Synthesis of novel methacrylate-containing polymers by anionic polymerization

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1985
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Virginia Polytechnic Institute and State University
Abstract

The advent of anionic "living" polymerization in the late 1950’s lead to developments in synthetic control not yet approached by other polymerization mechanisms. Parameters such as molecular weight, molecular weight distribution, stereochemistry, chain end functional groups, polymer architecture and sequence distribution may ideally be controlled with anionic polymerization.

The vast majority of anionic syntheses have dealt with the "hydrocarbon" monomers-styrene and its derivitives, butadiene, and isoprene. This attention has been due principally to these monomer's ability to polymerize in a "living" (non-terminating or transferring) fashion over a wide range of conditions. Alkyl methacrylate monomers have received very sparce synthetic attention, however. This is presumably due to the difficulty in defining non-terminating polymerization conditions and, more importantly, the inability to arrive at anionic polymerization—grade monomers (i.e., monomers that are free from terminating impurities such as alcohols).

A method has been developed which provides ultra-pure alkyl methacrylate monomers for anionic synthesis. This method takes advantage of the chemistry of trialkyl aluminum compounds - their reactivity with alcohols and moisture, and their complex formation with methacrylic esters which facilitates titration of impurities.

These anionic polymerization-grade monomers have lead to the synthesis of controlled molecular weight methacrylate polymers up to molecular weights of 105 g/mole, clean all-acrylic block copolymer systems with highly controllable phase separating properties, and styrene-methacrylate block copolymer systems which also serve as model systems for the study of phase separation of glass—glass systems. The methacrylate unit has also been controllably incorporated into copolymer systems (block copolymers) to serve as a "pre-ionic" functionality. Hydrolysis of the ester group leads to ionomers of controlled structure. These systems have properties quite different from more conventional "random" ionomers, e.g., highly extended rubbery plateau behavior and no change in Tg with ion content.

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