Side-chain Liquid Crystal Polysiloxanes Research Articles

The transfer and amplification of cyanostilbene molecular function to advanced flexible optical paints through self-crosslinkable side-chain liquid crystal polysiloxanes.

A self-crosslinkable side-chain liquid crystal polysiloxane containing cyanostilbene (Si-CSM) was newly synthesized for the development of a new generation of flexible optical paints. The photoisomerization of the cyanostilbene moiety at the molecular level was transferred and amplified to the phase transition of Si-CSM, resulting in changes in the macroscopic optical properties of the Si-CSM thin film. The self-crosslinking reaction between Si-H groups in the Si-CSM polymer backbone caused the self-crosslinked Si-CSM thin film to be very elastic and both thermally and chemically stable. Therefore, the self-crosslinked Si-CSM thin film endured stretching and bending deformations under relatively harsh conditions. In addition, the uniaxially oriented and self-crosslinked Si-CSM thin film generated linearly polarized light emission. Polarization-dependent and photopatternable secret coatings were fabricated via a spontaneous self-crosslinking reaction after coating the Si-CSM paint and irradiating ultraviolet (UV) light through a photomask. This newly developed flexible optical Si-CSM paint can be applied in next-generation optical coatings.

Synthesis of mesoionic side-chain liquid crystal poly(siloxane)s

Side-chain liquid crystal polysiloxanes containing mesoionic sydnonyl moieties have been synthesized. The polymers displayed a typical smectic schliren texture between 120 and 200 °C.

Transient rheological behavior of tumbling side-chain liquid crystal polymers and determination of their λ parameters

The transient rheological behavior of several thermotropic nematic side-chain liquid crystal polysiloxanes is investigated. A homopolymer with a low-temperature smectic phase and two random copolymers, one consisting of smectogenic and non-smectogenic mesogens, the other one containing two spacers of different lengths, are studied. All systems are of tumbling type and exhibit oscillations in transient shear stress and first normal stress difference. Only the copolymer with mixed spacers shows a temperature-dependent transition from tumbling to flow-aligning within the nematic phase. The rheological response is slightly different for each polymer. The reactive parameter λ was calculated from the period of the oscillations and compared with rheo-NMR results. For all polymers, λ increases with increasing temperature. The sign of λ, obtained from NMR experiments, is positive for the copolymer with mixed spacers and negative for the other two systems, indicating a prolate shape of the first system and oblate shapes of the other two.

Syntheses and characterization of new chiral side-chain liquid crystalline polysiloxanes

A new serial chiral side-chain liquid crystal polysiloxanes containing L-Tyr structures were synthesized at room temperature. Both of them exhibited Sc phase at room temperature.

Synthesis and characterization of side-chain liquid crystalline polysiloxanes

The synthesis and characterization are described for a series of side-chain liquid crystal polysiloxanes using polyhydrosilylation reaction between a poly(hydrogen methyl-co-dimethylsiloxanes),-(OSiHMe)x,-(OSiMe2)y-, where x/y was 13/87, 30/70, 55/45, 73/27 and 98/2, and [4-(allyloxy)benzoyll biphenyl mesogenic group. The side-chain liquid crystal polysiloxanes were characterized by1H NMR,13C NMR, IR, gel permeation chromatography (GPC), differential scanning calorimetry (DSC) and optical polarizing microscopy. The dimethylsiloxane segment factors governing thermal transition temperatures and activation energy (Ea) of the nematic-to-isotropic phase transition are discussed.

Isomer specific analysis of PCDD/F by HRGC-MS using polymeric liquid crystal stationary phases

Four different side chain liquid crystal polysiloxanes were synthesized and evaluated as stationary phases for dioxin and furan analysis, focusing on isomer specific separations and analysis of those containing substitution at positions 2,3,7 and 8. The selectivities of the stationary phases were found to vary according to their mesophase range and degree of order of the liquid crystalline lattice. Reproducibility was investigated by testing three separate batches of one of the products.

Liquid crystal polymers containing macroheterocyclic ligands. 2. Side chain liquid crystal polysiloxanes and polymethacrylates containing 4-(.omega.-alkan-1-yloxy)-4'-(4'-carboxybenzo-15-crown-5)biphenyl side groups

Preparation de polymethacrylate par polymerisation radicalaire du monomere corespondant et de polysiloxane par hydrosilylation de l'alcene correspondant par le poly (methylsiloxane). Les polymeres obtenus presentent les mesophases enantiotropes smectiques et nematiques alors que les monomeres ne montrent que des mesophases monotropes

Effect of Molecular Structure on the Properties of Schiff's Base Side-Chain Liquid Crystal Polysiloxanes

Abstract A series of smectic liquid crystal polymers with a polysiloxane backbone and Schiff s base side-chains is presented. In a three-step procedure, hydroxy-terminated Schiff s bases were first prepared and then converted to allyloxy-terminated derivatives. Only few of the resulting monomers were liquid crystals, even though all were potentially mesomorphic. When attached to a polysiloxane backbone via a 3-carbon spacer, all resulting polymers were smectic. Where comparisons were possible, the mesophase ranges for the polymers were greater than those for the corresponding side-chain precursors. Interesting trends were observed in the effect of the length of the alkyl and alkoxy terminal substituent on the liquid crystal properties. The chloro-terminated side-chain precursors did not exhibit liquid crystal properties, but gave the widest mesomorphic range polymers. The high transition enthalpies for the mesomorphic-isotropic transition are indicative of a smectic mesophase. The transition temperatures and entropies for the smectic-isotropic transitions for an alkoxy terminated series show odd-even alternations.

29Si N.M.R. investigations of polysiloxanes

Abstract A number of side chain liquid crystal polysiloxanes prepared from both homo-and co-polymeric backbones have been studied by 29Si N.M.R. and the chemical shifts assigned. Partly mesogenated poly(hydrogenmethylsiloxanes) have been similarly studied and chemical shift assignments made for sequence distributions. The data should prove helpful in studies of compositional variation in preparations of side chain copolymeric polysiloxanes.

Side chain liquid crystal polysiloxanes and their low Tgcopolymer analogues

Abstract A number of side-chain liquid crystal homopolymers derived from poly-(hydrogenmethylsiloxane) and their copolymeric analogues with the same mesogenic side chains appended to a poly(hydrogenmethyldimethylsiloxane) backbone have been prepared. The homo and copolymers exhibit the same mesophase types, but markedly different Tg values, mesophase transition temperatures and isotropisation enthalpies. These differences are interpreted in terms of the relative DP values and flexibilities of the backbones for the homo and copolymers.