Structural studies of polysiloxanes: crystal structure and fold conformation of poly(tetramethyl-p-silphenylene siloxane)

A study of the morphology of uniaxially drawn spherulites of TMPS-DMS block copolymers with TMPS contents ranging from 90 to 30 wt % was made especially by electron and optical microscopy. For the entire range of polymer compositions, the copolymers, like the TMPS homopolymer, form negatively birefringent spherulites when crystallized from solution, or from the supercooled melt. A banded spherulitic morphology is observed. The deformability of copolymer spherulites increases as the DMS amorphous component increases. The DMS component coexists with, but is physically excluded from the ordered TMPS “crystalline” phase. In samples having the higher TMPS compositions, deformation occurs through crack formation, mechanical slip, tilting and/or twisting of the lamellae that help comprise the spherulites. At high DMS contents this “soft” component is undoubtedly responsible for the flexible character of these copolymers. Sample clarity also increases with DMS content as the crystallinity decreases.

Deformation behavior of tetramethyl-p-silphenylenesiloxane (TMPS)-dimethylsiloxane (DMS) block copolymer spherulitic films

The previously unknown bromomethyl- and iodomethylacetoxysilanes of general formula (CH3)3−nXCH2-Si(OCOCH3)n (X = Br, I, n = 1-3) were synthesized by reacting the appropriate chloromethylacetoxysilanes with LiBr, NaBr, or NaI in refluxing anhydrous acetonitrile or acetone.

Bromomethyl- and iodomethylacetoxysilanes

In recent years there have been many investigations in the field of organosilicon compounds containing halogen-substituted organic groups. These investigations offer prospects of the use of these compounds in the synthesis of polyorganosiloxanes. The extensive data on methods of synthesis of halogen derivatives of alkyl(or aryl)halogenosilanes and tetrasubstituted silanes, their properties, and use are scattered in many periodicals. Monographs and review articles have so far examined only isolated aspects of the chemistry of organosilicon compounds. This has stimulated us to survey the accumulated experimental results, the analysis of which even now allows definite regularities to be found in the occurrence of certain reactions and processes in the synthesis and conversions of halogen derivatives of organosilicon compounds. There is a bibliography of 677 references.

https://iopscience.iop.org/article/10.1070/RC1969v038n03ABEH001737/pdf

K A Andrianov

Papers

Halogen Derivatives of Alkyl(or aryl)halogenosilanes and Tetrasubstituted Silanes