On the coagulation of polymer latices by freezing and thawing

The particle size characteristics of coagulates obtained by freezing and thawing emulsions of polymers which are hard and glassy at normal temperatures, particularly polystyrene and styrene copolymers, have been studied. It is shown that for a given polymer the particle size distribution is principally determined by the macrostructure of the frozen mass, such as the size of the ice crystals formed and the concentration of polymer in the initial emulsion. The effect of chemical structure of the polymer on the freezethaw coagulation process is discussed and from the results it is suggested that the usual concept of a second‐order (glass) transition is not applicable to very fine latex particles of rigid polymers. This may also explain the formation of continuous films from fine latices at temperatures below the transition temperature of the bulk polymer.