光散射技术在高分子表征研究中的应用

光散射技术是高分子领域中重要的表征手段之一.静态光散射和动态光散射的结合能够获得丰富的关于高分子的信息,如重均分子量、回转半径、第二维里系数、流体力学半径、尺寸分布、分子链构象等.除合成高分子外,光散射技术同样适用于研究生物大分子、微生物、胶体、纳米粒子、病毒、囊泡等在溶液或悬浮液中的行为.本综述重点介绍稀溶液中静态光...     

温敏性微凝胶的研究技术

温敏性微凝胶因具有尺寸小、对温度的变化响应速度快、渗透性好等优点,所以在许多领域显示出良好的应用前景.温敏性微凝胶的应用性能取决于由其结构所决定的物理化学性能.为了深入了解温敏性微凝胶的结构与性能关系,研究人员利用不同技术手段进行了广泛研究.本文主要综述了显微技术、示差扫描量热技术、光散射技术、中子散射技术、核磁共振及荧光光谱等在温敏性微凝胶结构与性能研究中的应用、主要研究结果,并对微凝胶未来的研究方向提出了一些建议.     

激光光散射表征寡链聚苯乙烯微胶乳粒子的方法

本文阐述了利用激光光散射表征寡链（ｐａｕｃｉ－ｃｈａｉｎ）聚苯乙烯微胶乳的方法。在静态光散射中，可测得微胶乳粒子的重均摩尔质量，结合粒子内所含高分子链的重均分子量，进而计算出每个微胶乳粒子内高分子链的平均数目；在动态光散射中，通过对时间相关光谱的拉普拉斯反演求出粒子的平动扩散系数分布Ｇ（Ｄ），进而得到流体力学半径（Ｒｈ）及分子量的分布。通过综合分析静态与动态光散射的结果，建立了计算球形粒子密度的光散射方法，并发现，寡链聚苯乙烯微胶乳的密度低于通常的胶乳粒子以及本体聚苯乙烯的密度     

光散射在高分子溶液和聚集态研究中的应用

本文较为详细的综述了光散射在聚合物研究中某些领域内的应用，并着重介绍了光散射在聚合物凝胶领域、聚合物稀溶液中、聚合物相行为领域以及聚合物加工领域中的发展历史和研究现状。     

凝胶化反应全过程的激光光散射跟踪研究

在苯乙烯（Ｓｔ） 二乙烯苯（ＤＶＢ）自由基共聚的凝胶化反应过程中定时取样，得到凝胶化点前后及至终点的一系列样品，然后用激光光散射技术，包括研究散射光强及其角度依赖性的静态光散射（ＳＬＳ）和研究散射光频移的动态光散射（ＤＬＳ），表征了这系列样品的重均分子量Ｍｗ、均方旋转半径Ｒｇ、第二维利系数Ａ２及流体力学半径Ｒｈ等静、动态参量及这些参量的变化规律，定量地描述了凝胶化反应全过程     

光散射技术在蛋白质晶体生长研究中的应用和进展

光散射技术广泛应用于生物大分子的晶体生长研究中,它包括静态光散射和动态光散射两种。利用静态光散射可以测定蛋白质溶液渗透的第二维里系数;利用动态光散射可以测定蛋白质溶液的平动扩散系数,获得溶液中蛋白质粒子的流体力学半径及分布情况,分离蛋白质结晶的成核与生长过程,研究大分子的聚集行为和晶体生长的动力学。借助光散射技术可以实现蛋白质晶体生长过程的动态控制。近些年光散射仪器向着小型化、轻便化的方向发展,光散射技术不断得到改进,日益完善,不仅用于地面实验,也应用于空间领域蛋白质晶体生长的研究中。     

一种四臂聚苯乙烯凝胶的激光光散射研究

采用原子转移自由基方法(ATRP)合成窄分布的末端基为巯基的四臂星型聚苯乙烯(4-PS-SH).巯基容易被空气中的氧气氧化生成二硫键,会引起四臂星型聚苯乙烯分子间交联.利用激光光散射研究了四臂聚苯乙烯在亚浓溶液中氧化交联生成大的胶束进而生成宏观化学凝胶的过程.静态激光光散射测量结果表明四臂聚苯乙烯亚浓溶液以及凝胶样品的时间平均散射光强不随测量位置的变化而涨落,说明此凝胶是结构均一的化学凝胶.动态光散射结果表明在四臂聚苯乙烯亚浓溶液氧化生成凝胶的过程中,动态强度-强度时间相关函数的慢运动衰减的贡献最初随着氧化时间的增加逐渐增强,当氧化反应进行到一定程度时慢运动的贡献又逐渐减弱,最终慢运动消失.生成的化学凝胶的相关函数与最初亚浓溶液的相关函数几乎重合.静态和动态激光光散射结果表明生成的四臂聚苯乙烯凝胶是结构均匀的化学凝胶.     

无皂高分子胶乳粒子的组成、单分散性和稳定性

分别用控压微波辐照法、常压微波辐照法和常压水浴合成法制备出无皂聚苯乙烯胶乳粒子.运用静态激光光散射和动态激光光散射对粒子的表观分子量及其粒径大小与分布进行了表征.结果表明,微波辐照加热法对于形成小尺寸、单分散的胶乳粒子起着很重要的作用.通过凝胶渗透色谱仪（GPC）测定聚合产物的分子量,并结合Zimm作图法,计算出胶乳粒子所含高分子链的数目.发现由控压微波辐照法所得到的聚苯乙烯胶乳粒子的表观分子量最大,而且粒子的分散性并不是由聚合物高分子链的分散性直接决定的.在微波辐照下的无皂乳液聚合,虽然聚合物的高分子链大小不一,但它们在乳液中缠结在一起而形成的胶乳粒子却具有单分散性.通过对均聚和共聚乳液进行静置考察,发现无皂高分子胶乳粒子的稳定性与制备方法、共聚单体的结构及性质有着密切的关系.     

聚丙烯酰胺凝胶结构非均匀性的动态光散射研究

利用动态光散射技术研究了聚丙烯酰胺 (PAAm)凝胶结构的非均匀性 ,分析了PAAm凝胶结构非均匀性的形成原因及凝胶动态光散射的数据处理方法和分析结果的物理意义 .研究结果表明 ,PAAm凝胶中含有动态相关长度 (LC)不同的两相 ,其中 ,LC 为 10～ 2 0nm的区域是聚合物稀疏相 ,LC 为 85nm左右的区域是聚合物密集相 ,两相的不均匀分布形成了PAAm凝胶结构的非均匀性 .分析表明 ,PAAm凝胶存在两相主要是由于单体和交联剂的溶解度存在差异所致 .随交联度增大 ,PAAm凝胶结构的非均匀性显著增强     

聚(N-异丙基丙烯酰胺)水凝胶微球体积相变的研究

窄分散的聚（Ｎ 异丙基丙烯酰胺）水凝胶微球用乳液聚合方法制备，并用动态和静态光散射对其体积相变进行了研究．与水中聚（Ｎ 异丙基丙烯酰胺）线性单链比较，水中凝胶微球的体积相变温度较高，对温度的响应比较平缓．相变是连续的，有别于大块凝胶非连续的体积变化．在体积相变过程中，凝胶微球始终是密度均一的热力学稳定球体．从相变过程网络密度的变化可以确定，绝大部分的水在收缩过程被排了出来，但在紧缩的凝胶微球中仍含有约７０％的水．     

Dynamic light scattering by weakly ionized gels: Effects of inhomogeneities and non-ergodicity

Small angle neutron scattering and light scattering experiments have been performed on partially neutralized poly(acrylic acid) solutions and gels. The structure factor obtained from small angle scattering and static light scattering reveals the absence of significant contribution from large scale inhomogeneities in the gels as soon as the ionization degree exceeds 9·10⁻³. The comparison of the time and ensemble averages of the autocorrelation function of scattered light intensity shows that the gels behave with respect to that experiment as ergodic media.     

Liquid flow through polymer gels

Slow neutron transmission technique was applied to investigate features of the solvent flow through quasi-porous matrices of gelatin, poly (acrylamide) and silica gels of different concentration/mesh sizes. We find the macromolecular friction coefficient for all gels to be proportional to the concentration of polymer network which correlates well with the predictions of the effective medium approach under the condition of negligible impact of hydrodynamic self-interactions. Determined values of the friction coefficient are used for evaluating the effective mesh sizes, which are in good agreement with the appropriate results of quasi-elastic light scattering for homogeneous poly (acrylamide) gels.     

Dynamic and static light scattering by weakly ionized gels and solutions

Dynamic light scattering (DLS) and static light scattering (SLS) experiments have been performed on partially neutralized poly(acrylic acid) and poly(methacrylic acid) solutions and gels. The gels exhibit a non-ergodic behavior, much less marked however than that observed in neutral systems. By combining DLS and SLS, the fluctuating part of the light scattered from PAA gel was separated from the total scattered intensity and found to be almost equal to the intensity scattered by the solution. Also the diffusion coefficient associated with the dynamic fluctuation was found to be the same in the PAA gel and the PAA solution.     

Ternary macromolecular gels made from propylene carbonate including an inorganic salt. Influence of the salt on mechanical properties of such gels

This study describes experimental conditions for preparing binary or ternary macromolecular gels. Both polyvinylformal and polyacrylonitrile used in this study have partially crystalline structures. Solutions of these polymers in propylene carbonate, with or without alkaline perchlorates, have been studied by means of viscometric, rheological, osmotic and gel melting point measurements. Gel formation originates in intermolecular interactions between crystallizable regions in the macromolecular chains. Mechanical properties of these gels are modified by adding a salt to the macromolecular solutions.     

Light Scattering Probes of Viscoelastic Fluids and Solids

In this article, we discuss recent advances in static and dynamic light scattering applied to soft materials. Special emphasis is given to light scattering methods that allow access to turbid and solid‐like systems, such as colloidal suspensions, emulsions, glasses, or gels. Based on a combination of single‐ and multispeckle detection schemes, it is now possible to cover an extended range of relaxation times from a few nanoseconds to minutes or hours and length scales below 1 nm up to several microns. The corresponding elastic properties of viscoelastic fluids or solid materials range roughly from below 1 Pa to several 100 kPa. Different applications are discussed such as light scattering from suspensions of highly charged colloidal particles, colloid and protein gels, as well as dense surfactant solutions.     

Dilute solutions of polyelectrolytes—III. Unperturbed dimensions of poly(methylene) N,N-dimethylpiperidinium chloride) in aqueous and methanolic solutions in presence of tetraethylammonium bromide

The behaviour of poly(methylene N,N-dimethylpiperidinium chloride) in aqueous and methanolic solutions in the presence of tetraethylammonium bromide has been investigated by light scattering; the parameters characterizing the macromolecular chain have been calculated. Peculiar behaviour of the macromolecules in aqueous solutions was attributed to the influence of the simple electrolyte co-ion due to hydrophobic interactions.     

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。     

Effect of ethanol on the micellization and gelation of pluronic p123

In certain applications copolymer P123 (E21P67E21) is dissolved in water-ethanol mixtures, initially to form micellar solutions and eventually to gel. For P123 in 10, 20, and 30 wt % aqueous ethanol we used dynamic light scattering from dilute solutions to confirm micellization, oscillatory rheometry, and visual observation of mobility (tube inversion) to determine gel formation in concentrated solutions and small-angle X-ray scattering (SAXS) to determine gel structure. Except for solutions in 30 wt % aqueous ethanol, a clear-turbid transition was encountered on heating dilute and concentrated micellar solutions alike, and as for solutions in water alone (Chaibundit et al. Langmuir 2007, 23, 9229) this could be ascribed to formation of wormlike micelles. Dense clouding, typical of phase separation, was observed at higher temperatures. Regions of isotropic and birefringent gel were defined for concentrated solutions and shown (by SAXS) to have cubic (fcc and hcp) and hexagonal structures, consistent with packed spherical and elongated micelles, respectively. The cubic gels (0, 10, and 20 wt % ethanol) were clear, while the hex gels were either turbid (0 and 10 wt % ethanol), turbid enclosing a clear region (20 wt % ethanol), or entirely clear (30 wt % ethanol). The SAXS profile was unchanged between turbid and clear regions of the 20 wt % ethanol gel. Temperature scans of dynamic moduli showed (as expected) a clear distinction between high-modulus cubic gels (G'max approximately 20-30 kPa) and lower modulus hex gels (G'max<10 kPa).     

Structural properties of partially charged poly (acrylic acid) gels as probed by light scattering

We report results of static light scattering for partially charged gels at different swelling degrees and different ionization degrees. We measured both the ensemble-average and the rms fluctuations of the scattered intensity by scanning through various positions in the gel. It is shown that the dynamic concentration fluctuations are, to the first order, the same as in semi-dilute solutions at the same concentration. The excess of scattering of the gel with respect to the solutions arises mainly from frozen-in scattering domains with spatial extent less than ∼ 300 Å.     

Characteristics of several kinds of polyethylene gel estimated by small‐angle light scattering under cross polarization

Unusual phenomenon was confirmed in the gelation of polymer solution when branched low molecular weight polyethylene (B‐LMWPE) and ultrahigh molecular weight polyethylene (UHMWPE) solutions were quenched at their gelation temperature. That is, polarized light scattering (Hv scattering) from B‐LMWPE gels containing 95% solvent yielded a four‐leaf clover type as like the scattering from a perfect spherulite under Hv scattering but the corresponding polarized optical microscopy (POM) showed dark image showing no spherulite with Maltese cross color indicating considerable orientation fluctuation between the optical axes with respect to the radial axis of the spherulite. Hv scattering from pristine UHMWPE gels containing more than 99% solvent had an X‐type pattern, which became clearer with time. The corresponding POM images change from being dark, indicating no superstructure, to being slightly brighter, indicating the presence of indistinct superstructures. To analyze this unusual phenomenon of Hv scattering from B‐LMWPE and UHMWPE gels, new models were proposed using a statistical approach and optically anisotropic elements in three‐dimensional space. The theoretical patterns were in agreement with observation. Thus, it came to a conclusion that Hv scattering from the gels is attributed to strong distance correlation between polar and rotational angles of two optically anisotropic elements in the polymer‐rich phase. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2010