Bilayer studies in mixedn-decanol/n-tetradecanol complexes ofn-decylammonium beidellite

Complexes have been prepared by treatment ofn-decylammonium beidellite with mixtures ofn-decanol andn-tetradecanol with different concentrations. Measurements of the basal spacings of the obtained complexes have been performed in a wide range of temperatures. Three different bilayer phases have been established between (20 and 70°C: the _i(C₁₀) phases (=bilayers ofn-decyl chains); the _i(C₁₀/C₁₄) phases (=mixed bilayers ofn-decyl andn-tetradecyl chains in molar ratio approximately 1:1) and the _i(C₁₄) phases (=bilayer ofn-tetradecy 1 chains with then-decylammonium ions included). In all bilayer phases the chains stand perpendicular to the silicate interfaces. In definite concentration ranges two of the phases coexist, i.e., miscibility gaps occur, which disappear at temperatures higher than the temperature of the _i/ transition. The miscibility gaps are reversible with temperature. The composition of the intercalated bilayers has been studied by HPLC of the excess alkanol mixture separated from the beidellite complexes after the equilibrium has been reached. There is preferential adsorption of one of two alkanols from the mixture, which is in agreement with the observed miscibility gaps. The space filling problem as well as the structure of the three bilayer phases observed have been discussed.     

LOW DENSITY POLYETHYLENE/CLAY NANOCOMPOSITES MODIFIED BY ETHYLENE COPOLYMERS： EFFECTS OF FUNCTIONALIZED SEGMENTS ON MORPHOLOGY

Melt extrusion was used to prepare binary nanocomposites of ethylene copolymers and organoclay and trinary nanocomposites of low-density polyethylene （LDPE）, ethylene copolymer and organoclay. X-ray diffraction （XRD） and transmission electron microscopy （TEM） were used to analyze the structure of the clay phase and the morphology of the nanocomposites. Influences of the comonomer in the copolymer and the content of the copolymer on the morphology of the resulting nanocomposites were discussed. The binary and the trinary composites may form intercalated or exfoliated structures depending on the interaction between the copolymer and the clay layers and the content of the copolymer.     

锂在共轭双键高分子中的电化学嵌入反应III. 锂嵌入聚噻吩的量子化学计算†

采用Gaussian软件和HF方法, 通过从头计算(ab initio)法选取4-31G基组计算锂离子嵌入聚噻吩过程中结构与结合能的变化关系. 发现噻吩聚合时主要生成三或四聚合物. 聚合物在Li原子(或Li^＋离子)嵌入后, 聚噻吩间距离明显变小, 同时发生电荷转移, 形成稳定嵌合物; 并使噻吩环的C-α—C-β键级变小. 同时, 研究了锂离子(或原子)嵌入后体系的HOMO, LUMO能级. 聚噻吩在嵌入锂离子时LUMO轨道能级变为负值, 成为电池反应得电子的正极. 而金属Li₂ 释放Li^＋后的Li^－的HOMO能级为＋0.7427 eV, 则成为给电子的负极. 由此, 可以完成由锂/聚噻吩在高氯酸锂电解质中组成的放电过程, 并提出嵌合键级概念用来表征锂在聚噻吩间的结合程度.     

PREPARATION AND CHARACTERIZATION OF POLYAMIDE 11/CLAY NANOCOMPOSITES

INTRODUCTIONIn recent years, polymer/clay nanocomposites have attracted great interest from researchers since they frequentlyexhibit unexpected hybrid properties synergistically derived from the two components. Compared to their microcounterparts and the pristine polymer matrix, polymer/clay nanocomposites exhibit improved tensile strength andmodulus, decreased thermal expansion coefficient, decreased gas permeability, increased swelling resistance,enhanced ion conductivity, and reduced fl…     

Synthesis and mesomorphic characterization of azoesters with a coumarin ring

We have synthesized a homologous series of azoesters consisting of a coumaryl moiety as the end group. Eleven derivatives of this series exhibit mesomorphism. The nematic mesophase is exhibited from ethyl homologue onward, while the smectic phase commences at the pentyl derivative and is exhibited along with the nematic phase up to the hexadecyl derivative. The N-I transition temperatures curves show the usual odd-even effect. All the compounds in this series are thermally stable and exhibit a wide mesomorphic range of nearly 120°C. Their thermal stabilities and other characteristics are discussed.     

表面预处理对镁铝水滑石结构性质和缓释性能影响

以Mg-Al-NO₃水滑石（LDHs）为载体,将5-氟尿嘧啶（5-FU）通过离子交换法插入其层间,得5-FU/LDHs缓释材料。并对水滑石表面进行弱酸预处理改性,利用XRD、FTIR、TG-DSC、SEM和零电荷点（pHPZC）等表征手段,考察酸预处理对水滑石表面化学性质及微观结构的影响。结果表明,5-FU/LDHs的层间距从0.858nm扩大到1.064nm,层间5-FU₂阴离子与主体层板通过氢键与静电作用,以呈一定角度单层交替排列于层间。酸预处理的水滑石粒径变小,层板正电荷密度增大。5-FU的释放机理是物理扩散、离子交换和药物溶解等协同作用,酸预处理可提高水滑石的缓释性能和稳定性。     

The B2–B7 phase transition in symmetrical bent‐shaped mesogens with methoxy substitution

New mesogens composed of achiral bent molecules with thermally stable ester linkages, and laterally substituted by a methoxy group symmetrically near the central benzene ring, were synthesized. Texture, calorimetric, electro‐optical, X‐ray and dielectric measurements were performed. In most of studied compounds the antiferroelectric B₂ phase was found on cooling from the isotropic phase, followed by the B₇ phase at lower temperatures. Undulation of layers in the B₇ phase was confirmed by precise synchrotron studies.     

Liquid crystal oligomers: going beyond dimers

This review focuses on structure-property relationships in liquid crystal oligomers, which consist of molecules containing two or more mesogenic units linked via flexible spacers essentially in a linear fashion and so does not consider, for example, liquid crystal dendrimers and tetrapodes. Previous reviews have tended to focus mainly on liquid crystal dimers in which just two mesogenic units are interconnected by a single spacer. By contrast, this review is largely devoted to higher oligomers such as liquid crystal trimers and tetramers containing three or four mesogenic units connected by two or three spacers, respectively.     

A comparative study of photo-optical behaviour of photosensitive chiral copolymers with cholesteric mesophases induced in nematogenic and smectogenic matrices

The photo-optical behaviour of two series of chiral photochromic acrylic copolymers with a chiral nematic phase has been studied. These copolymers contain identical chiral photochromic units, but have different structures of the phenyl benzoate mesogenic side groups which are responsible for the development of LC phases. This approach allowed us to examine specific features of the photo-optical behaviour of the copolymers as a function of the nature of the LC 'matrix' in which the cholesteric phase was induced. The action of UV irradiation was shown to lead to the E-Z isomerization of the chiral side groups and, as a consequence, to untwisting of the cholesteric helix of the copolymers. For copolymers of both series, the effective quantum yields of this photochemical process were calculated. In the case of copolymers in which the cholesteric mesophase is induced in a smectogenic matrix, the corresponding values of the quantum yield are lower and depend slightly on temperature. A plausible explanation of the above phenomena is suggested.     

Radiolysis of 5,10,15,20-tetrakis(N-methyl-4-pyridyl)-porphyrin or 5,10,15,20-tetrakis(4-sulfonatophenyl)-porphyrin in aqueous solution in the presence and in the absence of DNA or human serum albumin

The reduction of two free-base ionic porphyrins: 5,10,15,20-tetrakis(N-methyl-4-pyridyl)-porphyrin (TMPyP) and 5,10,15,20-tetrakis(4-sulfonatophenyl)-porphyrin (TSPP) by the hydrated electron was studied under neutral pH in aqueous solution in the absence and in the presence of biomolecules, DNA or HSA. Pulse radiolysis studies provided the spectra of the short-lived π-radical anions and steady-state radiolysis led to formation of stable phlorin or chlorin, the products of two-electron reduction and protonation at a meso and a pyrrolic nitrogen positions or at two β-pyrrole positions, respectively. Identification of the final reduction products was based on their reactivity to molecular oxygen—the phlorin, contrary to chlorine, was oxidized rapidly by O₂ to recover the original porphyrin. The stable product of TMPyP reduction was the phlorin, whereas for TSPP the chlorine and the phlorin were obtained. Addition of biomolecules to the solution resulted in changes of the porphyrins spectroscopic properties and in the decrease in rates of the occurring reduction processes proceeding with participation of the porphyrins.