Growth of polyoxymethylene crystals in the course of the polymerization of trioxane in solution

Abstract

AbstractIn order to pursue the possibility of the extended chain crystals of polymers formed in the course of polymerization, the cationic polymerization of trioxane in cyclohexane has been studied. The polymer, polyoxymethylene, was obtained in the form of a unique single crystal. From the morphological and physical studies of the resultant polymers as well as the kinetical studies of the polymerization, it has been revealed that long, needle‐like nuclei formed in the beginning of the polymerization grew into feather‐like platelets with twin habit. The degree of crystallinity of the nascent polymer was essentially 100% in terms of their densities. The molecular chains were fully extended and regularly aligned in the direction of the crystal growth. The growth of the crystal occurred as the polymerization proceeded. Thus it is considered that the crystal grows quite successively to the propagation of the chains through direct addition of the monomer molecules onto the reactive chain ends which are aligned two‐dimensionally on the growing surface of the crystal. The molecular length of the nascent polymer estimated from the solution viscosity, however, did not agree with the crystal dimensions measured in the direction of the molecular orientation, the former being rather small. The above results are explained in terms of the chain‐transfer reaction and the catalytic decomposition of the polymer chain.