疏水性微孔中水的结构和扩散性质的分子模拟

用分子动力学（MD）方法模拟了受限在疏水性微孔中的水的结构与动力学行为.分别考察了孔径、温度和压力对水在孔道方向的密度分布和自扩散系数的影响,计算了不同温度下水的径向分布函数.发现在小孔径的微孔中,随着温度的降低,水分子沿孔道的分布逐渐变得不均匀,最终导致气-液相分离,微孔孔道内有明显的分段现象.受限在小孔径微孔中水的自扩散系数大约为体相流体水的20％～30％,并且随着孔径的减小,自扩散系数也减小.同时还发现沿孔道方向的自扩散系数分量大约为孔径方向的4～5倍.提出了微孔中水自扩散系数的关联模型.     

H型(PS)2PEG(PS)2嵌段共聚物在旋涂过程中的结晶行为

采用原子力显微镜和X射线衍射等手段研究了H型(PS)₂PEG(PS)2嵌段共聚物在不同溶剂和不同浓度的溶液中旋涂所得薄膜的形貌, 并与聚乙二醇(PEG)均聚物进行了比较. 虽然(PS)₂PEG(PS)₂中PS的链长很短, 但对形貌有很大影响, PS链段的存在改变了聚合物在基底上的稳定性, 使用四氢呋喃为溶剂, 当溶液浓度较小时, 在旋涂过程中发生去润湿, 然后再发生结晶, 膜厚较大时去润湿被抑止, 所得形貌与PEG均聚物类似. 以甲苯为溶剂时, 由于PEG和PS与溶剂的相互作用不同, 共聚物在溶液中形成胶束, 从而改变了聚合物的结晶形貌.     

浓度效应对GPC保留体积的影响及其分离机理的讨论

本文对不同溶剂体系、不同浓度、不同分子量的PS标样测定了GPC保留体积随浓度的变化值,研究了流体力学体积情况,得到良溶剂的V_r～C曲线与不良溶剂的V_r～C曲线有交叉现象,交叉点随分子量增大而移向浓度小的方向,并探讨了其分离机理。     

超临界苯类溶剂对聚苯乙烯降解的影响

在高压间歇反应器中,温度340~370℃,以苯、甲苯、乙苯和对二甲苯为超临界溶剂研究了聚苯乙烯(PS)的降解特性.苯类物质是聚苯乙烯的优良溶剂,在超临界条件下其优异的传质、传热性能使聚苯乙烯快速降解.聚苯乙烯在不同超临界溶剂中降解转化率相近,而降解产物组成差别很大,分析了不同超临界溶剂对聚苯乙烯降解过程的影响.结果表明超临界甲苯对降解过程影响最小,苯乙烯收率最高.聚苯乙烯降解过程中,高分子链断裂和解聚同时进行,结合连续分布理论建立了聚苯乙烯降解的动力学模型,得到在超临界甲苯中聚苯乙烯链端解聚活化能为138.4 kJ.mol-1.     

在室温离子液体BPBF4中FeCl3电化学性质的研究

以室温离子液体——四氟硼酸正丁基吡啶(BPBF4)为溶剂,在293．15～343．15K温度范围内,测定了不同浓度FeCl3的伏安曲线,估算了在不同浓度和不同温度下Fe^3 的扩散系数D,进而求得了它在不同浓度下的扩散活化能ED,讨论了FeCl3浓度对扩散系数和扩散活化能的影响．     

液体分子自扩散系数的预测

基于液体层膜结构模型提出预测液体分子自扩散系数的方程,对24种液体在较宽温度范围内作了检验,平均偏差为3.8%。同时分析了层膜结构模型中位形参数ξ随温度和物质不同而变化的规律,这对了解液体的微观结构、扩散过程的机理和阐明层膜结构模型的合理性具有重要意义。     

高分子在溶液中的链叠加度

从高分子线团密度存在浓度依赖性角度出发,导出了从稀溶液至浓溶液范围内高分子链叠加度与浓度的定量关系式.以链叠加度为高分子溶液的结构参数,关联了文献中6种分子量的聚氯丁二烯在不同溶剂和温度条件下溶液相对黏度的变化.这表明,高分子溶液的宏观性质与溶液中高分子链叠加度这一微观结构参数密切相关.     

荧光光谱法研究PS分子链在不同溶剂中的荧光特性

利用荧光光谱法研究了溶剂和浓度对聚苯乙烯（PS）荧光特性的影响. 研究表明,PS在四氢呋喃溶液中的荧光发射波长为345 nm,其荧光强度达到最大时的饱和浓度为0.1 mg/mL;PS在甲苯溶液中的荧光发射波长为310 nm,其荧光强度达到最大时的饱和浓度为0.075 mg/mL. 造成这种现象的原因在于:四氢呋喃不具荧光性,不与PS分子链中的苯环发生相互作用,而甲苯溶剂自身具有苯环结构,PS和甲苯生色团荧光频率接近,同时PS分子链上苯环与甲苯上的苯环的间距非常小,相邻苯环上的π电子可以互相重叠,形成T型构造的苯环二聚体,使体系的荧光发射峰蓝移至310 nm. 另外,随着PS在溶液中浓度的增大,开始呈线性增加,当浓度大于饱和浓度C*后,随后其荧光强度呈现非线性下降,这主要是PS在溶剂中形成了二聚体.     

基于LFHB 理论模型关联和预测醇+惰性溶剂的1H NMR 化学位移

运用含氢键缔合的格子流体状态方程(LFHB), 仅用一个参数关联了一元醇-惰性溶剂共17个体系29套1H NMR化学位移数据. 并且用关联参数成功预测了不同温度下丁醇+环己烷的化学位移. 所得结果与化学缔合理论的结果进行了比较. 对于某些体系在稀浓度范围LFHB的计算氢键缔合度要低于化学缔合理论的结果. 并且分析了LFHB理论中的物理参数和化学参数对于缔合度计算的不同影响.     

极性和非极性溶剂在聚乙烯中的无限稀释扩散系数的测定

 气相法研究小分子溶剂与高分子聚合物材料之间的相互作用是一个快速、准确、方便的方法 ,可以测量多种小分子溶剂在聚合物中的溶解、扩散参数。通过气相法测定了 5种小分子溶剂 (正己烷、正庚烷、正癸烷、乙醇和水 )在固定液聚乙烯中的保留时间和半峰宽 ,运用vanDeemter模型进行数据处理 ,得到上述 5种小分子在聚乙烯中的无限稀释扩散系数 ,获得了十分有意义的结果。     

Solvent diffusion in amorphous glassy polymers

In this article, a mathematical model is proposed for predicting solvent self‐diffusion coefficients in amorphous glassy polymers based on free volume theory. The basis of this new model involves consideration of the plasticization effects induced by small molecular solvents to correctly estimate the hole‐free volume variation above and below the glass‐transition temperature. Solvent mutual‐diffusion coefficients are calculated using free volume parameters determined as in the original theory. Only one parameter, which can be predicted by thermodynamic theory, is introduced to express the plasticization effect. Thus, this model permits the prediction of diffusion coefficients without adjustable parameters. Comparison of the values calculated by this new model with the present experimental data, including benzene, toluene, ethyl benzene, methyl acetate, and methyl ethyl ketone (MEK) in polystyrene (PS) and poly(methyl methacrylate) (PMMA), has been performed, and the results show good agreement between the predicted and measured values. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 846–856, 2000     

Application of free‐volume theory to self diffusion of solvents in polymers below the glass transition temperature: A review

Theories based on free‐volume concepts have been developed to characterize the self and mutual‐diffusion coefficients of low molecular weight penetrants in rubbery and glassy polymer‐solvent systems. These theories are applicable over wide ranges of temperature and concentration. The capability of free‐volume theory to describe solvent diffusion in glassy polymers is reviewed in this article. Two alternative free‐volume based approaches used to evaluate solvent self‐diffusion coefficients in glassy polymer‐solvent systems are compared in terms of their differences and applicability. The models can correlate/predict temperature and concentration dependencies of the solvent diffusion coefficient. With the appropriate accompanying thermodynamic factors they can be used to model concentration profiles in mutual diffusion processes that are Fickian such as drying of coatings. The free‐volume methodology has been found to be consistent with molecular dynamics simulations. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

PS-b-PEO-b-PS三嵌段共聚物在选择性溶剂中的胶束化

应用原子转移自由基聚合,制备了一组窄分布的PS-b-PEO-b-PS三嵌段共聚物。用^1HNMR和TEM表征了它们在选择性溶剂中的胶束化行为。^1HNMR结果表明,共聚物苯环上的质子峰出现在良溶剂(CHCl~3)中,而在选择性溶剂水中消失,证明上述三嵌段共聚物在选择性溶剂水中可逆自组装成以PS为核、PEO为壳的胶束。通过TEM考察了胶束的形状及大小,发现体系胶束尺寸呈多分散、粒径大,对形成的原因也提出了可能的解释。     

A thermal decomposition study of polymers by tunable synchrotron vacuum ultraviolet photoionization mass spectrometry

The thermal decomposition of polymers (poly(vinyl chloride) (PVC) and polystyrene (PS)) has been studied with synchrotron VUV photoionization mass spectrometry at low pressure. Pyrolysis products formed at different temperatures have been identified by the measurement of photoionization mass spectra at different photon energies. The experimental results demonstrate the variation of the pyrolysis product pool of PVC at different temperatures, dividing the thermal decomposition process into two stages: the low‐temperature stage to form HCl and benzene, and the high‐temperature stage to form numerous large aromatic hydrocarbons. For the thermal decomposition of PS, four reaction categories are determined. This work reports a new application of synchrotron VUV photoionization mass spectrometry in the study of the thermal decomposition of polymers, and demonstrates its good performance in product analysis, which is expected to help understand the thermal decomposition mechanism of PVC, PS and other synthesized polymers. Copyright © 2009 John Wiley & Sons, Ltd.     

Study of the dissolution process of polystyrene in concentrated cyclohexane solution by MNR relaxation

 ¹³C-NMR relaxation times of polystyrene (PS) chains in its theta solvent, cyclohexane, have been measured at different temperatures. It was found that relaxation of carbon nuclei of the side-chain-phenyl groups and those of main chains have remarkably different temperature-dependent relaxation behaviors in the solvent. A two-step model for the dissolution process is proposed. According to the model, swelling of the polymer below θ temperature corresponds mainly to the gradual dispersion of the side-chain phenyl groups; while the complete dissolution above θ temperature corresponds mainly to the gradual dispersion of the main chains at a molecular level. These dispersions reflect the fact that cohesional interaction among side-chain-phenyl rings or main chains are weakened by solvent molecules, which shows the existence of the cohesional entanglements among polymer chains. The results of T ₁(C) are confirmed by the biexponential dependence of ¹H-NMR spin–spin relaxation on temperature. Received: 2 July 1997 Accepted: 21 October 1997     

槲皮素在溶液中的化学交换和自扩散运动

通过对溶于氘代二甲亚砜（DMSO d6）中的槲皮素的自扩散系数和槲皮素羟基质子与溶剂中水质子之间的交换速率常数的NMR测量,研究了交换速率常数与扩散系数随温度和含水量的变化情况.结果表明,化学交换与扩散系数是相互独立的两种运动,活泼质子的化学交换并不需要通过槲皮素分子的扩散而进行.但是活泼质子的表观扩散系数却显著地受化学交换的影响.当以活泼质子为对象时,这种影响需要引起足够的重视.     

A COMPARATIVE STUDY OF CHAIN DYNAMICS OF DI-AND TRI-BLOCK COPOLYMERS IN SEMIDILUTE SOLUTION IN A NON-SELECTIVE SOLVENT

The chain dynamics of a pair of diblock poly(styrene-b-butadiene) (PS210-b-PB960) and triblock poly(styrene-b-butadiene-b-styrene) (PS200-b-PB1815-b-PS200) copolymers in both dilute and semidilute toluene solutions has been comparatively studied by dynamic laser light scattering. As expected, the mutual diffusion of individual chain changes into a fast cooperative diffusion of the chain segments (“blobs“) between two neighboring entanglement points for both the copolymers as the solution changes from dilute to semidilute. Further increases of the concentration lead to a second slow relaxation mode. For the triblock chains, there exists an additional middle relaxation between the fast and the slow modes.with 0.33 ＜α＜ 0.44, much smaller than 0.75 predicted or 0.72 observed for linear homopolymer chains in good solvent. It implies that the solvent quality of toluene for PB might not be as good as that for PS. Due to such a difference in solubility, it is reasonable to speculate that the PB and PS blocks are transiently segregated in semidilute solution. The relaxation of these transient PB and PS richer domains leads to the observed slow relaxation. Such a speculation is supported by the appearance of an additional slow relaxation mode in the study of polyisoprene-b-polystyrene-b-polyisoprene in semidilute solution in cyclohexane, a non-selective solvent, in which we alternated the solubility difference by a variation of the solution temperature.     

7Li PGSE diffusion measurements on LiPPh2: a solvent dependence of the structure

The first application of 7Li pulsed-gradient spin-echo (PGSE) diffusion methods to structural lithium chemistry is reported. The data, which provide quantitative diffusion constants at 155 K, lead to a new method of estimating solvent viscosity at this temperature and clearly show a solvent dependence for the structure of LiPPh2. In THF, LiPPh2 exists as a mononuclear solvated species, whereas in Et2O, a dinuclear structure is found. D values for the model compound PHPh2 in THF have been measured.     

Molecular dynamics simulation of liquid water and ice nanoclusters using a new effective HFD‐like model

We have determined a new two‐body interaction potential of water by the inversion of viscosity collision integrals of water vapor and fitted to achieve the Hartree–fock dispersion‐like (HFD‐like) potential function. The calculated two‐body potential generates the thermal conductivity, viscosity, and self‐diffusion coefficient of water vapor in an excellent accordance with experimental data at wide temperature ranges. We have also used a new many‐body potential as a function of temperature and density with the HFD‐like pair‐potential of water to improve the two‐body properties better than the SPC, SPC/E, TIP3P, and TIP4P models. We have also used the new corrected potential to simulate the configurational energy and the melting temperatures of the (H₂O)₅₀₀, (H₂O)₈₆₄, (H₂O)₂₀₄₈, and (H₂O)₆₉₁₂ ice nanoclusters in good agreement with the previous simulation data using the TIP4P model. The extrapolated melting point at the bulk limit is also in better agreement with the experimental bulk data. The self‐diffusion coefficients for the ice nanoclusters also simulated at different temperatures. © 2017 Wiley Periodicals, Inc.     

Chemiluminescence study of PS–PVME compatible mixtures

The oxidation of polystyrene (PS), poly(vinyl methyl ether) (PVME), and their mixtures has been studied by the chemiluminescence method. It was found that luminescence versus temperature curves had sharp inflections that shifted to higher temperatures with increasing PS content of the blends. A linear relationship was obtained between inflection temperatures and onsets of oxidation exotherms as measured by calorimetry. The inflection points for the mixtures also correlated linearly with the temperatures of thermally induced phase separation