Kazuyoshi Iimura

Thermal and liquid crystalline properties of liquid crystalline polymethacrylates with ammonium units and their non-ionic family

Ionic and non-ionic liquid crystalline polymethacrylates were synthesized, and their thermal and liquid crystalline properties were compared. Both the ionic and non-ionic liquid crystalline polymethacrylates exhibited a thermotropic smectic A phase. An isotropization temperature of the ionic liquid crystalline polymethacrylate was higher than for the non-ionic liquid crystalline polymethacrylate. Moreover, the ionic liquid crystalline polymethacrylate showed a higher glass transition temperature when compared to the non-ionic liquid crystalline polymethacrylate. The ionic and non-ionic liquid crystalline polymethacrylates formed a partial bilayer structure in the smectic A phase. Copyright

Synthesis and Thermal Properties of Side Chain Type Liquid Crystalline Polymers With Chiral Unit in the Flexible Moiety

Abstract This paper is concerned with the synthesis and thermal properties for five families of side-chain type liquid crystal- line polymers. All these side-chain type polymers showed an enantiotropic mesomorphic nature. A sharp reflection was observed in the small angle region, whereas a broad halo or a relatively sharp peak was also detected in the wide angle region for all the polymers. The experimental values of the thickness of the smectic layer which can be easily assigned by the polarizing microscopic measurements were smaller than that of the calculated ones. This difference would be caused from the tilted arrangement in the smectic layer or smectic A like structure in which the side chains would be overlapped.

Thermal behavior of ionic liquid-crystalline side-chain polymer

Abstract Both nonionic liquid-crystalline side-chain polymer [P(A—CH3)) and ionic family [P(A—CH3/CH3I)] of P(A–CH3) were prepared. Nonionic P(A—CH3), having an alkylamine spacer, exhibited solidsmectic and smectic-isotropic phase transitions. Ionic P(A—CH3/CH3I), having an alkylammonium spacer, showed glassy-smectic and smectic-isotropic phase transitions. Ionic P(A—CH3/CH3I) exhibited the enhanced thermal stability by the aggregation of ammonium ions formed by Coulombs force in comparison with nonionic P(A—CH3). The enhanced thermal stability in ionic families was also concluded from experimental results obtained for nonionic and ionic low molecular weight liquid-crystalline compounds corresponding to mesogenic side groups of P(A—CH3) and P(A—CH3/CH3I).

Phase Transitions of Ionic Liquid-Crystalline Polymethacrylate Having a Piperidinium Skeleton

Abstract An ionic liquid-crystalline polymethacrylate [P-Pi/MeI having a piperidinium skeleton in a mesogenic side-chain was synthesized. Its nonionic family [P-Pi was also prepared, and phase transitions of P-Pi/ MeI and P-Pi were compared. Both P-Pi/MeI and P-Pi exhibit enantiotropically smectic phases. Ionic P-Pi/MeI shows enhanced thermal stability in comparison with nonionic P-Pi. A temperature of P-Pi/MeI, at which an isotropic phase forms, is higher than that of P-Pi. P-Pi/MeI also shows a higher glass transition temperature when compared to P-Pi. Also, nonionic and ionic low molecular weight model compounds were prepared, and their thermal properties were compared.

Thermal Properties and Order Parameter for Model Compounds of Liquid Crystalline Polymers

Abstract The thermal behavior and order parameter of two kinds of model compounds for liquid crystalline polyesters were studied by DSC and ESR spin probe methods, respectively. The transition temperatures for the twin model compounds which composed of structural sequences with a mesogen-flexible chain-mesogen demonstrated a dramatic odd-even alternation as increasing the number of methylene unit in the central flexible part. Both melting (Tm) and isotropization (Ti) temperatures for the twin model compounds with an even number of methylene lengths were higher than those with an odd number of methylene lengths. The strong alternation in the isotropization entropy change(ΔSi) and in the order parameter (S) were also observed in these twin compounds with variable spacer lengths. However, an inverse alternation regarding with the number of methylene length was found in Si and S for the azobenzene type of twin models which are composed of the inverse order of atoms in the ester linkage comparing with that of ...

Induced Smectic A and C Phases Formed by Binary Systems of Main-Chain Polymeric and Twin Nematics

The thermal and liquid crystalline properties of the new binary systems, consisting of a polycarbonate type of a main-chain liquid crystal polymer (PC) and a twin liquid crystal (TN-n: n = number of central methylene units) with a nitro terminal unit, were examined. The binary systems having PC and TN-n with even-numbered central methylene units (n = 6, 8) showed an induced smectic A phase with batonnets and a fan texture. However, the binary systems consisting of PC and TN-n with odd-numbered central methylene units (n = 5, 7) formed an induced smectic C phase in addition to an induced smectic A phase. In the induced smectic C phase, the schlieren with two and four brushes was observed.

13C Relaxation Times Study of Liquid Crystalline p-Methoxybenzylidene-p-Butylaniline

Abstract The 13C relaxation times T1 and T2 for all resolved carbon lines are reported as a function of temperature in the nematic and isotropic phases of MBBA. Also the NOE measurements were performed in the both nematic and isotropic phases. The discontinuity of 13C T2s was observed at the nematic-isotropic transition point. From T1 and T2 data, it is shown that a short range order remains in the small temperature range just above the isotropic-nematic transition point. The region of small temperature dependence was found in the plots of 13C T1 vs reciprocal temperature. The rotational motion around the molecular axis was estimated to be three orders faster than the motion around the axis perpendicular to the molecular axis.

Studies on Polymerization Activities by Soluble Catalysts Based on Compounds of Organotransition Metals and Aluminum Alkyls

Abstract Polymerization activities of the soluble Ziegler-type of catalyst systems, Ti(OR)4-AlEt3, Ti(NEt2)4-AlMe3, and V(NEt2)4-AlEt3, were investigated. In the catalyst system of Ti(OR)4-AlEt3, formation of two types of Ti(III) compounds, i.e., Ti(OR)2Et and its bridged complex with aluminum alkyl, was confirmed by IR and ESR measurements. With the addition of donor molecule to the system, it was found that the polymer yield decreased remarkably and that the bridged complex dissociated into a single or uncomplex Ti(III) paramagnetic species. It has been concluded that the bridged structure of Ti(III) species was responsible for the polymerization activity of styrene. Two reaction products of Ti(NEt2)3Me and Al(NEt2)Me2 were found by NMR spectroscopic observation with the Ti(NEt2)4-AlMe3 catalyst system. From the kinetic study of polymerization of styrene, it was found that Ti(NEt2)3Me is an active species. An anionic mechanism was proposed for the styrene polymerization by Ti(NEt2)3Me. In the polymeriza...

Induced smectic A and C phases formed by liquid-crystalline binary systems consisting of nematic twin compounds

The binary systems consisting of di[4-(4-substituted phenylazo)phenyl]alkanedionates, which are twin liquid crystals, were prepared. The twin liquid crystals having a nitro or a butyl terminal substituent exhibited only a nematic phase with a schlieren texture. The liquid-crystalline binary system (BS-8-n) containing di{4-[4-(nitro)phenylazo]phenyl}sebacate and di{4-[4-(butyl)phenylazo]phenyl}sebacate, which involve an even number of central methylene units, exhibited an induced smectic A phase with a fan texture. However, the liquid-crystalline binary system (BS-7-m) containing di{4-[4(nitro)phenylazo]phenyl}azelate and di{4-[4-(butyl)phenylazo]phenyl}azelate, which have an uneven number of central methylene units, showed an induced smectic C phase with broken fan and schlieren textures, as well as a nematic phase. This different liquid crystal formation can be related to the molecular shapes of the twin liquid crystals, due to the conformation of the central methylene chain.

Structure of Polymer Liquid Crystals and Electro-Optical Properties

Abstract Electro-optical properties of the comb-like and the main chain type liquid crystalline polymers were investigated in terms of the molecular weight and the polymer structures. The comb-like polymer has acrylic or methacrylic skeletal chain with 4-cyanobiphenylbenzoate as a mesogenic pendant group. The response time on application of DC field was longer for the methacrylic polymer owing to its less mobility of the skeletal chain. The main chain type polymer with α-cyanostilbene as a mesogenic moiety exhibited a relatively short response time as low as 200ms. This is likely originated from a large dielectric anisotropy of the mesogenic moiety.