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

近十年来，聚硅烷衍生物作为具有电子半导体性、非线性光学性质、高空穴漂移迁移率等特点的基础高分子材料引起了人们的极大兴趣。聚硅烷衍生物的这些有趣的物理性质本质上归因于Si主链的sigma电子的离域。然而，很难说共轭体系扩展到整个硅骨架上，因此，普遍的共识是硅骨架被划分为几个共轭硅段。问题是决定分子间空穴输运现象的因素是什么？然后，高极化聚硅烷薄膜的电子和光学表征可以预测硅骨架的电子结构以及分子间和分子内的关系。本研究以聚（甲基苯基硅烷）：PMPS和聚（-苯乙基甲基硅烷）：pmβ -ph作为初始聚硅烷，氯甲基化的PMPS或pmβ -ph与（CH_3） _2C_nH_<2n+1>N之间形成盐，得到两亲性聚硅烷。氯阴离子由几种反阴离子交换而成，聚合物堆积达1000层。堆积LB薄膜的光谱学表现为其吸收光谱的压致变色位移。在两亲性聚合物的高密度激发下，极化和密集LB薄膜（400-500nm宽发射）和随机溶剂铸造薄膜（580-600nm更长的发射带）的发射光谱存在差异。这两个发射带分别对应于铵基与硅骨架形成的分子内激络合物和分子间激络合物。结果表明，两亲性聚硅烷LB膜的能量弛豫过程与非晶膜不同，分子间的能量转移可以忽略不计。

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.