Chain Type Liquid Crystalline Polymer Research Articles

Preparation of photo-crosslinked films of new Chalcone-based side chain type liquid crystalline polymers and its application to alignment film

We synthesized two kinds of side chain type polymers containing chalconyl moieties to investigate the alignment's capability of photo-crosslinked polymer films. One is methacrylate type polymer having the chalconyl moiety in the side chain, and the other is imide type polymer. A smectic phase was exhibited for the methacrylate type polymers, while no mesophases were observed for the imide type polymer. These polymer films were irradiated with linearly polarized UV (LPUV) light (350 nm) under different conditions. The liquid crystalline (LC) cell was fabricated from the polymer film irradiated with LPUV light to examine the alignment properties of low molecular liquid crystal on the film. A mixture of a low molecular liquid crystal and a dichroic dye was filled in the LC cells. Alignment behavior of the low molecular liquid crystal was discussed by the dichroic ratio of the dichroic dye in the LC cell.

Smart property of homogeneous electrorheological fluid and its application in reducing seismic responses of engineering structures

The smart properties of homogeneous electrorheological fluid (HERF) containing side—chain type liquid crystalline polymer were studied and an actual HERF damper with an adjustable viscosity was produced. A mechanical model of the HERF smart damper was established on the basis of experiment and theoretical analysis. Then a controlled equation of SDOF structure by HERF damper was derived and a semi-active control strategy based on optimal sliding displacement of damper was presented. The simulation results for a single story frame structure indicate that HERF, which may avoid some defects of common particles-suspended ER fluids, is an excellent smart material with better stability. Using the semi-active control strategy presented, HERF smart damper controlled could effectively reduce seismic responses of structures and keeps the control stable at all times.

Thermal switching characteristics based on smectic-A↔chiral nematic phase transitions of (liquid crystals/chiral dopant) composites, with and without side chain-type liquid crystalline polymer

The light switching characteristics induced by a thermal smectic A (SmA) ↔ chiral nematic (N*) phase transition were studied for homeotropically aligned [smectic A liquid crystal (SmA-LC)/nematic liquid crystal (N-LC)/chiral dopant] and [side chain type smectic A liquid crystalline polymer (SmA-LCP)/N-LC/chiral dopant] composites. A drastic change from a transparent SmA phase to a light-scattering N* phase occurred in both composites upon heating. In the case of the heat-induced N* phase for the (SmA-LC/N-LC/chiral dopant) composite, the N* phase exhibited weak light scattering due to formation of a scroll texture. On the other hand, in the case of the heat-induced N* phase for the (SmA-LCP/N-LC/chiral dopant) composite, the N* phase showed strong light scattering due to formation of a focalconic texture. The existence of a SmA-LCP was responsible for a higher contrast ratio between the transparent SmA phase and the light scattering N* phase for the (SmA-LCP/ N-LC/chiral dopant) composite than for the (SA-LCN/N-LC/chiral dopant) composite.

Photoreaction of New Chalcone-Based Side Chain Type Liquid Crystalline Polymers and Alignment Behavior of Liquid Crystal on the Irradiated Films

Photoreaction of New Chalcone-Based Side Chain Type Liquid Crystalline Polymers and Alignment Behavior of Liquid Crystal on the Irradiated Films

(Homeotropically Oriented Polymer Network/Side Chain Type Liquid Crystalline Polymer/Liquid Crystals/Chiral Dopant) Composite with Thermally Addressed and Electrically Erasable Properties

A heat-induced drastic switching from a transparent smectic A (SmA) phase to a light-scattering nematic (N*) one was achieved for a (homeotropically oriented polymer network (HOPN)/side chain type liquid crystalline polymer (SCLCP)/liquid crystals (LCs)/chiral dopant) quaternary composite. In the case that the composite was rapidly cooled from the heat-induced light-scattering N* phase to the SmA one, the SmA phase exhibited a strong light-scattering state. When an a.c. electric field above the threshold valve was applied to the composite in the light-scattering state, the strongly light-scattering SmA phase was changed into a transparent SmA one. Both the transparent and the light-scattering SmA states could be maintained for a long time (∼years) at room temperature. Thus, the composite with thermally addressable and electrically erasable characteristics was newly proposed.

Thermal and Ionic-Conductive Behaviors of Main Chain Type Liquid Crystalline Polymers with Lithium Salt

Two types of the main chain type liquid crystalline polymer were synthesized and measured ionic conductivity. One of the polymers exhibited a smectic phase. The mixture with lithium salt at the ratio of 0.04 per repeating unit also exhibited a smectic phase. However, the mixture with lithium salt (0.11) showed a nematic phase. Ionic conductivity of the mixture with lithium salt (0.11) was larger than that of the mixture with lithium salt (0.04). The trans type polymer exhibited a liquid crystalline phase, while the cis type polymer didn't show. We found that the ionic conductivity of the trans type polymer with lithium salt mixture (0.11) was larger than that of the cis type polymer with lithium salt mixture (0.11) Moreover, the ionic conductivity of the ceramic-polymer with lithium salt composite was larger than that of the ceramic-free polymer with lithium salt. The other polymer showed a nematic phase. The mixture with lithium salt (0.04) or (0.11) also exhibited a nematic phase. Ionic conductivity of the polymer with lithium salt mixture (0.11) was smaller than that of the polymer with lithium salt mixture (0.04).

THERMAL EXPANSION OF LIQUID CRYSTALLINE POLYESTERS HAVING PHENANTHRENE MOIETIES Simultaneous DSC-XRD method

Phase transition process of polyester from phenanthrene, poly(oxyheptamethyleneoxy-2,7-phenantrenedicarbonyl), a main chain type liquid crystalline polymer, was investigated by simultaneous DSC-XRD measurements using the synchrotron radiation facility (PF). Three exothermic DSC peaks were observed during cooling from the isotropic liquid state. These DSC peaks were assigned to the transition from the isotropic liquid to the smectic A, that from the smectic A to C, and that from the smectic C to the crystalline state, respectively, as determined by XRD profiles. The rate of transition from the smectic A to C was very slow compared with the liquid crystalline transition and the crystallization. From the DSC-XRD results, the thermal expansion along c-axis in the crystal and smectic phases are 4.1×10−4 and 1.4×10−3 nm K−1 , respectively.

Mesomorphic Properties of Side-Chain type Polymers Containing Hydrogen Bonding Group

Side chain type liquid crystalline polymer(SLCP)s with a carboxylic acid or an amide group in the side chain were synthesized by radical polymerization to examine the influence of intermolecular interaction on thermal properties of the polymers. An enantiotropic smectic phase was induced for the butoxyazobenzene copolymers containing 50–60 mol% of carboxylic acid moiety, while two smectic phases were observed for amide type SLCPs with butoxy group as a mesogenic terminal group. It demonstrates that intermolecular hydrogen bonding formed between carboxylic acid groups and between each mesogenic group in the side chain plays an important role to exhibit the liquid crystalline phase by thermally controlled FT-IR measurements.

Light Transmission-Light Scattering Reverse Mode Switching of (Liquid Crystalline Polymer/Liquid Crystal)Composite System

ABSTRACTConventional (polymer/liquid crystal) composite films exhibit the normal mode electro-optical switching, that is, the light scattering-light transmission switching upon electric field OFF-ON states, respectively. The “reverse mode” electro-optical switching, that is, the light transmission-light scattering switching upon electric field OFF-ON states, respectively, has been investigated for a novel type of composite system being composed of a side chain type liquid crystalline polymer(LCP) and low molecular weight liquid crystals(LCs). The polarizing optical microscopic observation and X-ray diffraction study revealed that the two types of smectic-like short range ordering were present in the (LCP/LCs) composite system in a nematic state. It was confirmed from electric capacitance measurements of the homogeneous alignment cell that these phases with different smectic-like short range orderings each exhibited a different value of threshold voltage. Although the homogeneous alignment cell of the (LCP/LCs) composite system was in a light transmitting state in the absence of an electric voltage, the cell turned into a light scattering state upon the application of an electric voltage of 5-15 V for the cell of 14 µm thick (0.4−1.1 MV" m−1). The reversible change from the light scattering state to the transmission state was observed after removing the electric voltage. The light scattering state of the (LCP/LCs) composite system upon the application of electric voltage might be due to the appearance of optically heterogeneous structure induced by the different values of the threshold voltage between the two types of smectic-like phases with different short range orderings. These phases might be in a phase-separated state with an optical dimension (several hundred nm). The reversible “reverse mode” electro-optical switching was realized for the (LCP/LCs) composite system in a nematic state in which the two types of smectic-like short range orderings were separately formed in an optical size level.

Thermal Properties and FT-IR Investigation of Side Chain Type Liquid Crystalline Copolymers

In order to investigate the effect of hydrogen bonding formed between carboxylic acid groups on thermal properties of the side chain type liquid crystalline polymers, we synthesized the side chain type copolymers composed of a mesogenic monomer and a non-mesogenic monomer with carboxylic acid group. Hydrogen bonding was examined by thermally controlled FT-IR measurements. A mesophase was exhibited for the copolymers containing the mesogenic monomer above 40∼65 mol%. The mesomorphic temperature range(MR) of the copolymers increased in the order of the copolymer with methacrylic acid monomer, with benzoic acid monomer containing a flexible spacer and with benzoic acid monomer. This difference in the MR of the copolymers was demonstrated by FT-IR quantitative analysis of the area of the peak assigned to the dimer structure of the carboxylic acid group.

Steep electro-optical response of nematic liquid crystalline molecules induced by addition of polymeric chains

Abstract The steepness increases with a decrease in the ratio of elastic constants of the bend to the splay mode, K 3/K 1. The elastic constants of nematic directors are affected by the geometrical shape of a liquid crystalline molecule and a short range ordering for the alignment of liquid crystalline molecules. The magnitude of K 3/K 1 and the reorientational steepness of the nematic director were evaluated by an electric capacitance measurement of the (side chain-type liquid crystalline polymer (PS6EC)/low molecular weight liquid crystal (E7)) composite system cell. It became apparent from X-ray diffraction studies that the smectic-like short range ordering increases with increasing the fraction of PS6EC even in the nematic state of the composite system. Furthermore, a remarkably steep electro-optical response was successfully achieved.

Synthesis and Physical Properties of π -Conjugated Polymers Containing Mesogenic Group

AbstractNovel side chain type liquid crystalline polymers, polythiophene and poly(aryleneethynylene) [PAE], containing a mesogenic group in the side chain were synthesized. Polythiophene derivatives were obtained by dehalogenative polycondensation with zero-valence nickel complex under mild condition. PAE type polymers were obtained by coupling dihalo aromatic compound with diethynyl aromatic compound. Their thermal properties were examined by differential scanning calorimetry, optical microscopy and X-ray diffractometry. All polymers exhibited a smectic or nematic mesophase depending upon the polymer backbone and pendant mesogenic group. Polythiophene derivatives exhibited electrochemical activity. Annealing polythiophene derivatives led to a lower oxidation potential and a higher conductivity. The degree of the orientation of the polymer backbone was supported by polarized UV-vis measurement. An effective conjugated length became longer by introducing thiophene rings into the polymer backbone. A high quantum yield of fluorescence was observed for PAE type polymers.

Improvement in Response Speed for Bistable Light Switching of (Liquid Crystalline Polymer/Low Molecular Weight Liquid Crystals) Ternary Composite System in Induced Smectic State

Bistable light switching characteristics of the composite system composed of side chain type liquid crystalline polymer (LCP) and two kinds of low molecular weight liquid crystals (LCs) have been investigated. Each component was in a nematic state but the ternary composite showed an induced smectic phase over the wide ranges of both mixing concentration and temperature. The reversible turbid (light scattering)-transparent switching was observed upon the application of electric fields with low and high frequencies, respectively. Both transparent and turbid states of the ternary composite could be maintained stably, even though an electric field was turned off. The ternary composite system exhibited novel characteristics on bistable and reversible light switching. The response speed for bistable light switching could be remarkably improved by reducing the LCP fraction, maintaining an induced smectic state. Then, a novel type of the (LCP/LCs) composite system with a short response time at room temperature was realized for that with bistable and reversible light switching.

Aggregation states and electro-optical properties of the induced smectic phase by mixing a nematic liquid crystalline polymer and a low molecular weight liquid crystal

Aggregation states and electro-optical properties of a binary mixture by mixing a nematic side chain type liquid crystalline polymer (LCP) and a nematic low molecular weight liquid crystal (LC) have been studied. The nematic LC with a strong polar terminal group was miscible with the nematic LCP having a weak polar terminal group. The binary mixture showed an induced smectic phase over a wide range of mixing concentrations and temperature. The reversible turbid (light scattering)-transparent change was observed upon application of electric fields with low and high frequencies, respectively. Both transparent and turbid states of the binary mixture could be maintained stably even when the electric field was turned off (bistable and reversible light switching). A novel type of electro-optical effect based on light scattering was obtained for the mixture in the induced smectic state.

Aggregation States and Bistable Light Switching of (Liquid Crystalline Polymer)/(Low Molecular Weight Liquid Crystal) Mixture Systems

Abstract Binary mixtures composed of side chain type-liquid crystalline polymer (LCP) and low molecular weight liquid crystal (LMWLC) of which chemical structure is similar to the mesogenic side chain of LCP were prepared. Good miscibility between LCP and LMWLC was obtained in a mesophase state over a whole range of concentration. Response time of molecular reorientation by an imposed electric field remarkably decreased with an increase in the fraction of LMWLC. A new type of reversible and bistable electro-optical effect based on light scattering was proposed for the mixture system in a smectic state.

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.

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.