Solventless bulk copolymerization of 1,3,5-trioxane (TOX) with 1,3-dioxolane, 100 g each, was initiated with CF3SO3H, a nonoxidative superacid, dissolved in CH3NO2 or in n-butyl acetate (AcOBu) and, for comparison, with a BF3 complex; after the reaction ceased, aq. NH3 was added as deactivator With 0.5 ppm (based on TOX) of triflic acid in AcOBu vs. 25 ppm of the BF3 complex, induction took 4.9 vs. 10.9 s, and the residual TOX and the unstable fraction (thermally unstable semiacetal end-groups) were comparably high, 4.4 vs. 3.8% and 4.9 vs. 5.50%, resp. With CH3NO2 as medium, polytrioxane was yellow. In AcOBu, Mid acid was as effective and polytrioxane was white. When used as M regulator, dibutoxymethane gave rise to a higher MFR and affected chain termination and formation of stable end-groups, but the reaction was less rapid (< 120&DEG;C) and less polytrioxane was degraded. The residual initiator had to be deactivated, otherwise the unstable fraction was tripled. Although comparable with those of a standard polytrioxane, the property data were considered not satisfying and work is continued toward a more effective initiating system.