U.S. patent application number 11/331291 was filed with the patent office on 2007-05-24 for copolymerization and copolymers of aromatic polymers with carbon nanotubes and products made therefrom.
This patent application is currently assigned to William Marsh Rice University. Invention is credited to Zheyi Chen, Robert H. Hauge, Wen-Fang Hwang, Kazufumi Kobashi, James M. Tour.
Application Number | 20070118937 11/331291 |
Document ID | / |
Family ID | 37983367 |
Filed Date | 2007-05-24 |
United States Patent
Application |
20070118937 |
Kind Code |
A1 |
Hwang; Wen-Fang ; et
al. |
May 24, 2007 |
Copolymerization and copolymers of aromatic polymers with carbon
nanotubes and products made therefrom
Abstract
The present invention is generally directed to the block
copolymerization of aromatic polymers with carbon nanotubes (CNTs),
the CNTs typically being shortened, to form nanotube block
copolymers. The present invention is also directed to fibers and
other shaped articles made from the nanotube block copolymers of
the present invention.
Inventors: |
Hwang; Wen-Fang; (Midland,
MI) ; Tour; James M.; (Bellaire, TX) ; Chen;
Zheyi; (Houston, TX) ; Hauge; Robert H.;
(Houston, TX) ; Kobashi; Kazufumi; (Houston,
TX) |
Correspondence
Address: |
ROSS SPENCER GARSSON;WINSTEAD SECHREST & MINICK P.C.
P. O. BOX 50784
DALLAS
TX
75201
US
|
Assignee: |
William Marsh Rice
University
Houston
TX
|
Family ID: |
37983367 |
Appl. No.: |
11/331291 |
Filed: |
January 12, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10972560 |
Oct 25, 2004 |
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11331291 |
Jan 12, 2006 |
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60514186 |
Oct 24, 2003 |
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Current U.S.
Class: |
525/420 ; 524/1;
977/742; 977/848 |
Current CPC
Class: |
C08L 53/005 20130101;
C01B 2202/36 20130101; C08J 5/18 20130101; C08G 83/001 20130101;
B82Y 40/00 20130101; C01B 2202/34 20130101; C08K 3/041 20170501;
C01B 32/174 20170801; C08G 69/32 20130101; C08L 77/00 20130101;
B82Y 30/00 20130101; C01B 2202/02 20130101; C08J 2300/12 20130101;
C08L 77/10 20130101; C08K 9/08 20130101; C08L 77/10 20130101; C08K
3/041 20170501; C08L 53/005 20130101 |
Class at
Publication: |
977/742 ;
977/848; 524/001 |
International
Class: |
B22F 1/00 20060101
B22F001/00 |
Claims
1. A block copolymer comprising: a) a first block material
comprising short single-wall carbon nanotubes (SWNTs); and b) a
second block material comprising an aromatic polyamide polymer.
2. The block copolymer of claim 1, wherein said block copolymer is
selected from the group consisting of di-block copolymers,
tri-block copolymers, random-block copolymers, and combinations
thereof.
3. The block copolymer of claim 1, wherein the short single-wall
carbon nanotubes have lengths that range from about 5 nm about 100
nm.
4. The block copolymer of claim 1, wherein the short single-wall
carbon nanotubes aspect ratios that range from about 5 about
100.
5. The block copolymer of claim 1, wherein the aromatic polyamide
polymer is poly(p-phenylene terephthalamide) (PPTA).
6. The block copolymer of claim 1, wherein the aromatic polyamide
polymer comprises a number of repeat units that ranges from about 2
to about 2000.
7. The block copolymer of claim 1, wherein the aromatic polyamide
polymer comprises a number of repeat units that ranges from about 5
to about 50.
8. The block copolymer of claim 1, wherein the aromatic polyamide
polymer comprises a number of repeat units that ranges from about 5
to about 30.
9. The block copolymer of claim 1, wherein the block copolymer has
a SWNT/aromatic polyamide composition that ranges from about 1/99
SWNT/aromatic polyamide (wt/wt %) to about 99/1 SWNT/aromatic
polyamide (wt/wt %).
10. A method comprising the steps of: a) providing a first block
material comprising functionalized short single-wall carbon
nanotubes; b) providing a second block material comprising aromatic
polyamide polymers comprising amide-forming moieties on their ends;
and c) copolymerizing the first block material with the second
block material to form a block copolymer material.
11. The method of claim 10, wherein the functionalized short
single-wall carbon nanotubes are functionalized with chemical
moieties selected from the group consisting of carboxylic acid
groups, acyl chloride groups, and combinations thereof; and wherein
the chemical moieties are attached to the functionalized short
single-wall carbon nanotubes in a manner selected from the group
consisting of end-attached, sidewall attached, and combinations
thereof.
12. The method of claim 10, wherein the step of copolymerizing is
carried out in a aprotic solvent capable of dissolving both
reactants without degradation of either of said reactant.
13. The method of claim 10, wherein the short single-wall carbon
nanotubes have lengths that range from about 5 nm about 100 nm.
14. The method of claim 10, wherein the short single-wall carbon
nanotubes have aspect ratios that range from about 5 about 100.
15. The method of claim 10, wherein the second block material
comprising aromatic polyamide polymers comprises poly(p-phenylene
terephthalamide) (PPTA).
16. The method of claim 10, wherein the amide-forming moieties on
the ends of said second block material comprising aromatic
polyamide polymers comprise an amine moiety.
17. The method of claim 11, wherein the aprotic solvent in which
the first block material with the second block material are
copolymerized is selected from the group consisting of NMP, DMAc,
DMF, DMSO, DMI, and combinations thereof.
18. The method of claim 10 further comprising a step of spinning
the block copolymer material into a fiber.
19. The method of claim 10 further comprising a step of casting the
block copolymer material into a film.
20. The method of claim 10 further comprising a step of shaping the
block copolymer material into a particular shape.
21. A fiber comprising the block copolymer of claim 1.
22. A film comprising the block copolymer of claim 1.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This Application is a Continuation-ln-Part of U.S. patent
application Ser. No. 10/972,560, filed Oct. 25, 2004, which itself
claims priority benefit to U.S. Provisional Patent Application Ser.
No. 60/514,186, filed Oct. 24, 2003. Both of said Applications to
which this Application relates are hereby incorporated by reference
herein in their entirety-to the extent not inconsistent
herewith.
FIELD OF THE INVENTION
[0002] The present invention relates generally to carbon nanotube
materials. More specifically, the invention relates to block
copolymers comprising aromatic polymer blocks and short carbon
nanotube blocks.
BACKGROUND OF THE INVENTION
[0003] Carbon nanotubes (CNTs), comprising multiple concentric
shells and termed multi-wall carbon nanotubes (MWNTs), were
discovered by lijima in 1991 [lijima, Nature 1991, 354, 56-58].
Subsequent to this discovery, single-wall carbon nanotubes (SWNTs),
comprising single graphene sheets rolled up on themselves to form
cylindrical tubes with nanoscale diameters, were synthesized in an
arc-discharge process using carbon electrodes doped with transition
metals [lijima et al., Nature 1993, 363, 603-605; and Bethune et
al., Nature 1993, 363, 605-607]. These carbon nanotubes (especially
SWNTs) possess unique mechanical, electrical, thermal and optical
properties, and such properties make them attractive for a wide
variety of applications. See Baughman et al., Science, 2002, 297,
787-792.
[0004] The incorporation of CNTs into polymer matrices is currently
an area of considerable interest, as CNTs can impart unique
properties to the composite or blended material. See, e.g.,
Mitchell et al., Macromolecules, 2002, 35, 8825-8830; and Zhu et
al., Nano. Lett., 2003, 3,1107-1113. In some cases, CNTs have been
covalently integrated into such polymeric hosts.
[0005] Another area of interest is CNT-containing fibers. In some
reports, such fibers comprise a polymer matrix, whereas in other
cases they are largely CNTs. In such later cases, CNT fibers have
been spun from CNT suspensions in poly(vinylalcohol) [Vigolo et
al., Science, 2000, 290, 1331-1334] and intercalating acids [Zhou
et al., J. Appl. Phys., 2004, 95, 649-655; and Ericson et al.,
Science, 2004, 305, 1447-1450].
[0006] In light of the above-described advances in carbon nanotube
science, new polymeric systems into which CNTs have been integrated
into will continue to expand the range of applications with which
they can be associated.
BRIEF DESCRIPTION OF THE INVENTION
[0007] The present invention is generally directed to the block
copolymerization of aromatic polymers with carbon nanotubes (CNTs).
Such block copolymers, having a CNT block component and an aromatic
polymer block component, are referred to herein as "nanotube block
copolymers." The present invention is also directed to fibers and
other shaped articles made from these nanotube block copolymers of
the present invention.
[0008] In some embodiments, the CNT block component is a
single-wall carbon nanotube (SWNT). Typically, such SWNTs are first
cut with a cutting process to provide short SWNTs, then (or
simultaneously) end functionalized with moieties capable of
coupling to the aromatic polymer block component. However, to the
extent that suitably short SWNTs can be synthesized directly and
suitably end-functionalized, such cutting is not required.
[0009] In some embodiments, the aromatic polymer (block) is a
polybenzazole (PBZ). Block copolymers of the present invention
comprising SWNTs and PBZ components are referred to herein as
"SWNT/PBZ block copolymers." In some such embodiments, the PBZ
block is polybezoxazole (PBO), giving rise to "SWNT/PBO block
copolymers."
[0010] In some embodiments, the aromatic polymer is a aromatic
polyamide. In some embodiments, the aromatic polyamide polymer is
poly(p-phenylene terephthalamide) (PPTA). Block copolymers of the
present invention comprising SWNTs and PPTA components are referred
to herein as "SWNT/PPTA block copolymers."
[0011] Such above-described aromatic polymer blocks are typically
(but not necessarily) ridged rod polymers. Other suitable aromatic
polymer blocks include aromatic polyimides, aromatic polyesters,
and aromatic heterocyclic polymers.
[0012] In some embodiments, both the cutting of the SWNTs (to
produce shortened SWNTs) and the coupling of the shortened SWNTs to
aromatic polyamides enhances the solubility and processability of
SWNTs in aprotic solvents, strong acid solvents, and other
solvents. Additionally, the use of aromatic polymers, and
particularly aromatic polyamides, in such block copolymers is
advantageous in that it is both economical and preserves mechanical
properties intrinsic to the SWNTs.
[0013] The foregoing has outlined rather broadly the features of
the present invention in order that the detailed description of the
invention that follows may be better understood. Additional
features and advantages of the invention will be described
hereinafter which form the subject of the claims of the
invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] For a more complete understanding of the present invention,
and the advantages thereof, reference is now made to the following
descriptions taken in conjunction with the accompanying drawings,
in which:
[0015] FIG. 1 depicts a single-wall carbon nanotube
(SWNT)/polybezoxazole (PBO) copolymer, in accordance with some
embodiments of the present invention;
[0016] FIG. 2 depicts a SWNT/poly(p-phenylene terephthalamide)
(PPTA) copolymer, in accordance with some embodiments of the
present invention;
[0017] FIG. 3 (Scheme 4) schematically depicts the preparation of
p-phenylene benzobisoxazole 15 mers (15-mer PBO), in accordance
with embodiments of the present invention;
[0018] FIG. 4 (Scheme 5) schematically depicts the preparation of
p-phenylene benzobisoxazole 45 mers (45-mer PBO), in accordance
with some embodiments of the present invention;
[0019] FIG. 5 (Scheme 6) depicts sidewall functionalization of
short SWNTs with sulfanilic acid in oleum, in accordance with some
embodiments of the present invention;
[0020] FIGS. 6A and 6B are atomic force microscopy (AFM) images of
SWNTs before (6A) and after (6B) undergoing the functionalization
depicted in Scheme 6;
[0021] FIG. 7 (Scheme 7) schematically depicts copolymerization of
short SWNTs and PBO 15 mers, in accordance with some embodiments of
the present invention;
[0022] FIG. 8 (Scheme 8) schematically depicts the copolymerization
of short functionalized SWNTs and PBO 15 mers, in accordance with
some embodiments of the present invention;
[0023] FIG. 9 depicts Raman spectra (633 nm excitation) of SWNT/PBO
copolymer films synthesized in dilute concentration, where trace
(a) depicts copolymerized product (No.1, Table 1) from short SWNTs
and PBO 15 mers at the weight ratio of 67/33 (0.36 wt. %
concentration); and where trace (b) depicts PBO 15 mers;
[0024] FIG. 10 depicts Raman spectra (633 nm excitation) of
SWNT/PBO copolymer film prepared in higher concentration, where
trace (a) depicts copolymerized product from short SWNTs/PBO 15
mers (No. 4, Table 1); and where trace (b) depicts benzenesulfonic
acid-functionalized short SWNTs/PBO 15 mers (No. 5, Table 1) at the
concentration of 3.3 wt. %;
[0025] FIG. 11 depicts infrared (ATR-IR) spectra of
variously-prepared polymer films; where trace (a) depicts
benzenesulfonic acid-functionalized short SWNTs; where trace (b)
depicts PBO 15 mers; and where trace (c) depicts copolymerized
product (No. 5, Table 1) of benzenesulfonic acid-functionalized
short SWNTs/PBO 15 mers at the concentration of 3.3 wt %;
[0026] FIGS. 12A-12D are AFM images of a 2 mg sample/10 cc
methanesulfonic acid (MSA) solution spun onto a silicon disk and
vacuum dried at 100.degree. C overnight; wherein FIGS. 12A (height)
and 12B (amplitude) are the height and amplitude images,
respectively, depicting a physical mixture of functionalized short
SWNTs and PBO 15 mers at weight ratio of 49/51; and wherein FIGS.
12C (height) and 12D (amplitude) are the height and amplitude
images, respectively, depicting a copolymerized product (No. 5,
Table 1) from functionalized short SWNTs and PBO 15 mers at weight
ratio of 49/51;
[0027] FIG. 13 (Scheme 9) schematically depicts the
copolymerization of short SWNTs and PBO 45 mers, in accordance with
some embodiments of the present invention;
[0028] FIG. 14 (Scheme 10) schematically-depicts the
copolymerization of short, sidewall-functionalized SWNTs and PBO 45
mers, in accordance with some embodiments of the present
invention;
[0029] FIG. 15 depicts Raman spectra of SWNTs/PBO copolymer film
(633 nm excitation); wherein trace (a) depicts copolymerized
product from PBO 45 mers and benzenesulfonic acid-functionalized
short SWNTs (No. 7, Table 2); and wherein trace (b) depicts
copolymerized product from PBO 45 mers and short SWNTs (No. 6,
Table 2);
[0030] FIG. 16 depicts Raman spectra of SWNTs/PBO copolymer film
(780 nm excitation); wherein trace (a) depicts copolymerized
product from PBO 45 mers and benzenesulfonic acid-functionalized
short SWNTs (No. 7, Table 2); and wherein trace (b) depicts
copolymerized product from PBO 45 mers and short SWNTs (No. 6,
Table 2);
[0031] FIG. 17 depicts Raman spectra of SWNTs/PBO copolymer films
(514 nm excitation); wherein trace (a) depicts copolymerized
product from PBO 45 mers and benzenesulfonic acid-functionalized
short SWNTs (No. 7, Table 2); and wherein trace (b) depicts
copolymerized product from PBO 45 mers and short SWNTs (No. 6,
Table 2);
[0032] FIG. 18 depicts a conventional dry-jet wet spinning process,
in accordance with some embodiments of the present invention;
[0033] FIGS. 19A and 19B are scanning electron microscopy (SEM)
images of a PBO 45 mer fiber (19A) and a copolymer (No. 8, Table 2)
fiber of PBO 45 mers and benzenesulfonic acid-functionalized short
SWNTs at the weight ratio of 90/10 (19B);
[0034] FIG. 20 depicts blending of high molecular weight PBO and
copolymer of short SWNTs and PBO useful in the fiber spinning of
SWNTs/PBO fibers, in accordance with some embodiments of the
present invention;
[0035] FIG. 21 (Scheme 11) schematically depicts the synthesis of
PPTA with amine groups at both ends, in accordance with some
embodiments of the present invention; and
[0036] FIG. 22 (Scheme 12) schematically depicts the
copolymerization of short SWNTs and PPTA, in accordance with some
embodiments of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0037] In the following description, specific details are set forth
such as specific quantities, sizes, etc. so as to provide a
thorough understanding of embodiments of the present invention.
However, it will be obvious to those skilled in the art that the
present invention may be practiced without such specific details.
In many cases, details concerning such considerations and the like
have been omitted inasmuch as such details are not necessary to
obtain a complete understanding of the present invention and are
within the skills of persons of ordinary skill in the relevant
art.
[0038] The present invention is generally directed to the block
copolymerization of aromatic polymers with carbon nanotubes (CNTs).
Such block copolymers, having a CNT block component and an aromatic
polymer block component, are referred to herein as "nanotube block
copolymers." The present invention is also directed to fibers and
other shaped articles made from these nanotube block copolymers of
the present invention.
[0039] Block copolymers are polymers that comprise polymer or
oligomer chains of one type of polymer that are connected with
polymer or oligomer chains of one or more other types of polymers.
Such polymerization leads to polymer chains having structures like
that of the following di-block copolymer:
--AAAAAAAAAAAAAAAAA-BBBBBBBBBBBBBBBB--
[0040] or tri-block copolymer:
--AAAAAAAAAAA-BBBBBBBBBBB-AAAAAAAAAA--,
[0041] where "A" is a repeat unit (i.e., a "mer") for a first
polymer block, and "B" is a repeat unit for a second polymer block.
An example of a common block copolymer is
poly(styrene-butadiene-styrene), or SBS.
[0042] In the case of the nanotube block copolymers of the present
invention, at least one of the polymer blocks is a carbon nanotube
(itself an all-carbon rigid polymer) and at least one of the blocks
is an organic-based aromatic polymer or oligomer. For the purposes
of this discussion, oligomers are merely short polymer chains and
reference to polymer block components hereinafter as polymers will
be understood to include oligomers. While the block copolymers of
the present invention, referred to herein as nanotube block
copolymers, generally comprise at least one CNT block and at least
one aromatic polymer block, they may comprise blocks of other types
as well.
[0043] In some embodiments, because of the possibility of multiple
coupling (i.e., attachment) sites on the side-walls of the CNTs
and/or the CNT ends, one or both ends of the CNTs may be coupled to
multiple aromatic polymer blocks.
[0044] CNTs, according to the present invention, include, but are
not limited to, single-wall carbon nanotubes (SWNTs), multi-wall
carbon nanotubes (MWNTs), double-wall carbon nanotubes (DWNTs),
small-diameter (<3nm) carbon nanotubes (SDCNTs), buckytubes,
fullerene tubes, tubular fullerenes, graphite fibrils, and
combinations thereof. Such carbon nanotubes can initially be of a
variety and range of lengths, diameters, number of tube walls,
chiralities (helicities), etc., and can generally be made by any
known technique. The terms "carbon nanotube" and "nanotube" will be
used interchangeably herein. Such CNTs are often subjected to one
or more purification steps [see, e.g., Chiang et al., J. Phys.
Chem. B, 2001, 105, 1157-1161; Chiang et al., J. Phys. Chem. B
2001, 105, 8297-8301]. In some embodiments, the CNTs are cut by one
or more cutting techniques [see, e.g., Liu et al., Science, 1998,
280, 1253-1256; and Gu et al., Nano Lett., 2002, 2, 1009-1013].
[0045] In some embodiments, the aromatic polymer blocks are
polybenzazoles (PBZ) or other aromatic polymers. PBZs have the
general formula: ##STR1##
[0046] Other suitable such polymer blocks are cis- and
trans-polybezoxazole (PBO): ##STR2## and cis- and trans-
poly-p-phenylenebisbenzthiozole (PBT): ##STR3## and
poly-2,5-(benzoxazole) (ABPBO): ##STR4##
[0047] In some embodiments, SWNT blocks are coupled to aromatic
polymer blocks via a condensation reaction to form "SWNT block
copolymers." In some embodiments, the aromatic polymer (block) is a
polybenzazole (PBZ). Block copolymers of the present invention
comprising SWNTs and PBZ components are referred to herein as
"SWNT/PBZ block copolymers." In some such embodiments, the PBZ
block is polybezoxazole (PBO), giving rise to "SWNT/PBO block
copolymers."
[0048] In some embodiments, the aromatic polymer blocks are
aromatic polyamides or other aromatic polymers. Such aromatic
polyamides have the general formula:
--[--NH--Ar--NH--CO--Ar--CO--].sub.n--or --[--NH--Ar--CO--].sub.n--
where "n" is an integer indicative of the number of respective
repeat units.
[0049] For the above aromatic polyamide polymers, suitable aromatic
units, -Ar-, include, but are not limited to, 1,4-phenylene;
4,4'-biphenyly; 2,6-naphthylene; 1,5-naphthylene; N,N'-piperazine;
1,3,4-oxadiazol; phenylbenzimide; 1,4-xylylene; 2,5-pyridylene; and
combinations thereof. The aromatic units may comprise pendant
groups such as, but not limited to, alkyl, halogen, alkoxy, cyano,
acetyl, nitro, and the like. Aromatic polyamides may also comprise
bridging units between the aromatic units. Suitable such bridging
units include, but are not limited to, ether, sulfide, sulfone,
ketone, amine, ethylene, azo, ester, diazo and other like
linkages.
[0050] Other suitable aromatic polymer polymer blocks include
aromatic polyimides, aromatic polyesters, and aromatic heterocyclic
polymers.
[0051] As mentioned above, in some embodiments, SWNT blocks are
coupled to aromatic polymer blocks via a condensation reaction to
form "SWNT block copolymers."In some such embodiments, these
aromatic polymer blocks are poly(p-phenylene terephthalamide)
(PPTA). Block copolymers of the present invention comprising SWNTs
and PPTA components are referred to herein as "SWNT/PPTA block
copolymers."
[0052] In some embodiments, short SWNTs are covalently bonded to
PPTA, other aromatic polyamides, or other aromatic polymers of
finite length, to improve the solubility of SWNTs in aprotic
solvents, mineral acids, or other solvents, and to prevent the
formation of aggregates (ropes) of SWNTs.
[0053] In some embodiments, the spinning or casting of the
above-mentioned SWNT/PBZ copolymers and/or SWNT/PPTA copolymers can
be carried out from liquid crystalline solutions at higher
concentrations than previously possible. This affords a more
effective coagulation process and easy alignment of nanotube block
copolymers during the spinning or casting process.
[0054] In some embodiments, the coupling of aromatic polymers
(e.g., PBZ or PPTA) to short SWNTs improves the strength ("leg") of
spinning or casting solutions due to stronger interaction between
polymer molecules over that of neat SWNT solutions. This can
improve shaping processes and lead to shaped articles with
ultra-high performance properties afforded by SWNTs.
[0055] In some embodiments, the present invention is directed to
the synthesis of (i.e., methods of making) block copolymers
comprising short SWNTs and aromatic polyamide blocks and/or other
aromatic polymer blocks; fibers and other compositions containing
these block copolymers; processes for making shaped articles from
these block copolymers comprising aromatic polymer blocks and SWNT
blocks; and shaped articles made by these processes.
[0056] In some embodiments, the present invention is directed
toward physical blends of any of the above-described nanotube block
copolymers with their corresponding homopolymers; fibers and other
compositions containing these blends; processes for making shaped
articles from these blends comprising blockpolymers of SWNT and
aromatic polymers and the corresponding aromatic polyamide; and
shaped articles made by these processes.
[0057] In some embodiments, methods for making nanotube block
copolymers comprise a cutting and end-functionalizing of SWNTs,
followed by reaction with suitably functionalized aromatic polymer
blocks.
[0058] The synthesis of functionalized short SWNTs, according to
some embodiments of the present invention, is shown below in Scheme
1: ##STR5##
[0059] Referring to Scheme 1, SWNTs (1) are first cut in an
oxidative acid (e.g., HNO.sub.3) or acid mixture (e.g., piranha) to
yield short SWNTs bearing carboxyl species (e.g., --COOH groups) on
their open ends and/or on their side-walls (2). Such carboxyl
species can then be converted to acyl chloride species (--COCI) by
reaction with thionyl chloride (SOC1.sub.2) to yield (3). Such
above-described chemistry is known in the art. See, e.g., Liu et
al., Science, 1998, 280, 1253-1256; and Chen et al., Science, 1998,
282, 95-98
[0060] In some embodiments of the present invention, short SWNTs
are used to enhance the solubility of the SWNT blocks in aprotic
solvents such as N-methyl-2-pyrrolidone (NMP), dimethyl acetamide
(DMAc), N,N-dimethylformamide (DMF), 1,3 dimethyl-2-imidazolidinone
(DMI), dimethylsulfoxide (DMSO), and the like, or in strong acids
such as, but not limited to, sulfuric acid, oleum (fuming sulfuric
acid which is H.sub.2SO.sub.4 with dissolved S03 to remove trace
water), methanesulfonic acid (MSA), and the like. Similarly, the
short functionalized SWNT-COOH and SWNT-COCI will have improved
solubility in the above mentioned aprotic solvents or strong acids.
The enhanced solubility of short SWNTs and their functionalized
counterparts affords the advantage of SWNTs being processed (fibers
spun or films cast) at higher SWNT concentrations in aprotic
solvents or in strong acids. The shaped articles, fibers or films,
will generally have greater overall mechanical strength due to the
more effective process of coagulation and the enhanced
orientability of SWNTs in these higher concentrated solutions.
[0061] As mentioned above, in some embodiments of the present
invention, short SWNTs, generally with length of less than about
1000 nm, typically less than 100 nm, and more typically 5-50 nm,
are used. Typically, such individual SWNTs have diameters of about
1 nm. Accordingly, some embodiments of the present invention use
SWNTs with aspect ratios (defined as the length divided by
diameter) of less than about 1000; typically less than 100; and
more typically between 5-50. Likewise, the functionalized SWNTs
have aspect ratios generally less than about 1000, typically less
than 100, and more typically between 5 and 50.
[0062] In some embodiments, the functionalized group (i.e.,
chemical moiety) on the SWNT ends, shown as --COOH and/or --COCI in
Scheme 1, is an electron-deficient carbon group, but can generally
be any group containing a carbon atom that can react in the aprotic
solvents or mineral acids with the amine moiety at the end(s) of
aromatic polymers to form amide linkages between the SWNT and
aromatic polymer blocks. Suitable electron-deficient groups
include, but are not limited to, carboxylic acids, acid halide,
metal carboxylate salts, cyano groups and trihalomethyl groups.
Halogens in such electron-deficient carbon groups are typically
fluorine, chlorine, or bromine, and more typically chlorine.
[0063] A synthesis of amine-terminated aromatic polymer blocks such
as PPTA is shown below in Scheme 2, where an amide-forming moiety
(4) is reacted with a species comprising an electron-deficient
carbon moiety (5) to yield an amine-terminated aromatic polyamide
(6), in accordance with some embodiments of the present invention.
##STR6##
[0064] Referring to Scheme 2, suitable aromatic units, -Ar-,
include, but are not limited to, 1,4-phenylene; 4-4'-biphenyl;
2,6-naphthylene; 1,5-naphthylene; N,N'-piperazine; 1,3,4-oxadiazol;
phenylbenzimide; 1,4-xylylene; 2,5-pyridylene; and the like. Such
aromatic units may comprise pendant groups such as, but not limited
to, alkyl, halogen, alkoxy, cyano, acetyl, nitro, and the like.
Aromatic polyamides may also comprise bridging units between the
aromatic units. Suitable such bridging units include, but are not
limited to, ether, sulfide, sulfone, ketone, amine, ethylene, azo,
and other like linkages.
[0065] Referring again to Scheme 2, n can generally be as low as 2
and as high as practically feasible (e.g., 2000). Typically, n is
about 5 to 100, and more typically between 5 and 50. In the above
Scheme 2, the amide-forming moiety (4) is a p-amino-basic moiety
which is bonded to an aromatic group comprising a primary amine
group bonded to the aromatic group. The other reactant (5) in the
above reaction comprises an electron-deficient carbon group. As
mentioned above, this carbon group can be any group containing a
carbon atom that can react in the aprotic solvents or mineral acid
with an amino-basic moiety to form an amide. Suitable
electron-deficient carbon groups include, but are not limited to,
carboxylic acids, acid halides, metal carboxylate salts, cyano
groups and trihalomethyl groups. Halogens in electron-deficient
carbon groups are typically fluorine, chlorine, or bromine, and
more typically chlorine.
[0066] The solvents used in the above reaction can be any aprotic
solvents or mineral acid or their mixtures capable of dissolving
the polymerizing reactants and aromatic polyamide polymers. The
above acids and mixtures may also comprise P.sub.20.sub.5.
[0067] A key aspect of the present invention is the block
copolymerization of short, functionalized SWNTs (as shown in Scheme
1) with amine-terminated aromatic polymer blocks (as shown in
Scheme 2) in aprotic solvents such as NMP, DMAc, etc. or in strong
mineral acids capable of dissolving both reactants without any
detrimental reaction or degradation of the reactants. An exemplary
copolymerization reaction is shown in Scheme 3 below, where
shortened functionalized SWNTs (3) are reacted with
amine-terminated aromatic polyamides (6) to yield SWNT/aromatic
polyamide block copolymer (7). ##STR7##
[0068] In some such above-described embodiments, the reaction is
carried out in an aprotic solvent, such as NMP with CaCI.sub.2, and
optionally with a condensate agent. Additionally, the reaction may
optionally be carried out with an excess of amine-terminated
aromatic polyamide relative to the short functionalized SWNT.
[0069] In the above embodiments directed toward the formation of
SWNT/aromatic polyamide block copolymers in aprotic solvent, the
total concentration of the two reactants in the solvent (i.e., the
short functionalized SWNTs and the aromatic polyamide blocks) is
dependent upon the length of both of the block components.
Generally, the concentration should be controlled and optimized
such that the solution will have maximum concentration and minimum
bulk viscosity for ease of processing, such as in fiber spinning or
film casting. Dependent upon the concentration, the resultant
copolymer solution can be optically isotropic or optically
anisotropic, the latter of which can be liquid crystalline in form
and probably nematic. Although the reaction between (3) and (6) in
Scheme 3 shows the formation of an aromatic polyamide-SWNT-aromatic
polyamide tri-block copolymer (7, wherein the SWNTs are themselves
blocks), the reaction can be tailored to form di-block or random
block copolymers of SWNT with aromatic polyamide, dependent upon
the level and arrangement of --COOH, or --COCI groups on the SWNT,
i.e., how many --COOH moieties are bonded to each SWNT, and which
end or both ends, or even on the side-walls of the SWNTs that the
--COOH moieties are bonded to, and the functionality at the ends of
the aromatic polyamide reactant.
[0070] For the above-described SWNT/aromatic polyamide block
copolymers of the present invention, the product compositions
typically range from between about 5/95 SWNT/aromatic polyamide
(wt/wt %) to 95/5 SWNT/aromatic polyamide (wt/wt %). In some
embodiments, it is desirable to have as high a content of SWNT as
possible.
[0071] Advantages of block copolymerizing aromatic polymers with
SWNTs include minimal compromise in the resulting materials'
ultimate performance, as well as the economics and current
understanding of aromatic polymer systems, i.e., they are
relatively inexpensive, commercially available, and the fiber
spinning of aromatic polymer systems like PBZ and PPTA is well
known. Additionally, they are soluble in acid solvents.
[0072] Other aspects of the present invention are processes of
shaping the above solutions/compositions (i.e., Scheme 3) into
useful articles such as fibers or films. In some embodiments,
fibers made by the nanotube block copolymer compositions of the
present invention have superior mechanical properties; superior
chemical, thermal, thermo-oxidative, and dimensional stability;
ultra-light weight; and unique electrical/electro-magnetic
properties suitable for structural application as the fiber
component of advanced composites for aerospace and space vehicles.
Other utility can be found in electronic and electrical
applications, and also important utility in protective body
(personal, vehicular, structural) armor. The above-mentioned
properties can surpass those of state of the art organic fibers
such as ZYLON (Zylon.RTM. is a registered trademark of Toyobo Co.,
Ltd., Osaka, Japan), KEVLAR (Kevlar.RTM. is a registered trademark
of E.l. du Pont de Nemours and Co., Wilmington, Del.), and TWARON
(Twaron.RTM. is a registered trademark of Teijin Twaron B.V. Ltd.,
Arnhem, Netherlands) for example, or other advanced carbon fibers
currently being used in the above-mentioned applications.
[0073] The current art of spinning fibers of neat SWNTs (with
indiscriminate lengths) or casting neat SWNT films has had limited
success with regard to fully realizing the potential of SWNTs
[Ericson et al., Science, 2004, 304, 1447-1450]This is partly due
to the low solubility of SWNTs in common organic or mineral acid
solvents, and the intractability of SWNT ropes, i.e., aggregates of
individual SWNT, readily formed during or before the dissolution
process. Also, the current art of spinning composite SWNT fibers
from solutions of physical mixtures of SWNTs of indiscriminate
lengths (as opposed to the cut, shortened SWNTs used in some
embodiments of the present invention) with other polymers,
including PBO and PPTA, has had limited success due to the
relatively low level of dispersability of SWNTs in these
polymers.
[0074] The present invention teaches, in part, the covalently
bonding of short (e.g., shortened) SWNTs with aromatic polymers of
finite length. The shorter length improves the solubility of SWNTs
in aprotic solvents, mineral acids, and other solvents, and
minimizes the formation of aggregates (ropes) of SWNTs.
Furthermore, aromatic polymers like PBZ and PPTA are readily
soluble in such above-described aprotic solvents and acids and can
impart the short SWNTs with increased solubility (and
processability) when covalently attached to the short SWNTs in the
form of a block copolymer. Consequently, the spinning or casting of
SWNT-based nanotube block copolymers can be carried out with liquid
crystalline solutions at higher concentrations which afford a more
effective coagulation process and easy alignment of, e.g.,
SWNT/aromatic polyamide copolymers during the spinning process.
Also, in some embodiments, the incorporation of aromatic polyamide
with SWNT can improve the strength ("leg") of the spinning or
casting solutions due to stronger interaction between molecules.
This generally improves the shaping process and generally leads to
shaped articles with ultra-high performance properties afforded by
SWNT.
[0075] The following examples are provided to more fully illustrate
some of the embodiments of the present invention. It should be
appreciated by those of skill in the art that the techniques
disclosed in the examples which follows represent techniques
discovered by the inventors to function well in the practice of the
invention, and thus can be considered to constitute exemplary modes
for its practice. However, those of skill in the art should, in
light of the present disclosure, appreciate that many changes can
be made in the specific embodiments that are disclosed and still
obtain a like or similar result without departing from the spirit
and scope of the invention.
EXAMPLE 1
[0076] While not intending to be bound by theory, this Example
serves to illustrate, by virtue of Halpin-Tsai equations, the
reinforcing efficiency and therefore, the benefit of incorporating
short SWNTs into aromatic polymer block copolymer materials. For: E
c = .times. ( ( 1 + a .times. .times. .mu..upsilon. f ) / ( 1 -
.mu..upsilon. f ) ) .times. E m .times. a .about. 2 .times. ( l / d
) .mu. = .times. ( E f / E m - 1 ) / ( E f / E m + a ) ##EQU1##
[0077] Where:
[0078] Ec=Young's modulus of composite fiber
[0079] Em=Young's modulus of matrix (e.g., PPTA)
[0080] Ef=Young's Modulus of SWNT
[0081] I=length of SWNT, d=diameter of SWNT
[0082] a=2*(aspect ratio of SWNT)
[0083] .nu.f=volume fraction of SWNT
[0084] .nu.m=volume fraction of PPTA.
[0085] The reinforcement efficiency of SWNT is defined as:
RE=E.sub.c/(E.sub.f.nu..sub.f+E.sub.m.nu..sub.m) and
(E.sub.f.nu..sub.f+E.sub.m.nu..sub.m) represents the ultimate
linear rule-of-mixture modulus of a uniaxially oriented composite.
Thus, for a 50/50 v/v % SWNT/PPTA composite fiber, the calculated
RE, using the above equations, is 1 (or 100% reinforcement
efficiency) for SWNTs with aspect ratio of 32 and E.sub.f/E.sub.m
of 10. On the other hand, when a softer matrix is used, e.g.,
E.sub.f/E.sub.m=50, it would require the aspect ratio of SWNTs to
be at least 200 in order to achieve 95% of reinforcement
efficiency. This simply means that with a rigid matrix such as
PPTA, very short SWNTs can be utilized as reinforcement without any
degradation in reinforcement efficiency.
EXAMPLE 2
[0086] This Example serves to illustrate the preparation of
p-phenylene benzobisoxazole 15 mers, in accordance with some
embodiments of the present invention.
[0087] Referring to Scheme 4 (FIG. 3), 4.4765 g (21.01 mmol) of
diaminoresorcinol dihydrochloride and 4.0 g (19.70 mmol)
terephthaloyl chloride were added to a solvent mixture of 33.1529 g
of polyphosphoric acid (84.5% as P.sub.20.sub.5) and 0.4331 9 of
P.sub.20.sub.5 (total P.sub.20.sub.5 content in mixture =84.7 wt.
%) to yield a reaction mixture. The reaction mixture underwent a
dehydrochlorination step at 45.degree. C. for 16 hours; whereas an
oligomerization step was carried out at 95.degree. C. for 8 hours,
150.degree. C for 16 hours, and 190.degree. C. for 24 hours. This
yielded a p-phenylene benzobisoxazole oligomer with an inherent
viscosity of 1.96 dL/g.
EXAMPLE 3
[0088] This Example serves to illustrate the preparation of
p-phenylene benzobisoxazole 45 mers, in accordance with some
embodiments of the present invention.
[0089] Referring to Scheme 5 (FIG. 4), 6.5 g (30.51 mmol) of
diaminoresorcinol dihydrochloride and 6.0593 g (29.85 mmol)
terephthaloyl chloride were added to a solvent mixture of 48.9445 g
of polyphosphoric acid (84.5% as P.sub.20.sub.5) and 0.64 g of
P.sub.20.sub.5 (total P.sub.20.sub.5 content in mixture =84.7 wt.
%) to yield a reaction mixture. The reaction mixture underwent a
dehydrochlorination step at 45.degree. C. for 16 hours; whereas an
oligomerization step was carried out at 95.degree. C. for 8 hours,
150.degree. C. for 16 hours, and 190.degree. C. for 24 hours. This
yielded a p-phenylene benzobisoxazole oligomer (45 mer) with an
inherent viscosity of 7.06 dL/g.
EXAMPLE 4
[0090] This Example serves to illustrate sidewall functionalization
of short SWNTs with sulfanilic acid in oleum, in accordance with
some embodiments of the present invention. Such functionalization
is generally described in the following commonly-assigned
international patent application: Tour et al., "Functionalization
of Carbon Nanotubes in Acidic Media," Serial No. PCT/US05/09677
(Publication No. W02005113434), filed Mar. 24, 2005.
[0091] Referring to Scheme 6 (FIG. 5), 250 mg (20.81 mmol) of short
(ca. 60 nm) SWNTs were reacted with 14.4163 g (20.81.times.4 mmol)
of sulfanilic acid in a reaction mixture comprising 100 mL
H.sub.2SO.sub.4 (fuming, 20% free S0.sub.3), 5.7436 g
(20.81.times.4 mmol) sodium nitrite, and 683 mg (20.81.times.0.2
mol) 2,2'-azobisisobutyronitrile (AIBN). This yielded
water-soluble, sidewall-functionalized short SWNTs, as shown in
Scheme 6.
[0092] The sidewall-functionalized short SWNTs were characterized
by UV-vis spectroscopy as being devoid of van Hove singularities
FIGS. 6A and 6B are atomic force microscopy (AFM) images of the
short SWNTs before (FIG. 6A) and after (FIG. 6B) the
above-described functionalization. The AFM images show that the
short SWNTs were exofoliated into individuals and small bundles by
the sidewall-functionalization.
EXAMPLE 5
[0093] This Example serves to illustrate the copolymerization of
short SWNTs and PBO 15 mers, in accordance with some embodiments of
the present invention.
[0094] Referring to Scheme 7 (FIG. 7), 0.2 g of a polyphosphoric
acid (PPA) solution of p-phenylene benzobisoxazole 15 mer (the
solution comprising 25 mg of PBO 15 mer) was combined with a
suspension comprising 50 mg of short (ca. 60 nm) SWNTs, 10 g MSA,
10 g PPA (84.5% as P.sub.20.sub.5), and 0.15 g of P.sub.20.sub.5.
This was allowed to react at 100.degree. C. for 3 days to yield a
SWNT/PBO 15 mer block copolymer, as depicted in Scheme 7.
EXAMPLE 6
[0095] This Example serves to illustrate the copolymerization of
short sidewall-functionalized SWNTs and PBO 15 mers, in accordance
with some embodiments of the present invention.
[0096] Referring to Scheme 8 (FIG. 8), 0.4 g of a PPA solution of
p-phenylene benzobisoxazole 15 mer (comprising 50 mg of PBO 15 mer)
was combined with 36 mg of short (ca. 60 nm) benzenesulfonic
acid-functionalized SWNTs (see, e.g., EXAMPLE 4) in a reaction
mixture further comprising 10 g of MSA, 10 g PPA, and 1.0 g
P.sub.2O.sub.5. The reaction mixture was then heated at 100.degree.
C for 3 days to yield short sidewall-functionalized SWNT/PBO 15 mer
block copolymers, as depicted in Scheme 8.
EXAMPLE 7
[0097] This Example serves to illustrate Raman and infrared (IR)
spectroscopic analysis and AFM analysis of a series of SWNT/PBO 15
mer block copolymers prepared under a variety of conditions.
[0098] Table 1 details a variety of SWNT/PBO 15 mer block
copolymers prepared via copolymerization of short SWNTs and PBO 15
mers carried out in a mixed solvent of PPA/MSA with P.sub.2O.sub.5
for 3 days. TABLE-US-00001 TABLE 1 Wt ratio of PBO Molar ratio of
15 mers and short PBO 15 mers Wt ratio of Temp Concentration (wt %)
No. SWNTs to short SWNTs PPA and MSA (.degree. C.) PBO/SWNTs.sup.a
PBO SWNTs.sup.a 1 67/33 16 50/50 100 0.36 0.12 0.24 2 33/67 64
50/50 100 0.36 0.24 0.12 3 33/67.sup.b 64 50/50 100 0.36 0.24 0.12
4 33/67 64 17/83 150 3.3 2.2 1.1 5 33/67.sup.b 64 17/83 150 3.3 2.2
1.1 .sup.aCalculated based on SWNTs weight for benzenesulfonic acid
short SWNTs. .sup.bBenzenesulfonic acid functionalized short SWNTs
were used.
[0099] FIG. 9 depicts the Raman spectra (633 nm excitation) of
SWNT/PBO copolymer film synthesized in dilute concentration,
wherein trace (a) depicts copolymerized product No. 1 (see Table 1)
prepared from short SWNTs and PBO 15 mers at the weight ratio of
67/33 (0.36 wt. % concentration), and wherein trace (b) depicts PBO
15 mers. This confirms that the SWNTs are indeed incorporated
within the SWNT/PBO copolymer, as the PBO alone shows no
characteristic Raman bands in this region of the spectrum.
[0100] FIG. 10 depicts the Raman spectra (633 nm excitation) of
SWNT/PBO copolymer film prepared in higher concentration, wherein
trace (a) depicts copolymerized product No. 4 (see Table 1), and
wherein trace (b) depicts benzenesulfonic acid-functionalized short
SWNT/PBO 15 mers (copolymerized product No. 5, Table 1). The
copolymerized functionalized SWNT/PBO indeed shows the
characteristic functionalized SWNT Raman bands, confirming the
functionalized SWNTs are incorporated in the copolymer, i.e., it is
not merely PBO alone.
[0101] FIG. 11 depicts attenuated total reflectance-infrared
(ATR-IR) spectra of benzenesulfonic acid-functionalized short SWNTs
(trace a), PBO 15 mers (trace b), and the copolymerized product
(No. 5, Table 1) of benzenesulfonic acid-functionalized short
SWNT/PBO 15 mers at the concentration of 3.3 wt. %. The SWNT/PBO
copolymer spectrum is a composite (near summation) spectrum of the
independent SWNT and the independent PBO spectra, therefore
confirming the presence of both components in the copolymer.
[0102] Shown in FIGS. 12A-12D are AFM images of a 2 mg sample/10 cc
MSA solution spun onto a silicon wafer and vacuum dried at
100.degree. C. overnight. FIGS. 12A (height) and 12B (amplitude)
depict a physical mixture of functionalized short SWNTs and PBO 15
mers at a weight ratio of 49/51 as height and amplitude scans,
respectively. FIGS. 12C (height) and 12D (amplitude) depict
copolymerized product (No. 5, Table 1) from functionalized short
SWNTs and PBO 15 mers at a weight ratio of 49/51 as height and
amplitude scans, respectively. The physical mixture is clearly
different, at the nanoscale level, than the copolymerization
product. The latter (FIGS. 12C and 12D) have a thicker appearance,
due to the covalently-appended oligomers, which further keeps the
SWNT portions primarily as individuals, i.e., they do not tend to
bundle into longer structures.
EXAMPLE 8
[0103] This Example serves to illustrate the copolymerization of
short SWNTs and PBO 45 mers, in accordance with some embodiments of
the present invention.
[0104] Referring to Scheme 9 (FIG. 13), p-phenylene benzobisoxazole
45 mer was synthesized and then block copolymerized with short (ca.
60 nm) SWNTs, the short SWNTs comprising carboxylic acid (--COOH)
groups on the ends. The copolymerization was carried out in a
reaction mixture comprising 250 mg of short SWNTs, 2.0 g of a PPA
solution of PBO 45 mer (comprising 250 mg of PBO 45 mer), 15 g
methanesulfonic acid, and 1.5 g P.sub.20.sub.5. The
copolymerization was allowed to proceed at a temperature of
150.degree. C. for a period of 3 days to yield a SWNT/PBO 45 mer
block copolymer, as depicted in Scheme 9.
EXAMPLE 9
[0105] This Example serves to illustrate the copolymerization of
short sidewall-functionalized SWNTs and PBO 45 mers, in accordance
with some embodiments of the present invention.
[0106] Referring to Scheme 10 (FIG. 14), p-phenylene
benzobisoxazole 45 mer was synthesized and then block copolymerized
with short (ca. 60 nm) benzenesulfonic acid-functionalized SWNTs,
the short SWNTs comprising carboxylic acid (-COOH) groups on the
ends and benzene sulfonic acid groups on their sidewalls. The
copolymerization was carried out in a reaction mixture comprising
356 mg of the short benzenesulfonic acid-functionalized SWNTs, 2.0
g of a PPA solution of PBO 45 mer (comprising 250 mg of PBO 45
mer), 15 g MSA, and 1.5 g P.sub.20.sub.5. The copolymerization was
allowed to proceed at a temperature of 150.degree. C. for a period
of 3 days to yield a sidewall-functionalized SWNT/PBO 45 mer block
copolymer, as depicted in Scheme 10.
EXAMPLE 10
[0107] This Example serves to illustrate Raman spectroscopic
analysis, at a variety of excitation wavelengths, for a series of
SWNT/PBO 45 mer block copolymers prepared under a variety of
conditions.
[0108] Table 2 details a variety of SWNT/PBO 45 mer block
copolymers prepared via copolymerization of short SWNTs and PBO 45
mers carried out in a mixed solvent of PPA/MSA with P.sub.20.sub.5
for 3 days. TABLE-US-00002 TABLE 2 Wt ratio of PBO Molar ratio of
45 mers and short PBO 45 mers Wt ratio of Concentration (wt %) No.
SWNTs to short SWNTs PPA and MSA PBO/SWNTs.sup.a PBO SWNTs.sup.a 6
50/50 11 10/90 2.6 1.3 1.3 7 50/50.sup.b 11 10/90 2.6 1.3 1.3 8
90/10.sup.b 100 33/67 4.7 4.2 0.5 .sup.aCalculated based on SWNTs
weight for benzenesulfonic acid short SWNTs. .sup.bBenzenesulfonic
acid functionalized short SWNTs were used.
[0109] Various areas of the copolymer films were examined with 514
nm, 633 nm and 780 nm excitation. FIG. 15 depicts Raman
spectroscopic analysis (633 nm excitation) of SWNT/PBO 45 mer
copolymer film, wherein trace (a) depicts copolymerized product
from PBO 45 mers and benzenesulfonic acid-functionalized short
SWNTs (No. 7, Table 2), and wherein trace (b) depicts copolymerized
product from PBO 45 mers and short SWNTs (No. 6, Table 2). FIG. 16.
depicts Raman spectroscopic analysis (780 nm excitation) of
SWNT/PBO 45 mer copolymer film, wherein trace (a) depicts
copolymerized product from PBO 45 mers and benzenesulfonic
acid-functionalized short SWNTs (No. 7, Table 2), and wherein trace
(b) depicts copolymerized product from PBO 45 mers and short SWNTs
(No. 6, Table 2). FIG. 17 depicts Raman spectroscopic analysis (514
nm excitation) of SWNT/PBO 45 mer copolymer film, wherein trace (a)
depicts copolymerized product from PBO 45 mers and benzenesulfonic
acid-functionalized short SWNTs (No. 7, Table 2), and wherein trace
(b) depicts copolymerized product from PBO 45 mers and short SWNTs
(No. 6, Table 2).
[0110] Regarding FIG. 16, both traces (a) and (b) show that the
copolymers do indeed exhibit the expected presence of the SWNTs.
However, trace (a) shows an expected larger D-band to G-band ratio
than trace (b), due to the arylsulfonic acid sidewall
functionalization, further confirming that the sidewall
functionalization survives the copolymerization conditions.
[0111] Regarding FIG. 17, both trace (a) and trace (b) show that
the copolymers do indeed exhibit the expected presence of the
SWNTs. Again, however, trace (a) shows the expected larger D-band
to G-band ratio than trace (b), due to the arylsulfonic acid
sidewall functionalization, further confirming that the sidewall
functionalization survives the copolymerization conditions. Note
that the intensity of trace (a) is depressed because of the lack of
resonant Raman enhancement seen in functionalized SWNTs, and also
because it is further diluted with respect to there being a longer
PBO (45 mer) segment.
EXAMPLE 11
[0112] This Example serves to illustrate a conventional dry-jet wet
spinning process useful for spinning fibers of nanotube block
copolymers, in accordance with some embodiments of the present
invention.
[0113] Referring to FIG. 18, such a spinning process typically
involves a spinning apparatus 1800 coupled with the steps of: (a)
degassing of a nanotube block copolymer solution; (b) extrusion of
the degassed copolymer solution through a spinneret 1804 to form a
fiber; (c) coagulation of the fiber in a coagulation bath 1801
(directed by idle roll 1803); take-up of the fiber by take-up drum
1802; (d) washing the spun fiber; (e) drying the spun fiber; and
(f) various optional post treatments.
[0114] FIGS. 19A and 19B are scanning electron microscopy images
contrasting a PBO 45 mer fiber (FIG. 19A) with a copolymer (No. 8,
Table 2) of PBO 45 mers and benzenesulfonic acid-functionalized
short SWNTs at the weight ratio of 90/10 (FIG. 19B).
[0115] In the above or other embodiments, to enhance or modulate
the properties of the fibers produced, the nanotube block
copolymers can be blended with PBO homopolymers (or other aromatic
polymer), as depicted in FIG. 20.
EXAMPLE 12
[0116] This Example serves to illustrate the copolymerization of
short SWNTs and poly(p-phenylene terephthalamide) (PPTA).
[0117] First, PPTA, comprising amine groups at both ends, is
synthesized as shown in Scheme 11 (FIG. 21). Then, as depicted in
Scheme 12 (FIG. 22), this PPTA is then copolymerized with short
SWNTs in a reaction mixture comprising NMP, CaCI.sub.2, and
triphenyl phosphate/pyridine (condensate reagent).
[0118] All patents and publications referenced herein are hereby
incorporated by reference to the extent not inconsistent herewith.
It will be understood that certain of the above-described
structures, functions, and operations of the above-described
embodiments are not necessary to practice the present invention and
are included in the description simply for completeness of an
exemplary embodiment or embodiments. In addition, it will be
understood that specific structures, functions, and operations set
forth in the above-described referenced patents and publications
can be practiced in conjunction with the present invention, but
they are not essential to its practice. It is therefore to be
understood that the invention may be practiced otherwise than as
specifically described without actually departing from the spirit
and scope of the present invention as defined by the appended
claims.
* * * * *