Side-chain Liquid Crystalline Polysiloxanes Research Articles

Side Chain Liquid Crystalline Ionic Polysiloxanes

Abstract A variety of side chain liquid crystalline ionic polysiloxanes with quaternized ammonium groups incorporated into the mesogenic moiety or into the spacer have been synthesized and studied by a combination of DSC, TGA, polarizing microscopy and X-ray diffraction. The polysiloxanes exhibit a nematic mesophase. Due to their flexible main chain, the transition temperatures are low. Thermal stability and liquid crystallinity of quaternized and unquaternized polysiloxanes are compared. It appears that in these ionic polymers the geometry of the mesogenic group plays an important part in the development of the mesophase.

Synthesis of side-chain liquid-crystalline polysalts with a poly(methylsiloxane) backbone

The synthesis and thermal properties of side-chain liquid-crystalline polysiloxanes, incorporating quaternized pyridyl groups, are described. The polymers are obtained by hydrosilylation of poly(hydrogenmethylsiloxane) with a protected alcohol. Reaction of the deprotected polysiloxanes with 4-(hydroxymethyl)pyridine and subsequent reaction with mesogenic alkyl bromides of different structure yielded the desired poly[(6-{N-[ω-(4′-alkoxy-4-biphenylyloxy)alkyl]-4-pyridiniomethoxy}hexyl)methylsiloxane bromide]. Four different types of polymers are prepared with either octyl or dodecyl alkyl chain, and with either methoxy or S-2-methyl-1-butoxy as an alkoxy group. Degrees of quaternization up to 80% are obtained. First results of their liquid-crystalline behaviour investigated by optical polarizing microscopy and differential scanning calorimetry are reported.

Use of a long‐spacer‐side‐chain liquid crystalline polysiloxane containing a crown ether as a stationary phase for capillary gas chromatography

AbstractA new kind of side chain liquid crystalline polysiloxane containing a crown ether with a longer spacer (PSC‐11) has been prepared and coated on a fused silica capillary column. The main chroma‐tographic characteristics including efficiency, polarity, and selectivity have been examined. The phase exhibits the retention properties of both liquid crystal and crown ether stationary phases and possesses higher efficiency and better selectivity than PSC‐3, which has a shorter spacer between the main polysiloxane chain and liquid crystalline side chain.

Synthesis of ferroelectric liquid crystalline polysiloxanes containing (S)-2-methylbutyl 4-alkyloxybiphenyl-4?-carboxylate and (2S, 3S)-2-chloro-3-methylpentyl 4-alkyloxybiphenyl-4?-carboxylate

The synthesis of side-chain liquid crystalline polysiloxanes containing (S)-2-methylbutyl-4-alkyloxybiphenyl and (2S, 3S)-2-chloro-3-methylpentyl 4-alkyloxybiphenyl-4′-carboxylate moieties as mesogenic units and aliphatic spacers containing respectively three to eleven methylene units is presented. Differential scanning calorimetry, optical polarizing microscopy and X-ray diffraction measurements reveal chiral smectic mesomorphism for most of the obtained polymers. Two polysiloxanes that contain respectively three methylene units in their spacers exhibit an enantiotropic smectic A phase or no mesophase. Four polysiloxanes that contain respectively five, six and eleven methylene units in their spacers exhibit enantiotropic smectic A and chiral smectic C phases. The results seem to demonstrate that the tendency toward chiral smectic C mesomorphism increases with increasing spacer length. Incorporation of a chloro-containing chiral end group into the mesogenic core of a polymer will decrease the thermal stability of the mesophase formed.

Molecular motions of side-chain liquid crystalline polymers in the liquid crystalline phase studied by the thermally stimulated currents technique

In the present work the thermally stimulated currents technique was used to study the upper glass transition relaxations in two side-chain liquid crystalline polysiloxanes. The nature of those relaxations at the molecular level is a controversial subject, but our results lead us to suggest thay they correspond to the reorientational motions in the liquid crystalline phase of the longitudinal and transverse components of the dipole moment of the mesogenic side group. This assignment is compatible with the conclusions from extensive studies of the dipolar relaxation behaviour of side-chain liquid crystalline polymers by dielectric relaxation spectroscopy.

Synthesis and X-ray diffraction of ferroelectric liquid crystalline polysiloxanes containing 4?-(2-chloro-3-methylpentanoyloxy)-4-alkanyloxybiphenyl side groups

The synthesis and characterization of side-chain liquid crystalline polysiloxanes containing (2S,3S)-4′-(2-chloro-3-methylpentanoyloxy)-4-alkanyloxybiphenyl side groups are presented. All the obtained polymers exhibit smectic mesomorphism. Those polymers containing a spacer length longer than 8 methylene units reveal respectively enantiotropic SA, S * C and SB phases. The result demonstrates that the tendency toward the S * C phase increases with increasing the spacer length.

Comparison of crown ether side-chain polysiloxanes with and without liquid crystalline character as stationary phases for capillary gas chromatography

Two new GC stationary phases were prepared, one a side-chain liquid crystalline polysiloxane containing crown ether (PSC-11), and the other a new kind of side-chain crown ether (PSCP-11-15C-5) which has a similar structure to PSC-11. The main chromatographic characteristics, including efficiency, polarity and selectivity, were examined and compared. The mechanism of specific selectivity for positional isomer compounds based on the crown ether ring and liquid crystal is discussed.

The influence of lateral substituents on the phase behavior of side-chain liquid crystalline polysiloxanes containing trans-2,5-disubstituted-1,3-dioxane based mesogenic side groups

The synthesis and characterization of the polysiloxanes containingtrans-2,5-disubstituted-1,3-dioxane-based mesogenic side groups were described in this present study. Among three polysiloxanes containing three methylene units in their spacers, one without the lateral substituent exhibited two enantiotropic smectic phases while the other two polymers with a lateral methyl- or methoxy-substituent displayed an enantiotropic nematic phase. For polymers containing a longer spacer length (n ≥ 4), those without lateral substituent presented two enantiotropic smectic phases while the others containing a lateral substituent showed only an enantiotropic smectic A phase. The lateral substitution exerted a strong effect on the mesomorphic properties of the synthesized polymers.

Side-chain liquid crystalline polysiloxane containing crown ether used as stationary phase for capillary gas chromatography

A new stationary-phase, side-chain liquid crystalline polysiloxane containing crown ether was developed and used as a stationary phase in capillary gas chromatography. This phase can be easily coated on the fused-silica tubing and possesses a high efficiency and moderate polarity. It exhibits the retention properties of both liquid crystal and crown ether stationary phases and is suitable for the separation of a variety of isomeric compounds

Synthesis of liquid-crystalline polysiloxanes and polymethacrylates with broad temperature ranges of the chiral smectic C phase

The synthesis of side-chain liquid crystalline polysiloxanes and polymethacrylates containing oligooxyethylene spacers and 4-(S)-2-methyl-l-butyl (((4-hydroxybiphenyl-4'-yl)carbonylloxylbenzoate mesogenic side groups is presented. Differential scanning calorimetry, optical polarizing microscopy, and X-ray diffraction measurements reveal chiral smectic mesomorphism for all polymers. All three polysiloxanes present enantiotropic smectic A and chiral smectic C phases. The chiral smectic C phase covers a very broad temperature range (about 200 C). Among polymethacrylates prepared in this study, the polymethacrylate which contains three oxyethylene units in its spacer is the only one revealing smectic A and chiral smectic C phases. The results seem to demonstrate that the tendency toward a chiral smectic C phase increases with increasing the flexibility of the polymer backbone and the oligooxyethylene spacer can increase dramatically the thermal stability of the chiral smectic C phase, 3161

Effect of Palladium Coordination on Liquid Crystallinity of Imine Side Chain Polysiloxane

Abstract A new type of Pd-coordinating imine side chain liquid crystalline polysiloxane (Pd-ImLCP) has been synthesized by hydrolyzation reaction of N-(4-n-undecylenoxy-benzylidene)-4-dodecyloxyaniline with polymethylhydrogensiloxane (PMHS), then by ortho-palladation reaction of the obtained polymer ligand, imine side chain liquid crystalline polysiloxane (ImLCP), with various amounts of palladium acetate. The corresponding low molar mass Pd-coordinating imine complex (Pd-Im) has been also prepared for comparison. Their mesomorphic properties have been studied by polarizing microscopy, DSC and X-ray diffraction methods. The incorporation of Pd ions into the macromolecules ImLCP can affect the mesophase transitions in different ways. By increasing the molar percentage of Pd in the polymer, the textures turn from smectic to nematic phases and the transition temperatures almost stay constant up to 27 mole% and then decrease to 80 mole% at which crosslinking occurs. The clearing temperatures Tcl and enthalpy ...

Electrically-modulated variable permeability liquid crystalline polymeric membrane

Side chain liquid crystalline polysiloxane was synthesized and the effects of the DC electric field strength and the AC electric field frequency of an applied transmembrane field on membrane permeability were investigated. In this paper, the synthesis method of poly(methyl p-propyloxyphenyl, p-methoxy benzoate siloxane) and permeation data of p-aminoacetophenone through this polymer at 5°C are presented. Membrane permeability was observed to increase with increasing field strength and decrease with increasing frequency. Utilizing DC electric field, 28-fold increase in membrane permeability was obtained with a field strength of 4,200 V/cm. At a field strength of 4,900 V/cm, a 26-fold range in permeation rate was obtained between 0.001 Hz and 10 KHz. The response times required to achieve new steady state fluxes after changing frequency at 4,900 V/cm were observed to be nearly instantaneous in contrast to those observed on changing the DC electric field strength.

Synthesis and mesomorphic behavior of terminally carboxyl oligo(ethylene oxide) monomethyl ethers‐substituted side chain liquid crystalline polysiloxanes. I

AbstractA series of alkene monomers containing carboxyl biphenyl benzoate ester or carboxyl p,p′‐phenyl benzoate ester based on mesogenic core with a carboxyl (±)‐2‐methyl ethylene glycol monomethyl ether group or various lengths of carboxyl oligo (ethylene oxide) monomethyl ethers as the terminal group were synthesized. And they were grafted onto the poly(methylhydrosiloxanes) (PMHS) by the platinum catalyzed hydrosilylation process. Their molecular structure, the thermal transitions temperature, and mesophase texture of monomers and of polymers were characterized using 1H nuclear magnetic resonance, differential scanning calorimetry, and polarizing optical microscopy with hot stage. The polymers obtained all show smectic phase while their precursor monomers show both smectic and/or nematic phase, or in some cases, no mesophase. The factors governing mesophase texture and transition temperature are discussed. © 1993 John Wiley & Sons, Inc.

Structural studies of laterally attached liquid crystalline polymers

Abstract Structural studies of a series of laterally attached side chain liquid crystalline polysiloxanes have been made by X-ray diffraction. All but one exhibit a nematic phase with SC-like short range ordering. The diffraction has been interpreted in terms of a model in which the mesogenic units form a ‘jacket’ around the polymer backbone. The backbone conformation has been studied by small angle X-ray scattering from oriented samples of mesomorphic solutions and by infrared dichroism measurements on oriented samples of the polymers. In both cases the results were consistent with the mesogens being oriented parallel to the backbone which is consistent with the ‘mesogen jacket’ model.

Synthesis and characterization of side-chain liquid crystalline polysiloxanes containing oligooxyethylene spacers and 2,5-disubstituted-1,3-dioxane based mesogenic groups

The synthesis of side-chain liquid crystalline polysiloxanes containing oligooxyethylene spacers and 2,5-disubstituted-1,3-dioxane based mesogenic groups is presented. The phase behavior of both monomeric and polymeric liquid crystals was characterized by differential scanning calorimetry and optical polarized microscopy. All synthesized polysiloxanes present smectic mesomorphism. The transition temperatures of all the obtained monomers and polymers decrease with an increase of oxyethylene units. No side-chain crystallization was observed for all obtained polymers.

Synthesis and characterization of ferroelectric liquid-crystalline polysiloxanes and polymethacrylates containing [(S)-2-methyl-1-butoxy]phenyl 4-(alkyloxy)biphenyl-4'-carboxylate side groups

The synthesis of side-chain liquid crystalline polysiloxanes and polymethacrylates containing 4-[(S)-2-methyl-1-butoxy]phenyl 4-hydroxybiphenyl-4'-carboxylate moieties as mesogenic units and aliphatic spacers containing respectively three to eleven methylene units is presented. All polymers exhibited chiral smectic mesomorphism. Both polysiloxanes which contain respectively six and eleven methylene units in the spacers exhibit smectic A, chiral smectic C, and smectic B phases. The polymethacrylate containing eleven methylene units in its spacer was the only one revealing smectic A and chiral smectic C phases

Synthesis of side chain liquid-crystalline polysiloxane containingtrans-cyclohexane-based mesogenic side groups

Abstract The synthesis and characterization of nine new side chain liquid-crystalline polysiloxanes containing one cyclohexyl ring and another 2-4 aromatic rings in their mesogenic side groups are described. All synthesized polymers displayed nematic mesomorphism. Most of the polymers showed a very wide mesomorphic temperature range. The mesogenic core length has profound influence on the phase transitions of the polymers. The mesomorphic temperature range increased with increasing mesogenic core length.

Synthesis of side-chain liquid crystalline polyacrylates, polymethacrylates and polysiloxanes containing 4-cyano-biphenyl 4-alkanyloxybenzyl ether side groups

The synthesis and characterization of side-chain liquid crystalline polyacrylates, polymethacrylates and polysiloxanes containing 4-cyanobiphenyl 4-alkanyloxybenzyl ether side groups are presented. All polymers display respectively a smectic A mesophase. The influence of the polymer backbone flexibility on the phase transition temperatures of the synthesized side-chain liquid crystalline polymers is discussed. The results demonstrate that flexible backbones enhance the decoupling of the motions of the side chain and main chain. Therefore, among three kinds of polymer backbones which contain the same mesogenic side groups, the most flexible one, i.e., polysiloxane, reveals a highest isotropization temperature and a widest temperature range of mesophase.

Low-temperature side-chain liquid crystalline polysiloxanes used as stationary phases for capillary gas chromatography

Cinq polysiloxanes sont prepares et recouvrent des colonnes capillaires. Leurs proprietes chromatographiques sont etudiees en utilisant des isomeres de composes benzeniques

Chiral Smectic Liquid Crystalline Polymers

Abstract The synthesis of side-chain liquid crystalline polysiloxanes, copolysiloxanes and of tetracyclosiloxanes containing chiral mesogenic side groups, i.e, trans- 2[p-(l-undecanyl-ll-oxy)phenyl]-5-[(p-2(S)- methyl-1-butoxy)pheny1]-1,3-dioxane, trans- 2-[p-(2(S)-methyl-1-butoxy)phenyl]-5-(11- undecalenyl)-1,3-dioxane and 2-[4-(2(S)- methyl-butoxy)-phenyl]-5-(w-alkl)-l,3,2- dioxaborlnane with alkyl being undecanyl, octyl, and hexyl is discussed. Differential scanning calorimetry and thermal optical polarization microscopy revealed chiral smectic mesomorphism for polymers containing eleven methylene units in the flexible spacer. The polymers containing undecanyl spacers present a chiral smectic C mesophase. The polysiloxanes with hexyl spacers exhibit a chiral nematic mesophase.