Novel synthesis of triblock PDMS-PS-PDMS copolymers

Benzyl 6-(2'-pentamethyldisiloxanyl ethyl)-ortho-tolyl ketone (I) was prepa red by a ruthenium-catalyzed Mural reaction of benzyl ortho-tolyl ketone wi th vinyl pentamethyldisiloxane. The reaction of I with a mixture of styrene and a catalytic amount of picoline Cu(II) acetate yielded the telechelic p olystyrene alpha,omega-bis(2-pentamethyl-disiloxanyl ethyl)polystyrene (III ). The acid-catalyzed equilibration polymerization of octamethylcyclotetras iloxane into the Si-O-Si bonds of telechelic III yielded the polydimethylsi loxane-polystyrene-polydimethylsiloxane triblock soft-hard-soft copolymer. The molecular weights of the copolymers were studied by H-1 NMR end-group a nalysis and gel permeation chromatography. The thermal properties and morph ology of TV were examined by differential scanning calorimetry and transmis sion electron microscopy (TEM). (C) 2000 John Wiley & Sons, Inc.