Relationship between the Molecular Structure and the Behavior of σ-Conjugated Polymers

摘要

σ-Conjugated polymers, i.e. polysilanes, polygermanes, and polystannanes with various structures were synthesized and relationship between the molecular structure and the behavior of σ-conjugated system was studied. Dialkyl-substituted linear polymers showed well known discontinuous thermochromism. Transition temperature of the thermochromism was controlled by means of copolymerization of two monomers with different alkyl chain length. Reduction of trichloromonomers gave polymers with σ-conjugated network structures. They showed completely different characteristics compared to the linear polymers. For example, they showed no absorption peaks but their absorption tailed into the visible region. Introduction of branching structures into linear σ-conjugated polymers have been achieved by adding small amount of trichloro-monomers into dichloro-monomers. The movement of linear chain seemed to be restricted by the branching structures. The restriction of the linear chains was more clearly observed in linear σ-conjugated polymers with alkyl chain bridges. As the amount of bridging structures increased, the absorption peak of the polymer shifted to the shorter wavelength, the transition of the well known linear chains at low temperatures became more incomplete, and linear σ-conjugated chains were observed to be enforced to take conformations with less conjugation.