Kinetik und mechanismus der kationischen polymerisation von trioxan: Ein katalysierter kristallwachstumsprozeß

Abstract

Abstract The kinetics of the cationic polymerization of trioxane initiated by perchloric acid is analyzed as a simultaneous polymerization and crystallization process. The details of the crystal growth such as nucleation, distribution of crystal sizes, development of growth spirals etc. have been investigated by electron and light microscopic techniques. The mechanism of polymerization can be understood as a catalyzed crystal growth. A well defined population of crystals is formed during a nucleation event at the start of the polymerization. An adsorption equilibrium with regard to the catalyst is then established in the presence of the rather large surface area of the growing polymer crystals. Assuming a Langmuir‐type adsorption behaviour, the observed growth features (growth spirals) can be quantitatively interpreted on the basis of the BCF‐theory of crystal growth. The current concepts on the molecular mechanism of cationic polymerization of cyclic formals have been modified such as to take into account that each chemical step of the polymerization is a building step of the crystal too.