Syntheses of poly[(dimethyl)-co-(4,7,10,13-tetraoxatetradecylmethylsilanes)]. An evaluation of the use of C8K versus Na in the preparation of polysilanes

Full Paper: To evaluate the use of C8K versus Na as the reducing agent in t he preparation of polysilanes, the homopolymers poly(4,7,10,13-tetraoxatetr adecylmethyl-silanes) 1 and poly(dimethylsilane) 5 as well as the copolymer s poly[(dimethyl)-co-(4,7,10,13-tetraoxatetradecyl-methylsilane)] 2-4 were synthesized from 4,7,10,13-tetraoxatetradecylmethyldichlorosilane (6) and/o r dimethyldichlorosilane (7). C8K in comparison to Na gave an increased yie lds and enhanced purity, when used with polar monomers, such as 6, that per sumably intercalate not graphite. In the presence of increasing amounts of apolar 7 both a decrease in yield as well as purity is observed in the C8K based copolymerizations. In contrast, the type of monomer does not affect t he results of the Na based copolymerizations. Whereas at ambient temperatur es the introduction of dimethylsiline units in 2-4, causes minor changes in the polysilane optical properties, as compared to 1, at low temperatures d ifferences are discernible both in solution and the solid state (thin film) in the case of 4(Na). Apparently, the incorporated dimethylsilane moieties reduce the mean free energy of defect formulation E, i.e. at these low tem peratures the silicon backbone adopts a more extended confirmation as refle cted by the occurrence of an additional "abrupt" transition.