Synthesis, characterization and kinetic investigations of heterophase materials prepared using group transfer polymerization

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Virginia Polytechnic Institute and State University

The impact of multiphase polymeric materials has been enhanced by the preparation of well defined block and graft copolymers. Hence, there has been a growing emphasis on new synthetic methods for the preparation of blocks and grafts. Group Transfer Polymerization (GTP) is a relatively new synthetic method which provides a means to obtain poly(alkyl acrylate)s and poly(alkyl methacrylate)s via a "living" mechanism over a broad temperature range. The degree of control over molecular weight and molecular weight distribution rivals that afforded through living anionic techniques for the preparation of poly(alkyl methacrylate)s.

The objectives of this research were many fold. The first was to establish GTP as a routine synthetic tool for the preparation of poly(alkyl methacrylate)s in our laboratories. This involved utilizing a variety of initiators, catalysts and alkyl methacrylate monomers. Furthermore, kinetic studies of the GTP of MMA with a controlled temperature, "living" polymerization reactor and tetrabutylammonium benzoate as the selected catalyst were initiated. These investigations involved the determination of the reaction order with respect to initiator and catalyst concentrations. Also, the global energy of activation, under controlled reaction conditions, was elucidated.

To extend the synthetic utility of GTP, novel block and graft copolymers were synthesized. Transformation reactions and the macromonomer technique to interrelate different synthetic routes further extends the range of block and graft copolymers which can be prepared. Poly(dimethylsiloxane) (PDMS) macromers were prepared via the anionic ring opening polymerization of hexamethylcyclotrisiloxane, which is subsequently terminated with a chlorosilane derivative of allyl methacrylate. The macromonomer technique has been employed to synthesize poly(methyl— methacrylate)—g-poly(dimethylsiloxane) copolymers of controlled molecular weight and apparent narrow molecular weight distribution by GPC. Transformation of the methacrylate functional group on the PDMS provided a suitable macroinitiator for the GTP of methyl methacrylate, which leads to siloxane-b-methacrylate copolymers via a novel route.