Abrupt dissolution of polydiacetylenes

Polydiacetylenes, where R?? (CH₂)_3,4OCONHCH₂COO(CH₂)_1,3CH₃ dissolve almost instantaneously within a narrow range of temperature (ca. 3°C). The enthalpy of dissolution of these polymers is determined by differential scanning calorimetry to be 25–46kJ/mole of the repeat unit. The abruptness of dissolution is due to breaking of intramolecular H bonds, which appears to be a cooperative phenomenon. Supporting infrared evidence is cited.