LIQUID CRYSTAL POLYMERS WITH TWO-DIMENSIONAL MESOGENIC UNITS

A series of 'liquid crystal polymers with two-dimensional mesogeuic units' were synthesized by the polycondensations of the monomer 2, 5-dihydroxybenzylidene-4-phenetidine with a diacid chloride selected from a series of α, ω-bis(4-chloroformylphenyloxy)carbonylalkues. This is the first series of polymers reported under the newly proposed concept 'liquid crystal polymers with two dimensional mesogenic units'.

STUDY ON LIQUID CRYSTAL POLYMERS WITH TWO-DIMENSIONAL MESOGENIC UNITS

A series of liquid crystalline polymers with two-dimensional mesogenic units were synthesized by solution polycondensation at low temperature. All the polymers were liquid crystalline. The melting temperature T;（except that with substituent of methoxy） and the clearing temperature T;of the polymers change regularly with varying of the length of the alkyl substituent groups.

SYNTHESIS AND CHARACTERIZATION OF LIQUID CRYSTAL POLYMERS WITH T-SHAPED TWO-DIMENSIONAL MESOGENIC UNITS (Ⅱ)

A series of liquid crystalline polymers with T-shaped two-dimensional mesogenic unitswere synthesized via low temperature solution polycondensation of 2-(4'-alkoxy-phenyl)hydroquinone with various diacyl dichlorides. The polymers were found to be nematic andshown thermotropic liquid crystalline behaviors through observations using DSC, polarizedmicroscopy and X-ray diffraction. The melting temperature T_m and the isotropizationtemperature T_i of the polymers change regularly with varying of the monomer structures.

SYNTHESIS AND CHARACTERIZATION OF LIQUID CRYSTAL POLYMERS WITH T-SHAPED TWO-DIMENSIONAL MESOGENIC UNITS

Two series of new liquid crystalline polymers with T-shaped two-dimensional mesogenic units were synthesized by low temperature solution polycondensations of 4-substituted N-2, 5-dihydroxybenzylidene aniline monomers with different diacyl dichlorides. The polymers were found to be nematic and shown liquid crystalline behavior. The melting temperature T-m and the clearing temperature T-i of the polymers change regularly with varying of the monomer structures.

SYNTHESIS AND CHARACTERIZATION OF LIQUID CRYSTAL POLYESTERS WITH T-SHAPED TWO-DIMENSIONAL MESOGENIC UNITS(Ⅲ)

A new series of liquid crystal polyesters with T-shaped two-dimensional mesogenic units weresynthesized by melt polycondensation of the diacetates of 2-(4'-alkoxy -phenyl)-hydroquinones with 4,4'-alkylenedioxydibenzoic acid. The polymers were characterized by using polarized microscopy, DSC and X-ray diffraction. It was realized that all the polymers have nematic thermotropic liquid crystallinecharacteristics. The melting temperature (T_m) and isotropization temperature (T_i) of the polymers changeregularly with varying lengths of the alkoxy side group and the length of the alkylene group in the main chainin company with an even-odd effect. The mesophase temperature range also varies regularly with the polymerstructure. It is shown that the mesophase range has been widened.

SYNTHESIS OF MAIN CHAIN LIQUID CRYSTALLINE COPOLYESTERS WITH X-SHAPED TWO-DIMENSIONAL MESOGENIC UNIT AND CROWN ETHER CYCLE

A novel series of main chain liquid crystalline copolyesters with X-shaped two-dimensional mesogenic unit and crown ether cycle of cis-4,4＇-bis（4-hydroxyphenylazo） dibenzo-18-crown-6 was prepared via solution condensation polymerization from 4,4＇-（a;arhexanedioyloxy） dibenzoyl dichloride （MI）, 2,5-bis（p-octyloxybenzoyloxy） hydro-quinone （M2） and cis-4,4＇-bis（4-hydroxyphenylazo） dibenzo-18-crown-6 （M3）. Monomer MI was synthesized by esterification and substitution of adipoyl chloride with p-hydroxybenzoic acid, monomer M2 was synthesized by esterfication and reduction reaction of 2,5-dihydroxybenzoquinone and p-octanoxybenzoyl chloride and monomer M3 was synthesized by diazotization and coupling reaction of cis-diaminodibenzo-18-crown-6 with phenol. The molecular weights of copolyesters are not high, and the intrinsic viscosity [η] of copolyesters ranges from 0.25-0.35. The monomers＇ structures were identified by using elemental analysis, IR, UV, ^1H-NMR, MS, etc. All the copolyesters are yellowish powders and insoluble in THF and CHC13 at room temperature except cPg. The properties of copolyesters were investigated by using GPC, [η] , DSC, TG, WAXD and POM. It was found that all the copolyesters entered into liquid crystal phase when they were heated to above their melting temperature （Tin）. The typical smectic and nematic phase texture can be observed on POM. Their mesophase transition temperature and thermal stability change regularly with varying the content of cis-4,4＇-bis（4-hydroxyphenylazo） dibenzo-18-crown-6 unit in the copolyesters.

SYNTHESIS OF LIQUID CRYSTALLINE COPOLYESTERS WITH T-SHAPED TWO-DIMENSIONAL MESOGENIC UNIT AND CROWN ETHER CYCLE

A novel series of liquid crystalline copolyesters with T-shaped two-dimensional mesogenic unit and crown ether cycle of cis-4,4′-bis(4-hydroxyphenylazo)dibenzo-18-crown-6 was prepared via solution condensation polymerization from 4,4′-(α,ω-hexanedioyloxy)dibenzoyl dichloride(M_1),2-(4′-ethoxyphenyl)hydroquinone(M_2)and cis-4,4′-bis(4- hydroxyphenylazo)dibenzo-18-crown-6(M_3).The molecular weights of copolyesters are not high,and the intrinsic viscosity [η]of copolyesters ranges from 0.29-0.43.The monomers ...

SYNTHESIS AND CHARACTERIZATION OF MAIN CHAIN AROMATIC LIQUID CRYSTAL COPOLYESTERS WITH X-SHAPED AND ROD-SHAPED MESOGENIC UNITS

A series of main chain liquid crystal aromatic copolyesters with X-shaped and rod-shaped mesogenic units were synthesized via solution condensation polymerizations of 4,4'-(alpha,omega-octanedioyloxy)-dibenzoyl dichlorides with 2,5-bis(p-octanoxy benzoyloxy)-hydroquinone and diphenol. All of the copolyesters showed thermotropic liquid crystalline behaviors through observations using DSC, polarized microscopy and X-ray diffraction. The melting point (T-m) and the isotropization temperature (T-i) change regularly with varying the content of diphenol unit in the copolymers.

"LIVING" FREE RADICAL SYNTHESIS OF NOVEL RODCOIL DIBLOCK COPOLYMERS WITH POLYSTYRENE AND MESOGEN-JACKETED LIQUID CRYSTAL POLYMER SEGMENTS

The synthesis of rod-coil diblock copolymers was achieved for the first time by TEMPO-mediated 'living' free radical polymerization of styrene and 2,5-bis [(4-methoxyphenyl)oxycarbonyl] styrene(MPCS). The block architecture of the two diblock copolymers thus prepared, MPCS-b-St(5400/2400) and MPCS-b-St(10800/8700), was confirmed by GPC, DSC studies and the formation of multimolecular micelles. (Author abstract) 10 Refs.

SYNTHESIS AND PROPERTIES OF NEW MESOGEN-JACKETED LIQUID CRYSTALLINE POLYMERS

Some new mesogen-jacketed liquid crystalline polymers (MJLCP) with polymer backbones, spacers, and mesogenic units of different structures were synthesized by radical polymerization. The mesomorphic behavior of these polymers was examined using differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). Their liquid crystallinity is influenced by the variation of polymer backbone, spacer, mesogenic unit and its terminal groups. The results show that 1) a more flexible polymer main-chain is more favorable to the formation of a liquid crystal phase, while 2) a flexible spacer will decrease the 'Jacket Effect' and the liquid crystallinity and 3) a subtle modification of the terminal groups on the mesogenic unit may also have a significant influence on properties of the polymers.

THE EFFECT OF SUBSTITUENT ON THE THERMAL PROPERTIES OF POLYESTERS CONSISTING OF AROMATIC TYPE SCHIFF BASE MESOGENIC UNITS AND POLYMETHYLENE SPACERS

Polyesters consisting of substituted aromatic type Schiff base mesogenic unit andpolymethylene spacers were synthesized and their thermal transitions and liquid crystallineproperties were studied. The liquid crystalline behaviour has been characterized by differentialscanning calorimetry (DSC) and optical polarizing microscopy. Structural broadening bysubstitution of methoxy group in 2, 2' positions of the mesogenic core produce polymers withlower transition temperatures. Polymers synthesized from ortho and meta substituted phenylenediamine did not form a liquid crystal phase.

SYNTHESIS OF A GROUP OF MESOGEN JACKETED LIQUID CRYSTAL POLYMERS

A group of the mesogen jacketed liquid crystal polymers based on the monomers 2,5-bis (4-substituted benzoyl)oxystyrenes are synthesized. The substituents include alkoxy, alkyl, and cyano groups. The synthesis and the primary characterization of the liquid crystal phase of the monomers and the polymers are described. While some of the monomers give smectic textures the polymers are found to be nematic above their melting or glass transition temperatures. Interestingly the unsubstituted monomer and its polymer poly 2,5-di( benzoyloxy ) styrene are also liquid crystalline. The single crystal structure of one of the monomers is also discussed.

NITROXIDE-MEDIATED FREE RADICAL SYNTHESIS OF MESOGEN-JACKETED LIQUID CRYSTAL POLYMERS

The first TEMPO-mediated 'living' free radical polymerization of liquid crystalline monomer, 2, 5-bis[(4-methoxyphenyl)oxycarbonyl]styrene (MPCS), was carried out at 130 degrees C with BPO as an initiator. The molecular weight of the polymer can be varied from rather low values to high values while maintaining narrow polydispersity. It was observed that the polymerization of MPCS proceeded much faster than that of styrene. A tentative explanation for this fast polymerization was suggested.

SYNTHESIS OF A NOVEL "MESOGEN-JACKETED LIQUID CRYSTAL POLYMER" BASED ON VINYLTEREPHTHALIC ACID

Poly{2, 5-bis[(p-methoxyphenyl)oxycarbonyl]styrene} was successfully synthesized. This new polymer has a structure characteristic of mesogen-jacketed liquid cyrstalline polymers (MJLCPs) and does form a liquid crystal phase above its glass transition. It thus became the starting member of a new series of MJLCPs. The synthesis of the polymer as well as the liquid crystalline properties of the polymer and its monomer was discussed. A brief comparison of the new monomer and polymer with some previously reported counterparts was also included.

Restudy of the unusual phase behavior of the mesogen-jacketed liquid crystal polymers

A series of poly{2,5-bis[(4-butoxyphenyl)-oxycarbonyl]styrenes} (PBPCS) with low mo-lecular weight distribution was synthesized by atom transfer radical polymerization (ATRP). The me-somorphic properties were investigated by differential scanning calorimetry (DSC), polarizing optical microscopy (POM) and rheometer. PBPCS showed the phase transition from isotropic into liquid crystal (LC) phase, and the LC phase formed at high temperature and disappeared in the subsequent cooling procedure. Using the WAXD fiber pattern, the phase structure of the PBPCS at higher tem-perature showed hexagonal columnar nematic phase. Experimental results demonstrated that the driving force of the entropy is an important factor during the unusual LC phase formation of PBPCS.

甲壳型液晶高分子的一种非寻常热致液晶行为

A mesogen-jacketed liquid crystal polymer,poly{2,5 -bis［(4′-hexyloxyphenyl)oxycarbonyl］styrene}(PHPCS),with number-average d molecular weight of 1.28×１０5 and polydispersity of 1.48 was prepared vi a 2,2,6,6 -tetramethyl-piperidinyloxy mediated free radical polymerization.The thermotr opic behavior was studied by a combination of differential scanning calorimetry, thermogravimetry,polarized optical microscope and wide-angle X-ray diffracti on.PHPCS was not crystalline over the entire temperature region studied.On hea ting,PHPCS first became an isotropic melt at glass transition temperature (T g) and then a mesophase at temperatures much higher than T g.On subseq uent cooling,the formed ordered phase disappeared above T g.Contrary to t heoretical predictions and previous experimental observations,the transition fr om isotropic melt to liquid crystalline phase was an endothermic process and th e order-disorder transition took place with concurrence of heat release.

甲壳型液晶高分子的化学结构及其与性能间关系的研究

设计并合成了７种新型甲壳型液晶高分子，研究了液晶基元的化学结构和立体效应对单体及其聚合物液晶性的影响．发现在液晶基元的末端引入极性或可极化的原子基团提高了单体的熔点和液晶相的热稳定性；液晶基元的长径比越大，单体的熔点和清亮点越高；聚合使单体的液晶稳定性增加、液晶相温度范围变宽；侧链液晶基元的极性、刚性和空阻越大，聚合物的玻璃化温度越高；酰胺基团无论是在分子的末端还是在连接部位，都使单体的熔点和聚合物的玻璃化温度提高，但在分子末端时液晶相较稳定，作为中心桥键时不利于液晶相的稳定形成．

甲壳型液晶高分子研究进展与展望

简要介绍了甲壳型液晶高分子的模型理论,概述了当前国内外对甲壳型液晶高分子设计、液晶相态、性质及基于甲壳型液晶高分子的嵌段共聚物体系的设计和自组装性质等研究进展,展望了今后的研究方向.

含1,3,4-噁二唑甲壳型液晶聚合物的合成与表征

A series of monomers {2,5-bis[(5-alkyl-phenyl)-1,3,4-oxadiazole] styrene}(BOXE) were designed and synthesized.By radical polymerization initiated BPO with a novel series of mesogen-jacketed polymers containing 1,3,4-oxadiazole were prepared.Molecular weight and molecular weight distribution of polymers were measured by GPC.The glass transition temperature (T_g) and thermal stability of polymers were studied by DSC and TGA.The results indicate that these polymers have good thermal stability.These liquid crystal polymers have well defined structure,and possess special photo-electronic properties.

一类新的液晶共聚物的合成

以含液晶基元的单体４－［４′－（对正丁氧基－苯甲酰氧基）－苯甲酰氧基］－苯基丙烯酸酯和苯乙烯，通过自由基共聚合反应，首次合成了一系列含液晶性单体和非液晶性单体两种结构的共聚物。聚合物的液晶行为用ＤＳＣ、偏光显微镜和Ｘ射线衍射进行了表征，发现单体有热致液晶性；所有的共聚物均为向列型热致液晶高分子和具有较宽的液晶态温度范围；随共聚物中液晶性单体含量增加，共聚物分子量。