摘要:

The synthesis of two series of liquid crystalline polyoxiranes and polyoxetanes containing 4-(4-hydroxybiphenyl-4′-carbonyloxy)- phenyl (2S,3S)-2-chloro-3-methylvalerate side groups is presented. Differential scanning calorimetry, polarizing optical microscopy and X-ray diffraction measurements reveal liquid crystalline phases for all obtained polymers. A majority of the prepared polyoxiranes present cholesteric, smectic A, chiral smectic C and an undefined smectic phases. Most of the prepared polyoxetanes reveal only a chiral smectic C phase. Effect of polymer backbone and spacer length on the mesomorphic properties of the obtained polymers is discussed. Although the polyoxirane and polyoxetane backbone are more flexible than the polymethacrylate backbone, side-chain crystalization does not occur in any of the synthesized polymers.

ISSN:1058-725X    

DOI:10.1080/10587259808045372

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A series of novel thermotropic side-chain liquid crystalline polymer based on polymethacrylate backbone containing electron-accepting 4-(4′-nitrophenylazo)phenoxy as nonlinear optical active group and electrondonating 4(4′-methoxyphenyl) phenoxy group as mesogen attached covalently to the backbone through the flexible spacer was prepared and characterized, respectively. The results from differential scanning calorimetry showed that these series of copolymers were enantiotropic liquid crystal with single mesophase. The melting points and the relative enthalpy change of the copolymers depressed with increasing the molar percent of 4′-nitroazobenzene monomer units over 0∼50mol%, but the enthalpies change of the transition from mesophase to isotropic state increased for the copolymers containing 0∼50mol% 4′-nitroazobenzene units. The texture observed under polarized optical microscope identified that the copolymers containing 24molar% or more than 24mol% 4-nitroazobenzene monomer units could form smectic mesophase with the focal-conic texture. The results detected by WAXD were in good agreement with the results observed by POM.

ISSN:1058-725X    

DOI:10.1080/10587259808045373

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The second harmonic generations (SHG) of liquid crystalline main-chain type polymers were investigated. The sample polymers are copolymers of 2-hydroxy-6-naphthoic acid (HNA) with 4-hydroxy-benzoic acid (PHB), in various composition ratios. The SHG of the film samples was greatly affected not only by the polymerization conditions, but also by preparation conditions of the films. SHGs for the samples processed by mechanical stretching and for electrically poled samples were compared. The nonlinear optical coefficients dexpevaluated by Maker Fringe method of the electrically poled samples are 2–3 times larger than that of the mechanically oriented sample whose dexpis about 5pm/V. Trials of Quasi-Phase Matching of periodically inverted-polarized films show very effective to improve SH efficiency. A method mat can control SH efficiency by application of electric field is proposed.

ISSN:1058-725X    

DOI:10.1080/10587259808045374

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Optical switching behavior of polymer azobenzene liquid crystal (LC) was investigated by the use of reflection-mode analysis. Intensity of reflected light from the interface between glass substrate and sample changed in 300 μs on pulse irradiation. This response time is similar to that observed in the low-molecular-weight LCs. On the other hand, we obtained a slower decay than that observed in the low-molecular-weight LCs. The slower decay in the polymer LC may be due to slower diffusion and reorientation processes which are characteristic of the reflection-mode analysis. In the polymer, photoresponsive moiety is linked to a main chain through a chemical bond and mobility of the mesogen is suppressed, which leads to the slower diffusion and reorientation processes becomes slow in the polymer LC.

ISSN:1058-725X    

DOI:10.1080/10587259808045375

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The orientational behavior for a series of side-chain liquid-crystalline polysiloxanes incorporating azo chromophores, i.e., poly(3-{4-[(4-nitrophenyl)azo]phenyl]oxycarbonyl}propylmethylsiloxane)-co-(3-carboxypropylmethylsiloxane) (P1), poly {3-[(6-{[4-[(4-nitrophenyl)azo]phenyl]oxy}hexyl)oxycarbonyl]propylmethylsiloxane}-co-(3-carboxypropylmethylsiloxane) (P2), and poly{3-[(11-{[4-[(4-nitrophenyl)azo]phenyl]oxy}undecyl)oxycarbonyl]propylmethylsiloxane}-co-(3-carboxypropylmethylsiloxane) (P3) were investigated by UV-Vis and polarized FTIR-ATR spectroscopy as well as X-ray diffraction measurement using their thin films.P1exhibited highly-ordered smectic and nematic phases as the mesophases. On the other hand,P2andP3showed only smectic C phase. The mesogenic chromophores of these polymers in smectic phases and the once-annealed solid were spontaneously aligned nearly normal to a substrate surface. In the case ofP1, the tilt angle of the mesogenic chromophores in the nematic phase was found to be larger than that in the smectic phase. The tilt angles of the mesogenic chromophores of these polymers in the smectic phase and in the once-annealed solid increased with the increase in the side-chain methylene spacer units. The dependence of the tilt angle on the spacer length was concluded to be attributable to the changes in intermolecular interactions with relation to the degree of the motion decoupling between the side-chain and main-chain.

ISSN:1058-725X    

DOI:10.1080/10587259808045376

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Polyethers with p-alkoxyphenyl groups in the side chain (PEn) were prepared by ring opening polymerization of the corresponding glycidyl ether derivatives. These polyethers exhibited highly ordered smectic phase depending upon the alkoxy chain length. A liquid crystalline phase was formed at the alkoxy chain length of below 12. The mesomorphic properties for the mixed system were originated from adding an alkali metal salt into the non-mesomorphic side chain type polyethers. The mesomorphic temperature range for the mixed system was wider with increasing amount of alkali metal salt. The occurrence of the complexed the side chain type polyethers with the alkali metal salt was confirmed by Raman spectroscopy and X-ray photoelectron spectroscopy measurements (XPS).

ISSN:1058-725X    

DOI:10.1080/10587259808045377

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Constant pressure Monte Carlo simulation is used to discuss the structure of binary mixtures of parallel hard spherocylinders and hard spheres. Results of the simulation indicate that, the smectic layer periodicity is stretched when we add the spheres to the smectic-A phase of the spherocylinders.

ISSN:1058-725X    

DOI:10.1080/10587259808045378

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Monte Carlo simulation based on the Luckhurst-Romano potential has been performed to evaluate the ordering property of liquid crystals in a cell with aligned surfaces. The transition temperature from the nematic to the isotropic phase is the same as that of the bulk system, but the high ordering state is induced near the surface around the transition. In addition, the direction of ordering can be regulated by the ordered particle on the surface. The effect of the alignment surface on the liquid crystal order in the nematic and isotropic phases is estimated by changing the number of alignment particles on the surface.

ISSN:1058-725X    

DOI:10.1080/10587259808045379

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A new liquid crystal polyester with improved moldability (high flow ability and high thermal stability) was developed by controlling molecular structure. This new chemical structure enabled the commercialization of this material in the field of precision electronic parts particularly for the surface mount technology (SMT).

ISSN:1058-725X    

DOI:10.1080/10587259808045380

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Magnetic orientation of poly(ethylene-2,6-naphthalate) (PEN) and isotactic polystyrene (iPS) has been reported. The orientation starts to occur during the induction period of isothermal melt crystallization process, i.e. during the initial stage of crystallization process where no crystal growth is yet observed with respect to the wide angle X-ray diffraction. In the case of PEN, the crystallites obtained at later stages of crystallization were aligned with itsc-axis parallel to the magnetic field, while in the case of iPS, the crystallites obtained were aligned with itsc-axis perpendicular to the magnetic field. X-ray, infrared, and magnetic birefringence measurements indicated that mesophases appearing during the induction period could be responsible for the magnetic orientation of these polymers.

ISSN:1058-725X    

DOI:10.1080/10587259808045381

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor