乙烯基对苯二甲酸类甲壳型液晶高分子的形状记忆性能

通过自由基聚合合成了四种基于乙烯基对苯二甲酸类甲壳型液晶高分子(PBPCS,PMPCS,PDCHVT,Pbi PCS)。TGA和DMA表征结果表明,这四种甲壳型液晶高分子均具有较好的热稳定性,其侧基末端基团刚性越大,相对应的片材在30~80℃温度区间刚性越大。形状记忆弯角回复测试表明:四种聚合物热压成型的片材都具有很好的形状记忆固定率,均接近100%。形状记忆回复效果与聚合物侧基的末端基团有关,侧基末端基团分别为对丁氧基苯基和环己基(对应聚合物分别为PBPCS和PDCHVT)时,片材显示出较好的形状记忆性能,形状记忆回复率分别为87%和100%。将PDCHVT通过熔融纺丝制成纤维,采用形状记忆循环DMA测试表征其形状记忆性能,结果表明PDCHVT纤维具有稳定的优异的形状记忆性能。     

甲壳型液晶高分子成纤及其纤维结构性能初探

研究了不同相对分子质量的甲壳型液晶高分子聚乙烯基对苯二甲酸二(对丁氧基苯)酯(PBPCS)的成纤和纤维结构性能。结果表明:PBPCS在液晶态和各向同性态熔融挤出,所制备的初生纤维力学性能基本相同,纤维强度不高,且比较脆;数均相对分子质量为6.38×105的聚合物制备的初生纤维最大拉伸强度为18.8 MPa,断裂伸长率为2.4%;在130℃,0.3 N的拉伸张力下,对该初生纤维进行5倍拉伸后,纤维的拉伸强度达32.3 MPa,断裂伸长率达37.1%;初生纤维取向指数约60%,经过5倍拉伸后纤维的取向指数达78.3%,比初生纤维提高了25.9%。     

含磺酸基的席夫碱型液晶离聚物的合成与性能

先通过席夫碱反应合成了末端基为磺酸基的介晶基元(4–羟基–4'–磺酸基苯亚甲基苯胺),再接枝到聚硅氧烷主链上,制得含磺酸基团的侧链液晶离聚物,产物通过红外表征进行了确定;并对该化合物的液晶性能进行了测试,偏光显微镜(POM)分析表明该化合物属于近晶型棒状织构;差示扫描量热仪(DSC)分析证明其具有较高的熔点和清亮点温度,液晶温区为172.24~232.17℃,并且具有稳定的液晶性能,可用于热塑性高分子材料的共混改性。     

氰基取代苯基噻吩棒状线圈嵌段分子的合成与液晶行为研究

以Suzuki偶合反应为关键步骤,合成了以苯基噻吩为刚性棒状核,核的一端是带在噻吩环上的氰基,另一端是带在苯基上的极性多醚链的两亲性嵌段分子,采用POM测试方法考察了极性多醚链的末端基团为羟基、羧酸钠盐及可聚合的丙烯酰基的嵌段分子的液晶性质,以及通过丙烯酰基聚合形成的侧链型高分子的液晶性质,仅在极性多醚链的末端基团为羧酸钠盐的嵌段分子中观察到了层列相的液晶性质,而其他的嵌段化合物及高分子都没有热致性的液晶性质,对挑选出的样品的溶致性液晶性能也进行了研究,加水可以导致液晶相形成,提高液晶相的稳定性。     

氧化酯化法合成双酯基多环芳香醛类液晶

双酯基多环芳香醛类化合物是一类具有线形结构的液晶分子，在分子结构中具有酯基刚性桥键、端基烷基（C3和C5）与末端基团醛基。     

液晶聚合物的研究进展

综述了近年来液晶聚合物的研究状况和合成技术进展,重点讨论了主链型液晶聚合物、侧链型液晶聚合物及甲壳型液晶聚合物的分子结构设计、合成方法及主要性能。同时对液晶聚合物的发展趋势及应用前景进行了分析和展望。     

形状记忆CTBN/CE嵌段共聚物的制备与性能

氰酸酯(CE)树脂的刚性结构致使其本身不具备形状记忆行为,而将含有柔性链段的端羧基液体丁腈橡胶(CTBN)改性CE并形成共聚物后,共聚物体系则具备较好地形状记忆行为。通过力学性能测试、DMA分析和形状记忆行为研究对CTBN/CE共聚物进行了表征,结果表明:随CTBN含量的增加,共聚物的弯曲强度由83 MPa降至48 MPa,且储能模量和玻璃化转变温度(Tg)也逐渐减小,从而实现了共聚物的Tg可控性。形状记忆测试表明随CTBN含量的增加,共聚物的形状记忆性能逐渐提高,回复时间由532 s缩短至90 s。     

液晶高分子新型材料：Ⅱ 液晶高分子的合成

1 液晶基元、连接基团和液晶单元合成的任务在于先用适当的聚合方法将小分子的液晶基元通过刚性连接基团连接成较大分子量的液晶单元,将这些液晶单元再通过刚性连接基团连接成刚性液晶大分子链或通过亚甲基连接基团连接成重复单元并进而聚合成为半刚性液晶性大分子链,最后由这些大分子链构成聚合物本体并赋予其液晶性。     

聚对羟基苯甲酸侧链液晶高分子的合成与表征

合成了对羟基苯甲酸二聚体，四聚体，并分别接枝到苯乙烯－马来酸酐无规共聚物（SMA）上，得到侧链工度均匀的液晶高分子；同时在N，N'－二环己基碳二亚胺催化下采用溶液缩聚法制备了SMA接枝聚对羟基苯侧链液晶高分子。用FT-IR,DSC，偏光显同镜等方法表征了产物的结构作性质，讨论了液晶侧链对聚合物形态和热性质的影响。     

可逆交联单壁碳纳米管/聚酰胺复合材料的研究

通过在聚合物基体中添加纳米填料制备高性能和具有多种功能性聚合物基纳米复合材料是扩大其应用范围的有效手段。利用呋喃基团与单壁碳纳米管(SWNTs)在温和条件下的Diels-Alder反应制备了侧链含呋喃基团的芳香族聚酰胺(fPA)和SWNTs可逆交联复合材料(SWNTs/fPA)。结果表明,添加质量分数为0. 6%的SWNTs就能显著改善fPA的机械性能。SWNTs/fPA复合材料具有良好的循环加工性能,并且SWNTs的加入改善了fPA的形状记忆性能。     

液晶高分子的分子设计

简单介绍了液晶高分子的结构特点，分类及其应用状况，详细介绍了主链型和侧链型液晶高分子设计的新进展，根据溶臻主链型液晶高分子和热臻主链型液晶高分子分子结构的不同，提出今后设计主链液晶高分子的主要任务，从主链结构，液晶基元类型和柔性间隔出发介绍了侧链液晶高分子分子设计的关键，最后介绍了液晶高分子分子设计的发展趋势。     

Influence of chirality on phase behaviour of side chain liquid crystalline polymers

Summary Two kinds of chiral side chain liquid crystalline polyacrylates were synthesized and characterized by DSC, POM and x-ray diffraction. The results indicated that chirality of side chain end group and spacer length strongly influence the phase behaviour of the polymers. The polymer P-I with one asymmetric carbon atom of end group exhibits enantitropic Smectic S_A and S_C phases. The polymer P-III having two asymmetric carbon atoms displays enantitropic Smectic S_A and S_B phases. Formation of liquid crystalline polymorphism of polymers depends on spacer length of side chains.     

Synthesis of side-chain liquid crystalline polyacrylates,polymethacrylates and polysiloxanes containing 4-cyano-biphenyl 4-alkanyloxybenzyl ether side groups

Summary The synthesis and characterization of side-chain liquid crystalline polyacrylates, polymethacrylates and polysiloxanes containing 4-cyanobiphenyl 4-alkanyloxybenzyl ether side groups are presented. All polymers display respectively a smectic A mesophase. The influence of the polymer backbone flexibility on the phase transition temperatures of the synthesized side-chain liquid crystalline polymers is discussed. The results demonstrate that flexible backbones enhance the decoupling of the motions of the side chain and main chain. Therefore, among three kinds of polymer backbones which contain the same mesogenic side groups, the most flexible one, i.e., polysiloxane, reveals a highest isotropization temperature and a widest temperature range of mesophase.     

Preparation and characterization of shape memory polymer networks based on carboxylated telechelic poly(ɛ-caprolactone)/epoxidized natural rubber blends

Shape memory polymer networks were prepared from blends of end-carboxylated telechelic poly(?-caprolactone) (XPCL) and epoxidized natural rubber (ENR). The XPCL/ENR blends can form cross linked structure via interchain reaction between the reactive groups of each polymer during molding at high temperature. Degree of crosslinking of the blend network and their thermomechanical properties were characterized by gel content measurement, DSC and DMA. We found that the degree of crosslinking and crystalline melting transition temperatures was dependent upon the blend compositions as well as the molecular weight of the XPCL segment in the blends. The blends showed a good shape memory behavior such as good shape fixity as well as a high final recovery rate when they exhibit crystalline melting transition with a sufficiently high degree of crosslinking. And the response temperature of the recovery was well matched with T_m of the samples.     

Photopolymerized Thiol-Ene Systems as Shape Memory Polymers

In this study we introduce the use of thiol-ene photopolymers as shape memory polymer systems. The thiol-ene polymer networks are compared to a commonly utilized acrylic shape memory polymer and shown to have significantly improved properties for two different thiol-ene based polymer formulations. Using thermomechanical and mechanical analysis, we demonstrate that thiol-ene based shape memory polymer systems have comparable thermomechanical properties while also exhibiting a number of advantageous properties due to the thiol-ene polymerization mechanism which results in the formation of a homogeneous polymer network with low shrinkage stress and negligible oxygen inhibition. The resulting thiol-ene shape memory polymer systems are tough and flexible as compared to the acrylic counterparts. The polymers evaluated in this study were engineered to have a glass transition temperature between 30 and 40 °C, exhibited free strain recovery of greater than 96% and constrained stress recovery of 100%. The thiol-ene polymers exhibited excellent shape fixity and a rapid and distinct shape memory actuation response.     

新型纤维增强高分子形状记忆固定材料研究

本文回顾了高分子形状记忆绷带材料研究的方法与理论,并详细介绍了目前现有的新型纤维增强医用聚氨酯、聚己内酯类高分子形状记忆材料,特别是GF增强PVC共混体系得到的固定材料,最后对高分子形状记忆绷带材料的发展作出了分析和展望.分析表明,纤维增强形状记忆固定材料的研究是有意义和发展前途的.     

Reinforcement in the mechanical properties of shape memory liquid crystalline epoxy composites

In this work, novel thermoresponsive shape memory composites based on glass fiber and nanosilica‐modified liquid crystalline epoxies (LCEs) with lateral substituent were prepared and characterized. According to the comprehensive analysis of polarized optical microscopy, wide‐angle X‐ray diffraction measurements, and tan δ data, the orientation of mesogen units were hindered by the introduction of nanosilica and lateral substituents of liquid crystalline epoxies, so that additional physical cross‐links except for similar chemical cross‐links emerged with the introduction of surface‐treated nanosilica. And the increased cross‐links could enhance the shape memory properties of the composites which could recover to their original state quickly in a time shorter than 30 s with high shape fixing ratios (>96%) and high shape recovery ratios (>98%), which indicated the composites could be applied into self‐deployable structural materials. Moreover, the reinforcement in the dynamic storage moduli, tensile modulus, and the tensile strength and shape memory properties indicated that glass fiber and nanosilica‐modified shape memory liquid crystalline epoxy composites could be high‐performance composites and could be used as new candidates for aerospace smart materials. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42616.     

Monte Carlo simulations of properties of side‐chain liquid‐crystal polymers

This paper presents a computational conformational study of side‐chain liquid‐crystal polymers to predict the optical and liquid‐crystalline properties of a series of polyepicholorohrdrin, polyacrylate, poly(methyl acrylate), and polystyrene‐based side‐chain polymers using a Monte Carlo simulation method. Some of the simulated side‐chain polymers were synthesised by chemical modification or polymerisation. The predictive capability of the orientational order parameter has been utilised to predict the liquid‐crystalline isotropic transition temperature of the investigated polymers, which was used to infer the type of distribution in the synthesised polymers. The predictive possibilities of this criterion are explored in the estimation of the nematic–isotropic transition temperatures of the simulated polymers. Evidence is presented to suggest that for side‐chain liquid‐crystalline polymer molecules the nematic to isotropic transition occurs when the order parameter reaches a value of 0.43 according to Maier–Saupe mean‐field theory. Copyright © 2006 Society of Chemical Industry     

Synthesis, characterization and liquid crystalline behavior of poly(monomethyl itaconate)s with new pendant cholesterol moieties

In order to investigate the effects of cholesteryl pendant groups on inducing liquid crystalline (LC) phase formation, a new series of cholesteryl-modified poly(monomethyl itaconate) (PMMI-Chol-C₆) have been synthesized from poly(monomethyl itaconate) (PMMI) and 6-(cholesteryloxycarbonyloxy) hexanol (Chol-C₆) with different degrees of substitution (DS_chol). All the obtained compounds were characterized by conventional spectroscopic methods. The DS_chol values of the modified PMMI were obtained by ¹H NMR spectroscopy and conductometric titration. The inherent viscosities of polymers were determined by an Ubbelohde viscometer at 35 °C in DMSO solution. The resulting products of modified PMMA polymers were soluble in a variety of organic solvents, and the solubility improved by increasing the DS_chol. Thermal behavior and optical properties of Chol-C₆ and PMMI-Chol-C₆ polymers were investigated by thermal gravimetric analysis, differential scanning calorimetry and hot-stage polarizing optical microscopy. The glass transitions of the modified PMMI polymers occurred at lower temperatures than the parent PMMI. It was found that among the synthesized polymers with different molar ratios of the substitution, only the PMMI-Chol-C₆ (1) polymer bearing 77 mol% of the side chains, with reduced melting point and increased thermal stability, formed thermotropic liquid crystalline smectic phases. This polymer exhibited wider mesophase than the mesogenic side chain Chol-C₆ and amorphous morphology. The results of a comparative study on the structure and properties of the polymers showed that liquid crystalline polymers may be achieved through the attachment of mesogenic cholesterol side chain onto the main chain via methylene chains of side branches.     

Thermal and shape memory properties of cyanate/polybutadiene epoxy/polysebacic polyanhydride copolymer

A novel thermal‐induced shape memory polymer was synthesized by copolymerization of a new kind of epoxy resin‐polybutadiene epoxy (PBEP), bisphenol A‐type cyanate ester (BACE), and polysebacic polyanhydride (PSPA) with different mass ratios. Fourier transform infrared spectroscopy (FTIR), bending test, dynamic mechanical analysis (DMA), and shape memory property were investigated systematically. It was found that the PSPA significantly enhanced the bending strength and flexural modulus. The DMA results showed that the glass transition temperature reduced with increasing content of PSPA. Furthermore, the shape memory tests proved that the copolymer possessed excellent shape memory properties. The shape recovery time decreased with increasing content of PSPA and temperature. The shape memory rate increased as the PSPA content increased. The shape recovery ratio decreased with increasing cycle times. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42045.