Electrochemical copolymerization

Thiols also provide good binding points toward a metal surface such as gold for the synthesis of polymer brushes, etc. A protected initiator (FI-24) gave thiol-functionalized PMMA with Ni-2 as a catalyst.334 The thiophene-capped PMMA from FI-25 can be employed as a macromonomer for electrochemical copolymerization with pyrrole,335 as with those from FI-20 (see above). 

There are several examples of graft copolymers obtained from macromonomer prepared by the metal-catalyzed polymerizations. Conventional radical copolymerization of TV-vinylpyrrolidione and vinyl acetate-capped polystyrene synthesized with copper catalysts gave graft copolymers G-2, which formed hydrogels in water.337 Electrochemical copolymerization of pyrrole and thiophene-capped poly(MMA) affords G-3.335... 

Xiang, C., Xie, Q., Hu, J., and Yao, S. (2006). Studies on electrochemical copolymerization of aniline with o-phenylenediamine and degradation of the resultant copolymers via electrochemical quartz crystal microbalance and scanning electrochemical microscope. Synthetic Metals. 156(5-6), 444-453. 

Figure 2 shows the band structures of several homopolymers and pyrrole-bithiophene copolymers estimated by electrochemical and optical methods as examples. A combination of these homopolymers and/or copolymers implies various kinds of superlattice structures. The electrochemical preparation of both homopolymer multiheterolayers and/or copolymer multiheterolayers results in a superlattices. The electrochemical copolymerization method as used to prepare heterolayers was easier than in the homopolymer heterolayers. The copolymer multi heterolayers are prepared by simply changing the applied electrode potential. On the contrary, the latter needs exchange of the mother solutions. The present electrocopolymerization method which makes compositionally modulated copolymer heterolayers possible is considered to be one of the most fascinating methods to fabricate organic superlattices. 

Electroactive random copolymer was produced by the electrochemical copolymerization of pyrrole and aniline in acetonitrile in the presence of an organic acid and supporting electrolyte [52]. For the pyrrole and aniline system, changes in the order of coating and synthesis medium affected the structure and properties of the resultant samples, as shown in Table 8.3 [53]. It was also reported that there was a clear dependency of polymerization rate and yield, solubility, ability to form films, molecular weight, thermal stability, and conductivity of the copolymers on the pyrrole/ethylaniline comonomer ratio [54]. 

Reynolds, J.R., R.A. Roropatic, and R.L. Toyooka. 1987. Electrochemical copolymerization of pyrrole with N-substituted pyrroles. Effect of composition on electrical conductivity. Macromolecules 20 958. 

Li, X., M. Lu, and H. LL 2002. Electrochemical copolymerization of pyrrole and thiophene nanofibrils using template-synthesis method. J Appl Polym Sci 86 2403. 

Wei, Y., R. Hariharan, and S.A. Patel. 1990. Chemical and electrochemical copolymerization of aniline with alkyl ring-substituted anilines. Macromolecules 23 (3) 758. 

As an illustrative example, the cyclic voltammograms obtained during the electrochemical copolymerization of aniline (ANI) and o-aminophenol (OAP) are shown inFig. 4.12 [135]. 

The method of electrochemical copolymerization has many advantages including ... 

H. Q. Tang, A. Kitani, S. Ito, Electrochemical copolymerization of aniline and aniline-2,5-disulfonic acid, Electrochimica Acta 1997, 42, 3421. 

C. H. Yang, T. C. Wen, Polyaniline derivative with external and internal doping via electrochemical copolymerization of aniline and 2,5-diaminobenzene-sulfonic acid on Ir02-coated titanium electrode, of the Electrochemical Society 1994,141, 2624. 

Y. Sahin, K. Pekmez, A. Yildiz, Electrochemical copolymerization of aniline and anilinesulfonic acids in FSOsH/acetonitrile solution, of Applied Polymer Science 2002, 85, 1227. 

The electrochemical copolymerization of pyrrole and thiophene is difficult due to the large differences in the oxidation potentials of the monomers. According to Tourillon and Gamier [192], the electropolymerization of pyrrole occurs at around 0.6 V (versus SCE), and that of thiophene occurs around 1.65 V (versus SCE). Inganas et al. [201] attempted to refine the electronic properties of conducting polymers by varying the molecular composition of the polymers. Terthiophene... 

Thiophene was electrochemically copolymerized with pyrrole [125]. The production of copolymers... 

Later, another study [10] demonstrated that electrochemical copolymerization of thiophene (0.1 M) with pyrrole (2.0 x 10 M) in acetonitrile containing 0.1 M LiC104 as the supporting electrolyte occurs. The strategy employed here was to oxidize pyrrole under diffusion-limiting conditions at potentials where... 

In addition to the routine characterization of these copolymers with UV-visible, near IR and FTIR spectroscopy, XPS, elemental analysis and four-point probe conductivity measurements, Mossbauer [17] and photoluminescence (PL) [18,19] spectroscopy of the copolymer were used. When the thiophene content in the copolymer is higher than 50 mole%, there are three peaks at 2.0, 1.8 and 1.7 eV in the PL spectra of the copolymer. Below 50 mole%, the copolymer does not exhibit photoluminescence. Details of the fabrication of a type II conducting polymer heterolayer superlattice by the electrochemical copolymerization of pyrrole and bithiophene by the potential-programmed electropolymerization (PPEP) method are given in a recent review [19]. 

In the electrochemical copolymerization of thiophene and 3-thiopheneacetic acid, both solubility and molecular weight of the copolymer increase with increasing... 

However, there are only two papers [58,59] on the copolymerization with 3-MT. The random electrochemical copolymerization was studied by Sato [58,59], who observed that the visible and IR spectra of the neutral copolymers indicated that the copolymerization is random and that 3-MT reacted faster than 3-DDT. With increasing concentration of 3-MT units in the copolymer, conductivity increased and the solubility of the neutral copolymers decreased. Proton NMR spectra of the copolymer show two chemical shifts for the a(l)- and j8(2)-methylene protons of the monomeric units of 3-DDT as well as for the methyl protons of the monomeric imits of 3-MT. What is more, the intensity of the doublet peaks suggests that the DP of PDDT is about 170 [59]. The structure of the repeating unit of the copolymers is shown in Figure 11.14. 

Pyrrole electrochemically copolymerizes with 2-phe-nylthiophene in acetonitrile containing lithium perchlorate, but only when the concentration of the thiophene is very high [100]. Copolymer composition depends on deposition potential and monomer ratio in the feed. IR and UV-vis spectroscopy was used to characterize the copolymers. 

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