Synthesis of alpha,omega-dicarboxypropyl oligodimethylsiloxanes by ion-exchange resin catalyzed equilibration polymerization

A series of alpha,omega-dicarboxypropyl oligodimethylsiloxanes of predeterm ined molecular weights was synthesized from octamethylcyclotetrasiloxane, D -4, and 1,3-bis-(3-carboxypropyl)tetramethyldisiloxane (BCPTMDS) by a heter ogeneously catalyzed equilibration polymerization reaction using a macropor ous cation-exchange resin as an acidic catalyst. The structure of the obtai ned linear oligomers was verified by IR,H-1- and C-13-NMR spectroscopy, whi le their molecular weights were determined by H-1-MNR spectroscopy, vapor p ressure osmometry, functional group analysis and gel permeation chromatogra phy. It was shown that the expected target molecular weights, ranging betwe en 600 and 300, were achieved with a satisfactory accuracy. (C) 2000 Elsevi er Science BN. All rights reserved.