Crystalline Polymer Networks Research Articles

Synthesis and characterization of semi-interpenetrating liquid crystalline polymer networks LCP/PAN

A new type of interpenetrating polymer network based on a liquid crystalline polymer: a semi-interpenetrating liquid crystalline polymer network comprising the liquid crystalline polymer (LCP) PET/60PHB and crosslinked polyacrylonitrile (PAN)(for short: semi-ILCPN LCP/PAN) was successfully prepared. The compatibility and thermal properties of the semi-ILCPNs with different amounts of the crosslinking agent were investigated by FTIR, SEM, DSC, and TGA.

Synthesis and characterization of semi‐interpenetrating liquid crystalline polymer networks LCP/PAN

Synthesis and characterization of semi‐interpenetrating liquid crystalline polymer networks LCP/PAN

The Effect of Polymer Stabilization on the Alignment Structure of Surface-Stabilized Ferroelectric Liquid Crystals

It has been shown that a polymer network, formed in the SmA phase by UV photocure of photocurable liquid crystalline monoacrylates that are doped in a surface-stabilized ferroelectric liquid crystal (SSFLC), eliminates zig-zag defects in the SmC* phase, Since a chevron layer structure is transformed into a quasi-bookshelf layer structure by the polymer main chain. In this study, we have observed the electrooptical (EO) effect of this polymer-stabilized SSFLC (PS-SSFLC) with the aim of exploring the effect of the liquid crystalline polymer network on the alignment structure of FLC molecules. As experimental results, it was found that liquid crystalline side chains bond strongly with a main chain and attract FLC molecules in the rubbing direction. Furthermore, we propose and demonstrate a new PS-SSFLC fabricated also by UV photocure of doped monoacrylates particularly at a temperature where the LC medium is in the SmC* phase under the simultaneous application of a monopolar electric field. This device exhibits monostable EO characteristics with a high contrast ratio owing to being defect free, having grayscale capability without threshold, and a fast response speed.

P‐80: Controlling the Threshold Voltage of SSFLCDs Using Polymer Networks

AbstractIn this research, we have reported a method to realize grayscale operation of SSFLCDs by controlling the threshold voltage of the samples. The control of the threshold voltage is achieved by forming liquid crystalline polymer networks in a FLC cell using a UV curable liquid crystalline monomer. It is found that the threshold voltage of the samples decreases with increasing the concentration of the doped monomer. These results indicate that, if the amount of the polymer network formed in a FLC medium is varied from a region to a region in one pixel, we can get a quasi‐multi‐stable SSFLCD, resulting in a grayscale operation of the device by a passive matrix addressing.

Liquid Crystalline Polymer Stabilized FLCDs with Conventional Rubbed Polyimide Films or with Photo Alignment Films of Poly(vinyl Cinnamate)

Polymer stabilized SSFLCDs have been successfully fabricated. A liquid crystalline polymer network in a device cell is formed by the photo-cure of UV photo-currable liquid crystalline monomers that are doped in an FLC, where both the rubbed polyimide (PI) and non-rubbed but linearly polarized UV irradiated poly(vinyl cinnamate) (PVCi) films are utilized as surface FLC molecular alignment. The actual monomers adopted is acrylate with a mesogenic side chain. The PVCi is one of the photo alignment polymer. The fabrication process of these SSFLC cells is as follows; first the photo-cure is done on a monomers and initiators doped LC medium at the temperature where this material takes SmA phase and then the cell is cooled down to room temperature, at which the medium takes SmC* phase. The layer structure of the liquid crystalline polymer stabilized (LC-PS) FLC cells has been investigated by X-ray diffraction measurement. As the experimental results, it is found that the formed polymer network suppresses the formation of a chevron layer structure, resulting in the formation of a quasi-bookshelf layer structure; the only C1-uniform state is spontaneously formed without giving a high surface pretilt angle; and a fairly good memory state with an excellent contrast ratio and a low threshold voltage are obtained for a low concentration of doped monomers (2 ∼ 3 wt%) in particular with photo-alignment layers of PVCi; and furthermore, in a cell with a higher concentration of doped monomers (4 wt%) an excellent electroclinic like behavior (called the quasi-electroclinic effect) is obtained.

Determination of the 13C magnetic shielding tensor in partially oriented polymer systems

It is shown that, for an oriented sample, the 13C magnetic shielding tensor of a specific nucleus can be determined from the spinning sideband intensities in a 2D spectrum obtained from a 13C rotor-synchronized 2D CPMAS experiment, originally designed by Harbison and co-workers (G.S. Harbison, V. Vogt and H.W. Spiess, J. Chem. Phys., 86(3) (1987) 1206; G.S. Harbison, H.W. Spiess, Chem. Phys. Lett., 124 (1986) 128). In our fitting procedure, we combined their multilinear regression analysis for the determination of the order parameters with a variation both of the principal values of the magnetic shielding tensor and of the direction of the principal axes relative to the molecule. The magnetic shielding principal elements of the nonprotonated aromatic carbon in poly(ethylene terephthalate) (PET) fibres and of the aromatic carbons in the central ring of an oriented liquid crystalline polymer network are reported. We estimate that the accuracy of the principal values is within 5 ppm.

Preparation of cross-linked aliphatic polyester and application to thermo-responsive material

The aim of this study is to investigate the application of a crystalline polymer network to a thermo-responsive material. To achieve this purpose, cross-linked aliphatic polyesters containing a poly-ϵ-caprolactone (poly-CL) segment were prepared from tetrafunctional star-shaped macromonomers. The macromonomers were synthesized by ring-opening polymerization of CL and L-lactide (LA) initiated with pentaerythritol followed by condensation with methacryloyl chloride to introduce a functional group at the chain ends. The cross-linked polyester membranes were prepared by way of a radical polymerization of the macromonomers with visible light irradiation in the presence of initiator and sensitizer. The obtained materials, which consisted of CL homopolymer and LA/CL block copolymer, exhibited a phase transition temperature derived from the melting of polyCL segment. The transition temperatures of the macromonomers and the corresponding cross-linked polyesters depended on the length of poly-CL segment. In order to examine the thermo-responsive properties, the permeation of a model drug, indomethacin, through the membrane composed of cross-linked polyester was investigated by using a 2-chamber diffusion cell. The permeability of the drug increased steeply at around the phase transition with increasing temperature. In addition, the relationship between the degree of crystallinity and the increase of the drug permeability was discussed. From the analysis of permeation profiles, it was revealed that the partition of the drug from the donor phase to the membrane surface considerably increased above the phase transition. Also, the reversible control of the drug permeation through the membrane in response to the repeating temperature change (20°C and 40°C) was observed.

Networks from Liquid Crystalline Segmented Chain Polymers

The synthesis and the phase behavior of three liquid crystalline polymer network and of the linear polymers upon which the networks are based are presented. The linear polymers, that are characterized by the presence of -OC 6 H 4 -p-COOC 6 H 3 -o-OH-p-CH=NC 6 H 4 -p-O- groups connected by flexible molecular segments, exhibit enantiotropic liquid crystalline properties of nematic and/or smectic nature. They have been moderately (≤10%) cross-linked by reaction with ClOCC 6 H 4 -p-O(CH 2 ) 12 O-p-C 6 H 4 COCl in an isotropic o-dichlorobenzene dilute solution. The network form as isotropic gels and undergo anisotropization with enthalpy release on cooling at room temperature