Direct copolymerization conductivities

Kuwabata et al. [210] have reported the direct copolymerization of pyrrole and thiophene through electrochemical oxidation [211]. Their polymerization was carried out potentiostatically in an acetonitrile solution containing 0.1 M thiophene, a pyrrole concentration as low as 2.0 X 10" M, and 0.1 M lithium perchlorate. As previously mentioned, the difference in the oxidation potentials between pyrrole and thiophene is rather large. Kuwabata et al. oxidized pyrrole under diffusion limiting conditions at potentials at which thiophene oxidation occurs. Conductivities of the polymer films prepared at potentials between 1.37 and 2.07 V (versus Ag/Ag" ) were between 0.15 and 44 S cm". Although much greater conductivities... 

The methanol permeability through the proton exchange membranes was proportional to the proton conductivities, as shown in Fig. 4.16. That is, the proton conductivity has a trade-off in its relationship with the methanol permeability. Target membrane would be located in the upper left-hand comer, of which the fluorenyl copolymers show the same tendency. Series of sulfonated poly(aryl ether ketone)s membranes obtained by direct copolymerization using various sulfonated monomers are listed in Table 4.2. The water content and proton conductivities of these membranes are shown in Fig. 4.17. 

Copolymerization of thiophenes and pyrroles offers the promise of combining the higher stability associated with thiophene-based polymers with the higher conductivity characteristic of polypyrroles. Three different methods have been used to prepare such copolymers. These are (1) direct copolymerization of pyrrole and thiophene monomer mixtures, (2) copolymerization of pyrrole with bi- or a-terthiophene, and (3) polymerization ofa-linked pyrrole-thiophene monomers. The last case includes both two- and three-ring systems. 

Direct feedback of recovered monomer in recycle copolymerization may lead to buildup of inert materials that can affect the polymerization reaction. This point is illustrated in the copolymerization of styrene and a-methylstyrene. A 22-day experiment was conducted in which the feed was a mixture of 25% a-methylstyrene and 75% styrene and polymerization was effected at 125° C. The monomer contained about 0.5% of inerts, consisting primarily of ethylbenzene... 

Interfacial radical alternating copolymerization of hydrophilic vinylethers with hydrophobic maleates can be conducted in direct [181] and in inverse [182] miniemulsion, leading to encapsulation of organic liquids or water, respectively. Since the monomers do not homopolymerize, the alternating copolymerization can only take place at the interface where both monomers meet. The polymerization is initiated by an interfacially active azo initiator. The authors could show that the water soluble dye Rhodamine B can be encapsulated in the inverse miniemulsion process and released from the capsules [182]. 

Copolymers are usually prepared by copolymerizing the two monomers. Different concentration (feed) ratios of the monomers are used to vary the composition of the resulting copolymer. (See also Sect. 2.4 and the citations thereia) These efforts have mainly been directed at improving the mechanical properties and processability as well as altering the conductivity and optical and other properties of the polymeric material for special practical purposes. 

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