Mastication of rubber. VIII. Preparation of block polymers by mechanical shear of polymer–monomer systems

The mastication of polymers brought into a rubbery state by admixture with monomers causes polymerization of the monomer. The reaction shows dependence on rate of shearing, temperature, and monomer concentration expected for a mechanism of mechanical rupture of the polymer to free radicals which initiate polymerization. Fractional precipitation methods for separating block polymers of polymethyl methacrylatepolystyrene from the homopolymers are applied to the products after masticating both initial polymer‐monomer combinations. The products of reaction indicate that the block polymer does not contain many segments of each polymer. When the two polymers are present either as free or block polymers, the polymethyl methacrylate is preferentially ruptured to form initiation sites.