Copolymers alkyl polysilane

The observation that more soluble, less crystalline materials containing larger alkyl substituents (6) or aromatic groups (7,8) could be synthesized suggested additional applications for polysilane derivatives. In this regard, West and co-workers have reported that a soluble copolymer 1 produced by the... 

Semi-empirical understanding of PM-transition characteristics and main chain stiffness of rod-like polysilanes thus leads to the new idea that minute structural modification of the achiral and chiral alkyl side groups could critically modify the transition characteristics, as indeed demonstrated in a series of 16-based copolymers, poly ((S)-3,7-dimethyloctyl-3-methylbutylsilane)-co-((S)-3,7-dimethyloctyl-2-methylpropylsilane) (22) and poly ((S)-3,7-di-methyloctyl-3-methylbutylsilane)-co-((P)-3,7-dimethyloctyl-2-methylpropyl-silane) (23) (see Scheme 5). 

Typically, polygermane-polysilane copolymers have similar UV properties as compared with polygermane and polysilane homopolymers . The thermochromic behaviour of the copolymers depends on their monomer-to-monomer ratios in the polymer chain and on the identity of the alkyl substituents. In principle, the fine tuning of the absorption maximum can be achieved by a controlled copolymerization. Unfortunately, the copolymers reported so far often have relatively low molecular weights, which in turn results in the kmax values being even lower than those observed for high molecular weight polysilanes (Table 4). 

Photoablation of Copolymers, Other workers have also investigated the phenomenon of polysilane self-development. Zeigler and co-workers (13) have studied the self-development of a number of polysilane homo- and copolymers and found that self-development eflSciencies increase with the size of substituents. They also suggested that the material removal process for alkyl-substituted poly silanes at low fluences (<50 mj/cm per pulse) is predominantly photochemical rather than photothermal. By using a 1 1 copolymer, poly(methyl-n-propylsilane-co-isopropylmethylsilane), images were generated by excimer laser exposure at 248 nm. 

Polysilane is usually synthesized from dichlorosilane (RiR2SiCl2) by dechlorination condensation reaction with sodium. Various types of alkyl or aryl groups can be added to (the changing monomers) main -Si-Si- chain. Polysi-lastyrene is a representative copolymer synthesized by this method of mixing the monomers [7] dimethyldichlorosilane and phenylmethyldichlorosilane [8]. 

In order to produce polysilanes with controlled optical properties, the substituents have to be picked up properly thus, poly(alkyl(methoxyphenyl)silane) homo and copolymers are reported by Nakashima and Fujiki [40], who found that poly(alkyl(alkoxyphenyl)silane) with methyl, ethyl and n-hexyl moieties showed a typical absorption peak around 340-360 nm atUibuted to the delocalized cr-conjugation. 

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