Conductivity polypyrrole copolymers

Several simple substituted polypyrroles and polypyrrole copolymers have been prepared and studied <83MI 204-02,94H(37)2069). For example, poly(3-alkylpyrroles) have been prepared by electrochemical polymerization and found to have conductivities comparable to that of PPy itself <89CC475,... 

Yin, W., and E. Ruckenstein. 2001. A water-soluble self-doped conducting polypyrrole-based copolymer. J Appl Polym Sci 79 86. 

This chapter is divided into two main parts polythiophene copolymers and polypyrrole copolymers. Each part reviews the random copolymerization of the heterocyclic monomer and important derivatives, principally those with substituents at the 3-position of thiophene and at the 1- and 3-positions of pyrrole. Alternating, block and graft copolymers are covered in both segments. Because applications of conducting polymers are reviewed in Volume 4, only applications unique to specify copolymers are covered here. In addition, a few theoretical studies dealing with conducting copolymers are reviewed. 

Common conductive polymers are poly acetylene, polyphenylene, poly-(phenylene sulfide), polypyrrole, and polyvinylcarba2ole (123) (see Electrically conductive polymers). A static-dissipative polymer based on a polyether copolymer has been aimounced (124). In general, electroconductive polymers have proven to be expensive and difficult to process. In most cases they are blended with another polymer to improve the processibiUty. Conductive polymers have met with limited commercial success. 

A similar process has been used to make polypyrrole-poly(vinyl alcohol) composites by electropolymerization from aqueous solution into a cross-linked poly(vinyl alcohol) film301 . The conductivity decreased and the elongation to break increased 10x with respect to polypyrrole. A conducting composite of 6% polypyrrole in a vinyl-idenefluoride-trifluorethylene copolymer showed an extension to break of 120% 302). 

The second method is the synthesis of copolymers or derivatives of a parent conjugated polymer with more desirable properties. This method is the more traditional one for making improvements to a polymer. It modifies the structure of the polymer to increase its processibility without compromising its conductivity or its optical properties. All attempts to do this on polyacetylene have failed as they always significantly reduced its conductivity. However, such attempts on polythiophenes and polypyrroles proved more fruitful. 

Both electrochemical and chemical oxidation have been used to produce 3-substituted alkylsulfonated pyrroles [106]. Electrochemical polymerisation was achieved using acetonitrile as solvent to form a solid deposit on the electrode. Alternatively, FeCl3 was used as oxidant. Conductivities in the range 0.001-0.500 S cm were obtained, with lower conductivity products obtained from chemical polymerisation. Others [107,108] have prepared homopolymers and copolymers of polypyrroles with alkyl sulfonate groups attached via the N-group. This N-group substitution decreases the polymers inherent conductivity. 

Depending on their structure, the polymers containing heterocycles have various applications. For example, poly(furfuryl alcohol) is used in composite materials with fillers such as sand and concrete, in copolymers with formaldehyde, etc. Some of the polymers from this group have special properties such as good electrical conductivity (after appropriate doping). Among these polymers are poly(thiophene-2,5-diyl) and particularly polypyrrole, CAS 109-97-7, (usually in carbon black doped with an organic acid anion). The structure of this polymer is shown below ... 

Figure 10.2 Oxidation of molecular hydrogen dissolved in 0.1 M HCIO4 at a stationary gold electrode modified by 0.1 mg cm of platinum dispersed in different electron conducting polymers sweep rate = 5 mV s T = 25°C (—) polyaniline (---) polypyrrole (—) poly(3-methylthiophcnc) (...) pyrrole-dithiopene copolymer, (Reprinted with permission from ref 133)...

Figure 10.1 Atomic force microscopy (AFM) image of one 100-nm-wide polypyrrole wire that bridges the ends of two polypyrrole microelectrodes (size 9 pm x Wpm). (Reprinted with permission from Advanced Materials, Patterning of Conducting Polymers Based on a Random Copolymer Strategy Toward the Facile Fabrication of Nanosensors Exclusively Based on Polymers by B. Dong, D. Y. Zhong, L. F. Chi and FI. Fuchs, 17, 22, 2736-2741. Copyright (2005) Wiley-VCH)...

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