手性丙烯酸酯侧链液晶共聚物的研究

手性丙烯酸酯侧链液晶共聚物的研究何流，张树范，漆宗能，王佛松（中国科学院化学研究所北京１０００８０）关键词手性液晶，近晶相，丙烯酸酯共聚物侧链液晶聚合物既具有小分子液晶的光电敏感性，又具有高分子聚集态结构性质，在光学记录、贮存和显示材料领域有潜在的实...     

含不同柔性链的(甲基)丙烯酸酯类液晶高分子的合成及其液晶行为研究

通过改变侧链中柔性间隔基的长度,合成了一系列含有两个手性中心的侧链液晶（甲基）丙烯酸酯类聚合物.红外、核磁和GPC表征各中间体、单体及聚合物的结构和分子量.通过DSC和热台偏光显微镜系统地研究了单体和聚合物的液晶态织构.结果表明,含有六个碳的柔性间隔基的丙烯酸酯类聚合物表现为近晶SA和手性近晶SC^＊液晶相.     

具有氟烷基边链和手性中心液晶化合物的合成及液晶性研究

本文设计合成了十个含氟烷基边链和手性中心的液晶化合物，并通过DSC和偏光显微镜对它们的液晶性进行了研究。其中二环系液晶化合物不显示液晶相或仅显示单边近晶A相。三环系液晶化合物中较长的氟烷基边链有利于近晶相的形成，且当液晶核另一端的烷氧基链的长度适中时，在氟烷基边链和液晶核之间具有手性中心的液晶分子显示了手性近晶C相和其它液晶相。     

手性席夫碱型液晶化合物的合成与表征

手性席夫碱型液晶化合物的合成与表征田颜清，林凤，赵英英，汤心颐，苏峰煜，赵晓光，周恩乐（吉林大学化学系长春１３００２３）（中国科学院长春应用化学研究所长春）关键词近晶相液晶，手性液晶，席夫碱，合成，表征自从１９７５年Ｍｅｙｅｒ等［１］首次合成铁电液晶...     

对-2,2,3,3,4,4,5,5-八氟戊氧基苯甲酸胆固醇酯的合成和液晶相变研究

液晶显示技术中主要应用的是向列相液晶,但是向列相液晶显示模式几乎已接近极限,从TN到STN直至TRF,对其应用没有新的理论模式.因而,人们将目光转移到了近晶相液晶上,目前各近晶相中的手性近晶C相,即铁电相引起人们广泛兴趣.铁电液晶具备向列相液晶所不具备的高速度(微秒级)和记忆性的优异特征,它们在最近几年得到大量研究.含氟链分子容易形成近晶A相和近晶C相,常作铁电液晶配方.这些铁电液晶(FLC)化合物包含一个或多个手性中心,而甾体可作为廉价的手性源,其衍生物有形成铁电相的可能.虽然理论已经预测到铁电现象在非手性液晶中也是可能的,但实际上长期以来铁电性只在手性分子的SmC*相中被发现.如Vill等[1]报道过包含一个长烷基链的甾类液晶,即对十六烷基苯甲酸胆甾醇酯和对十六环氧苯基碳酸盐,均显示了单变铁电性.Janulis等[2]已经列举(CH2)n作为氟化链和刚性核之间的空间间隔对获得介晶C相有利.我们在此报道对-2,2,3,3,4,4,5,5-八氟戊氧基苯甲酸胆固醇酯的合成及其液晶相变研究的结果.     

环氧液晶弹性体材料的制备与力学性能研究

传统的液晶弹性体材料多采用丙烯酸酯类或聚硅氧烷类分子,通过自由基聚合制备.然而由于自由基聚合易被氧气阻聚,固化过程收缩率高且内应力大,传统液晶弹性体材料的力学性能并不是很优异.为解决这一问题,本文合成了带有环氧基团的液晶单体和交联剂,使用碘鎓盐作为引发剂,通过光引发阳离子反应,用原位聚合交联法制备了环氧液晶弹性体材料.光引发阳离子聚合和传统自由基聚合相比,不受氧气影响且弹性体固化时体积收缩率小.对制备出的液晶弹性体材料的晶相和力学等性能进行探究和表征,发现其比传统的丙烯酸酯类或者聚硅氧烷类液晶弹性体材料具有更优异的力学性能,在清亮点以上,其弹性模量达到了0.92 MPa.     

胆甾相液晶结构色的光调控

胆甾相液晶是一类具有周期性螺旋超结构的软光子晶体,能够选择性地反射不同波长的光产生结构色.在向列相液晶中掺杂光响应手性分子是制备光响应胆甾相液晶的普遍方法.在外界光源的刺激下,光响应手性分子的空间结构改变,诱导螺旋超结构的螺距发生变化,从而调控胆甾相液晶的结构色,因此光响应胆甾相液晶在滤光器、传感器、可调光学激光器和动态显示等领域具有广阔的应用前景.总结了不同光响应手性分子构筑的胆甾相液晶体系,分析了手性分子结构设计对胆甾相液晶结构色调控的影响,最终讨论了光响应胆甾相液晶目前面临的挑战以及未来的发展方向.     

液晶性芳香醛化合物的合成

以对羟基苯甲醛和对烷氧基联苯酰氯为原料,采用爱因宏反应,合成了一系列4-(4'-烷氧基联苯基-4-羧基)苯甲醛.化合物的结构通过元素分析、红外光谱、核磁共振和质谱等方法确证.化合物的液晶行为用示差扫描量热法、偏光显微镜和旋光仪等方法表征.结果表明,所有的化合物加热至各自的熔点以上都能形成液晶态.在液晶态可以观察到手性近晶C相、近晶相、胆甾相和向列相的典型织构.含手性中心的化合物都有较高的旋光性,而且在合成反应中旋光性得到保持.随着分子末端烷氧基碳原子数增加,化合物(除2a和4a外)的熔点(T_m)和液晶态的清亮点(T_i)呈规律性变化,近晶相范围和近晶相-向列相转变温度渐增,而向列相温度范围递减,至十二烷基时,仅呈现近晶性.     

在电场和磁场下手性侧链丙烯酸酯液晶聚合物的行为

在电场和磁场下手性侧链丙烯酸酯液晶聚合物的行为江雪平金顺子漆宗能张树范（中国科学院化学研究所北京１０００８０）关键词手性侧链丙烯酸酯液晶聚合物，红外二向色性，液晶分子排列含有手性液晶基团的聚合物，分子中含有不对称碳原子，在一定条件下使液晶聚合物...     

新型手性近晶C相液晶共聚酯的设计与合成

以对苯二甲酰氯 ,2 ,5 二 [4 ((s) 2 甲基丁氧基 )苯甲酰氧基 ]对苯二酚和乙二醇、一缩乙二醇、二缩三乙二醇、三缩四乙二醇和聚乙二醇为单体 ,采用低温溶液缩聚方法 ,合成了一系列新的手性近晶C相串型液晶共聚酯 .共聚酯通过GPC、DSC、TG、WAXD、偏光显微镜和旋光仪等方法表征 .发现所有的共聚酯加热至各自的熔点以上都能形成液晶态 ,在液晶态可以观察到近晶相的焦锥织构 ,所有的手性化合物和共聚酯都有较高的旋光性 .通过变温X 射线衍射研究结合偏光显微镜观察和旋光分析证明它们为手性近晶C相 .所有共聚酯的熔融温度 (Tm)和各向同性温度 (Ti)随共聚酯中不同柔性链段长度的增加逐渐降低 ,液晶态温度范围变宽     

Alkyl chain length effects on copolymerization kinetics of a monoacrylate with hexanediol diacrylate

Copolymerizations of hexanediol diacrylate with three monoacrylates were analyzed using high-throughput conversion analysis to elucidate the effects of varying alkyl pendant groups at different compositions. Each analyzed copolymerization system contained hexanediol diacrylate (HDDA), and copolymerizations with 30-60 wt % monoacrylate reached nearly complete conversion after 30 s of exposure time. For higher amounts of monoacrylate, the photopolymerization kinetics of the hexyl acrylate (HA) copolymerization were significantly slower than the copolymerization with either ethylhexyl acrylate (EHA) or dodecyl acrylate (DDA). With 20 wt % HDDA, conversion at 30 s with a comonomer of HA was 62+/-3%, as compared to 76+/-3% and 84+/-3% when copolymerized with EHA and DDA, respectively. Model kinetic parameters were estimated for all four monomer systems, with HDDA monomer parameters found to be within the same error when estimated from any of the copolymerizations. With kinetic parameters for each monomer, comparison maps showing the difference in conversion between two copolymerizations were generated. These comparison maps allow for an assessment of two comonomer systems to determine the optimal photopolymerization conditions. Slower photopolymerization kinetics for HA occur at nearly all compositions containing monoacrylate, with the largest reduction occurring between 20 and 40 wt % monoacrylate.     

Thermal properties and ionic conductivity of a polymer prepared by the in situ photopolymerization of a vinylimidazole monomer containing a mesogenic group

We have synthesized liquid crystalline polymers containing an imidazolium salt moiety and a mesogenic group by the in situ photopolymerization of a liquid crystalline vinylimidazole monomer in order to investigate the relationship between their thermal properties and ionic conductivity. A smectic phase was shown by the vinylimidazole monomer. The in situ photopolymerization of the monomer was carried out in the temperature range of the smectic phase. The polymer thus prepared displayed a highly ordered smectic phase in the temperature range between room temperature and about 200°C. The ionic conductivity of the polymer increased with increasing temperature. Anisotropic ionic conductivity behavior was observed for the polymer. The ionic conductivity of the polymer aligned homogeneously is larger than when homeotropically aligned.     

不同醇对聚合物分散液晶光聚合动力学及其电光特性的影响

以丙烯酸-2-乙基己酯(EHA)、二甲基丙烯酸乙二酯(EDMA)/季戊四醇四丙烯酸酯(PETTA)为混合单体、液晶P0616A为液晶相、Irgacure 184为光引发剂,通过UV光引发制备了聚合物分散液晶(PDLCs),研究了不同烷基链长醇,即乙醇(EtOH)、正丁醇(nBA)、正己醇(nHA)、正辛醇(nOA)和正十四醇(nTA)对体系光聚合动力学及其PDLCs液晶相变温度及电光特性的影响.结果表明引入醇分子显著加快了丙烯酸酯/液晶复合体系的光聚合反应速率,提高了单体的最终转化率,其中以正丁醇体系最为明显.随着醇分子烷基链的增长,体系的转化率趋于降低,但依然明显高于不含醇的体系.醇分子的加入降低了PDLCs中液晶相的TNI,且随着醇分子烷基链长的增长,PDLCs液晶相的TNI总体上呈降低的趋势.醇分子的加入增加了PDLCs液晶微区中向列相液晶的含量,而含正丁醇和正十四醇的体系液晶微区中向列相液晶低于其它3个含醇体系.醇分子的加入明显降低了PDLCs的阈值电压和饱和电压以及对比度.结合体系的光聚合速率和单体转化率,正丁醇是改善PDLCs性能的最佳选择.     

Polymerization and viscoelastic behavior of networks from a dual‐curing,liquid crystalline monomer

The network formation and viscoelastic behavior of a liquid crystalline monomer, whose structure includes both acrylate and acetylene reactive groups, have been studied. By combining both photo and thermal polymerization, the networks can be formed in two separate steps, with the initial photopolymerization dominated by acrylate crosslinking and subsequent thermal polymerization dominated by acetylene crosslinking. In addition, the monomer exhibits a liquid crystalline phase. Photopolymerization while in the liquid crystal phase locks in the molecular ordering. Dynamic mechanical analysis shows that networks formed from the liquid crystalline phase have lower crosslink densities and narrower distributions of molecular weights between crosslinks when compared to networks formed from the isotropic phase (and at higher polymerization temperatures). After thermal postcure at 250°C, the networks formed from the isotropic monomer have a 23% higher dynamic mechanical storage modulus (in the glassy state) than the networks formed from the liquid crystalline monomer. The thermally postcured networks have unusually high glass‐transition temperatures, which exceed 300°C. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1183–1190, 1999     

KCD/MDEA/TA三元引发剂引发丙烯酸酯/液晶复合体系光聚合动力学

采用配有441.6 nm滤光片的光差示扫描量热仪研究了3,3'-羰基双(7-二乙胺香豆素)(KCD)/N-甲基二乙醇胺(MDEA)/2-(4-甲氧苯基)-4,6-双(三氯甲基)-1,3,5-三嗪(TA)三元引发剂引发丙烯酸酯/液晶复合体系光聚合动力学行为. 结果表明, 在KCD/MDEA复合引发剂中添加TA, 显著提高了丙烯酸酯/液晶复合体系的最大光聚合速率[R_p(max)]和单体转化率, 当TA质量分数为0.5%时, 体系的R_p(max)和单体转化率分别提高了100%和69%. 同时, 随着光照强度的增加, 该体系的R_p(max)和单体转化率呈增大的趋势, 当光强从1.5 mW/cm⁺²提高到35.2 mW/cm⁺²时, 其R_p(max)和最终单体转化率分别提高了2.5和2.8倍.     

Polymer nanostructure development of fluorinated and aliphatic monoacrylates in smectic liquid crystals via photopolymerization

To develop viable polymer stabilized liquid crystal systems, it is crucial to understand the factors that affect polymer nanostructure evolution. This work examines the influence of the photopolymerization of aliphatic and fluorinated monoacrylate monomer within a room temperature smectic liquid crystal (LC). Additionally, the effect of LC order on polymerization kinetics, monomer and polymer organization, and the effect of the polymer on LC properties have been examined. Through this work, insight has been gained regarding the impact that the introduction of a fluorinated monoacrylate monomer has on polymerization kinetics, LC organization, and monomer/polymer segregation and organization within a polymer/LC system. Fluorinated moieties lower the surface energy of the monomer to enhance segregation between the smectic layers of the LC as compared with an analogous aliphatic monomer. Additionally, the enhanced segregation significantly increases the polymerization rate in the smectic phase and drives the continued segregation of the fluorinated polymer during and after polymerization. Fluorination also leads to the formation of an ordered polymer nanostructure if polymerized in ordered LC phases. This ordering is particularly evident when the fluorinated monomer is polymerized in the smectic phase in which the monomer is organized between the smectic layers of the LC. In addition, the ordered polymer structure found with the fluorinated monomer in the smectic phase leads to continued birefringence above the clearing point of the LC due to surface interactions between the LC and the ordered fluorinated polymer. The continued birefringence offers an exceptional opportunity to examine how factors such as polymer molecular mass and UV light intensity affect the overall polymer morphology of these polymer/LC systems. As the initiator concentration and UV light intensity are decreased, longer polymer chains form lattice-type morphologies; whereas, shorter polymer chains form smoother morphologies that more closely mirror the texture of the LC smectic phase.     

Polymer nanostructure development of fluorinated and aliphatic monoacrylates in smectic liquid crystals via photopolymerization

To develop viable polymer stabilized liquid crystal systems, it is crucial to understand the factors that affect polymer nanostructure evolution. This work examines the influence of the photopolymerization of aliphatic and fluorinated monoacrylate monomer within a room temperature smectic liquid crystal (LC). Additionally, the effect of LC order on polymerization kinetics, monomer and polymer organization, and the effect of the polymer on LC properties have been examined. Through this work, insight has been gained regarding the impact that the introduction of a fluorinated monoacrylate monomer has on polymerization kinetics, LC organization, and monomer/polymer segregation and organization within a polymer/LC system. Fluorinated moieties lower the surface energy of the monomer to enhance segregation between the smectic layers of the LC as compared with an analogous aliphatic monomer. Additionally, the enhanced segregation significantly increases the polymerization rate in the smectic phase and drives the continued segregation of the fluorinated polymer during and after polymerization. Fluorination also leads to the formation of an ordered polymer nanostructure if polymerized in ordered LC phases. This ordering is particularly evident when the fluorinated monomer is polymerized in the smectic phase in which the monomer is organized between the smectic layers of the LC. In addition, the ordered polymer structure found with the fluorinated monomer in the smectic phase leads to continued birefringence above the clearing point of the LC due to surface interactions between the LC and the ordered fluorinated polymer. The continued birefringence offers an exceptional opportunity to examine how factors such as polymer molecular mass and UV light intensity affect the overall polymer morphology of these polymer/LC systems. As the initiator concentration and UV light intensity are decreased, longer polymer chains form lattice-type morphologies; whereas, shorter polymer chains form smoother morphologies that more closely mirror the texture of the LC smectic phase.     

Sesamin as a co-initiator for UV photopolymerization

Sesamin, a nature compound from sesame seed, which contains two cyclic acetal structures, was used as a co-initiator for UV polymerization initiator system, and 1,6-Hexanedioldiacrylate was used as the photopolymerization monomer. Photopolymerization kinetics was recorded by real-time infrared spectroscopy. For BP/Sesamin initiator system, the double bond conversion increased with the increase of Sesamin concentration and light intensity. Combination of p-chlorobenzophenone and Sesamin had the highest initiating reactivity. The polymerization rate and final double bond conversion of acrylate monomer were higher than that of methacrylate monomer.     

Photopolymerization behavior in nanocomposites formed with thiol–acrylate and polymerizable organoclays

Because of the inherent characteristics of the thiol–ene step growth mechanism in preparation of thiol–ene photopolymer clay nanocomposites, the ratio between thiol and ene functional groups at and near the organoclay surfaces may have a significant effect on the polymerization behavior. This study investigates the influence of monomer composition and the type of polymerizable organoclay on thiol–acrylate photopolymerization behavior in preparation of photocurable clay nanocomposite systems. To this end, two types of polymerizable organoclays with acrylate or thiol functional group on the clay surfaces were compared in monomer compositions with different polarity and functionality. Real‐time infrared spectroscopy was used to characterize polymerization behavior in conjunction with photo‐DSC. The degree of clay exfoliation was evaluated using small angle X‐ray scattering and correlated with photopolymerization behavior. Higher chemical compatibility of components induced enhanced clay exfoliation resulting in increase in photopolymerization rate. By affecting the stoichiometric ratio of functional groups in the clay gallery, thiolated organoclays enhance thiol–ene reaction, whereas acrylated organoclays encourage acrylate homopolymerization. In addition, inducing more propagating thiyl radicals on the organoclay surfaces by increasing functionality of thiol monomer also facilitates thiol–ene copolymerization, whereas the increase of acrylate functionality reduces final thiol conversion. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Study on new chiral liquid crystalline monomers and polymers containing menthyl groups

A series of new chiral monomers (M1–M4) and the corresponding siloxane polymers (P1–P4) containing menthyl groups were synthesised to establish the relationship between their structure and liquid crystalline properties. The effect of the mesogenic core rigidity and the spacer length on the phase behaviour of the monomers and polymers obtained in this study was discussed. The selective reflection of light for the chiral monomers was studied with UV-Vis spectrometer. Polarising optical microscopy, differential scanning calorimetry, X-ray diffraction and thermogravimetric analysis were used to characterise the phase behaviour and thermal stabilities. It was found that these chiral monomers and polymers were beneficial for the formation of the mesophases when a flexible spacer was inserted between the mesogenic core and terminal menthyl groups. M1–M3 showed enantiotropic chiral smectic C phase and cholesteric phase, and monotropic cubic blue phase on cooling cycle. M4 only showed cholesteric phase. P1–P4 showed a smectic A phase. With increasing the mesogenic core rigidity or decreasing the spacer length, the corresponding melting temperatures, glass transition temperatures and isotropic temperatures all increased.