Solid-state NMR and the thermal polymerization of 2,4-hexadiyne-1,6-diol bis-(p-toluenesulfonate)

The solid-state thermal polymerization of crystalline 2,4-hexadiyne-1,6-diol bis-(p-toluenesulfonate) (PTS) was investigated by solid-state 13C NMR, the first application of this technique to such a process. The kinetics of the thermal process was examined at temperatures of 40.5, 51.0, and 59.5 °C, with a magic angle spinning (MAS) rate of 5 kHz. The first-order rate constants associated with the induction (k0) and autocatalytic (kmax) periods were calculated by monitoring signal intensities (conversion) throughout the course of the thermal polymerization. While estimations of the activation energy (Ea∼20kcal/mol) from the NMR experiments are similar to values obtained by other analytical techniques, estimations of the autocatalytic effect (kmax/k0∼22) were significantly lower. Likely causes for the unusually small autocatalytic effect are discussed.