Improving the electrical conductivity of polymer acid-doped polyaniline by controlling the template molecular weight

Abstract

We report the synthesis and characterization of a series of polyanilines (PANI) that are templated with a polymer acid at varying molecular weights. The polymer acid template of choice, poly(2-acrylamido-2-methyl-1-propanesulfonic acid), or PAAMPSA, was synthesized via conventional free-radical polymerization with molecular weights ranging from 45 kg mol 21 to 724 kg mol 21 . Subsequent aniline polymerization in the presence of PAAMPSA yielded waterdispersible, conductive PANI-PAAMPSA. The electrical conductivity of PANI-PAAMPSA increases by approximately three-fold with decreasing PAAMPSA molecular weight. This trend is accompanied by significant structural changes, including increases in PANI crystallinity and conjugation length. These conductivities (0.4-1.1 S cm 21 ) exceed the highest reported for polymer acid-doped PANI systems.

Directly patternable, highly conducting polymers for broad applications in organic electronics

“…When PANI is template synthesized with high molecular weight PAAMPSA, PANI-PAAMPSA is only partially doped due to mass transfer limitations of the polymer acid (21). This 5-fold increase in conductivity of PANI-PAAMPSA is thus attributed to HCl doping of residual imine sites along the PANI backbone (21). Because HCl is a bad solvent for PAAMPSA, it cannot induce the dramatic structural changes or the accompanying conductivity enhancement seen with DCA treatment of PANI-PAAMPSA.…”

“…1A; magnified in inset). Given the slope of the current-voltage (I-V) characteristics and the film dimensions, the conductivity of pristine PANI-PAAMPSA is 0.38 AE 0.05 S∕cm; we obtain comparable values via the transmission line method (21,22). After DCA treatment, applying a 10 V bias across the same films results in current levels that are two orders of magnitude higher (representative data presented as dashed line in Fig.…”

“…PANI-PAAMPSA was synthesized according to previously published procedures (21). To synthesize PANI-PSS, we first converted commercially available PSS-Na (Alfa Aesar; M w ¼ 500 kg∕mol) to its acidic form via ion exchange.…”

“…The electrical conductivities of conducting polymer films were measured using the four-point probe method (21,33) with an Agilent 4155C Semiconductor Parameter Analyzer. We measured the thicknesses of the conducting polymer films before and after DCA treatment using a Dektak 3.21 profilometer.…”

“…To synthesize PANI-PSS, we first converted commercially available PSS-Na (Alfa Aesar; M w ¼ 500 kg∕mol) to its acidic form via ion exchange. PSS was then used to template synthesize PANI-PSS according published procedures (21).…”