Glass transition of the antiferroelectric hexatic smectic phase is reported for the 3F5HPhH6 compound. The relationship between the cold crystallization kinetics and the molecular dynamics is determined.

A two-sublattice compressible pseudospin model has been constructed to describe the behaviour of the spontaneous polarisation of PMACB in the temperature region comprising the ferroelectric phase transition ( T = 307 K) and the isomorphous anomaly ( T = 180K).Astrongcouplingofpseudospinswitha"pancake"strain-(2~~~ -E , I -E 2 2 ) / 3 resulting from the comparison of the model with the experimental spontaneous polarisation agrees with the existing data on the dielectric susceptibility, and on the specific heat. The ferroelectric phase transition then turns out to be close to a tricritical point. The numerical values of the parameters of the model show how the ferroelastic phase transition (T= 260K) can occur in this crystal without any discernible effect on the specific heat and on the dielectric susceptibility.

No abstract

High-resolution (ΔE/E ∼ 2−3%) incoherent inelastic neutron scattering spectra of polyisobutylene and cis-1,4-polyisoprene have been obtained on the TFXA spectrometer at the ISIS pulsed neutron scattering facility. The observed bands are assigned with reference to available infrared and Raman data, and the differences observed are discussed. Particular emphasis is placed on the methyl group torsions which are not observable with the optical techniques. These bands are significantly broadened compared to the instrumental resolution, and this is attributed to a Gaussian distribution of local environment potentials for the methyl group, in agreement with present theoretical models. For polyisoprene, this assignment is confirmed by independent molecular dynamics simulations.

New chalcopyrite quaternary compound CuAlxIn1-xSe2 (0