New Phases in the Ferroelectric Liquid Crystal MHPOBC Studied by Differential Scanning Calorimetry

Abstract

This paper demonstrates that powerful laser radiation causes changes in the absorbance spectra of epoxy resin, polyethylene and polysulfone. Thin polymer films were located between IR AgBrCl optical fibres and exposed to the radiation of a CO 2 laser. The output of the laser source was varied in the range 0-8.5 W. The absorbance spectra were recorded using a Fourier transform infrared (FTIR) spectrophotometer. It was revealed that characteristic polymer absorbance peaks decay under exposure to the powerful IR light. The apparent dependence of peak magnitude on IR radiation power has been established. We showed that the phenomenon of the absorbance peak disappearances associated with the polymers-thermoplastic (including an engineering polymer such as polysulfone) and thermosetting-is of a threshold nature. The mathematical theory of the observed effect was derived. We propose that the effect under discussion is caused by the oxygen-free thermal action of IR radiation on the chemical structure of the polymer materials. The revealed effect could be effectively used to lower the losses in adhesive contacts of IR optical elements. The novelty of the proposed method lies in the fact that thermal treatment is localized strictly within the adhesive layer; optical elements to be contacted (fibres, lenses, etc) which are highly IR transparent do not experience the IR radiation, but the polymer adhesive is subjected to a temperature rise.

Polymorphism of Chiral Thioester Studied by Dielectric Spectroscopy

“…Since 1988 when antiferroelectric liquid crystals (AFLCs) were synthesized for the rst time [1], a lot of experimental [2] and theoretical [3] work has been done to study their dielectric and electrooptic properties. AFLCs have become a very interesting eld of research due to their practical applications in science and technology.…”

Electric-Field Induced Tricritical Points in Antiferroelectric Liquid Crystal

“…Among these, the SmC * α phase is unique. This phase was already found by DSC measurement in 1989 [1,2], but it took 10 years to clarify the structure by such sophisticated experiments as resonant X-ray diffraction [3] and differential optical reflectivity [4]. It was found that the SmC * α phase has a helical structure like the ferroelectric SmC * phase, but the pitch is very short.…”

Anomalous Dielectric Spectra of Ferro- and Ferrielectric Liquid Crystalline Phase in MHPNBC

“…The prototype of the AFLC compound was MHPOBC. It has been found that AFLC materials [2,3] exhibit not only the SmC * and SmC * A phases, but additionally there may appear three other sub-phases, which were much more dicult to be recognized. These sub-phases appear in a phase diagram when the optical purity of the sample increases.…”