The photochemical polymerization of methyl methacrylate vapour

Abstract

It is rather a remarkable fact th a t although the study of polymerization reactions has increased enormously within the past few years, gas-phase polymerization has received scant attention. By performing such experiments in the gas phase all the exact technique of gas kinetics is at once available to unravel the complex sequence of collision types which make up a polymeric reaction. Once the essential features of the reaction are discovered, it is in many cases a comparatively simple matter to control these over wide limits. It has long been recognized that polymerization processes are chain reactions. If the reaction is initiated thermally, then the observed kinetics of the overall reaction may become rather complicated, so that it is difficult to calculate the absolute velocities of the reactions comprising the whole process. As in ordinary chain reactions, this difficulty can be overcome by adopting photochemical methods of controlling the initiation reaction. Having started the growth of the polymer the velocity of growth is then dependent primarily on the inherent properties of the molecule but may be modified by altering gas pressure and temperature. The termination reaction may be one of a number of types and hence control may or may not be possible. In certain reactions control can often be exercised in one direction, namely, in limiting the growth of the polymer by the introduction of specific inhibitors.