Morphological effects on the bulk polymerization of trioxane in the solid state by γ-radiation

The solid-state polymerization by ..gamma..-radiation and postpolymerization of bulk samples of trioxane has been investigated. Different thermal treatment results in radically different initial morphologies of the melt-crystallized trioxane which in turn have a profound influence on the yield and morphology of the resulting poly(oxymethylene) (POM). The polymerization yield increases in the following series: melt-crystallized trioxane with an opaque (small grains) morphology, as-grown needles, trioxane with a quasi-transparent morphology, and finally thermally oriented crystals. Furthermore, little additional POM is formed during repeated polymerization cycles. The observation of an extensive nodulation of the polymer fibrils when the yield is high is consistent with a multiple-stage growth model for the solid-state polymerization of trioxane.