PREPARATION OF POLYSTYRENE POLY(ETHYLENE GLYCOL) DIBLOCK COPOLYMER BYLIVING FREE-RADICAL POLYMERIZATION

Amphiphilic diblock copolymer containing segments of polystyrene and m onomethoxypoly(ethylene glycol) (PS-b-PEG) was synthesised by a novel method. Initially, the adduct (BZ-TEMPO) obtained by reacting benzoyl peroxide, styrene, and 2,2,6,6-tetramethyl-piperidinyl-1-oxy (TEMPO) w as isolated, characterised and hydrolysed. Conditions for the synthesi s and hydrolysis of BZ-TEMPO were investigated and the hydrolysed prod uct (HO-TEMPO) containing a primary hydroxyl group has been isolated i n improved yield. The hydroxyl group of HO-TEMPO was coupled with tosy lated PEG to yield the macroinitiator PEG terminated with a TEMPO unit (MPEG-TEMPO), which was further used to prepare the diblock copolymer PS-b-PEG by 'living' free radical polymerisation of styrene. The prod uct was purified and identified by H-1 n.m.r. and GPC. However, large amounts of homopolystyrene was also formed by simultaneous thermal ini tiation and polymerisation. (C) 1997 Elsevier Science Ltd.