The synthesis of block polymers by use of polyazoesters

Abstract

A great number of radically polymerizable monomers and monomer mixtures can be combined to block polymers starting with a polyinitiator. The use of polyazoesters allows the synthesis of block polymers in a two step procedure. Polyazoesters are synthesized from AIBN and a diol according to Pinner. A fraction of the azo groups is decomposed in presence of a monomer. Thus, a prepolymer containing azo groups is formed. The decomposition of the residual azo groups in presence of a second monomer results in block polymers. The reaction is studied with styrene/methyl methacrylate as a model. Other examples given are S/MA, S/N-vinylprrolidone. The block polymers show phase separation with the typical structure of spheres, rods, and lamellae. The domain sizes were found to be 100–300 A. In both steps monomer mixtures can be used. Thus, each block may consist of a copolymer. Poly((styrene-co-butadiene)-block-(styrene-co-acrylonitrile)) is discussed as an example. Polyacrylamides containing azo groups are soluble in water and have surface activity. They can be used as emulsifying polyinitiators and allow emulsion polymerization without additional emulsifiers.