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Latices of polyvinyl acetate polymerized under the influence of gamma-rays have been used to initiate the polymerisation of methyl methacrylate. Extensive grafting occurred. If the conditions of preparation were suitable, discrete fractions of graft copolymer could be isolated. The structure of these graft copolymers has been discussed from the point of view of available rate constants for chain transfer of polymethyl methacrylate radicals.In systems where styrene is used in the second stage, little or no grafting could be detectedthe main product being pure polystyrene of high molecular weight.

The kinetics and mechanisms of emulsion polymerisations initiated by gamma-irradiation were investigated. Styrene and methyl methacrylate emulsions polymerised either by direct irradiation or by polyvinyl acetate latices, prepared by irradiation, conformed to a SMITH-EWART Case I1 mechanism. Vinyl acetate emulsions polymerised more slowly than predicted by the SMITH-EWART theory and were probably retarded by side reactions. ZUSAMMENFASSUNG:Kinetik und Mechanismus von durch Gamma-Strahlen angeregten Emulsionpolymerisationen wurden untersucht. Emulsionen von Styrol oder von Methylmethacrylat, die entweder durch direkte Bestrahlung oder durch Bestrahlung praparierter Polyvinylacetat-Latices polymerisiert wurden, richten sich nach einem SMITH-EwART-Mechanismus (Fall 11). Emulsionen von Vinylacetat polymerisierten langsamer, als die SMITH-EWART-Theorie vorhersagt, und wurden in ihrer Geschwindigkeit wahrscheinlich durch Nebenreaktionen verlangsamt.