Phenyl Benzoate Side Groups Research Articles

Influence of End Groups in Photoinduced Reorientation of Liquid Crystalline Polymer Films Based on Axis-Selective Photo-Fries Rearrangement

Photoreactive liquid crystalline polymethacrylates with phenylbenzoate side groups with different molecular terminal were synthesized and their photoresponsive behavior was investigated. All polymer films underwent axis-selective photo-Fries rearrangement and generated photoinduced optical anisotropy upon exposure to linearly polarized ultraviolet (LPUV) light. In addition, annealing the photoreacted films enhanced molecular reorientation perpendicular to polarization direction of LPUV light, and the molecular terminal groups strongly affected the reorientation behavior.

Molecularly Oriented Liquid Crystalline Polymer Films Based on Axis-Selective Photo-Fries Rearrangement

Four kinds of liquid crystalline polymers (LCPs) with phenyl benzoate side groups were synthesized and their photoinduced reorientation behavior was investigated using linearly polarized (LP) UV light based on the axis-selective photo-Fries rearrangement and thermally induced self-organization of the mesogenic side groups of the materials. Due to different effect of the axis-selectively photoreacted side groups, reorientation direction and its performance depended on the chemical structure of the side groups. Both alignment ability and the molecular rotation of the photoreacted side groups played an important role in the reorientation behavior.

Photoinduced Reorientation of a Liquid Crystalline Polymer with Phenyl Benzoate Mesogenic Side Groups on the Basis of an Axis-Selective Photo-Fries Rearrangement

Many types of photoreactive polymers have been investigated to regulate their molecularly orientated structures for polarization-controlled optical and display applications. Herein, we demonstrate the axis-selective photoreaction of thin films and their molecular reorientation behaviors using four types liquid crystalline poly(meth)acrylates with phenyl benzoate side groups and linearly polarized (LP) 248 nm light. These simple liquid crystalline polymers (LCPs) exhibit sufficient photoinduced molecular reorientations. Photoinduced molecular reorientation based on an axis-selective photo-Fries rearrangement is simultaneously generated with an in-plane order parameter (S) up to 0.33 when the irradiation temperature is in the lower part of the LC temperature range of the material, but multidomain formation of the mesogenic groups inhibits reorientation. To prevent thermally generated multidomain formation, an axis-selective photoreaction of an amorphous film followed by thermally generated self-organization...

Photoinduced Cooperative Reorientation of Photoreactive Liquid Crystalline Copolymer Films Comprised of Cinnamic Acid and Phenylbenzoate Side Groups

Photoinduced Cooperative Reorientation of Photoreactive Liquid Crystalline Copolymer Films Comprised of Cinnamic Acid and Phenylbenzoate Side Groups

Axis-Selective Photo-Fries Rearrangement and Photoinduced Molecular Reorientation in Liquid Crystalline Polymer Films

The thermally enhanced photoinduced molecular reorientation based on an axis-selective photo-Fries rearrangement was explored for the first time using three liquid crystalline polymethacrylates with 4-(2′-(4″-methoxyphenyl)ethynyl)phenyl benzoate side groups (1a), 4-methoxybiphenyl benzoate side groups (1b), and 4-methoxyphenyl benzoate side groups (1c). All the polymeric films exhibited an axis-selective formation of the photo-Fries products at the phenyl benzoate derivatives side groups by irradiating with linearly polarized (LP) UV light. Annealing the films in the liquid crystalline temperature range of the material greatly amplified the photoinduced small optical anisotropy of the irradiated films. For 1a and 1b, the photoinduced small anisotropy was amplified in a direction parallel to the polarization (E) of LPUV light and the reorientational order (S) was greater than 0.7. In contrast, the orientation direction was perpendicular to E for 1c (S ∼ 0.57). Finally, a simple double-exposure method usin...

Chiral liquid-crystalline copolyacrylates with biphenyl and phenyl benzoate side groups

The phase behavior and structure of liquid-crystalline phases of three series of copolymers with mesogenic units belonging to the families of biphenyls and phenyl benzoates have been studied, with the former mesogenic units containing a chiral center in a flexible spacer. A variation in the isotropization temperature as a function of composition is well described by the additivity rule, whereas the tilt angle of mesogenic groups in smectic layers changes nonlinearly. This angle decreases beginning from homopolymers and attains the minimum value for the copolymers of the equimolar composition, which show the highest ferroelectric activity among the polymer systems under study.

New liquid-crystalline homo-and copolymers with phenyl benzoate side groups and a chiral center in a flexible spacer

The phase behavior and structure of liquid-crystalline homo-and copolymers based on structurally isomeric units belonging to the family of phenyl benzoates that differ in orientation of an ester link situated between benzene rings have been studied with X-ray diffraction, scanning calorimetry, and polarization optical microscopy. The orientation of this link in the monomer unit affects the temperature of phase transition, the type of the smectic phase, and the packing mode of side mesogenic groups in smectic layers of homopolymers. When monomer units commensurable with the monomer units of the basic component in terms of geometry but not identical to them in terms of smectogenity are randomly incorporated into macromolecules of the LC polymer, the resulting copolymer is characterized by layered packing not typical of either of the components.

An infrared spectroscopic study of photo-induced reorientation in dye containing liquid-crystalline polymers

Abstract Infrared spectroscopy is used to study simultaneously the orientational behaviour of different segments of dye containing liquid-crystalline side group copolymers in sandwich type films of about 2 μm thickness. Under continuous irradiation with polarized light above and below T g of the polymers both azobenzene and phenyl benzoate side groups reorient preferentially normal to the film plane leading to a strongly biaxial orientation distribution. The analysis of the kinetics reveals that the reorientation is essentially a mono-exponential process with an additional faster process only found for the azobenzene dye and assigned to the initial trans to cis isomerization step. Investigation of an isotropic copolymer system containing azobenzene in the side groups shows that an anisotropy can be induced through irradiation with polarized light that is strongly dependent on temperature.

Ferroelectric liquid-crystalline polymethacrylates

Abstract The ferroelectricity in the chiral smectic C phase of two comb-shaped liquid-crystalline polymers with a methacrylic main chain, phenyl benzoate side groups and chiral fragments of different types have been studied using the pulse pyroelectric method. The spontaneous polarization, pyroelectric coefficient and some relaxation times associated with two different molecular motions have been evaluated.

Mesophases in polymers with phenylbenzoate side groups

Polyacrylates with phenylbenzoate mesogenic side groups were synthesized. Their structure and phase transitions were studied by optical microscopy, X-ray diffraction, and differential scanning calorimetry. Polymers with short alkyl substituents in the mesogenic group form only nematic mesophases. A nematic mesophase characterized by hexagonal ordering of the mesogenic groups was found to exist in one of the prepared polymers. Polymers carrying alkyl substituents with 3 to 4 carbon atoms are capable to form smectic and nematic mesophases. The arrangement of mesogenic groups in oriented samples was found to depend on the type of liquid crystalline order existing in the polymer during orientation.

High-ordered smectic phases and polymorphic transformations in comb-like liquid crystal polymers

The structural ordering of high-ordered smectic phases in comb-liquid crystalline polymers having main chains (backbones) of different nature (acrylate and methacrylate) but identical phenyl benzoate side groups and also the structural transitions between than are studied. The correlational lengths along the layer plane and normal to it are evaluated from small and wide angle X-ray scattering data, and it is concluded that low and high temperature smectic phases of the acrylate polymer can be assigned to type B and A smactic types respectively. The polymorphic transformations of the methacrylate polymer follow the scheme: F smectic-C smectic-A smectric isotropic liquid.

Structure of Polymers With Phenyl Benzoate Side Groups By X-Ray Evidence

Abstract Structure of four polymers were studied: poly-p-methacryloyloxy phenyl esters of p-n-hexyloxy benzoic acid (PMB-6), p-n-heptyl benzoic acid (PMH-7) and p-n-heptyl - trans-cyclohexane carboxylyc acid (PMC-7) and poly-p-n-hexyloxy phenyl ester of pmethacryloyloxy benzoic acid (PM-06). Diffractions parameters and polymer organization were discussed in terms of both crystallinity and paracrystal. The structural organization of PMB-6, PMH-7 and PM-06 was interpreted on the basis of block model. Structure of PMC-7 assumed to be organized similar to cybotactic nematics.

Thermal effects on liquid‐crystalline order in polymers with mesogenic side groups

AbstractX‐ray studies on polymers with phenyl benzoate side groups separated from the main chain by spacer groups of various lengths have been performed. It was found that the dimensions of liquid‐crystalline regions are 15–20 nm, and they contain four to six close‐packed layers. Thermal changes in x‐ray scattering are associated with the variation of sizes and concentration of liquid‐crystalline regions determined by the mobility of the main chain.

Influence of length of the aliphatic group on the character of liquid-crystalline orderliness in polymers with phenyl benzoate side groups

An X-ray investigation has been made of a number of polymers with side mesogenic groups and different degrees of bonding of side groups and the main chain. Models of layered packing are proposed for the members of the series studied. It was found that with increase in the length of the spacer groups by more than 1·2 nm separate packing of the chains and side mesogenic groups takes place. The corresponding polymer is crystalline at room temperature. On melting this polymer the smectic B-phase forms. Rise in temperature leads to increase in the concentration and size of the regions of liquid crystalline orderliness in polymers with strong bonding of the main chains and side groups and worsening of the orderliness in the polymer with independent packing of the main chains and side groups.

Microheterogeneous structure of liquid crystalline polymers

Liquid crystalline polymers with phenyl benzoate side groups with various lengths of flexible chain-end were synthesized. Small-angle X-ray scattering studies were carried out. Layer structures in the liquid crystalline polymers were characterized and the microheterogeneous structure was investigated. It was concluded that the microstructure is dependent on the length of the flexible mesogenic chain-end.