Electro–optic studies on polymer‐dispersed liquid crystal composite films. I. Composites of PVB–E7

The electro‐optic performance characteristic of polymer‐dispersed liquid crystal (PDLC) composite films out of poly(vinyl butyral) (PVB) and nematic liquid crystal (E7) have been studied for a wide range of PVB–E7 composite compositions (20–70 wt % of E7). Composites were prepared by solvent casting from chloroform at room temperature. A scanning electron microscopy study showed that a E7 phase is continuously embedded in chink‐like structure of PVB matrix. Optical transmittance of the composite films (of 60 and 70 wt % loading of E7) under an alternating current (ac) electric field (0–250, V_p‐p) and frequency (50 Hz to 1 KHz) were measured employing He Ne laser (λ = 632.8 nm). The results indicate that the (PVB–E7) composite exhibits a memory effect. In the memory state, higher transmittance is preserved without applying voltage. The memory state can be erased and changed to the scattering Off‐state by heating the film to the clearing temperature of the liquid crystal. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 3485–3491, 1999     

Hyperstructured polyacetylene

Current progress in the synthesis and properties of conjugated polymers is presented by focusing on recently put forward hyperstructured helical polyacetylene. Interfacial polymerization of acetylene has been carried out in an asymmetric reaction field consisting of chiral nematic liquid crystal (N*‐LC) and Ziegler–Natta catalyst. Since the chiral nematic liquid crystal is composed of nematic liquid crystal and a chiral compound such as axially chiral binaphthyl derivative with R‐ or S‐configuration, the screw directions of the polyacetylene chain and fibril bundle and even the spiral morphology are rigorously controlled by selecting the chirality of the chiral compound. Surprisingly, the screw directions of the fibril and the bundle of fibrils in helical polyacetylene were found to be opposite to that of N*‐LC. It is worthwhile to emphasize that the hierarchical spiral morphology involving the primary to higher order structure is generated in a synthetic polymer such as polyacetylene by using N*‐LC as an asymmetric polymerization solvent. Copyright © 2007 Society of Chemical Industry     

Synthesis and characterization of chiral smectic side‐chain liquid crystalline polysiloxanes and ionomers containing sulfonic acid groups

The synthesis of new chiral smectic A (S_A) side‐chain liquid crystalline polysiloxanes (LCPs) and ionomers (LCIs) containing 4‐allyloxy‐benzoyl‐4‐(S‐2‐ethylhexanoyl) p‐benzenediol bisate (ABB) as mesogenic units and 4‐[[4‐(2‐propenyloxy)phenyl]azo]benzenesulfonic acid (AABS) as nonmesogenic units is presented. The chemical structures of the monomers and polymers are confirmed by FTIR spectroscopy or ¹H–NMR. Differential scanning calorimetry (DSC), optical polarizing microscopy, and X‐ray diffraction measurements reveal that all the polymers P_I–P_IV and ionomers P_V–P_VI exhibit S_A texture. The results seem to demonstrate that the tendency toward the S_A‐phase region increases with increasing sulfonic acid concentration, and the thermal stability of the S_A phase is determined by the flexibility of the polymer backbones and the interactions of sulfonic acid groups. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2335–2340, 2001     

Axial Chiral Liquid Crystals–Synthesis of Trisubstituted Allenyl Ethers

The synthesis of racemic and enantiomerical enriched axial chiral liquid crystalline compounds incorporating a trisubstituted allene unit is described. All compounds 16 – 28 display the smectic C-phase and mostly also a nematic mesophase. All investigated enantiomerically enriched compounds have a ferroelectrically switchable chiral smectic S_C*-phase.     

Side‐chain copolymers containing smectic monomer and chiral reagent—Synthesis and characterization

A series of new chiral side‐chain liquid‐crystalline polymers were prepared containing smectic‐nematic monomer and nonmesogenic chiral monomer. All polymers were synthesized by graft polymerization using polymethylhydrosiloxane as backbone. The mesomorphic properties were investigated by differential scanning calorimetry, polarizing optical microscopy, thermogravimetric analyses, and X‐ray diffraction measurements. The chemical structures of the monomers and polymers obtained were confirmed by Fourier transform infrared, proton nuclear magnetic resonance spectra (¹H NMR). M₁ showed smectic (S_B, S_C) and nematic phase on the heating and the cooling cycle. Polymers P₀–P₂ were in chiral smectic A phase, while P₃–P₅ were in cholesteric phase, P₆ has bad LC properties, and P₇ has no LC properties. Experimental results demonstrated that nonmesogenic chiral moiety and LC mesogenic with long carbochain offered the possibility of application because of its lower glass transition temperature, and the glass transition temperatures and isotropization temperatures and the ranges of the mesophase temperature reduced with increasing the contents of chiral agent. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis and phase behavior of new cholesteric liquid‐crystalline copolymers containing chiral mesogenic groups derived from menthol derivatives

The synthesis of a new chiral mesogenic monomer ( M₁ ), a nematic monomer ( M₂ ), and a series of side chain cholesteric copolymers ( P₂ – P₆ ) containing the mesogenic menthyl groups is described. The chemical structures of the compounds were confirmed by FTIR and ¹H NMR. The mesomorphic properties and phase behavior were investigated by differential scanning calorimetry, thermogravimetric analysis, and polarizing optical microscopy. M ₁ showed an enantiotropic cholesteric phase, and M₂ revealed a nematic phase. The homopolymers P₁ and P₇ , respectively, displayed a chiral smectic A (S_A) phase and a nematic phase, while the copolymers P₂ – P₆ exhibited the Grandjean texture of the cholesteric phase. T_g, T_i, and ΔT of P₁ – P₇ increased with increasing the concentration of M₂ in the polymers. All of the obtained polymers displayed very good thermal stability and the wide mesophase temperature range. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis and mesomorphic properties of a new side‐chain,chiral smectic,liquid‐crystalline elastomer

The synthesis of the new chiral monomer 4‐(10‐undecylen‐1‐yloxy)biphenyl‐4′‐[(S)‐2‐methyl‐1‐bu‐ toxy]benzoate (M₁), the nematic crosslinking agent biphenyl 4,4′‐bis(10‐undecylen‐1‐yloxybenzoate) (M₂), and the corresponding liquid‐crystalline elastomer is described. The chemical structures of the chiral monomer and crosslinking agent have been characterized with Fourier transform infrared, elemental analyses, and proton and carbon‐13 nuclear magnetic resonance spectra. The mesomorphic properties have been investigated with differential scanning calorimetry, polarizing optical microscopy, and X‐ray diffraction. Monomer M₁ shows different smectic phases (smectic A, chiral smectic C, and smectic B) and a cholesteric phase, and M₂ exhibits a nematic phase. The liquid‐crystalline elastomer shows smectic A and chiral smectic C phases. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4234–4239, 2006     

First liquid single crystal elastomer containing lactic acid derivative as chiral co-monomer: Synthesis and properties

For the first time new type of liquid single crystal elastomers forming the chiral smectic A^* (SmA^*) phase has been prepared using chiral lactic acid derivative as a co-monomer. The synthesis and the basic characterization of the ferroelectric liquid crystalline co-monomer based on differential scanning calorimetry and small/wide-angle X-ray scattering are reported and discussed. The monomer possesses the paraelectric SmA^* and the ferroelectric SmC^* phases over a broad temperature range. The preparation of new smectic liquid crystalline elastomers together with characterization of their mesomorphic and structural properties is also reported. New elastomers possess the orthogonal paraelectric SmA^* phase over 50 K broad temperature range.     

Preparation of novel liquid crystalline polymeric film material and its photoinduced alignment behavior

Two kinds of novel oxetane monomers, containing biphenyl, flexible spacer and cinnamoyl group, were synthesized. The liquid crystal phase behavior of the corresponding polymers was investigated and isotropic–nematic, nematic–smectic and smectic–crystal transitions were identified during cooling. Both polymers exhibited clear fan texture morphology under a polarized optical microscope. Irradiation of a polymer film with linearly polarized UV light led to cycloaddition of the cinnamoyl groups, causing simultaneous alignment of the liquid crystal unit.     

Injection molding of polypropylene: X-ray investigation of the skin–core morphology

The skin–core morphology of injection-molded polypropylene bars has been investigated employing X-ray small-and wide-angle scattering. The small-angle scattering has been evaluated by means of interface distribution functions. It is found that skin and core exhibit different morphologies. In the skin, the crystal lamellae are oriented primarily around the c axis, but a (small) fraction of a^*-axis-oriented lamellae also exists. The lamellar thickness in the skin layer measured from the meridional small-angle X-ray scattering shows higher values than in the core. The composition of the monoclinic α₁, α₂ crystal modifications show dependencies that are typical for the cooling conditions in the mold during injection. © 1993 John Wiley & Sons, Inc.     

Bistable light scattering effects in a (side chain liquid crystalline polymer)/(low molecular weight liquid crystal) composite and in a ferroelectric liquid crystalline polymer

The electro-optical effects and aggregation states of liquid crystalline polymer (LCP)/ low molecular weight liquid crystal (LC) composite and ferroelectric liquid crystalline copolymer (FLCP) have been investigated. The nematic LCP was observed to be miscible with the nematic LC over wide ranges of concentration and temperature. The binary mixture showed an induced smectic phase in the range of 80/20-20/80 mol%. The electro-optical effects of the LCP/LC composite in an induced smectic phase could be classified into the turbid (light- scattering) and the transparent states upon application of AC and DC electric fields, respectively. The transient scattering mode was obtained by repeated voltage polarity reversal in the chiral smectic C phase of FLCP. The reversible transparent-opaque (light scattering) change was observed in the chiral smectic C state upon application of DC and AC electric fields, respectively. Both transparent and light-scattering states of the LCP/LC composite and the FLCP could be maintained, even after the electric field had been turned off (memory effect). The bistable effects of LCP/LC composite and FLCP are opposite under the same conditions. A novel type of electro-optical effect on light scattering was obtained for liquid crystalline polymer in the smectic states.     

Nematic-to-Isotropic Phase Transition in Poly(L-Lactide) with Addition of Cyclodextrin during Abiotic Degradation Study

Poly(L-lactide) is capable of self-assembly into a nematic mesophase under the influence of temperature and mechanical stresses. Therefore, subsequent poly(L-lactide) films were obtained and characterized, showing nematic liquid crystal properties both before and after degradation. Herein, we present that, by introducing β-cyclodextrin into the polymer matrix, it is possible to obtain a chiral nematic mesophase during pressing, regardless of temperature and time. The obtained poly(L-lactide) films exhibiting liquid crystal properties were subjected to degradation tests and the influence of degradation on these properties was determined. Thermotropic phase behavior was investigated using polarized optical microscopy, X-ray diffraction, and differential scanning calorimetry. The degradation process demonstrated an influence on the liquid crystal properties of pressed polymer films. The colored planar texture of the chiral nematic mesophase, which was not observed prior to degradation in films without the addition of β-cyclodextrin, appeared after incubation in water as a result of the entrapment of degradation products in the polymer matrix. These unusual tailor-made properties, obtained in liquid crystals in (bio)degradable polymers using a simple method, demonstrate the potential for advanced photonic applications.     

Synthesis and characterization of a series of smectic liquid crystalline elastomers

A series of new smectic and cholesteric liquid crystalline elastomers was prepared by graft polymerization of mesogenic monomer with the chiral and nonmesogenic crosslinking agent using polymethylhydrosiloxane as backbone. The chemical structures of the monomers and polymers obtained were confirmed by Fourier transform infrared (FTIR), proton nuclear magnetic resonance spectra (¹H‐NMR). The mesomorphic properties were investigated by differential scanning calorimetry (DSC), polarizing optical microscopy (POM), and X‐ray diffraction measurements (XRD). M₁ showed smectic (S_B, S_C, S_A) and nematic phases during the heating and the cooling cycles. Polymer P₀ and elastomer P₁ exhibited smectic B phase, elastomers P₂–P₅ showed smectic A phase, P₆ and P₇ showed cholesteric phase, and P₈ displayed stress‐induced birefringence. The elastomers containing less than 15 mol % M₂ displayed elasticity and reversible phase transition with wide mesophase temperature ranges. Experimental results demonstrated that the glass transition temperatures decreased first and then increased; melting temperatures and the isotropization temperatures and the mesophase temperature ranges decreased with increasing content of crosslinking unit. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 498–506, 2005     

Influence of chirality on phase behaviour of side chain liquid crystalline polymers

Summary Two kinds of chiral side chain liquid crystalline polyacrylates were synthesized and characterized by DSC, POM and x-ray diffraction. The results indicated that chirality of side chain end group and spacer length strongly influence the phase behaviour of the polymers. The polymer P-I with one asymmetric carbon atom of end group exhibits enantitropic Smectic S_A and S_C phases. The polymer P-III having two asymmetric carbon atoms displays enantitropic Smectic S_A and S_B phases. Formation of liquid crystalline polymorphism of polymers depends on spacer length of side chains.     

Long‐Range Ordered Structure of Ti–B–C–N in a TiB2–TiCxN1−x Eutectic Composite

A TiB₂–TiC_xN_1?x quasi‐binary eutectic composite, with a rod‐like faceted texture and a long‐range ordered structure of Ti–B–C–N, was prepared by the arc‐melting of TiB₂, TiC, and TiN powders. Hexagonal single‐crystalline TiC_xN_1?x rods were grown in a single‐crystalline TiB₂ matrix with a crystal orientation relationship of TiB₂ //TiC_xN_1?x and TiB₂ [0001]//TiC_xN_1?x [111]. A long‐range ordered structure of Ti–B–C–N was formed by the intermixing of the coherent interplanar spacings of seven TiB₂ (0001) and nine TiC_xN_1?x (111) planes.     

Nematic–isotropic transition in polymer‐confined and polymer‐free liquid crystal mixtures

Depending on the processing conditions in liquid crystal (LC) display manufacturing, LC/polymer composite films may exhibit unusual properties with respect to the compositional and phase behavior of the LC constituents. In particular, we have observed extraordinary large shifts of phase transition temperatures in LC/polymer composites, which can not be explained by preferential solvation or adsorption. Therefore, the influence of real manufacturing conditions such as thermal stress, storage in vacuum, and UV irradiation on the nematic–isotropic (n–i) transition temperatures of commercial nematic mixtures was investigated. Shifts of the clearing temperature of up to 88 K, presumably due to partial evaporation or UV degradation, were observed. Furthermore, we found that annealing may lead to the replacement of the nematic phase by the smectic A phase at room temperature in both LC/polymer composites and pure LC samples. Among the tested commercial LC blends, the mixtures E7, MLC‐6650, and L101 showed the smallest stress effects. Practical consequences of our results are discussed. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Main‐chain chiral smectic liquid‐crystalline ionomers containing sulfonic acid groups

Three series of main‐chain liquid‐crystalline polymers (P1, P2, and P3) were synthesized by an interfacial condensation reaction of sebacoyl dichloride with various amount of brilliant yellow, isosorbide, and 4,4′‐biphenydiol. P1 series are polyesters prepared from sebacoyl chloride and various amount of 4,4′‐biphenyldiol and isosorbide. P2 series are polyesters prepared from sebacoyl chloride and various amount of 4,4′‐biphenyldiol, brilliant yellow, and isosorbide. P3 series are polyesters prepared from sebacoyl chloride and various amount of 4,4′‐biphenyldiol and brilliant yellow. P2 and P3 are main‐chain liquid‐crystalline ionomers. P1₂ and P3 series were prepared as model polymers for comparison with the liquid crystalline behavior of ionomers, P2 series. The structures of the polymers were characterized by IR and UV spectroscopy. Differential scanning calorimetry was used to measure the thermal properties of the polymers. The mesogenic properties were investigated by polarized optical microscope, differential scanning calorimetry, and X‐ray diffraction measurements. The results show that P2 series are chiral smectic C (S_mC*) and chiral smectic B (S_mB*) liquid crystalline ionomers exhibiting broken focal‐conic texture and schlieren, as is the polymer P1₂, which has the same amount of 4,4′‐biphenydiol and isosorbide. The introduction of ionic units in P2 series leads to an increase of clearing point, but has not affected the mesogenic type and texture, as compared with the corresponding polymer P1₂. The introduction of chiral units in P2 series leads to a change of mesophase, as compared with P3 series, which exhibit smectic C mesogetic phase. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1254–1263, 2006     

Polymers with terminally cyanobiphenyl-substituted side chains

Summary Two acrylate side chain polymers in which the mesogenic moiety is a 4-cyano-biphenyl-4-yl group have been synthesized and characterized by d.s.c., optical microscopy and X-ray diffraction. If the mesogenic moiety is linked to the polymer backbone by a -O-CO-(CH₂)-₅ group, the resultant polymer is nematic. For a -O-(CH₂)-₆ group, the unusual NS_AN_re sequence is observed. X-ray diffraction has shown that the S_A phase has a partially bilayer structure : the molecules are arranged in an antiparallel, overlapping interdigitated structure with a layer spacing of about 1.4 times the length of the side chains. Monolayer fluctuations are also observed in this S_A phase.     

Solubilization Behavior of Organic Mixtures in Optimum Winsor Type III Microemulsion Systems of Sodium Dodecyl Sulfate

Solubilization selectivity and synergism behavior were investigated for the optimum Winsor type III sodium dodecyl sulfate (SDS) microemulsion systems of organic mixtures. The organic mixtures used include toluene and 1 of the following 3 normal alkanes: n‐octane, n‐heptane, and n‐hexane. Selective solubilization toward toluene was observed in the optimum Winsor type III SDS microemulsion system for the toluene/n‐octane mixture. Toluene selectivity showed a decrease trend with the increase of its content in the excess oil phase, salinity showed little influence on the trend, and increasing of the SDS content leads to lowering of the selectivity. Synergism exists in the solubilization of the 2 organics for all the binary mixtures used in this work. A clear reduction of the n‐butanol content (A*) to obtain the optimum formulation and rise of the optimum solubilization parameter (SP*) were seen with the mixing of 2 single components. Coincident relation between A* and equivalent alkane carbon number (EACN) for organic mixtures of toluene with the 1 or 3 of n‐hexane, n‐hexane, and n‐octane was obtained, which is a parabolic curve with a minimum point. At the same time, all the SP*–EACN data fall in the same kind of parabolic curve with a maximum. The EACN for the minimum A* and maximum SP* are both in the range of 3.0–3.5. The A*–EACN curve shifts vertically with the change of the SDS content or ln S* (S* is salinity of the aqueous phase), while the change of salinity also leads to slight deformation of the curve, which can be omitted in a small range of salinity change.     

Synthesis and characterization of thermotropic liquid crystalline poly(ester‐imide‐ketone)

A series of poly(ester imide ketone)s derived from N,N′‐hexane‐1,6‐diylbis(trimellitimide), 4,4′‐dihydroxybenzophenone, and p‐hydroxybenzoic acid (PHB) were synthesized by the direct polycondensation method in benzene sulfonyl chloride, dimethylformamide, and pyridine with varied PHB contents. The liquid crystalline behavior and thermal properties of the poly(ester imide ketone)s were characterized by polarized‐light microscopy, wide‐angle X‐ray diffraction, thermogravimetric analysis, differential scanning calorimetry, and temperature‐modulated differential scanning calorimetry (MDSC). The results showed that the synthesized polymers possessed a nematic thermotropic liquid crystalline characteristic and high thermal stability. The liquid crystalline polymers, with a PHB content ranging from 0 to 50 mol %, exhibited multiple phase transitions as evidenced by the MDSC results. A transitional smectic phase from solid state to nematic thermotropic liquid crystalline state was observed, and a transition model is proposed. Under certain conditions, the polymer with 33 mol % PHB content showed two significantly different liquid crystalline textures. This type of liquid crystalline polymer exhibited excellent fiber forming. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1045–1052, 2003