Abstract
Cyclic oligomers [(CH 3) 2Si(CH 2) 4(CH 3) 2SiO] x with x=2−10 were found to be present in poly(2,2,7,7-tetramethyl-1-oxa-2,7-disilacycloheptane) samples prepared by monomerpolymer equilibrations using concentrated sulphuric acid as catalyst. The molar cyclization equilibrium constants, K x , for cyclics [(CH 3) 2Si(CH 2) 4(CH 3) 2SiO] x with x=1−6 were measured for undiluted equilibrates at 298, 333, 383 and 423K. Apart from K 1 for the monomer, the K x values were found to be independent of the temperature of equilibration. Experimental molar cyclization equilibrium constants K x for the cyclics with x⩾3 were close to theoretical values calculated by the Jacobson-Stockmayer theory, using a rotational isomeric state model to describe the statistical conformations of chains in the undiluted equilibrates and assuming that the chains obey Gaussian statistics.
Published Version
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