Electronic Supplementary Information

Organic dispersion of polyaniline and single-walled carbon nanotubes and polyblends with

poly(methyl methacrylate)

Thomas Farrell,1 Kan Wang,1 Cheng-Wei Lin,1 and Richard B. Kaner 1,2 *

1 Department of Chemistry and Biochemistry and California NanoSystems Institute, University of California, Los Angeles, Los Angeles, California, 90095, USA

2 Department of Materials Science and Engineering, University of California, Los Angeles, Los Angeles, California, 90095, USA

*Corresponding author:

E-mail: kaner@chem.ucla.edu; Fax: +1-310-206-4038; Tel: +1-310-825-5346

Experimental section

Chemicals:

Single-walled carbon nanotubes (AP-SWCNT, 60-70% purity) were purchased from Carbon Solutions Inc. and used

without further purification. All other chemicals were obtained from Sigma-Aldrich and used as received.

Polyaniline emeraldine base (PANI EB)

Polyaniline was synthesized using a rapid mixing method1. In a typical synthesis, aniline (29.8 g, 0.32 mole) is

dissolved in 1 L of 1.0 M HCl. In a separate container, ammonium peroxydisulfate (18.25 g, 0.08 mole) is dissolved in

1 L of 1.0 M HCl. The two solutions are then rapidly mixed and shaken for ~10 s, after which the reaction is left

undisturbed for 1 day. The crude product is then filtered and washed with another 2 L of distilled water. The polymer

was collected on a Buchner funnel and then dedoped in 1 L of 0.1 M NH4OH, after which time the product was filtered

again and washed thoroughly with distilled water. The product was then dried at 40 °C under vacuum for one day to

obtain polyaniline emeraldine base (yield is ~20%).

PANI/DBSA solution in CHCl3

PANI/DBSA solutions in chloroform were prepared by a previously reported method2. 0.5 g of polyaniline emeraldine

base powder and 1.8 g of DBSA (DBSA/aniline molar ratio is 1.0) were placed in 100 ml of chloroform. The mixture

was sonicated for 24 h. The minor insoluble solid was removed by filtration through glass wool to obtain a deep green

solution (conc. of PANI EB is ~5 mg/ml). The preparation of PANI solution in other dopant/solvent systems was

carried out under similar conditions. The concentration of PANI EB was set at 5 mg/ml; DBSA/aniline and

CSA/aniline molar ratio were chosen at 1.0 and 0.5, respectively.

PANI/SWCNT solution in DBSA/CHCl3

A desired amount of SWCNTs were added into 10 ml of a PANI/DBSA chloroform solution. The mixture was treated

in an ultrasonic bath for 24 h. The solution was then passed through glass wool to remove any minor insoluble solids.

10 wt%, 25 wt %, 50 wt% and 100 wt% SWCNT were loaded into the composite (relative to PANI EB content), and

the resulting solutions were named PANI/SWCNT0.1, PANI/SWCNT/0.25, PANI/SWCNT0.50 and

PANI/SWCNT1.0, respectively. Transparent films were obtained by spin-coating the corresponding dispersions onto a

microscopic glass slide and dried at 50 °C. PANI-SWCNT composites were prepared in the same way for other

dopant/solvent systems.

PANI-SWCNT composites in polyblends with PMMA

The polyblend solutions were prepared by mixing PANI-SWCNT dispersion and 10 w/v% PMMA solutions in

DBSA/chloroform at the desired ratios. Transparent polyblend films were obtained by spin-coating the corresponding

solutions onto microscopic glass slides and dried at 50 °C.

Characterization

Dispersions of PANI-SWCNT composites and polyblends were drop-cast onto silicon wafers or TEM grids to prepare

samples for scanning electron microscope (SEM, JEOL, JSM-6700) and transmission electron microscope (TEM, FEI

Tecnai TF20), respectively.

UV-vis spectra of diluted solutions and coated thin films were collected on a Shimazu UV-3101 PC UV-vis-NIR

Scanning Spectrophotometer.

To prepare the Fourier Transformed Infrared (FTIR) samples, diluted solutions of PANI and PANI-SWCNT were drop-

cast on NaCl IR plates and air-dried. The spectra were measured using a Jasco FTIR 420 spectrometer.

For the conductivity measurements, dispersions of the PANI-SWCNT composites and polyblends were spin-coated on

microscopic glass slides and air-dried. Silver electrodes were deposited on the resulting thin films. The resistances were

measured by a 2-probe technique using a multi-meter. Film thicknesses were obtained with a Dektak 150 Surface

Profile Measuring System.

References

1. J. Huang and R. B. Kaner, Angew. Chemie, 2004, 116, 5941–5945.

2. Y. Cao, P. Smith, and A. J. Heeger, Synth. Met., 1992, 48, 91–97.

Table S1 Conductivity Measurements of PANI-SWCNT Composite Films Cast From DBSA/CHCl3

SWCNT loading Film Thickness (nm)

Corrected transmittance*

Sheet resistance (kΩ/☐)

Conductivity (S/cm)

PANI 73 88.3% 134.3 1PANI/SWCNT0.1 75 87.6% 18.6 7.2PANI/SWCNT0.25 100 87.4% 5.2 19.2PANI/SWCNT0.5 130 83.4% 2.3 33.4PANI/SWCNT1.0 226 79.4% 1.2 36.9

*Transmittance is measured at 580 nm, and corrected to that of a 100 nm thick film.

Table S2 Conductivity Measurements of PANI-SWCNT and PMMA Polyblends Cast From DBSA/CHCl3

PANI-SWCNT fraction

Film thickness (nm) Corrected transmittance*

Sheet resistance (kΩ/☐)

Conductivity (S/cm)

4.8% 311 99.0% 1610 0.0209.1% 346 97.9% 164.2 0.17616.7% 433 96.3% 35.2 0.65628.6% 199 93.9% 31.6 1.590

* Transmittance is measured at 580 nm, and corrected to that of a 100 nm thick film.

Table S3 Maximum loading of SWCNTs in Different Organic Solvent Systems

Dopant/Solvent Maximum SWCNT loading* CommentsHCOOH/HCOOH ~25%CSA/CHCl3 ~25%DBSA/toluene ~50% Composite gelates at 100% loading

during the sonication.DBSA/CHCl3 ~100% Dispersion with 100% SWCNT is not

stable over days.CSA/m-cresol ~100% Dispersion with 100% SWCNT is stable

over months.* Percentage of SWCNT is based on the weight of PANI base.

Scheme S1. A typical synthesis of a PANI-SWCNT composite and its polyblend with PMMA.

Fig. S1. SEM images of PANI/SWCNT0.25 samples cast from the DBSA/CHCl3 system. From (a) to (d), as the same area is exposed to the electron beam, the polymer matrix is burned away and SWCNTs are revealed.

Fig. S2. UV-vis spectra of (a) PANI, (b) PANI/SWCNT0.1, (c) PANI/SWCNT0.25, (d) PANI/SWCNT0.5, and (e) PANI/SWCNT1.0 dispersions in DBSA/CHCl3 system; (f) SWCNT dispersion in ethanol.

Fig. S3. FTIR spectra of (a) PANI, (b) PANI/SWCNT0.1, (c) PANI/SWCNT0.25, (d) PANI/SWCNT0.5, and (e) PANI/SWCNT1.0 from the DBSA/CHCl3 system.

Fig. S4. UV-vis-NIR spectra of PANI films in the system of (a) CSA/CHCl3, (b) HCOOH/HCOOH, (c) DBSA/toluene, (d) DBSA/CHCl3, and (e) CSA/m-cresol. The PANI-SWCNT composite films show similar spectra for each system.

Fig. S5. From left to right, spin-coated PANI-SWCNT composite films out of the DBSA/CHCl 3

system with 0%, 10%, 25%, 50% and 100% SWCNT loading. The high transparencies of the films can be observed directly from the words printed on the paper underneath each of the glass squares.