羟基卟啉衍生物LB膜的紫外可见光谱表征

研究了两种具有两条脂链的羟基卟啉在气液界面上的成膜性能及其ＬＢ膜。ＵＶ－Ｖｉｓ光谱表明,两种卟啉在ＬＢ膜中的聚集态不同,卟啉环上脂链和羟基呈对称了代时形成Ｊ－聚体,呈同侧取代时形成氢键聚集体。利用偏振ＵＶ－Ｖｉｓ吸收谱测定了ＬＢ膜中卟啉环的取向。结果表明,侧链和羟基的相对位置对环的取向没有影响,但影响膜中平均分子截面积的大小和环间的距离,因而影响膜中分子的聚集态。     

Characterization of the flow properties of sodium carboxymethylcellulose via mechanical and optical techniques

Sodium carboxymethylcellulose (NaCMC) in solution represents a complex rheological system, since it forms aggregates and associations and hence higher-level structures and, depending on the synthesis, is only found in a molecularly dispersed form in exceptional cases. Rheo-mechanical investigations of the viscoelasticity showed that the Cox-Merz rule is not fulfilled. The aim was therefore to examine whether rheo-optics could be employed to provide more detailed conclusions about the parameters that influence the flow behavior of NaCMC than has hitherto been available with mechanical methods. The flow birefringence, Δn ^′, rises as the degree of polymerization increases, and exhibits the same dependence on molar mass as does the viscosity: Δn ^′∝M _w ^3.4. As the degree of polymerization increases while the shear rate remains constant, the polymer segments become more distinctly aligned in the direction of shear. Hence increasing the degree of polymerization also affects the solution structure, i.e. the interaction of the molecules with one another. The stress-optical rule only applies to a limited extent for this system. The stress-optical coefficient, C, is almost independent of the shear rate, but is strongly influenced by the concentration and attains a limiting value of 3 × 10⁻⁸ Pa⁻¹. C was determined for a polymer in dilute solution and the curve obtained also enabled transitions in the solution structure to be recognized. Received: 1 May 1998 Accepted: 5 October 1998     

聚甲基丙烯酸三氟乙酯单体与分子链在金属有机框架中吸附及取向特性的理论研究

本文结合分子动力学、密度泛函理论和蒙特卡洛方法,研究了光学损耗低的氟化聚合物单体分子甲基丙烯酸三氟乙酯（TFMA）及其分子链在[Zn2(BDC)2TED]n和[Zn2(BPDC)2TED]n两种结构有序的金属有机框架（MOFs）材料中的吸附特性,得到相应的吸附数量和取向程度,以探索提高聚合物材料双折射性的有效途径。通过分析结果得出影响TFMA单体分子在这两种MOF孔道中吸附及取向特性的三个因素：a）由于MOF孔道壁是由金属离子和有机配体组成的极性表面,MOF孔壁与极性分子TFMA之间的静电相互作用对TFMA单体分子在孔道内的吸附和取向有促进作用;b）在受限空间中的聚合物单体分子之间的静电相互作用使其分子间隙更加紧密,同样也对其分子取向有促进作用;c）在这个两种孔洞与聚合物单体分子相对大小不同的MOF中,单体分子和分子链的取向度基本一致,但单体分子在孔径较大的MOF中吸附数量更多。这三个因素的重要影响,为聚合物单体或MOF的选取、对聚合物链取向及双折射性的控制提供理论预测方法。     

以构象概念为主线的高分子物理教学实践

提出以构象概念作为教学主线,论述了构象概念的意义以及构象概念与力学状态、橡胶弹性、取向态、流变性和凝聚态的内在关系。     

Quasi-linear elliptic differential equations for mappings of manifolds,II

We study questions related to the orientability of the infinite-dimensional moduli spaces formed by solutions of elliptic equations for mappings of manifolds. The principal result states that the first Stiefel–Whitney class of such a moduli space is given by the ℤ₂-spectral flow of the families of linearised operators. Under an additional compactness hypotheses, we develop elements of Morse–Bott theory and express the algebraic number of solutions of a non-homogeneous equation with a generic right-hand side in terms of the Euler characteristic of the space of solutions corresponding to the homogeneous equation. The applications of this include estimates for the number of homotopic maps with prescribed tension field and for the number of the perturbed pseudoholomorphic tori, sharpening some known results. Mathematics Subject Classifications (2000): 35J05, 58B15, 58E05, 58E20, 53D45     

Time-resolved polymer deformation using polarized planar array infrared spectroscopy

Polarized planar array infrared (PA-IR) spectroscopy is shown for the first time to be a powerful approach to study the mechanical deformation of polymers. A dual-beam PA-IR spectrometer was built to enable the simultaneous recording of parallel- and perpendicular-polarized spectra at the same sample spot. The technique provides orientation and structural information during and after fast irreversible deformations with a low-ms (or sub-ms) time resolution and a low data scatter. In proof-of-concept experiments, the possibilities of polarized PA-IR spectroscopy are illustrated by studying the deformation of poly(ethylene terephthalate) thin films.     

Morphology and physical properties of a liquid–crystalline main-chain polymer with flexible side chains

A molecular laminate model is used to explain the properties of unoriented and oriented films of poly(p-phenylene-2,5-didodecyloxyterephthalate) cast from solution. In oriented films the two different crystal modifications, A and B, give rise to room temperature tensile moduli of 15 and 30 GPa respectively. The packing (in clusters) of the side chains in modification A, leading to a glass–like transition in the side-chain regions around ?40°C, is largely responsible for this difference. Oriented films of modification A and B have coefficients of thermal expansion of +0.3×10^?5 and ?1× 10^?5 K^?1 respectively. It is concluded that the properties of this class of polymers can be adjusted in a systematic way.     

Ca+RBr→CaBr+R(R=CH3,C2H5,n-C3H7)反应的矢量相关和产物的转动取向

采用准经典轨线方法研究了碰撞反应 Ca RBr(R=CH_3,C_2H_5 和 n-C_3H_7)的矢量相关性质和产物 CaBr 分子的转动取向.计算了不同碰量相关撞能情况下产物分子的转动取向参数和反应物与产物之间的矢分布几率函数.矢量相关由角分布函数 P(θ_r)!P(φ_r)和 P(θ_r,φ_r)以及极化相关微分截面来描述.Ca CH_3Br 反应产物 CaBr 的 P(θ_r)峰值大于 Ca C_2H_5Br 和 Ca n-C_3H_7Br 反应产物 CaBr 的 P(θ_r)峰值.对于反应 Ca RBr 的 P(θ_r)在φ_=3π/2处的峰值明显大于φ_r=π/2处的峰值.计算结果表明,在碰撞反应过程中,产物 CaBr 分子的转动角动量不仅发生取向,而且沿着垂直于散射面方向发生定向：产物 CaBr 分子强烈地沿着反应物相对速度方向向前散射；产物分子转动角动量的定向和取向将不同程度地影响产物的散射方向.     

On cyclically orientable graphs

Graph G is called cyclically orientable (CO) if it admits an orientation in which every simple chordless cycle is cyclically oriented. This family of graphs was introduced by Barot et al. [Cluster algebras of finite type and positive symmetrizable matrices, J. London Math. Soc. (3) 73 (2006) 545-564]. The authors obtained several nice characterizations of CO-graphs, being motivated primarily by their applications in cluster algebras. Here we obtain several new characterizations that provide algorithms for recognizing CO-graphs and obtaining their cyclic orientations in linear time. We show that the edge maximal CO-graphs are 2-trees; that is, G=(V,E) is a 2-tree if and only if G is CO and G^′=(V,E^′) is not CO whenever E is a proper subset of E^′.     

Dynamic analysis of aggregation of methylene blue with polarized optical waveguide spectroscopy

Polarized optical waveguide (POW) spectroscopy permits analysis of the changing molecular state of methylene blue (MB), including aggregate order and orientation at the waveguide surface. Monomer or dimer, dissolved randomly in MB aqueous solution, tends to aggregate at the waveguide surface during air drying. Furthermore, POW spectroscopy dynamically revealed that MB molecules became oriented vertically to the waveguide surface with increasing aggregation order.