The polymerization of 1,3‐dioxolane. I. Structure of the polymer and thermodynamics of its formation

We have polymerized 1,3‐dioxolane in our adiabatic reaction calorimeter under vacuum in methylene dichloride with anhydrous perchloric acid as catalyst. We confirm previous findings that the polymer consists of a regularly alternating sequence of “formaldehyde” and “ethylene oxide” units. The polymer prepared in the presence of water has terminal OH groups, but that prepared under strictly anhydrous conditions has no detectable end groups, and we conclude that it is cyclic; we suggest a reaction mechanism involving ring expansion. The polymerization is an equilibrium involving polymer and monomer only, without side reactions. For a one molar solution the ceiling temperature is +1°C., Δ S ss ° = −18.6 ± 1.2 cal. deg. −1 mole −1 : Δ H ss ° = −5.2 ± 0.2 kcal./mole, direct calorimetric measurements for polymerization and depolymerization, and calculation from d log K / dT giving identical results.