Diblock copolymers, triblock copolymers andmodel networks synthesized by sequential anionic polymerization of styrene and 2,3-epoxypropyl methacrylate

Abstract

Diblock and triblock copolymers were synthesized, under standard conditions, by sequential anionicpolymerization of styrene and 2,3-epoxypropyl methacrylate or glycidyl methacrylate (GMA). In both cases, suitable initiators were selected. The ‘living’ carbanions originating from the polymerization of styrene are able to attack GMA. The reverse reaction (attack of styrene monomer by poly (glycidyl methacrylate) anions) 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-diphenylethylene. The polymer thus, fitted at chain end(s) with diphenylmethyl anions, served as macroinitiator for the subsequent polymerization of GMA. The synthesis of poly (styrene)-b-poly (GMA) diblock copolymers were carried 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-poly (GMA) triblock copolymer is desired. The poly (styrene) ‘precursors’ and the block copolymers were characterized by size exclusion chromatography, proton nuclear magnetic resonance and analytical titration of the oxirane functions. These methods allowed us to determine the weight- and number-average molar mass of each block, the molar mass distribution 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 bisunsaturated monomer, such as ethylene dimethacrylate.