Talha Jazouli, D. Reyx, M. Thomas
Dec 1, 1989
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0
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Journal
Macromolecular Chemistry and Physics
Abstract
The reaction of acetic, benzoic and methacrylic acids with 3-chloromethylheptamethyltrisiloxane and 3,5-bis(chloromethyl)octamethyltetrasiloxane in toluene in the presence of triethylamine was studied. Beside the expected transformation of oxy(chloromethyl)methylsilanediyle (A) units into oxy(acyloxymethyl)methylsilanediyle (C) units, redistributions of A, C and trimethylsilyl/oxytrimethylsilyl (M) were observed. The conversion versus time curves of distribution of the former oligomers (mole fractions of trisiloxanes: F1 = mM-X-M = mM-A-M + mM-C-M and tetrasiloxanes: F2 = mM-X-X-M = mM-A-A-M + mM-A-C-M + mM-C-C-M) were followed. The reaction rates were not only controlled by the acid used but also by the starting oligosiloxane (trisiloxane or tetrasiloxane). The distributions of the homogeneous and heterogeneous oligomers seem to result from controlled combinations of A, C and M according to orientations of cleavages and to relative affinities of RCOOH/NEt3 towards various siloxanes. For the total conversions the mole fractions F1 and F2 fit with those calculated by a law based on a hazard combination of C and M. This result may be explained by the compensation of electronic and steric factors.