Molecular Structure Modification and Characterization of Langmuir-Blodgett Films made of Amphiphilic Polysilane through Ionizing Radiation

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Since the last decade, polysilane derivatives have been elicited great interest as fundamental polymer materials showing lelctronic semiconductivity, nonlinear optical property, high hole drift mobility, and so on. These interesting physical properties of polysilane derivatives are essentially attributed to the delocalization of sigma-electrons of the Si backbone. However, it is hardly to say that the conjugated system is extended over the entire silicon skeleton, therefore, it is common consensus that a silicon skeleton is divided into several conjugated silicon segments. The question is which determine the hole transport phenomenon in intermolecular or interesting hopping. Then, electronic and optical characterization of highly polarized polysilane films may predict the electronic structure of silicon skeleton and inter-and intra-molecular relation.In the present work, poly (methylphenylsilane) : PMPS and poly (beta-phenethylmethylsilane) : PMbeta-PhS employed as an initial polysilane, and amphiphilic polysilanes were obtained by the salt formation between chloromethylated PMPS or PMbeta-PhS and (CH_3) _2C_nH_<2n+1>N.Chlorine anion exchanged by several kinds of counter anions and the polymer piled up to 1000 layrs. Optical spectroscopy of these piled LB films represented piezochromic shifts in their absorption spectra. High dense excitation of these amphiphilic polymers showed a deference in emission spectra of polarized and dense LB films (400-500nm broad emission) and random solvent casted films (another longer emission band at 580-600nm). These two emission bands were assigned to intramolecular exciplex formation between ammonium groups and silicon skeleton and intermolecular one, respectively. It can be condluded that energy relaxation processes are different in LB films in comparison with amorphous films, intermolecular energy transfer can be neglected in LB films of amphiphilic polysilanes.