Pyrrole/3-methylthiophene copolymers

Figure 11.12. Chemical structure of 3-methylthiophene/ pyrrole copolymer.

Electrically conductive copolymers of 3-methylthio-phene are insoluble, infusible and unstable in the presence of moisture. Random copolymerization of 3-methlthiophene with 3-alkylthiophenes where the alkyl chain contains four or more carbons confers solution processability to the undoped polymer. The PPEP method is an effective process for fabricating heterolayers of 3-methylthiophene/pyrrole copolymers. 

Other early work in this field included the use of tetrakis(p-aminophenyl)-porphyrin (Fig. 7a), which was electrodeposited onto glassy carbon and showed a near-Nernstian response to iodide [76]. Electrodeposited methylthiophene-methylpyrrole copolymer was deposited and shown to give a near-Nernstian response to bromide [77]. Pyrrole-3-boronate (Fig. 7b) could be deposited to give films with a good response and marked selectivity to fluoride [78]. A cobalt aminophthalocyanine could also be electropolymerised to give a good sensor for nitrite [79] or sulphide ion [80]. 

Figure 11. Cyclic votammetry (top) and in situ electronic conductivity from rotating-disk voltammetry [ , Fig. 9(C)] and sandwich electrode voltammetry [ , Fig. 9(B)] for poly(3-methylthiophene) in acetonitrile containing 0.1 M BU4CIO4.60 (Reprinted from J. Ochmanska and P. G. Pickup, In situ conductivity of poly-(3-methylthiophene) and (3-methylthiophene)x,-[Ru(2,2 -bipyridine)2 (3- pyrrol-l-ylmethyl pyridine)2]2+ copolymers, J. Electroanal. Chem. 297, 211-224, 1991, with kind permission from Elsevier Sciences S.A.)...

M. Lu, X.H. Li, and H.L. Li, Synthesis and characterization of conducting copolymer nanofibrils of pyrrole and 3-methylthiophene using the template-synthesis method. Mater. Sci. Eng. A Struct. Mater. Prop. Microstruct. Proc., 334(1-2), 291-297 (2002). 

Utilizing an electrocopolymerization technique, various conducting copolymer layered structures were constructed. The copol)mier composition, and the thickness of the polymerized copolymer, are controlled easily in the electrolytic polymerization process (Fig. 7). Fig. 8 is an example of such depth profile-controlled multilayers, consisting of polypyrrole and copoly(pyrrole/3-methylthiophene). The present method will allow nm-level thickness control. 

A copolymer of pyrrole and thiophene nano-fibrUs was electrochemically polymerized within the pores of microporous, anodic, aluminum oxide template membranes [105]. The copolymer nucleated and grew on the pore wall of the membrane since the polymers were cationic and the membrane had anionic sites on the pore wall. The length, thickness, and diameter of the copolymer nanofibrils could be controlled and with higher applied potential, more thiophene units were incorporated into the copolymer nanofibrUs [105]. Copolymer nanofibrils of pyrrole and aniline were also electrochemically polymerized within the pores of microporous, anodic, aluminum oxide template membranes [106]. Copolymer nanofibrils of PPy and poly(3-methylthiophene) prepared chemically in the microporous aluminum oxide template showed higher conductivity than the homopolymers did [107]. 

The polymerization reaction, i.e., the reaction of two radical cations or the reaction of a radical cation with a neutral monomer molecule, depends on the conditions during electrochemical polymerization [58, 627, 629, 630]. During the electrocopolymerization of 3-methylthiophene and 3-thienylacetic acid, a radical cation (of 3-methylthiophene) attacks at a neutral monomer (3-thienylacetic acid). It is possible to produce the copolymer at a potential at which only one of the monomer species can be oxidized [108]. Fig. 19 shows a partial model of interfacial reactions taking place during the electrogeneration of PT or poly(pyrrole) from acetonitrile solutions containing the electrolyte LiClO. . The relative influence of each of these reactions depends on the chemical and electrical conditions of synthesis [629] ... 

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