CHARACTERIZATION OF THE STRUCTURES AND PROPERTIES OF POLY(DIMETHYLSILYLENE-CO-DI-N-HEXYLSILYLENE)

In this report we describe the structures and properties of poly(dimethylsilylene-co-di-n-hexylsilylene) (PM-co-HS), as determined by solution- and solid-state NMR, X-ray diffraction, DSC, and UV spectroscopy. A comparison is made between the structures and properties of the copolymer and those of the homopolymers, poly(dimethylsilylene) (PDMS) and poly(di-n-hexylsilylene) (PDHS), formed from each of the comonomers. While the two homopolymers adopt the same chain conformation in the solid state, they differ significantly in their absorption characteristics and in the nature of their solid-state transitions. At room temperature PM-co-HS is found to be mostly disordered with a small amount of a well-ordered crystalline phase in which the silicon backbone adopts an all-trans conformational arrangement as is observed for the PDHS homopolymer. The copolymer does not contain any ordered region similar to that of the PDMS homopolymer. Upon cooling of PM-co-HS, there is a slight increase in the PDHS-like structure, and between -10 and -20-degrees-C the conformationally disordered phase partly crystallizes into a trans-like structure with a much larger intersilicon-backbone spacing than either PDMS or PDHS. The absorption characteristics of the copolymer and PDHS are similar, and, upon heating above 42-degrees-C, the copolymer exhibits the same solid-state transition observed in PDHS.