The new material (R)-4-(5-acryloyloxy-4-methylpentanoyloxy)-4'-octanoyloxy biphenyl has been synthesised and characterised by POM, DSC, X-ray diffraction, IR dichroism, pyro- and piezoelectric techniques. The acrylate was shown to exhibit direct isotropic to smectic H* phase transition. The natural texture of the H* phase separates from the isotropic phase in the form of batonnets and rounded domains, the latter develop into a mosaic. The mesophase was found to align in a thin cell of KBr plates with homeotropic anchoring independently of the type of surface treatment. The molecular organisation in the H* phase strongly favours fast and efficient polymerisation when the initial orientation retains upon the reaction. The structure of the crystal and H* phases is mono-layer, the molecules pack monoclinic in antiparallel fashion with long-range polar ordering. The pyroelectric coefficient Was found to be very high in the crystal (gamma = 2.0 divided by 2.9 nC/cm(2).K) and H* (gamma = 2.9 divided by 1.0 nC/cm(2).K) phases. The direction of the macroscopic polarisation was not shown to be controlled by an external voltage. The piezocoefficient is stable and constant within the crystal phase (d(31) = 0.41 nC/N).
A New Chiral LC Acrylate that Exhibits Pyroelectricity
PACI, MASSIMO;MAGAGNINI, PIER LUIGI;
1999-01-01
Abstract
The new material (R)-4-(5-acryloyloxy-4-methylpentanoyloxy)-4'-octanoyloxy biphenyl has been synthesised and characterised by POM, DSC, X-ray diffraction, IR dichroism, pyro- and piezoelectric techniques. The acrylate was shown to exhibit direct isotropic to smectic H* phase transition. The natural texture of the H* phase separates from the isotropic phase in the form of batonnets and rounded domains, the latter develop into a mosaic. The mesophase was found to align in a thin cell of KBr plates with homeotropic anchoring independently of the type of surface treatment. The molecular organisation in the H* phase strongly favours fast and efficient polymerisation when the initial orientation retains upon the reaction. The structure of the crystal and H* phases is mono-layer, the molecules pack monoclinic in antiparallel fashion with long-range polar ordering. The pyroelectric coefficient Was found to be very high in the crystal (gamma = 2.0 divided by 2.9 nC/cm(2).K) and H* (gamma = 2.9 divided by 1.0 nC/cm(2).K) phases. The direction of the macroscopic polarisation was not shown to be controlled by an external voltage. The piezocoefficient is stable and constant within the crystal phase (d(31) = 0.41 nC/N).I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
