【作者】 刘聪；

【导师】 胡建设；

【作者基本信息】 东北大学 ， 高分子化学与物理， 2008， 硕士

【摘要】 手性液晶材料是目前液晶研究领域的热点之一,因其独特的光学、电学性质而日益受到广泛重视。这类液晶材料的分子因手性中心的存在而形成螺旋结构,螺旋结构的存在使其具有一般液晶高分子所不具有的光学性质,其液晶类型一般为胆甾相或近晶相。目前直接以薄荷醇为手性中心合成的液晶化合物,尚未见国内外报道。本论文主要是合成与研究含薄荷基的手性液晶单体及弹性体的结构与性能。本论文设计并合成了五种含薄荷基手性液晶单体和三种液晶交联剂,手性液晶单体分别为4-孟氧基乙酸-4′-十一烯酸对联苯酚双酯(M1)、4-孟氧基乙酸-4′-十一烯酰氧基苯甲酸对联苯酚双酯(M2)、4-孟氧基乙酰氧基苯甲酸-4’-十一烯酸对联苯酚双酯(M3)、4-孟氧基乙酰氧基苯甲酸-4’-十一烯酰氧基苯甲酸对苯二酚双酯(M4)、4-孟氧基乙酰氧基苯甲酸-4’-十一烯酰氧基苯甲酸对联苯酚双酯(M5)；液晶交联剂分别为4-烯丙氧基苯甲酸-4’-十一烯酸对苯二酚双酯(N1)、4-烯丙氧基苯甲酸-4′-十一烯酸对联苯酚双酯(N2)与4-烯丙氧基-4′-十一烯酰氧基苯甲酸对联苯酚酯(N3)。然后分别将手性单体与PMHS通过自由基聚合制备了均聚物P1系列；再将M3与N1、Ms与N2分别与PMHS共聚,制得了手性液晶弹性体P2系列和P3系列。所合成单体、交联剂及弹性体的结构通过了红外光谱仪(FT-IR)和核磁共振仪(1H-NMR)的表征,液晶性能通过了偏光显微镜(POM)、差示扫描量热仪(DSC)和热失重分析仪(TGA)的分析,其旋光性通过了旋光分析仪的表征,讨论了分子结构及手性中心对单体的旋光性、相转变温度、相变类型及液晶织构的影响以及交联剂含量对弹性体的相行为的影响。所合成的手性液晶单体、交联剂及弹性体均未见国内外报道,其结构均符合分子设计。研究结果表明,手性单体M1-M5均为左旋化合物,其比旋光度绝对值随化合物刚性的增加而降低,而对于液晶刚性大小接近的单体,其比旋光度绝对值变化很小。除单体M1外,M2-M5均为热致互变液晶化合物,升降温过程均出现手性近晶C(SC*)相和胆甾相的转变,呈现SC*相的破碎扇形织构及胆甾相的油丝织构和焦锥织构；M2-M5样品在Sc*相区升温反射波长发生“红移”,而在胆甾相区升温反射波长发生“蓝移”。交联剂N1-N3在升降温过程中均呈现典型的向列相纹影织构和丝状织构。此外,N2在降温过程中还呈现近晶A(SA)相的扇形织构、近晶C(Sc)相的破碎扇形织构和近晶B(SB)相的马赛克织构；交联剂N3在降温过程中还呈现SA的扇形织构。对于手性单体与交联剂,但随着液晶核刚性(芳香环数目)的增加,对应单体的熔点(Tm)与清亮点(Ti)升高,且Ti升高的幅度要大于Tm的增加幅度。对比M2和M3,N2和N3它们是由完全相同的原料合成,即分子量相同,其中M2和M3相变温度略有差异,而相变类型和液晶织构不变；N2和N3虽然相变温度差异也不大,但相变类型和液晶织构均出现较大的变化。均聚物P1-1～P1-5均为非晶液晶高分子,呈现胆甾相的Grand-jean织构,该系列的玻璃化温度(Tg)和Ti的变化趋势与对应单体的趋势相同。尽管单体M1没有液晶性能,但对应的均聚物P1-1却呈现了液晶性能。液晶弹性体P2系列和P3系列呈现彩色的Grand-jean织构。随着液晶交联剂含量的增加,这两个系列弹性体的Tg均呈现上升趋势,P2系列的Ti呈现下降趋势。对于P2系列弹性体,当交联剂N1的含量从4mol%增加到20mol%时,对应的Tg从27.2℃增加到33.4℃,而Ti则从141.7℃降低到131.4℃。所合成的均聚物和弹性体热分解温度均在340℃以上,具有良好的热稳定性能。更多还原

【Abstract】 Chiral liquid crystalline polymers （LCPs） were a hotspot of LC research domains at the present time. Due to the unique photo-electrical property, they have obtained more and more attention. LCPs with helical supermolecular structure can form cholesteric phase and chiral smectic C （Sc） phase. To the best of our knowledge, research on chiral LC monomers and polymers containing menthyl groups have not been reported.In this paper, five new chiral LC monomers containing menthyl groups and three LC crosslinking agents were synthesized, which include,4-（10-undecylen-1-yloxy）biphenyl-4’-menthyloxyacetate （M1）,4-（10-undecylen-1-yloxybenzoyloxy）biphenyl-4’-menthyloxyacetate （M2）,4-（10-undecylen-1-yloxy）biphenyl-4’-menthyloxyacetyloxybenzoate （M3）,4-（10-undecylen-1-yloxybenzoyloxy）phenyl-4’-menthyloxyacetyloxybenzoate （M4）,4-（10-undecylen-1-yloxy-benzoyloxy）biphenyl-4’-menthyloxyacetyloxybenzoate （M5）,4-（10-undecylen-1-yloxy）phenyl-4’-allyloxybenzoate （N1）,4-（10-undecylen-1-yloxy）biphenyl-4’-allyloxybenzoate （N2）, 4-allyloxybiphenyl-4’-（10-undecylen-1-yloxy）benzoate （N3）. The homopolymers （P1 series） were prepared by graft polymerization with reacting M1～M5 and PMHS, respectively. The elastomers （P2 and P3 series） were synthesized by one-step polymerization with reacting M2, N1, and PMHS; and M3, N2 and PMHS, respectively. The chemical structures of the monomers, crosslinking agents, homopolymers, and elastomers were characterized by FT-IR and 1H-NMR. The mesomorphic properties and phase behavior were investigated polarizing optical microscopy （POM）, differential scanning calorimetry （DSC）, and thermogravimetric analysis （TGA）. The special optical rotations were measured by a polarimeter. The effect of molecular structures on the optical rotations, phase transition temperatures, phase types and textures is discussed. Moreover, the influence of the crosslinking units on the phase behavior of elastomers is also discussed.The monomer M1～M5 were levorotatory compounds, their absolute values of specific rotation declined with increasing rigidity, but for the compounds with near rigidity and same molecular weight, their values hardly changed. Besides M1, M2～M5 were thermotropic LC compounds. They displayed break fan-shaped textures of Sc* phase, cholesteric oily-streak textures and focal-conic textures on heating and cooling process. Selective reflection properties appeared in Sc* phase, the selective reflection shifted to long wavelength （"red shift"）, and short wavelength （"blue shift"） in cholesteric phase with increasing temperature. Crosslinking agents N1～N3 showed typical nematic threaded texture and schlieren texture. In addition, N2 also exibited fan-shaped texture of smetic A （SA） phase, break fan-shaped texture of smetic C （Sc） phase and mosaic texture of smetic B （SB） phase on cooling cycle. N3 displayed fan-shaped texture of SA phase. With increasing the phenyl rings number, Tm and Ti of M2-M5 incresed, and Ti increased more than Tm. Compared M2 with M3, N2 with N3, they have same molecular weight, synthetic method and raw material were same, and M2 and M3 had a little different in phase transition temperatures, but phase types and textures have not changed. However, the phase types and textures of N2 and N3have changed.Homopolymers P1₁-P1-5 were amorphous LCPs, and displayed cholesteric Grand-jean textures. Although M1 did not show any mesmorphic property, the corresponding P1-1 showed cholesteric phase. LC elastomers P2 and P3 series displayed cholesteric Grand-jean textures. Effect of the content of crosslinking units on LC phase transition temperatures and thermal property of LC elastomers has been discussed. With increasing the content of the crosslinking units in the elastomers, the crossponding Tg increased and Ti decreased. For the P2 series, when content of the crosslinking agent increased from 4mol% to 20%, Tg increased from 27.2℃to 33.4℃, but Ti decreased from 141.7℃to 131.4℃. TGA showed that the temperatures at which 5% weight loss occurred （Td） were greater than 340℃for the elastomers P2 and P3 series, this indicated these elastomers have good thermal stability.更多还原