Potential-programmed electropolymerization

We develop the potential-programmed electropolymerization method for modulating the composition of conducting polymer composite thin films to the depth direction. In this study, nm-order compositional control of composite thin films of conducing polymer, the... 

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]. 

Potential-Programmed Electropolymerization (PPEP). This technique allows compositional modulation over distances of the order of 100 A. Mesoscopic layered structures with high lateral quality are produced by the PPEP method. An improvement of the flatness and uniformity of the layered structure is achieved by careful choice of an appropriate working electrode (silicon single-crystal wafer), monomer (pyrrole/bithiophene or pyrrole/3-methyl-thiophene) and solvent (propylene carbonate). The PPEP method can produce materials having desirable properties tailored by the quantum size effect [703-705]. 

T. lyoda, H, Toyoda, M. Fujitsuka, R. Nakahara, H. Tsuchiya. K. Honda, and T. Shimidzu, The 100-A-order depth profile control of polypyrrole-poly(3-methylthiophene) composite thin film by potential-programmed electropolymerization, J. Phys. Chem. 95 5215 (1991). 

Fig. 1 Ultrathin conducting polymer heterolayers by the potential sweep programmed electropolymerization of pyrrole (25mM) and 3-methylthiophene (50mM) in CH3CN containing lOOmM LiC104. Potential sweep programs and TEM pictures of their cross sections.

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