Temperature-modulated calorimetry of hexacontane and oligomer fractions of poly(oxyethylene) and poly(oxytetramethylene)

The paraffin hexacontane, C60H122, and oligomeric fractions of poly(oxyethylene), POE, and poly(oxytetramethylene), POTM, of varying low molar masses were studied with temperature-modulated calorimetry. The analyses were by standard differential scanning calorimetry (DSC) and quasi-isothermal, temperature-modulated DSC, TMDSC. Small sample masses were examined with temperature amplitudes from 0.05 to 2.5 K, using periods of 60 s. The supercooling decreases with molar mass for all three types of samples. The melting varied between fully irreversible, reversing, and largely reversible. There are no major differences in supercooling between extended- and folded-chain crystals. Due to conformational contributions, all crystals increase their heat capacities within the melting range from the level set by the vibrational spectrum to that of the liquid.