THE FERROELECTRIC PHASE-TRANSITION OF THE DISUBSTITUTED DIACETYLENE 1,6-BIS(2,4-DINITROPHENOXY)-2,4-HEXADIYNE (DNP) - ANALYSIS BY HEAT-CAPACITY MEASUREMENTS

The ferroelectric phase transition of 1,6-bis(2,4-dinitrophenoxy)-2,4-hexadiyne (DNP) is characterized by specific heat measurements for monomer and thermally polymerized polymer single crystals. The data support a tricritical phase transition of monomer crystals, with the transition enthalpy clearly lower than that corresponding to an order-disorder transition. A lowering of the transition temperature and the transition enthalpy with increasing polymer content is observed, in agreement with the known dielectric data.