Kinetic study of alpha,omega-dihydroxy polydimethylsiloxane condensation in aqueous emulsion

The polycondensation of alpha,omega-dihydroxy poly(dimethylsiloxane) (PDMS) was investigated in a cationic emulsion process, using benzyldimethyldodec ylammonium hydroxide (BDDOH) as an inisurf. Studying the condensation react ion without competing redistribution and polymerization reactions remains d ifficult. A comparative study of the variation of (M) over bar(w) and (M) o ver bar(n) with conversion shows that the broadening of the molecular weigh t distribution is due to the short chains formed by polymerization of octam ethylcyclo-tetrasiloxane (D-4), which is produced from back-biting reaction s. Kinetic apparent constants were also determined.