Thermodynamics of polymerization of heterocyclic compounds: Part 6. The heat capacity, entropy, enthalpy and free energy of 1,3-dioxepan and poly-1,3-dioxepan

Abstract

An adiabatic vacuum calorimeter and a differential scanning calorimeter have been used to measure the heat capacities of 1,3-dioxepan and poly-1,3-dioxepan from 80°K to 360°K. An estimate has been made of heat capacity values below 80°K for both monomer and polymer. Entropy, enthalpy and free energy values have been derived and are listed at 10°K intervals for the monomer and 50% crystalline polymer. For 1,3-dioxepan the melting temperature and heat of fusion were found to be 197·60 ± 0·05°K and 96·78 ± 0·30Jg −1, respectively. For the poly-1,3-dioxepan the glass transition temperature, melting point and heat of fusion were found to be 189°K, 296 ± 1°K and 140·3 ± 2·8Jg −1, respectively. Estimates have been made of the heat capacities of 100% crystalline and completely amorphous poly-1,3-dioxepan. The increase in heat capacity of the amorphous polymer at the glass transistion temperature, 10·7J°K −1 mole bead −1, is in agreement with that predicted on the basis of the hole theory of melting. The entropy of polymerization ΔS 0 gc′ has been calculated as −181·5 ± 6·4J°K −1 mole −1.