聚对苯二甲酰对苯二胺草席晶形态的细微结构

本文采用溶剂腐蚀技术和电子显微镜法研究了聚对苯二甲酰对苯二胺(PPTA)草席晶形态的细微结构,发现了PPTA草席晶的真实形态结构系为沿剪切应力方向平行取向排列,并周期性地弯曲成锯齿状的微纤结构。其锯齿周期的大小平均约为1微米左右,正好与在偏光显微镜正交偏振片下所观察到的草席晶形态中一条晶带宽度的尺寸相当,因此可以认为在偏光显微镜下所看到的草席晶图像只不过是这种锯齿状微纤规则弯曲所形成周期性结构的一种光学效应而已。同时也直接观察到单个分离的微纤,它是由于液晶态溶液微区结构中取向的刚性链分子在剪切应力作用下产生滑移而形成的。     

聚对苯二甲酰对苯二胺取向态结晶的超分子结构

本文以光学显微镜和扫描电子显微镜法研究了聚对苯二甲酰对苯二胺的100％硫酸溶液剪切取向下凝固结晶所形成的超分子结构,发现各向异性态溶液中取向了的微区结构在不同松弛阶段凝固结晶时可以形成球晶、串晶和草席晶等结晶形态的微区结构的聚集体。     

氰乙基纤维素/二甲基乙酰胺液晶溶液的取向态织构

本文用偏光显微镜、小角光散射和消偏振光法对受切应力后取向的氰乙基纤维素/二甲基乙酰胺液晶溶液的织态结构进行了研究。证明在取向的液晶溶液中,分子链沿切应力方向高度取向。相邻条纹间的分子链取向稍有不同。     

ECEC/AA液晶溶液取向态织构及其自由基聚合

利用光学显微镜和小角光散射等方法研究了乙基氰乙基纤维素(ECEC)/丙烯酸(AA)取向液晶态织构。在切应力作用下ECEC/AA液晶溶液形成带状结构,其中大分子链沿切应力方向呈锯齿形取向,溶液浓度越高,取向液晶溶液中大分子链有序性越高,带状织构中的条带愈窄。通过紫外光引发聚合方式获得了保持取向液晶态中带状织构的复合物膜。     

聚对苯二甲酸乙二酯形态结构的光散射研究

在不同结晶条件下,聚对苯二甲酸乙二酯样品出现了三种不同的光散射图形(正常球晶、异常球晶和混合球晶散射图形)。并假定正常球晶的光轴方向与半径垂直;异常球晶的光轴方向与半径夹+45°角或-45°角;混合球晶则是正常球晶与异常球晶叠加的结果。基于这些假定,按照Clough的计算公式,用二维球晶模型分别对具有上述各种光轴取向的球晶进行了计算。结果表明,计算出的H_v、V_v散射图形与实验所得的散射图形符合得很好。偏光显微镜的观察结果也进一步证实了这些模型的假定。     

Co60γ-射线辐照对熔融结晶聚乙烯形态的影响——Ⅰ.形态的保持和破坏效应

本系列工作的此部分系用小角激光光散射,小角χ光散射,广角χ光衍射等技术考察了高密度聚乙烯的球晶、片晶和微晶等宏观和微观结构在不同辐照条件下的行为和变化,发现辐照交联对聚乙烯球晶结构有保持效应,且这种效应随辐照剂量的增大而加强;辐照交联对聚乙烯的片层结构也有保持效应,但对片晶内部却有破坏效应,辐照导致了聚乙烯结晶的晶胞膨胀,用"片晶内部破坏"机理解释χ光小角散射积分不变量随辐照剂量单调下降比用"片晶表面破坏"机理解释更为合适。     

Co~(60)γ-射线辐照对熔融结晶聚乙烯形态的影响——Ⅰ.形态的保持和破坏效应

本系列工作的此部分系用小角激光光散射,小角x光散射,广角x光衍射等技术考察了高密度聚乙烯的球晶、片晶和微晶等宏观和微观结构在不同辐照条件下的行为和变化,发现辐照交联对聚乙烯球晶结构有保持效应,且这种效应随辐照剂量的增大而加强;辐照交联对聚乙烯的片层结构也有保持效应,但对片晶内部却有破坏效应,辐照导致了聚乙烯结晶的晶胞膨胀,用“片晶内部破坏”机理解释x光小角散射积分不变量随辐照剂量单调下降比用“片晶表面破坏”机理解释更为合适。     

各向异性光交联作用对液晶在起伏光栅表面的取向影响

以含肉桂酸基团的光敏聚酰亚胺为"墨水",通过软印刷技术制备了一种新型的可进一步光交联的表面起伏光栅,研究了各向异性光交联对光栅热稳定性和光栅诱导液晶取向的影响.研究结果表明,在经过紫外光交联后,光栅的热稳定性有较大提高,在经过高于未交联聚酰亚胺的玻璃化转变温度31℃处理2 h后,光栅形貌未发生变化.曝光前后光栅都能诱导液晶分子在表面均一沿面排列.当线性偏振紫外光的偏振方向与光栅沟槽垂直时,光交联能促进光栅对液晶的定向能力,反之则降低的定向能力.通过改变辐照光的偏振方向,调节光栅深度,能控制液晶分子在光栅上的取向方向.将这种软印刷得到的光栅用作液晶定向层,不仅可具有更好的热稳定性和定向能力,还可以调节液晶分子在光栅上的取向方向,实现多畴取向.     

含柔性间隔基的热致液晶性共聚酯的结晶形态

采用偏光显微镜、扫描和透射电镜从不同层次的结构水平上研究了含柔性间隔基热致液晶性共聚酯的结晶形态。在偏光显微镜下观察到典型的负光性球晶形态,透射电镜揭示了球晶是由厚度为10nm并沿着径向生长的片晶结构所组成,分子链沿晶片厚度方向取向排列。并研究了分子链的刚性程度对热致聚芳酯结晶性质的影响。结果表明,分子链刚性越大其结晶性和球晶的完善性越高。     

氰乙基纤维素/二甲基乙酰胺液晶溶液的研究

本文利用Abbe折射仪,热台偏光显微镜,小角光散射等方法研究了氰乙基纤维素/二甲基乙酰胺液晶溶液的形成,形态结构和某些性质。溶液随浓度的增加,从各向同性态经过两相共存状态,转变成为单一的液晶态。该液晶是胆甾型的。溶液的双折射Δn随浓度的增加或温度的降低而增大。在无外力作用时,液晶相由许多无规分布的取向微区组成。液晶溶液受切应力后形成“条纹结构”,大分子链沿切应力方向取向,并在各条纹中排列有序。     

聚对苯撑对苯二甲酰胺液晶的相态转变

本工作以H(?)ppler流变粘度计、退偏振光法及小角激光光散射法研究了聚对苯撑对苯二甲酰胺的浓硫酸溶液在不同浓度和温度下的粘性行为、光学性质和区域结构的变化,发现聚对苯撑对苯二甲酰胺的各向异性溶液在不同温度下呈现向列型液晶和胆甾型液晶特征,说明芳香聚酰胺的液晶体系与小分子液晶相类似,也具有多种中介相的转变现象。这里的中介相转变是由向列型转变为胆甾型,但不是直接的同时是一个单变性的相转变过程。     

Quiescent and strain-induced crystallization of poly(p-phenylene terephthalamide) from sulfuric acid solution

Quiescent and strain-induced crystallization of poly(p-phenylene terephthalamide) (PPTA) from sulfuric acid solution has been studied. Negative spherulites (SA-PPTA spherulites) are formed from hot concentrated solutions by cooling. The spherulite consists of radiating fibrous lamellae several hundred angstroms wide. The electron diffraction pattern indicates that PPTA molecules are oriented perpendicular to the long axes of the fibrous lamellae and that the [010] or [110] direction of the modification I crystal and [010] direction of the modification II crystal are parallel to the long axes of the fibrous lamellae. The width of the lamellae is much smaller than the chain length of the starting PPTA. It appears that hydrolysis of PPTA during melting crystallization determines the chain length, i.e., the width of the fibrous lamella. Stacked, lamellar structures like “row structures” are formed under shear. The longer axes of the fibrous lamellae are oriented perpendicular to the shear direction. It is confirmed by electron diffraction studies that the PPTA molecules are oriented parallel to the shear direction. Well-developed fibrils with the PPTA molecules oriented to the fibril axis, are formed by adding the SA-PPTA spherulites to water with vigorous stirring.     

Light scattering and x-ray characterization of amylose films

Small-angle light scattering (SALS) in the solid state and x-ray diffraction were used to investigate the development of anisotropic structure in water-cast amylose films prepared under various conditions. The conditions investigated were different temperatures and relative humidities maintained during the drying of the films and different aging times and temperatures of the amylose solution prior to the casting of films. As revealed by SALS, the predominant morphology developing in these films was based on rod-like scattering units of considerable size. At times, a low degree of spherulitic character was also evident in the films. All four experimental conditions affected the development of anisotropic structure, with the aging time and temperature producing the most noticeable effects. Increasing aging time and/or decreasing aging temperature markedly increased the rod-like morphology of the films. On the other hand, crystallite sizes as measured by x-ray diffraction remained constant at 24–28 Å, indicating no influence on the part of experimental conditions. These findings are discussed in the light of starch retrogradation.     

MORPHOLOGICAL STUDY ON THE ORIENTED CHITOSAN FILM OBTAINED FROM PRE-SHEARED LIQUID CRYSTALLINE SOLUTION IN DICHLOROACETIC ACID

The oriented chitosan films obtained from pre-sheared liquid crystalline chitosan/dichloroacetic acid (DCA)solutions were studied by means of polarized optical microscopy (POM), scanning electron microscopy (SEM), infra-reddichroism technique and wide angle X-ray diffraction (WAXD). The shear induced band texture in the film was found tocorrespond to the sinusoidal fibrillar microstructure along the shearing direction on the basis of POM and SEM observations.The sinusoidal fibril was found to be lying within the film plane. The model of chitosan molecular orientation in the pre-sheared film with band texture can be established assuming that the main chain orients in the shearing direction and the sidegroup is perpendicular to the shearing direction. The WAXD azimuthal scanning at 2θ= 20° indicates that the (002) planeorients perpendicular to the shearing direction.     

Structure–electrical property study of anisotropic polyaniline films

The relationships of the structure and electrical properties of anisotropic HCl‐doped polyaniline (PANI) films cast from N,N′‐dimethylpropylene urea (DMPU) solutions and stretched to different draw ratios were studied. The anisotropic structure of the stretched PANI films was examined by X‐ray diffraction, near‐infrared wave‐guide coupling, and polarized infrared measurements. The PANI emeraldine base (EB) films cast from DMPU solutions had a single‐phase noncrystalline structure, and stretching of the films did not cause crystallization to occur. The transition moment angles of two weakly absorbing infrared bands were determined, and the Hermans' orientation functions for the PANI EB films were calculated. The PANI films were then doped with HCl, and the electrical properties were determined by impedance spectroscopy. With a specially designed test fixture, the in‐plane and through‐plane impedance was obtained. The conductivity along the stretch direction increased with orientation. The in‐plane conductivity was significantly higher than the through‐plane conductivity. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 823–841, 2003     

Structural investigations of polymer liquid-crystalline solutions: Aromatic polyamides,hydroxy propyl cellulose,and poly(γ-benzyl-L-glutamate)

A comparative structural investigation of the characteristics of polymer liquid-crystalline solutions including Kevlar® (PPD-T)/sulfuric acid, poly(Cl-p-phenylene terephthalamide) (Cl-PPD-T)/sulfuric acid, poly(γ-benzyl-L-glutamate) (PγBLG)/dioxane, and hydroxypropyl cellulose (HPC)/water was undertaken. Experimental procedures included polarized light microscopy, light scattering, absorption spectra, and x-ray diffraction on solutions at various concentrations and temperatures. Both the two-phase region at the onset of liquid-crystal formation and the wholly anisotropic phase were investigated. Each solution exhibited distinctive characteristics. The PPD-T and Cl-PPD-T solutions were nematic, and the PγBLG and HPC solutions were cholesteric. In the two-phase region the PPD-T, Cl-PPD-T, and PγBLG (but apparently not the HPC) exhibited negatively birefringent spherulites and aggregates of spherulites. The HPC solutions only exhibited spherulitic structures in the single-phase anisotropic system. The structures and orientations in the anisotropic phase for the various polymer solutions is considered. The helicoidal structural characteristics of the PγBLG and HPC solutions are contrasted.     

聚酰亚胺薄膜结构研究Ⅱ

以小角激光光散射、偏光显微镜、X光衍射、电子显微镜、力学性能测定及红外光谱等方法研究了几种聚酰亚胺薄膜的聚集态结构。结果表明,它们在取向状态、球粒和链球结构、表面状况及球晶结构等方面有明显差异,而化学组成相同,因此认为聚集状态的这些差异是导致力学性能不同的主要原因.文中还提出方位角Q_d可作为检测PI薄膜取向状况的参照指标.     

ORIENTED TEXTURE OF MESOMORPHIC SOLUTIONS OF CYANOETHYL CELLULOSE/DIMETHYL ACETAMIDE

Textures of the oriented mesomorphic solutions of cyanoethyl celluloss/dimethyl acetamide were studied by polarized light microscopy, small angle light scattering and depolarized light transmission. If the mesomorphic solutions were sheared, they could form the band-like texture. Molecular chains in the solutions highly oriented almost along the shear direction. But the orientation directions of the molecular chains in the bands neighbouring each other were slightly different.