DIBLOCK COPOLYMERS, TRIBLOCK COPOLYMERS AND MODEL NETWORKS SYNTHESIZED BY SEQUENTIAL ANIONIC-POLYMERIZATION OF STYRENE AND 2,3-EPOXYPROPYL METHACRYLATE

Diblock and triblock copolymers were synthesized, under standard condi tions, by sequential anionic polymerization of styrene and 2,3-epoxypr opyl methacrylate or glycidyl methacrylate (GMA). In both cases, suita ble initiators were selected. The 'living' carbanions originating from the polymerization of styrene are able to attack GMA. The reverse rea ction (attack of styrene monomer by poly (glycidyl methacrylate) anion s) cannot occur. Consequently, styrene was polymerized first, yielding well defined poly (styrene) 'precursors'. The high reactivity of poly (styryl) carbanions was reduced by the addition of 1,1-diphenylethyle ne. The polymer thus, fitted at chain end(s) with diphenylmethyl anion s, served as macroinitiator for the subsequent polymerization of GMA. The synthesis of poly (styrene)-b-poly (GMA) diblock copolymers were c arried out using sec-butyllithium as the monofunctional initiator, in the presence of lithium chloride. Potassium-naphthylide was chosen as the bifunctional initiator whenever a poly (GMA)-b-poly (styrene)-b-po ly (GMA) triblock copolymer is desired. The poly (styrene) 'precursors ' and the block copolymers were characterized by size exclusion chroma tography, proton nuclear magnetic resonance and analytical titration o f the oxirane functions. These methods allowed us to determine the wei ght-and number-average molar mass of each block, the molar mass distri bution and the copolymer composition. The above 'living' bifunctional species were used as polymeric 'precursors', leading to the formation of model networks by an endlinking process, upon addition of a bisunsa turated monomer, such as ethylene dimethacrylate. (C) 1998 Published b y Elsevier Science Ltd. All rights reserved.