Naoyuki Koide

Thermal degradation and combustion process of liquid crystalline polyesters studied by directly coupled thermal analysis-mass spectrometry

Thermal degradation and combustion processes of commercial liquid crystalline polyesters (LCPs) were studied by directly coupled thermal analysis-mass spectrometry (TA-MS) under inert and quasi-air atmosphere. The first major degradation step of LCPs was the ester linkage rupture reaction. In the case of fully aromatic LCPs, this process was little influenced by 20% oxygen atmosphere. The main evolved gaseous products at this step were CO, CO2, H2O and phenol for fully aromatic LCP samples, in addition, aliphatic products for a semi-aromatic LCP sample. Evolution of CO2 was followed by that of flammable organic products for fully aromatic LCPs, while flammable organic products evolved prior to CO2 for semi-aromatic LCP. The flame resistant and self-extinguishing mechanisms of LCPs are discussed on the basis of their thermal degradation behavior.

Synthesis and Properties of Polythiophene Containing Mesogenic Group at 3-Position of Thiophene Ring

Abstract Various kinds of polythiophene derivatives were synthesized and thermal properties were examined by DSC, polarized microscopic and X-ray diffraction observations. Fusibility and solubility of these polymers deeply depends upon the polymerization methods and polarity of the mesogenic group. Polymerization was carried out by oxidation and polycondensation methods. The polarity at the end of mesogenic group plays an important role for solubility and fusibility of the polymer in the case of oxidative polymerization. 3-Substituted polythiophene having polar group such as cyano or nitro at the end of mesogenic group was soluble in polar solvent and fusibility at higher temperature. The polymer having polar group at the end of mesogenic group prepared by mild polymerization condition such as polycondensation exhibited a clear smectic texture and also showed electrochemically active by cyclic voltamograms.

Synthesis, Characterization and Some Aspects for Application of Polymer Liquid Crystals

Abstract Recent developments of thermotropic liquid crystalline polymers are reviewed. The charaterizations of thermotropic liquid crystalline polymer for the type and thermal properties are discussed throuhg the use of differential scanning calorimetry, polarizing microscopy and small and wide anlge X-ray differaction. The recent workds with the order parameter, the alignment and the effects of an field of liquied crystal polymes are also described. Some aspects for applications of the thermotropic liquid crystalline polymers are illustrated: (1)Storage or memory materials, (2)photoelastic liquid crystal, (3) immobilization of liquied crystal structure, and (4) coloured liquid crystal polymers.

Synthesis and thermal properties of new chalcone-based side-chain polymers

We synthesized two types of photocrosslinkable side-chain liquid crystalline polymers (SLCPs) with a chalcone derivative in the side chain. One is a polymer having the chalconyl moiety directly connected to the benzoate component, the other is a polymer with a spacer group introduced between the cyanobiphenyl and the chalconyl moiety. The thermal properties of these polymers were investigated by polarizing optical microscopy measurements and differential scanning calorimetry measurements. Mesophase structures of these polymers were examined by X-ray measurements. A smectic phase was exhibited for the polymers.

THERMAL PROPERTIES AND IONIC CONDUCTIVITY OF IMIDAZOLIUM SALT DERIVATIVES HAVING A CALAMITIC MESOGEN

We synthesized low molar mass liquid crystals having imidazolium salt to investigate thermal properties and ionic conductivity. Two smectic (smectic A and smectic E) phases were shown for imidazolium salt derivatives, regardless of spacer length. The ionic conductivity of imidazolium salt derivatives in the smectic E phase increased with increasing temperature. The ionic conductivity of imidazolium salt derivatives was about 10−8–10−7 Scm−1 near room temperature. The highest value of ionic conductivity for imidazolium salt derivatives was about 10−3 Scm−1 at 140°C.

Heat curing of UTMA-based hybrid resin : effects on the degree of conversion and cytotoxicity

This study was designed to determine the effects of the heat curing time on a urethane tetramethacrylate (UTMA)-based hybrid resin and specifically on the degree of conversion (DC) and cytotoxicity. The materials used in this study were Estenia, a new-generation hybrid resin, and an experimental fiber reinforcement, Br-100. The DC values of the hybrid resin samples were measured using a Fourier transform infrared (FTIR) spectrophotometer after 180 s of light curing followed by heat curing (0, 15, 30, and 60 min). A method comparing intensities of C = C and N—H vibrations of the sample was used to calculate the final DC values. FTIR spectra were measured both inside and on the surface of the sample. The calculated DC values increased by increasing the heat curing times. After light curing only and after 15-min heat curing, the DC values inside the samples were smaller than the corresponding DC values at the surfaces of the samples. After 60 min of heat curing, the samples achieved homogeneous polymerization (DC% = 65). The cytotoxicity of the material was studied from the glass fiber-reinforced hybrid resin samples, which were first light cured and then heat cured (15, 30, and 60 min). Cytotoxicity was tested using both direct contact and extract methods. For the extract tests, the test specimens were incubated in a cell culture media at 37°, 54°, or 72°C for 24 h. The heat curing times used had no effect on cytotoxicity. The incubation temperature, however, did have a significant effect. The extract obtained from 72°C incubation showed a cytotoxic effect whereas the others did not. The direct contact test did not show cytotoxicity.

Thermal Transition Behavior and Second Nonlinear Optical Properties of Polymers Containing Mesogenic Side Chains

Abstract Azo-type nonmesogenic monomer and mesogenic monomers which tend to be arranged in homogeneous or in homeotropic alignment were synthesized. Copolymers were obtained using these monomers by radical polymerization. Thermal and nonlinear optical properties of these copolymers were investigated. The second order nonlinear optical susceptibility enhancement due to liquid crystalline orientation has been observed.

Synthesis and thermal properties of side chain-type liquid crystalline polyurethanes

Abstract The synthesis of side chain-type polyurethanes is described. Their thermal properties were investigated by differential scanning calorimetry and polarizing microscopy and are discussed in terms of the dependence of the polymer backbone on temperature as shown by FT-infrared spectroscopy. The hydrogen bonding which arises from the rather flexible polymer backbone plays a more important role in determining the thermal stability than does the rigid polymer backbone.

Synthesis and thermal properties of combined liquid crystalline epoxy resins

Liquid crystalline epoxy resins were prepared by the curing reaction of epoxy and amine compounds with a mesogenic group in the mesomorphic temperature range. Some epoxy resins exhibited a typical liquid crystalline phase. Curing reaction of a mesogenic epoxy compound with an aliphatic amine compound containing cyano biphenyl group was faster than that of another epoxy resins confirmed by thermally controlled Fourier transform infrared measurements. The glass transition temperature of the liquid crystalline epoxy resin containing cyano biphenyl group increased with increasing curing reaction time.

Influence of rubbing conditions of polyimide alignment layer on optical anisotropy of immobilized liquid crystal film

The relationship between the molecular orientation of a rubbed polyimide film (alignment layer) and that of mesogens in a photopolymerized liquid crystal (LC) coated on the film has been investigated using optical measurements. LC monomers were deposited on the alignment layer and were aligned in one direction. The LC monomers were subsequently photocured. Alignment layers under various rubbing conditions were prepared. It was found that the inclination angle of the refractive index ellipsoid and the optical retardation of photopolymerized LC films are strongly related to the optical anisotropy of the rubbed polyimide film. The photopolymerized LC film exhibited high optical anisotropy when alignment layers with an inclination angle of the refractive index ellipsoid smaller than 6° were used.