Removable and Recyclable Conjugated Polymers for Highly Selective and High-Yield Dispersion and Release of Low-Cost Carbon Nanotubes

Article abstract of DOI:10.1021/jacs.5b12797

High-purity semiconducting single-walled carbon nanotubes (s-SWNTs) with little contamination are desired for high-performance electronic devices. Although conjugated polymer wrapping has been demonstrated as a powerful and scalable strategy for enriching s-SWNTs, this approach suffers from significant contaminations by polymer residues and high cost of conjugated polymers. Here, we present a simple but general approach using removable and recoverable conjugated polymers for separating s-SWNTs with little polymer contamination. A conjugated polymer with imine linkages was synthesized to demonstrate this concept. Moreover, the SWNTs used are without prepurifications and very low cost. The polymer exhibits strong dispersion for large-diameter s-SWNTs with high yield (23.7%) and high selectivity (99.7%). After s-SWNT separation, the polymer can be depolymerized into monomers and be cleanly removed under mild acidic conditions, yielding polymer-free s-SWNTs. The monomers can be almost quantitatively recovered to resynthesize polymer. This approach enables isolation of "clean" s-SWNTs and, at the same time, greatly lowers costs for SWNT separation.

Full text of DOI:10.1021/jacs.5b12797

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Communication
Removable and Recyclable Conjugated Polymers for Highly Selective
and High-Yield Dispersion and Release of Low-Cost Carbon Nanotubes
Ting Lei, Xiyuan Chen, Gregory Pitner, H.-S. Philip Wong, and Zhenan Bao
J. Am. Chem. Soc., Just Accepted Manuscript • DOI: 10.1021/jacs.5b12797 • Publication Date (Web): 05 Jan 2016
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Removable and Recyclable Conjugated Polymers for Highly
Selective and High-Yield Dispersion and Release of Low-Cost
Carbon Nanotubes
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Ting Lei,† Xiyuan Chen,‡ Gregory Pitner,§ H.-S. Philip Wong,§ and Zhenan Bao*,†
Departments of †Chemical Engineering, ‡Materials Science & Engineering and §Electrical Engineering, Stanford University, Stan-
ford, California 94305, United States
Supporting Information Placeholder
mer/SWNT interactions. (2) The amount of polymers used is
about the same weight as the unpurified SWNTs. However, the
costs of most conjugated polymers are comparable or even higher
than those of SWNTs. For example, poly(9,9-di-n-
dodecylfluorenyl-2,7-diyl) (PFDD) and regioregular poly(3-
dodecylthiophene-2,5-diyl) (r-P3DDT), two widely used poly-
mers for SWNT seperation,4c,4f cost $729/g and $642/g from Sig-
ma-Aldrich, respectively; whereas the large-diameter SWNTs cost
about $10~35/g for the grade with ~30% SWNT content, and
$45~280/g for the grade with ~70% SWNT content (Table S1).
Thus, conjugated polymers can account for a large fraction of the
cost for purification. Additionally, their presence lowers the elec-
trical performance of SWNT networks due to the lower conduc-
tion of the polymers compared with SWNTs. To address these
issues, three strategies have been reported: (1) releasing SWNTs
using conformational switchable polymers;6 (2) employing non-
covalently linked supramolecular polymers, which break into small
units by acid;7 (3) irreversible depolymerization into small units.8
Strategy (1) requires special molecular design and has not demon-
strated good selectivity for s-SWNTs so far. Strategy (2) requires
multi-step synthesis of non-covalent bonding moieties, and in situ
polymerization during sorting process makes it harder to inde-
pendently optimize the sorting conditions. In addition, an exces-
sive amount of acid is needed to depolymerize, which may cause
p-doping of s-SWNTs.9 Strategy (3) does not allow the polymer to
be recycled and the sorting selectivity and yield achieved so far
still need much improvement. An ideal polymer used for SWNT
separation should be low-cost, removable, recyclable, high selec-
tivity and cause little damage to SWNTs. However, it is challeng-
ing to fulfill all these criteria.
Polyimines, also known as polyazomethines or Schiff-base pol-
ymers, are a family of conjugated polymers constructed from
imine bonds (C=N) in backbone and have been used for some
optoelectronic applications and covalent organic frameworks
(Figure 1a).10 The conjugated aromatic imine bonds are relatively
stable,11 however, imine bonds break readily with exposure to
catalytic amount of acid.10b Gerstel et al. reported the use of imine-
based polymer for dispersing s-SWNTs.5c However, they did not
show the important “removable” and “recyclable” advantages of
imine polymers and only used the polymers for dispersing small-
diameter SWNTs. Here we take advantage of the imine bonds to
design conjugated polymers for the separation of large-diameter
semiconducting SWNTs with little polymer contaminations while
lower polymer costs by recycling the monomers (Figure 1b). An
imine-based polymer poly[(9,9-di-n-dodecyl-2,7-fluroendiyl-
ABSTRACT: High-purity semiconducting single-walled carbon
nanotubes (s-SWNTs) with little contaminations are desired for
high-performance electronic devices. Although conjugated poly-
mer wrapping has been demonstrated as a powerful and scalable
strategy for enriching s-SWNTs, this approach suffers from signif-
icant contaminations by polymer residues and high cost of conju-
gated polymers. Here, we present a simple but general approach
using removable and recoverable conjugated polymers for separat-
ing s-SWNTs with little polymer contamination. A conjugated
polymer with imine linkages was synthesized to demonstrate this
concept. Moreover, the SWNTs used are without pre-purifications
and very low cost. The polymer exhibits strong dispersion for
large-diameter s-SWNTs with high yield (23.7%) and high selec-
tivity (99.7%). After s-SWNT separation, the polymer can be
depolymerized into monomers and be cleanly removed under mild
acidic conditions, yielding polymer-free s-SWNTs. The mono-
mers can be almost quantitatively recovered to re-synthesize pol-
ymer. This approach enables isolation of “clean” s-SWNTs and, at
the same time, greatly lowers costs for SWNT separation.
Single-walled carbon nanotubes (SWNTs) are promising materi-
als for next-generation electronics, such as field-effect transistors,
photovoltaics, bio/chemical sensors.1 In particular, SWNT net-
works are solution-processable and are of great interest for flexible
and stretchable electronics.2 Most of these applications specifically
require semiconducting (s-) SWNTs with minimal metallic (m-)
SWNT impurities. However, large-scale synthetic methods for
SWNTs always produce a mixture of semiconducting and metallic
SWNTs. Recently, various methods for the separation of s-
SWNTs and m-SWNTs, including DNA wrapping, density gradi-
ent ultracentrifugation, and gel chromatography techniques, have
been reported.3 However, these methods are either time-
consuming or not easily scalable.
Conjugated polymers have been intensively studied for enrich-
ing s-SWNTs, because they allow extraction of s-SWNT via simple
sonication and centrifuge steps within a few hours.4 Additionally,
conjugated polymers with certain molecular design can selectively
extract a specific chirality (n, m) of s-SWNTs.5 Although conju-
gated polymer wrapping provides a fast, low-cost and scalable
method for SWNT separation, this method has two major draw-
backs: (1) the purified s-SWNTs retain a substantial amount of
conjugated polymers on their surface. Removal of the polymers is
difficult due to tight polymer wrapping and strong poly-
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Figure 1. Imine-based conjugated polymers for SWNT separation. (a) A general design for removable conjugated polymers. (b) Proposed
separation cycle. The polymer is removable and recyclable, giving polymer-free s-SWNTs. Inset photos show the polymer solution, sorted
s-SWNT solution, and s-SWNT solution after depolymerization and release. (c) Synthesis of polymer PF-PD.
dimethine)-(1,4-phenylene-dinitrilomethine)] (PF-PD) was syn-
thesized to prove this concept (Figure 1c).Compared with small-
diameter s-SWNTs, large-diameter s-SWNTs (1.2~1.7 nm) are
more desired for electronic devices due to their smaller Schottky
barrier for good electrical contacts and higher current density.1d,12
To realize low-cost for separated s-SWNTs, a cheap raw SWNT
starting material is needed. Here, we use one of the lowest priced
SWNTs available commercially with diameters of 0.9−1.5 nm and
a purity of 30% SWNT content (RN-020, $10/g from Raymor
Industries Inc). All other reports typically employ higher purity
SWNT starting materials with 50~70% SWNT content.4c,4e,7b Nev-
ertheless, PF-PD exhibited high yield and high selectivity for dis-
persion of large-diameter s-SWNTs even with low-cost SWNT
raw materials. After separation, the wrapping polymers can be
removed by depolymerization into monomers with catalytic
amount of acid and subsequently recycled, thus demonstrating a
new scalable and low-cost approach for separating high-purity
polymer-free s-SWNTs.
A high concentration solution of large-diameter s-SWNTs with
barely detectable metallic peaks in the M11 region (Figure 2b) can
be readily obtained with 1 hour of processing time (see Support-
ing Information). The optical density (OD) at 939 nm for PF-PD
sorted SWNTs is up to 2.498 in a 1 cm path-length cuvette, corre-
sponding to a SWNT concentration of 0.0705 mg/mL. The OD
value is significantly higher (2~100 times) than many reported
polymer sorting methods used for large-diameter SWNTs,4c,4e,13
indicating the strong dispersion ability of PF-PD. Compared with
previous sorting methods using more expensive pre-purified
SWNTs (50~70% purity, prices are usually 4~8 times higher,
Table S1),4c,4e,7b our results demonstrate that the as-produced raw
SWNTs (30% purity) can be directly used together with our pol-
ymer sorting process without affecting the sorting yield and selec-
tivity (Figure S3). The pre-purification processes of as-produced
SWNTs typically involve strong acidic and/or harsh oxidative
conditions,14 which are costly and also give rise to chemical de-
fects. Thus the ability to sort raw SWNTs is beneficial in terms of
cost and may additionally provide better electronic properties.15
Polymer/SWNT ratio and concentration are important factors
that strongly affect the sorting yield and selectivity (Figure S4 and
Figure S5). The sorting yield was determined by absorption inten-
sity of the S22 peak (see Supporting Information).4c,4d The selectiv-
ity was evaluated based on ϕ value, which is defined by the ratio of
peaks and background area of both S22 and M11 absorptions.4c
Higher ϕ values indicate higher s-SWNT purities, and ϕ values >
0.40 were correlated to purities > 99%.4c,7b Figure S4 plots the
relationship between the yield and selectivity for different poly-
mer/SWNT ratios. Compared with literature reports that high ϕ
values > 0.40 usually resulted in low yields (< 5%) for large-
diameter SWNTs,4c,7b polymer PF-PD simultaneously demon-
strated both a high ϕ value of 0.407 and a high yield of 23.7% (vs.
theoretical s-SWNTs in the starting SWNTs) (Figure S4b), sug-
gesting the strong dispersion ability and high selectivity of this
polymer. Reducing the polymer/SWNT ratio led to an even high-
er selectivity with a ϕ value up to 0.445 and a relatively lower yield
of 13.6%. Polymer concentrations were also varied from 0.2
mg/mL to 2 mg/mL (Figure S5). Under the same poly-
mer/SWNT ratio (1:1), a higher concentration resulted in a
slightly higher selectivity but a lower yield. This inverse relation-
ship between yield and selectivity was also observed in many other
polymer systems.4c,7b,16 We also compared the absorption spectrum
Polyfluorenes are one of the most widely used polymers for
SWNT sorting.4a,4d Fluorene monomers are readily synthesized at
low-cost and thus used as the building block to demonstrate our
concept. Starting from a commercially available building block
9,9-didodecyl-2,7-dibromofluorene (1), two aldehyde groups
were introduced with a high yield of 88%. Polymer PF-PD was
synthesized through a direct condensation of the dialdehyde
monomer with p-phenylenediamine in dry toluene under the ca-
talysis by p-toluenesulfonic acid (5% eq.). An internal drying
agent anhydrous CaCl2 was employed to remove the generated
H2O and thereby increase the molecular weight of the polymers
(Figure 1b). Compared with traditional conjugated polymers that
usually synthesized with cross-coupling reactions (e.g. Suzuki or
Stille coupling),4c PF-PD was synthesized without any noble metal
catalysts or toxic phosphorous ligands. Thus the synthesis of imine
polymers is economical and environmentally friendly. Additional-
ly, they are stable under ambient conditions with decomposition
temperature above 400 °C (Figure S1), and no polymer degrada-
tion was observed for over six-month storage. Upon an addition of
catalytic amount of acid, PF-PD depolymerizes quickly, usually
within several minutes (Figure 2a). After depolymerization, the
absorption of the polymer at longer wavelengths completely dis-
appears and the spectrum is almost identical as that of the mono-
mer, suggesting a quantitative depolymerization.
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Figure 2. (a) Absorption spectrum changes in the PF-PD depolymerization process. (b) Absorption spectra of the raw SWNTs dispersed by
PF-PD and NMP (1 cm cuvette). Inset photo shows the high concentration solution. (c) Raman spectra of the raw SWNTs and PF-PD
sorted SWNTs (785 nm). (d) PLE map of SWNTs dispersed by the PDPP4T-2 polymers. (e) Absorption spectra of the as-sorted SWNTs,
sorted SWNTs redispersed in NMP and surfactant sodium cholate (SC) (1% aqueous), monomer (F-CHO) after depolymerization, and
polymer PF-PD. (f) XPS results for the PF-PD wrapped SWNTs (red) and released SWNTs (black).
of PF-PD sorted s-SWNTs with that of the commercially available
99.9% s-SWNTs (Figure S6). PF-PD sorted s-SWNTs showed
even higher selectivity as indicated by the “deeper valley” in the
M11 region (600~760 nm). To further validate the enrichment of
s-SWNTs, Raman spectra of the pristine SWNTs and the polymer
sorted SWNTs were measured (Figure 2c and Figure S7). Under
785 nm excitation, strong radial-breathing-mode (RBM) peaks of
metallic tubes in the range of 140~190 cm–1 were observed for the
pristine SWNTs. After sorting, this peak almost completely disap-
peared. Other laser excitations (532 and 633 nm) also confirmed
the removal of m-SWNTs. To determine the diameters of the
sorted SWNTs, photoluminescence excitation (PLE) mapping
was used (Figure 2d). At least 10 different chiralities with diame-
ters in the range of 1.25−1.38 nm were observed.
The dialdehyde monomer F-CHO cannot disperse any SWNTs
(Figure S8), suggesting its weak interactions with SWNTs. To
release the s-SWNTs, a small amount of trifluoroacetic acid (TFA,
0.1% v/v) and one drop of water was added to the sorted solution.
The solution was sonicated for 30 mins to ensure completion of
the hydrolysis reaction. s-SWNT precipitates were formed after
depolymerization (Figure 1c, inset photo). The s-SWNT precipi-
tates were centrifuged and collected by filtration through a 0.2 μm
PTFE membrane. The absorption spectra of the filtrate only
showed the monomer absorption, indicating that all the enriched
s-SWNTs were quantitatively collected (Figure 2e). The filtered s-
SWNTs can be redispersed in NMP or in aqueous solutions using
surfactants, providing similar absorption features in both M11 and
S22 region (Figure 2e), indicating that the sorted SWNTs can also
be used for NMP or aqueous based deposition methods.2c,17 No
polymers or monomers can be detected by absorption spectrosco-
py for the redispersed SWNTs in NMP and aqueous solution,
demonstrating the quantitative removal of the polymers. This
result was further confirmed by X-ray photoelectron spectroscopy
(XPS) measurement, where the N 1s peaks attributed to the N
atoms in the polymers almost disappeared in the released SWNT
samples (Figure 2f). We found that a large fraction of the conju-
gated polymers (about 1/2 to 2/3) were absorbed by the sediment
containing undispersed s-SWNTs, m-SWNTs, and amorphous
carbons. Thus, to fully recycle the polymer, polymers in sediment
were depolymerized and collected using similar methods as de-
scribed above. The filtrates can be collected and purified by run-
ning a short flash column chromatography to obtain the pure fluo-
rene dialdehyde monomer, which was then used for polymer re-
synthesis. We did not attempt to collect and purify the p-
phenylenediamine co-monomer as it is readily available commer-
cially at low cost. Absorption spectrum measurement indicates
that the monomer F-CHO was almost quantitatively recycled (>
98%). After column purification, we determined the recycling
yield to be 93% and the purity is sufficient for polymerization.
Absorption spectroscopy cannot be used to quantify high purity
tubes due to the complicated nature of SWNT absorption spec-
trum.3e,18 To further substantiate the purity comparison, FET
devices with channel length of 500 nm were fabricated on SiO2
(36 nm)/Si wafers. Since most of the sorted tubes exhibited tube
lengths in the range of 0.5 to 2 μm, the short channel devices used
here will short if there are m-SWNTs bridging directly across the
channel. 190 devices were measured with 8 shorted devices (Fig-
ure 3a and Figure S9). Each device contains on average ~12 tubes,
as characterized using scanning electron microscope (SEM) imag-
es. Thus ~2300 tubes were measured. We assume that any shorted
devices were caused by one m-SWNT because of the high purity
of our sorted tubes. Thus the purity of PF-PD sorted s-SWNT is
estimated to be 99.7% [(1–8/2300) × 100% = 99.7%], which is
one of the highest purity values reported to date for polymer
sorted large-diameter s-SWNTs characterized by direct electrical
measurement.4a-e,13
Thin-film transistors (TFTs) were also fabricated by drop-
casting the PF-PD sorted SWNT solution on patterned Au
(source-drain)/SiO2 (300 nm)/doped Si substrates. The devices
were then rinsed with toluene containing a small amount (0.1 %
o
v/v) of TFA to remove polymer residues and annealed at 200 C
for 20 min. Toluene rinsing was used to degrade and remove the
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(2) (a) Liang, J.; Li, L.; Chen, D.; Hajagos, T.; Ren, Z.; Chou, S.-Y.; Hu,
polymer residues. Annealing led to better tube-tube junctions and
improved source/drain contacts. Figure S10 displays the atomic
force microscopy (AFM) image showing a SWNT network with a
tube density ca. 50 tubes/μm2. TFT devices with various channel
lengths from 5 to 30 μm all showed good on/off ratios (Figure
S11). High hole mobilities in the range of 20−49 cm2 V−1 s−1 with
on/off ratios > 106 were obtained for devices with channel lengths
> 10 μm (Figure 3b). Compared to the unsorted raw SWNTs with
on/off ratios lower than 10, the high on/off ratios further
confirmed the high purity of the sorted s-SWNTs.
W.; Pei, Q. Nat. Commun. 2015, 6, 7647; (b) Chen, H.; Cao, Y.; Zhang, J.;
Zhou, C. Nat. Commun. 2014, 5, 4097; (c) Wang, C.; Hwang, D.; Yu, Z.;
Takei, K.; Park, J.; Chen, T.; Ma, B.; Javey, A. Nat. Mater. 2013, 12, 899.
(3) (a) Hersam, M. C. Nat. Nano. 2008, 3, 387; (b) Tu, X.; Manohar, S.;
Jagota, A.; Zheng, M. Nature 2009, 460, 250; (c) Arnold, M. S.; Green, A.
A.; Hulvat, J. F.; Stupp, S. I.; Hersam, M. C. Nat. Nano. 2006, 1, 60; (d)
Moshammer, K.; Hennrich, F.; Kappes, M. Nano Res. 2009, 2, 599; (e)
Tulevski, G. S.; Franklin, A. D.; Afzali, A. ACS Nano 2013, 7, 2971; (f)
Liu, H.; Nishide, D.; Tanaka, T.; Kataura, H. Nat. Commun. 2011, 2, 309.
(4) (a) Samanta, S. K.; Fritsch, M.; Scherf, U.; Gomulya, W.; Bisri, S. Z.;
Loi, M. A. Acc. Chem. Res. 2014, 47, 2446; (b) Nish, A.; Hwang, J.-Y.;
Doig, J.; Nicholas, R. J. Nat. Nano. 2007, 2, 640; (c) Ding, J.; Li, Z.;
Lefebvre, J.; Cheng, F.; Dubey, G.; Zou, S.; Finnie, P.; Hrdina, A.; Scoles,
L.; Lopinski, G. P.; Kingston, C. T.; Simard, B.; Malenfant, P. R. L.
Nanoscale 2014, 6, 2328; (d) Mistry, K. S.; Larsen, B. A.; Blackburn, J. L.
ACS Nano 2013, 7, 2231; (e) Gomulya, W.; Costanzo, G. D.; de Carvalho,
E. J. F.; Bisri, S. Z.; Derenskyi, V.; Fritsch, M.; Fröhlich, N.; Allard, S.;
Gordiichuk, P.; Herrmann, A.; Marrink, S. J.; dos Santos, M. C.; Scherf,
U.; Loi, M. A. Adv. Mater. 2013, 25, 2948; (f) Lee, H. W.; Yoon, Y.; Park,
S.; Oh, J. H.; Hong, S.; Liyanage, L. S.; Wang, H.; Morishita, S.; Patil, N.;
Park, Y. J.; Park, J. J.; Spakowitz, A.; Galli, G.; Gygi, F.; Wong, P. H. S.;
Tok, J. B. H.; Kim, J. M.; Bao, Z. Nat. Commun. 2011, 2, 541; (g) Jakubka,
F.; Schießl, S. P.; Martin, S.; Englert, J. M.; Hauke, F.; Hirsch, A.;
Zaumseil, J. ACS Macro Lett. 2012, 1, 815; (h) Berton, N.; Lemasson, F.;
Tittmann, J.; Stürzl, N.; Hennrich, F.; Kappes, M. M.; Mayor, M. Chem.
Mater. 2011, 23, 2237.
(5) (a) Ozawa, H.; Fujigaya, T.; Niidome, Y.; Hotta, N.; Fujiki, M.;
Nakashima, N. J. Am. Chem. Soc. 2011, 133, 2651; (b) Akazaki, K.;
Toshimitsu, F.; Ozawa, H.; Fujigaya, T.; Nakashima, N. J. Am. Chem. Soc.
2012, 134, 12700; (c) Gerstel, P.; Klumpp, S.; Hennrich, F.; Poschlad, A.;
Meded, V.; Blasco, E.; Wenzel, W.; Kappes, M. M.; Barner-Kowollik, C.
ACS Macro Lett. 2014, 3, 10.
(6) (a) Liang, S.; Zhao, Y.; Adronov, A. J. Am. Chem. Soc. 2014, 136, 970;
(b) Zhang, Z.; Che, Y.; Smaldone, R. A.; Xu, M.; Bunes, B. R.; Moore, J.
S.; Zang, L. J. Am. Chem. Soc. 2010, 132, 14113; (c) Umeyama, T.;
Kawabata, K.; Tezuka, N.; Matano, Y.; Miyato, Y.; Matsushige, K.;
Tsujimoto, M.; Isoda, S.; Takano, M.; Imahori, H. Chem. Commun. 2010,
46, 5969.
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Figure 3. (a) Electrical characterization of PF-PD sorted SWNTs
using short channel devices with a channel length of 0.5 um. Inset:
SEM image of a device. (b) Transfer characteristics of a typical
TFT device measured in vacuum (L = 20 um W = 400 um).
In summary, an imine-based conjugated polymer has been
developed for selective dispersion of s-SWNTs. PF-PD exhibits
strong dispersion ability for large-diameter s-SWNTs with high
yield (23.7%) and high selectivity (99.7%). After separation, the
polymers can be depolymerized, removed, and recycled, providing
polymer-free high-purity s-SWNTs. Compared with other sorting
methods, our approach offers significant advantages, such as low-
cost, high-selectivity, removable, recyclable, and less-damage to
SWNTs, yet only uses cheap and versatile building blocks. More
importantly, both dialdehyde and diamine groups can be readily
introduced to other π-conjugated structures, thus demonstrating a
general approach for low-cost separation of “clean” s-SWNTs.
(7) (a) Toshimitsu, F.; Nakashima, N. Nat. Commun. 2014, 5, 5041; (b)
Pochorovski, I.; Wang, H.; Feldblyum, J. I.; Zhang, X.; Antaris, A. L.; Bao,
Z. J. Am. Chem. Soc. 2015, 137, 4328; (c) Llanes-Pallas, A.; Yoosaf, K.;
Traboulsi, H.; Mohanraj, J.; Seldrum, T.; Dumont, J.; Minoia, A.;
Lazzaroni, R.; Armaroli, N.; Bonifazi, D. J. Am. Chem. Soc. 2011, 133,
15412.
(8) (a) Wang, W. Z.; Li, W. F.; Pan, X. Y.; Li, C. M.; Li, L.-J.; Mu, Y. G.;
Rogers, J. A.; Chan-Park, M. B. Adv. Funct. Mater. 2011, 21, 1643; (b)
Lemasson, F.; Tittmann, J.; Hennrich, F.; Sturzl, N.; Malik, S.; Kappes, M.
M.; Mayor, M. Chem. Commun. 2011, 47, 7428.
ASSOCIATED CONTENT
Supporting Information
Polymer synthesis, SWNT dispersion/characterization, device
fabrication and supplementary figures. This material is available
free of charge via the Internet at http://pubs.acs.org.
(9) Geng, H.-Z.; Kim, K. K.; So, K. P.; Lee, Y. S.; Chang, Y.; Lee, Y. H. J.
Am. Chem. Soc. 2007, 129, 7758.
(10) (a) Hu, B.; Zhu, X.; Chen, X.; Pan, L.; Peng, S.; Wu, Y.; Shang, J.;
Liu, G.; Yan, Q.; Li, R.-W. J. Am. Chem. Soc. 2012, 134, 17408; (b)
Belowich, M. E.; Stoddart, J. F. Chem. Soc. Rev. 2012, 41, 2003.
(11) Yang, C.-J.; Jenekhe, S. A. Macromolecules 1995, 28, 1180.
(12) Tulevski, G. S.; Franklin, A. D.; Frank, D.; Lobez, J. M.; Cao, Q.;
Park, H.; Afzali, A.; Han, S.-J.; Hannon, J. B.; Haensch, W. ACS Nano
2014, 8, 8730.
(13) Tange, M.; Okazaki, T.; Iijima, S. J. Am. Chem. Soc. 2011, 133,
11908.
(14) Wang, Y.; Huang, L.; Liu, Y.; Wei, D.; Zhang, H.; Kajiura, H.; Li, Y.
Nano Res. 2009, 2, 865.
(15) Neophytou, N.; Kienle, D.; Polizzi, E.; Anantram, M. P. Appl. Phys.
Lett. 2006, 88, 242106.
(16) Lei, T.; Lai, Y.-C.; Hong, G.; Wang, H.; Hayoz, P.; Weitz, R. T.;
Chen, C.; Dai, H.; Bao, Z. Small 2015, 11, 2946.
(17) Geier, M. L.; McMorrow, J. J.; Xu, W.; Zhu, J.; Kim, C. H.; Marks, T.
J.; Hersam, M. C. Nat. Nano. 2015, 10, 944.
(18) Kim, W.-J.; Lee, C. Y.; O’brien, K. P.; Plombon, J. J.; Blackwell, J.
M.; Strano, M. S. J. Am. Chem. Soc. 2009, 131, 3128.
AUTHOR INFORMATION
Corresponding Author
Zhenan Bao (zbao@stanford.edu)
ACKNOWLEDGMENT
We thank John To for XPS measurement. This work is supported
by BASF Co.
REFERENCES
(1) (a) Franklin, A. D. Science 2015, 349, 704; (b) Cao, Q.; Kim, H.-s.;
Pimparkar, N.; Kulkarni, J. P.; Wang, C.; Shim, M.; Roy, K.; Alam, M. A.;
Rogers, J. A. Nature 2008, 454, 495; (c) Cao, Q.; Han, S.-j.; Tulevski, G.
S.; Zhu, Y.; Lu, D. D.; Haensch, W. Nat. Nano. 2013, 8, 180; (d) Brady, G.
J.; Joo, Y.; Wu, M.-Y.; Shea, M. J.; Gopalan, P.; Arnold, M. S. ACS Nano
2014, 8, 11614; (e) Jain, R. M.; Howden, R.; Tvrdy, K.; Shimizu, S.;
Hilmer, A. J.; McNicholas, T. P.; Gleason, K. K.; Strano, M. S. Adv. Mater.
2012, 24, 4436; (f) Ye, Y.; Bindl, D. J.; Jacobberger, R. M.; Wu, M.-Y.;
Roy, S. S.; Arnold, M. S. Small 2014, 10, 3299; (g) Snow, E. S.; Perkins, F.
K.; Houser, E. J.; Badescu, S. C.; Reinecke, T. L. Science 2005, 307, 1942.
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