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Liquid-Crystalline Polymer (liquid-crystalline + polymer)

Distribution by Scientific Domains

Polymers and Materials Science	93%

Distribution within Polymers and Materials Science

Polymer Science & Technology General	53%
General & Introductory Materials Science	46%

Selected Abstracts

Ionic Liquids: Electropolymerization of a Bifunctional Ionic Liquid Monomer Yields an Electroactive Liquid-Crystalline Polymer (Adv. Funct.

ADVANCED FUNCTIONAL MATERIALS, Issue 13 2010
Mater.
M. A. Firestone et al. present a polymer that incorporates an electronic component with an ionic liquid and produces a mixed ionic and electronic conductor on page 2063. Electropolymerization of a bifunctional imidazolium-based ionic liquid monomer incorporating both vinyl and thiophene groups yields a liquid-crystalline polymer that adopts an interconnected network structure formed by two orthogonally oriented lamellar sheets. The structural ordering leads to enhanced electrical conductivity. [source]

Electropolymerization of a Bifunctional Ionic Liquid Monomer Yields an Electroactive Liquid-Crystalline Polymer

ADVANCED FUNCTIONAL MATERIALS, Issue 13 2010
Sungwon Lee
Abstract The preparation and polymerization of a bifunctional imidazolium-based ionic liquid (IL) monomer that incorporates both a vinyl group and a thiophene moiety is reported. Potentiodynamic electropolymerization of the monomer produces an optically birefringent polymer film that strongly adheres to the electrode surface. Fourier transform IR spectroscopy shows that polymerization occurs through both the vinyl and thienyl groups. Cylic voltammetry (CV) is used to determine the polymer oxidation potential (1.66,V) and electrochemical bandgap, Eg, of 2.45,eV. The polymer exhibits electrochromism, converting from yellow in the neutral form (,max,=,380,nm) to blue in the polaronic state at 0.6,V (,max,=,672,nm) and to blue-grey in the bipolaronic state at 1.2,V (,max,>,800,nm). Topographic atomic force microscopy (AFM) images reveal isolated (separated) fibrils. Grazing-incidence small-angle X-ray scattering (GISAXS) studies indicate a lamellar structure with a lattice spacing of 3.2,nm. Wide-angle X-ray diffraction (WAXD) studies further suggest that the polymerized thiophene sheets are oriented perpendicular to the polymerized vinylimidazolium. The electrical conductivity, as determined by four-probe dc conductivity measurements was found to be 0.53,S cm,1 in the neutral form and 2.36,S cm,1 in the iodine-doped state, values higher than typically observed for polyalkylthiophenes. The structural ordering is believed to contribute to the observed enhancement of the electrical conductivity. [source]

Liquid-Crystal Polymers: Liquid-Crystalline Polymer with a Block Mesogenic Side Group: Photoinduced Manipulation of Nanophase-Separated Structures (Adv. Funct.

ADVANCED FUNCTIONAL MATERIALS, Issue 23 2009
Mater.
The inside cover image represents a novel azobenzene liquid-crystalline (LC) polymer with a block mesogenic side group, which exhibits a lamellar structure after annealing in an LC phase. Whereas irradiation with linearly polarized light aligns the lamellae parallel to the polarization, irradiation with unpolarized light erases the surface morphology accompanied by photochemical phase transition, as reported by K. Okano et al. on page 3804. [source]

Liquid-Crystalline Polymer with a Block Mesogenic Side Group: Photoinduced Manipulation of Nanophase-Separated Structures

ADVANCED FUNCTIONAL MATERIALS, Issue 23 2009
Kunihiko Okano
Abstract In this report, a novel type of photoresponsive liquid crystalline polymer with a block mesogenic side-group is demonstrated. The block mesogene is an amphipathic molecule containing a hydrophobic mesogene (azotolane moiety) and hydrophilic oligooxyethylene moieties in the same unit. The block mesogene in the polymer plays a role in liquid crystalline, amphiphilic and photoresponsive properties. As expected, a film prepared from the polymer exhibits phase separation of a lamellar structure due to cooperative motion between liquid crystal assembly and nanophase separation. The morphology of the lamellae can be aligned upon irradiation of linearly polarized light. Moreover, a photochemical phase transition induced by unpolarized UV irradiation erases the surface morphology. The erased nanostructure can be recovered by annealing or irradiation of linearly polarized light, meaning that the surface morphology is rewritable via a photochemical process. [source]

Azobenzene Liquid-Crystalline Polymer for Optical Switching of Grating Waveguide Couplers with a Flat Surface

MACROMOLECULAR RAPID COMMUNICATIONS, Issue 9 2007
Chong-Uk Bang
Abstract Grating waveguide couplers with a flat surface were fabricated in an azobenzene liquid-crystalline polymer film by holographic lithography using Ar+ laser beams at 488 nm. When a probe beam at 633 nm was incident to one grating of a grating waveguide coupler, the beam propagated in the waveguide and an output beam came out from the other grating with the throughput coupling efficiency of ,5%. Upon irradiation of the film between two gratings with UV light to cause trans,cis photoisomerization of the azobenzene moiety, the intensity of the output beam was repeatedly switched. It was found that the alternating irradiation at 366 and 436 nm induced reversible changes in the intensity of the guided probe beam. [source]

Photoresponsive Ferroelectric Liquid-Crystalline Polymers

ADVANCED FUNCTIONAL MATERIALS, Issue 1 2007
P. Beyer
Abstract The photoresponse of ferroelectric smectic side-chain liquid-crystalline (LC) polymers containing a photoisomerizable azobenzene derivative as a covalently linked photochromic side group is investigated. By static measurements in different photostationary states, the effect of trans,cis isomerization on the material's phase-transition temperatures and its ferroelectric properties (spontaneous electric polarization PS and director tilt angle ,) are analyzed. It turns out that the Curie temperature (transition SC* to SA) can be reversibly shifted by up to 17,°C. The molecular mechanism of this "photoferroelectric effect" is studied in detail using time-resolved measurements of the dye's optical absorbance, the director tilt angle, and the spontaneous polarization, which show a direct response of the ferroelectric parameters to the molecular isomerization. The kinetics of the thermal reisomerization of the azo dye in the LC matrix are evaluated. A comparison to the reisomerization reaction in isotropic solution (toluene) reveals a faster thermal relaxation of the dye in the LC phase. [source]

Phase Separation and Organisation of Colloidal Spheres Suspended in Sheared Lyotropic Liquid-Crystalline Polymers

MACROMOLECULAR RAPID COMMUNICATIONS, Issue 11 2005
Shanju Zhang
Abstract Summary: Organisation behaviours of spherical particles suspended in sheared, lyotropic, liquid-crystalline polymer solutions have been investigated using polarizing optical microscopy. We find that in a nematic phase the particles phase separate and adopt anisotropic chain-like structures along the director. An earring defect is observed around a single particle whereas a cross or strings defect between neighbouring particles is found to serve as a repulsive barrier to prevent the particles from contacting each other. A theoretical analysis is presented to explain this new phenomenon. An optical micrograph of 0.01 wt.-% glass spheres suspended in a nematic solution of 40 wt.-% ethyl cellulose in chloroform under an external shear force. [source]

Microstructures Based on Thermotropic Liquid-Crystalline Polymers in the Low Molar Mass Nematogenic 5CB

MACROMOLECULAR SYMPOSIA, Issue 1 2005
Fabiano V. Pereira
Abstract Summary: The unique characteristics of two polyacrylates having the same side chain chiral mesogenics groups and different spacer lengths allowed the stabilization of ordered polymer rich-phases in solution with the nematic solvent 5CB. These microstructures are smectic having fibrous-like and rode-like morphologies, in spite of the mesophases of the polymers in bulk. The interactions between the mesogenic groups in the polymer and the solvent 5CB stabilize the microstructures and leads to birefringence at temperatures above the 5CB clearing point. Polarized optical microscopy data are complemented by SAXS to fully describe the mesomorphic behavior of the mixtures. [source]

Correlation of Intramolecular Excimer Emission with Lamellar Layer Distance in Liquid-Crystalline Polymers: Verification by the Film-Swelling Method,

ANGEWANDTE CHEMIE, Issue 8 2010
Wang-Eun Lee
Aufgequollen: Aufgrund der Stapelung von Phenylgruppen in den Seitenketten zeigen Poly(diphenylacetylen)-Derivate mit unterschiedlich langen Alkylgruppen eine intramolekulare Excimer-Emission, die intrinsisch mit dem Schichtenabstand in Filmen zusammenhängt. In Quellexperimenten konnte die Excimer-Emission durch Veränderung dieses Abstands variiert werden (siehe Bild). [source]

Ionic Liquids: Electropolymerization of a Bifunctional Ionic Liquid Monomer Yields an Electroactive Liquid-Crystalline Polymer (Adv. Funct.

An Azotolane Liquid-Crystalline Polymer Exhibiting Extremely Large Birefringence and Its Photoresponsive Behavior

ADVANCED MATERIALS, Issue 4 2006
K. Okano
A liquid-crystalline polymer (LCP) containing an azotolane group in the mesogenic moeity has been synthesized (see Figure). A homogeneously aligned film of the LCP exhibits an extremely large birefringence in a wide wavelength range. Upon irradiation by a pump laser beam, a large change in birefringence is quickly induced as a result of destruction of the homogeneous alignment of the azotolane moieties. [source]

Synthesis of a novel hybrid liquid-crystalline rod,coil diblock copolymer

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 12 2003
Yi Yi
Abstract A series of novel rod,coil diblock copolymers on the basis of mesogen-jacketed liquid-crystalline polymer were successfully prepared by atom transfer radical polymerization from the flexible polydimethylsiloxane (PDMS) macroinitiator. The hybrid diblock copolymers, poly{2,5-bis[(4-methoxyphenyl)oxycarbonyl]styrene}- block -polydimethylsiloxane, had number-average molecular weights (Mn's) ranging from 9500 to 30,900 and relatively narrow polydispersities (,1.34). The polymerization proceeded with first-order kinetics. Data from differential scanning calorimetry validated the microphase separation of the diblock copolymers. All block copolymers exhibited thermotropic liquid-crystalline behavior except for the one with Mn being 9500. Four liquid-crystalline diblock copolymers with PDMS weight fractions of more than 18% had two distinctive glass-transition temperatures. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1799,1806, 2003 [source]

Flow behaviour and microstructure evolution in novel SiO2/PP/LCP ternary composites: effects of filler properties and mixing sequence

POLYMER INTERNATIONAL, Issue 2 2003
Mun Wai Lee
Abstract When silica (SiO2) fillers were introduced into the polypropylene (PP) and liquid-crystalline polymer (LCP) blend, it was found that the mixing sequence, the filler size, and the filler surface nature affected the rheology of the composites and the morphology of the LCP phase in the ternary composite. In particular, the compatibility between the filler and the PP matrix was found to exert a strong influence on the droplet-fibril transition. The incorporation of the hydrophobic silica to the LCP/PP blend facilitated the fibrillation of LCP because the hydrophobic filler demonstrated affinity towards the hydrophobic PP matrix. The preferential residence of the hydrophobic silica in the PP phase would minimise the LCP domain disruption leading to the formation of LCP fibrils with high aspect ratios. The use of fine filler and in situ blending, which promoted the filler,LCP interaction, could prevent coalescence, inhibit deformation and hinder fibril development as well. © 2003 Society of Chemical Industry [source]

Studies on the modification of poly(,-bromoalkyl-1-glycidylether)s with 4,-methoxybiphenyl-4-oxy mesogenic groups

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 23 2005
J. M. Montornés
Abstract A series of poly[,-(4,-methoxy-biphenyl-4-oxy)alkyl-1-glycidylether]s were synthesized by chemically modifying the corresponding poly(,-bromoalkyl-1-glycidylether)s with the sodium salt of 4-hydroxy-4,-methoxybiphenyl. New high-molecular-weight side-chain liquid-crystalline polymers were obtained with excellent yields and almost quantitative degrees of modification. They were all insoluble in THF and other common solvents. Characterization by 13C NMR confirmed that all the polymers had the expected structure. The liquid crystalline behavior of the polymers was analyzed by DSC and polarized optical microscopy, and mesophase assignments were confirmed by X-ray diffraction studies. Polymers that had alkyl spacers with n = 2 and 4 were smectic C, those that had spacers with n = 6 and 8 were nematic cybotactic, and those that had longer spacers (n = 10 and 12) were smectic C again. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5998,6006, 2005 [source]

Living free-radical polymerization (reversible addition,fragmentation chain transfer) of 6-[4-(4,-methoxyphenyl)phenoxy]hexyl methacrylate: A route to architectural control of side-chain liquid-crystalline polymers

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 19 2003
Xiaojuan Hao
Abstract Side-chain liquid-crystalline polymers of 6-[4-(4,-methoxyphenyl)phenoxy]hexyl methacrylate with controlled molecular weights and narrow polydispersities were prepared via reversible addition,fragmentation chain transfer (RAFT) polymerization with 2-(2-cyanopropyl) dithiobenzoate as the RAFT agent. Differential scanning calorimetry studies showed that the polymers produced via the RAFT process had a narrower thermal stability range of the liquid-crystalline mesophase than the polymers formed via conventional free-radical polymerization. In addition, a chain length dependence of this stability range was found. The generated RAFT polymers displayed optical textures similar to those of polymers produced via conventional free-radical polymerization. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2949,2963, 2003 [source]