heated to cross-link through the azide
functionality, and thoroughly rinsed to remove any non-cross-linked
materials. Surface energies of these films were obtained by
goniometry with water, glycerol, and diiodomethane contact angles.
Several measurements were made over the entire wafer, and the error
was consistently +/-2 dyne/cm. FIG. 4 displays these data and shows
that the substituents affect the surface energy of the film.
Additionally, the surface energies of non-cross-linked homopolymer
films of PS and PMMA and a wafer cleaned with piranha were
measured, and these values are consistent with the literature [2,
13].
[0024] In one embodiments, the invention relates to the PS-b-PMMA
films of various thicknesses were coated on the PXSTs. These were
annealed and investigated by AFM. The AFM images display very
different process windows for perpendicular orientation of the
PXSTs. The Cl-substituted PXST resulted in perpendicular cylinders
for block film thicknesses of 30 to 35 nm, and the PXST with a Br
substituent had a process window from 23 to 41 nm (FIG. 5). These
process window results are similar to other polymeric surface
treatments reported by Nealey [14] and Hawker and Russell [10, 15,
16]. This leads to the conclusion that a PXST need not consist of
the same monomers as the BC being coated.
DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
[0025] It is not intended that the present invention be limited to
specific block polymers. However, to illustrate the invention,
examples of various copolymers are provided. In one embodiment, the
invention relates to the synthesis of the polystyrene-containing
block copolymer "PS-b-PMMA." PS-b-PMMA was anionically synthesized
via standard Schlenk line techniques (FIG. 1) [11, 12]. .sup.1H-NMR
showed the resulting polymer is 31 mol % PMMA, which corresponds to
a volume fraction of 0.27 [17]. This is within the range for
cylinder morphology [1]. The Mn of the PS aliquot was 45.8 kDa with
a PDI of 1.18; the total molecular weight was 65.6 kDa with a PDI
of 1.18. FIG. 2 shows GPC chromatograms of the PS aliquot and
PS-b-PMMA.
[0026] In one embodiment, the invention relates to the synthesis of
P(SR)-r-P(SBnAz). In a procedure similar to Hawker et al. [9],
several commercially available styrene derivatives were radically
copolymerized with vinyl benzyl chloride to investigate the role of
substituents on the surface energy of PS. Upon isolation of 2,
nucleophilic substitution of the chloride with azide ion led to
cross-linkable polymers 3 (FIG. 3). The presence of the azide was
confirmed by IR, and the resulting polymers are described in Table
1.
General Materials and Methods
[0027] Materials.
[0028] All reagents were purchased from Sigma-Aldrich Chemical Co.
and used without further purification unless otherwise noted. THF
was purchased from JT Baker. 100 mm silicon wafers were purchased
from Silicon Quest International.
[0029] Instrumentation.
[0030] All .sup.1H and .sup.13C NMR spectra were recorded on a
Varian Unity Plus 400 MHz instrument. All chemical shifts are
reported in ppm downfield from TMS using the residual protonated
solvent as an internal standard (CDCl.sub.3, .sup.1H 7.26 ppm and
.sup.13C 77.0 ppm). Molecular weight and polydispersity data were
measured using an Agilent 1100 Series Isopump and Autosampler and a
Viscotek Model 302 TETRA Detector Platform with 3 I-series Mixed
Bed High MW columns against polystyrene standards. Polymer
solutions were filtered with 0.20 .mu.m PTFE filters prior to spin
coating. Films were spin coated and baked on a Brewer CEE 100CB
Spincoater & Hotplate. Film thicknesses were determined with a
J. A. Woollam Co, Inc. VB 400 VASE Ellipsometer using wavelengths
from 382 to 984 nm with a 70.degree. angle of incidence. Contact
angles were measured with a Rame-Hart, inc. NRL C.A. Goniometer
(Model #100-00). A Heraeus Vacutherm Type VT 6060 P from Kendro was
used to thermally anneal the films under reduced pressure. A
Digital Instruments Dimension 3100 atomic force microscope with
NCHR Pointprobe.RTM. Non-Contact Mode tips with a force constant of
42 N/m was used to collect AFM images.
Example 1
Synthesis of poly(styrene-b-methyl methacrylate) (PS-b-PMMA
(1))
[0031] PS-b-PMMA was synthesized as previously reported by
sequential anionic polymerization of styrene and methyl
methacrylate in THF at -78.degree. C. under Ar atmosphere via
standard Schlenk line techniques [11]. The initiator was sec-BuLi;
diphenyl ethylene was used to properly initiate MMA, and NO was
added to suppress side reactions during MMA propagation [12].
Example 2
P(SR)-r-P(SBnAz) (3)
[0032] In a procedure adopted from Hawker et al. [9], a substituted
styrene (20 mmol) and vinyl benzyl chloride (0.62 mmol) were
radically copolymerized in refluxing THF (20 mL) for 48 h with
enough AIBN to obtain a theoretical MW of 25 kDa. Once polymer 2
was precipitated in 0.degree. C. MeOH, filtered, and dried in
vacuo, the mol ratio of substituted styrene to vinyl benzyl
chloride was determined by 1H-NMR. Taking into account this ratio
and the Mn as determined by GPC, polymer 2 (1.0 g) and sodium azide
(3 equiv/BnCl) were dissolved in DMF (20 mL) and stirred overnight
at room temperature (rt). The polymer was precipitated in MeOH,
filtered, redissolved in THF (10 mL), and stirred with H.sub.2O (1
mL) to remove any unreacted salts. Finally, the polymer was
isolated by precipitation in 0.degree. C. MeOH, filtered, and dried
in vacuo to yield white powder 3. Typical yields over these two
steps were 50%; IR (KBr) 2100 cm-1. Complete characterization is
shown in Table 1.
Example 3
Surface Treatment with PXSTs
[0033] A film of P(SR)-r-P(SBnAz) was spin coated from a 1.0 wt %
solution in toluene at 3770 rpm for 30 sec onto a wafer that had
been rinsed with IPA and acetone. The wafer was immediately baked
at 250.degree. C. for 5 min to cross-link the film. The wafer was
then submerged in toluene for 2 min, blown dry, submerged again for
2 min, and blown dry. Typical film thicknesses as determined by
ellipsometry were 15-20 nm.
Example 4
Surface Energy Measurements by Goniometry
[0034] Contact angles were measured with H.sub.2O, diiodomethane,
and glycerol, and analyzed via the Young-Dupre equation (Eq 1) and
the Acid-Base Surface Energy Model (Eq 2) [18].
.gamma..sub.SV=.gamma..sub.SL+.gamma..sub.LV cos
.theta.-.pi..sub.eq Eq 1
.gamma..sub.SV is the surface energy of the solid-vapor interface,
.gamma..sub.SL is the interfacial energy of the solid-liquid
interface, .gamma..sub.LV is the surface tension of the fluid,
.theta. is the angle between the solid and liquid, and .pi..sub.eq
is the equilibrium spreading pressure, which is approximately zero
for polymeric surfaces.
.gamma..sub.12=.gamma..sub.12.sup.LW+.gamma..sub.12AB Eq 2
-.gamma..sub.2 cos
.theta.=.gamma..sub.2.sup.LW-2(.gamma..sub.1.sup.LW.gamma..sub.2.sup.LW).-
sup.1/2+2[(.gamma..sub.2.sup.P+.gamma..sub.2.sup.P-).sup.1/2-(.gamma..sub.-
1.sup.P+.gamma..sub.2.sup.P-).sup.1/2-(.gamma..sub.1.sup.P-.gamma..sub.2.s-
up.P+).sup.1/2] Eq 3
[0035] Briefly, Eq 2 describes the interfacial energy between two
components (.gamma..sub.12) as the sum of the dispersion
(.gamma..sub.12.sup.Lw) and acid-base components
(.gamma..sub.12.sup.AB). Eq 3 relates the surface energy of the
film and cosine of the contact angle (-.gamma..sub.2 cos .theta.)
to the dispersion (.gamma..sub.2.sup.LW), Lewis acid
(.gamma..sub.2.sup.P+), and Lewis base components
(.gamma..sub.2.sup.P-). Using literature values for H.sub.2O,
diiodomethane, and glycerol, a system of equations was solved to
obtain the surface energy of the PXST films.
[0036] Spin Coating and Annealing.
[0037] A clean, surface-treated wafer was spin coated with a film
of PS-b-PMMA from toluene at various speeds and concentrations to
give 20-70 nm films as determined by ellipsometry. Once cast, the
wafer shards were annealed at 170.degree. C. under reduced pressure
for 12-18 h.
REFERENCES
[0038] 1. Bates, F. S., and Fredrickson, G. H. (1999) Block
Copolymers--Designer Soft Materials Phys. Today 52, 32-38. [0039]
2. Peters, R. D., Yang, X. M., Kim, T. K., Sohn, B. H., and Nealey,
P. F. (2000) Using Self-Assembled Monolayers Exposed to X-Rays to
Control the Wetting Behavior of Thin Films of Diblock Copolymers,
Langmuir 16, 4625-4631. [0040] 3. Niemz, A., Bandyopadhyay, K.,
Tan, E., Cha, K., and Baker, S. M. (2006) Fabrication of Nanoporous
Templates from Diblock Copolymer Thin Films on
Alkylchlorosilane-Neutralized Surfaces, Langmuir 22, 11092-11096.
[0041] 4. Ruiz, R., Kang, H., Detcheverry, F. A., Dobisz, E.,
Kercher, D. S., Albrecht, T. R., de Pablo, J. J., and Nealey, P. F.
(2008) Density Multiplication and Improved Lithography by Directed
Block Copolymer Assembly, Science 321, 936-939. [0042] 5.
Stoykovich, M. P., Muller, M., Kim, S O., Solak, H. H., Edwards, E.
W., Pablo, J. J. d., and Nealey, P. F. (2005) Directed Assembly of
Block Copolymer Blends into Nonregular Device-Oriented Structures,
Science 5727, 1442-1446. [0043] 6. Kim, S. 0., Kim, B. H., Kim, K.,
Koo, C. M., Stoykovich, M. P., Nealey, P. F., and Solak, H. H.
(2006) Defect Structure in Thin Films of a Lamellar Block Copolymer
Self-Assembled on Neutral Homogeneous and Chemically Nanopatterned
Surfaces, Macromolecules 39, 5466-5470. [0044] 7. Mansky, P., Liu,
Y., Huang, E., Russell, T. P., and Hawker, C. (1997) Controlling
Polymer-Surface Interactions with Random Copolymer Brushes Science
275, 1454-1457. [0045] 8. Han, E., In, I., Park, S.-M., La, Y.-H.,
Wang, Y, Nealey, P. F., and Gopalan, P. (2007) Photopattemable
Imaging Layers for Controlling Block Copolymer Microdomain
Orientation, Adv. Mater 19, 4448-4452. [0046] 9. Bang, J., Bae, J.,
Lowenhielm, P., Spiessberger, C., Given-Beck, S. A., Russell, T.
P., and Hawker, C. J. (2007) Facile Routes to Patterned Surface
Neutralization Layers for Block Copolymer Lithography, Adv. Mater.
19, 4552-4557. [0047] 10. Ham, S., Shin, C., Kim, E., Ryu, D. Y,
Jeong, U., Russell, T. P., and Hawker, C. J. (2008) Microdomain
Orientation of Ps-B-Pmma by Controlled Interfacial Interactions,
Macromolecules 41, 6431-6437. [0048] 11. Uhrig, D., and Mays, J. W.
(2005) Experimental Techniques in High-Vacuum Anionic
Polymerization, J. Polym. Sci. A. 43, 6179-6222. [0049] 12. Allen,
R. D., Long, T. E., and McGrath, J. E. (1986) Preparation. of High
Purity, Anionic Polymerization Grade Alkyl Methacrylate Monomers
Polym. Bull. 15, 127-134. [0050] 13. Jung, Y. S., and Ross, C. A.
(2007) Orientation-Controlled Self-Assembled Nanolithography Using
a Polystyrenea 'Polydimethylsiloxane Block Copolymer, Nano Lett. 7,
2046-2050. [0051] 14. Han, E., Stuen, K. O., Leolukman, M., Liu,
C.-C., Nealey, P. F., and Gopalan, P. (2009) Perpendicular
Orientation of Domains in Cylinder-Forming Block Copolymer Thick
Films by Controlled Interfacial Interactions, Macromolecules 42,
4896-4901. [0052] 15. Ryu, D. Y, Wang, J.-Y., Lavery, K. A.,
Drockenmuller, E., Satija, S. K., Hawker, C. J., and Russell, T. P.
(2007) Surface Modification with Cross-Linked Random
Copolymers:A.Salinity. Minimum Effective Thickness, Macromolecules
40, 4296-4300. [0053] 16. Ryu, D. Y, Ham, S., Kim, E., Jeong, U.,
Hawker, C. J., and Russell, T. P. (2009) Cylindrical Microdomain
Orientation of Ps-B-Pmma on the Balanced Interfacial Interactions:
Composition Effect of Block Copolymers, Macromolecules 42,
4902-4906. [0054] 17. Fetters, L. J., Lohse, D. J., Richter, D.,
Witten, T. A., and Zirkel, A. (1994) Connection between Polymer
Molecular Weight, Density, Chain Dimensions, and Melt Viscoelastic
Properties, Macromolecules 27, 4639-4647. [0055] 18. Van Oss, C.
J., Good, R. J., and Chaudhury, M. K. (1988) Additive and
Nonadditive Surface Tension Components and the Interpretation of
Contact Angles, Langmuir 4, 884-891.
* * * * *