INFLUENCE OF PRESSURE ON THE FERROELECTRIC PHASE-TRANSITION IN A SYMMETRICAL POLYMERIZABLE DIACETYLENE CRYSTAL DNP

DNP is a symmetrical disubstituted polymerizable diacetylene R-C=C-C=C -R where R is CH2-O-phi-(NO2)(2). The monomer crystal of DNP undergoes a ferroelectric phase transition at low temperature; it disappears in fully polymerized DNP crystal because polymerization changes the diac etylene backbone conformation. We show that hydrostatic isotropic pres sure also stabilizes the ferroelectric phase in the DNP monomer crysta l by enhancing van der Waals interactions between side groups.