CaCl2对聚间二苯砜对苯二甲酰胺/DMF溶液特性的影响

为了研究CaCl₂对聚间二苯砜对苯二甲酰胺(mt-PSA)在DMF中分子构象和形态的影响,采用流变仪测定了mt-PSA/DMF/CaCl₂浓溶液的流变行为,并通过乌氏黏度计和激光光散射研究其稀溶液的溶液黏度和高分子形态尺寸。结果表明:CaCl₂的加入增大了大分子与溶剂在mt-PSA/DMF/CaCl₂浓溶液和其稀溶液中的相互作用,同时CaCl₂使大分子链段得到舒展。但大分子的重均分子量没有发生明显的变化,说明CaCl₂未使mt-PSA高分子链段发生聚集或者坍塌。     

随机共聚高分子凝胶溶胀和体积相变行为的分子热力学模型

基于随机共聚高分子溶液的格子模型,建立了一个可以描述温度和pH双重响应的随机共聚高分子凝胶溶胀行为的分子热力学模型。该模型考虑了溶剂与不同高分子的混合、高分子网络的弹性以及包含小分子离子在凝胶内外分布的Donnan平衡和聚合物网络上的大分子离子及其反离子之间的静电相互作用的离子影响对化学势的贡献。与其他模型不同的是,该模型还考虑了高分子的组成f。该模型有两类可调的模型参数,一类是溶剂与不同高分子网络之间的相互作用能参数ε槇ij,另一类是高分子网络自身的尺寸参数Mc。研究结果表明,该分子热力学模型只需较少的模型参数就可较好地描述温度和pH双重敏感的随机共聚高分子凝胶的溶胀行为。     

高分子聚合物中溶剂扩散系数的预测

溶剂分子在高分子聚合物中的扩散现象广泛存在于日常生活和工业生产中,对其研究具有普遍意义.Vrentas-Duda模型以自由体积理论为基础,所有参数不需扩散实验测量,由溶剂和高分子的分子性质独立确定,可用于预测高分子聚合物中低相对分子质量溶剂扩散系数.研究Vrentas-Duda模型对典型高分子/溶剂体系中溶剂扩散系数的预测准确性,通过将预测值与实验值比较,评价该模型在不同高分子体系中的适用情况.对处于橡胶态的各向同性高分子聚合物体系,Vrentas-Duda模型能够准确计算除存在氢键以外多数体系的溶剂扩散系数;相对于溶剂互扩散系数而言,溶剂自扩散系数的预测精度更高.     

天然高分子溶液流变性研究进展

天然高分子是一种储量丰富的可再生资源,在许多领域有广泛的应用前景。流变学作为研究天然高分子溶液的性质具有独特的优势。通过流变学研究能够获得许多溶液的性质,包括溶液粘弹性变化规律、溶胶凝胶转变条件和高分子链在溶液中的运动学等信息,并能为天然高分子溶液纺丝等应用提供一定程度的理论支持。综述了近几年来纤维素、甲壳素、壳聚糖、天然蛋白等天然高分子在离子液体/有机试剂、纯离子溶剂,以及氢氧化钠尿素水溶液等溶剂体系中的流变性研究进展,并对天然高分子溶液的流变学理论发展和溶解技术进行了展望。     

硝酸锂在二甲亚砜溶液中离子溶剂化和离子缔合的红外光谱研究

利用ATR-FTIR光谱研究了硝酸锂在二甲基亚砜溶液中离子溶剂化和离子缔合,溶剂分子谱带的变化说明,锂离子与溶剂分子之间发生了强烈的相互作用,这种相互作用主要是通过SO中的氧原子进行的,利用光谱曲线拟合技术定量计算了阳离子溶剂化数,确定溶液中离子的存在状态(直接接触离子对、自由离子).     

基础理论

961030流变和加工条件对湿纺聚苯胺薄膜和纤维的力学和电性能的影响Hardaler 5.…;Ameriean Ch〔mjeal Soeiety,Abstracts Of paper PartZ:pMSE,1995,180,p.1(英)因流变和加工条件变化聚苯胺纤维和薄膜在制造时经历明显的形态和结构的变化。聚苯胺纤维可由不同的溶剂,包括二甲基毗咙脉,纺丝。这种溶剂阻碍了具有16se20多聚苯胺溶液形成纤维的有效时间内凝胶作用。溶剂对预纺聚合物溶液成形的影响也强烈影响纤维抗张性能和电性能。新的研究着重于最佳流变条件的确定,不同溶剂Q点的计算,加工对分子量影响,剪切变稀行为和聚苯胺系统的综合…     

溶液中高分子尺寸的测定

溶液中高分子尺寸的测定,广泛用于研究高分子链在溶液中的形态。高分子在稀溶液里的一些性质如表观粘度、扩散速度等都取决于溶液中高分子尺寸的大小。本文推荐一种粘度计,采用粘度法测得高分子溶液的特性粘数,从而计算高分子链的尺寸。原理溶液中高分子的形状和尺寸不仅与其本身的结构有关,还与溶剂性质、溶液浓度以及实     

聚对苯撑苯并双噁唑纳米纤维的制作和应用

正聚对苯撑苯并双嗯唑(PBO)是分子链不能弯曲的刚直高分子。以强酸为溶剂,通过液晶纺丝经热处理、拉伸制得的PBO纤维具有高强度、高弹性模量和高耐热性。纳米纤维的制造方法有复合熔融纺丝、熔喷、静电纺丝等。刚直高分子PBO只溶解于浓硫酸,不溶解于有机溶剂,所以不能采用一般的纳米纤维制造方法来制备。以硫酸为溶剂,PBO的稀溶液结晶化时,可得到各种形态的单结晶。本试验探讨利用稀溶液的急     

相反电荷聚电解质浓溶液复合体系的粘弹性

考察了相反电荷聚电解质浓溶液的复合体系形成宏观单相的可能性,发现只有当聚电解质所带电荷被完全屏蔽时才可能呈宏观单相体系.弱聚电解质NaPAA与PDADMAC复合体系当聚合物总浓度大于13.3wt%时即为均相溶液,具有与中性高分子稀溶液相似的流变行为.而强聚电解质ADPy/PDADMAC、NaPSS/PDADMAC复合体系为悬浮液.粘弹性测试表明NaPSS/PDADMAC体系中形成了由聚离子桥链连接复合物粒子构成的三维网络.     

高分子液晶

<正> 高分子液晶是指具有液体的流动性和晶体的各向异性的液晶介态的高分子化合物。和低分子液晶一样,高分子液晶可以是在加入溶剂后在溶液状态形成,称为溶致性液晶,也可以是在加热过程中,在熔融状态形成,称为热致性液晶。根据分子排列有序性的不同,高分子液晶的织态也可区分为近晶型、向列型、胆甾型和圆盘型(图1)。     

Sulfonated polyisobutylene telechelic ionomers. XIII. Viscosity behavior in nonpolar solvents and nonpolar–polar solvent mixtures

The effect of molecular variables upon the dilute solution viscosity of sulfonated polyisobutylene telechelic ionomers has been studied in both nonpolar solvents and nonpolar–polar solvent mixtures. In nonpolar solvents, association of the terminal salt groups results in an increase in viscosity and gelation at very low concentrations. The concentration at which gelation occurs was found to be dependent upon molecular variables such as architecture, molecular weight, neutralizing cation, extent of neutralization, and the type of solvent. Addition of a small amount of a more polar cosolvent tends to break up ionic associations between polymer chains and thus reduces viscosity. Finally, such solutions with a small amount of polar cosolvent may display dramatic increases in viscosity with increasing temperature due to a dynamic equilibrium between the ionic groups on the polymer chain, the nonpolar solvent, and the polar cosolvent. The results of this work suggest that these ionomers may potentially be useful as viscosity modifiers or “thermal thickeners” in some applications.     

Influence of molecular weight and rheological behavior on electrospinning cellulose nanofibers from ionic liquids

Dissolving pulp was depolymerized with 2.5M HCl into cellulose fractions with decreasing molecular weight relative to acid treatment time. The cellulose fractions were dissolved at various concentrations in the ionic liquid 1‐ethyl‐3‐methylimidazolium acetate (EmimAc) with co‐solvent DMSO at ratio 1 : 1 (w/w) and electrospun. Size exclusion chromatography was used to evaluate the molecular weight distributions and the rheological properties were characterized with a cone‐and‐plate rheometer. Scanning electron microscope was used to evaluate the fiber morphology, and thereby spinnability. Zero shear viscosity as a function of cellulose concentration show that all the solutions in this study are in the entangled semi‐dilute regime; where the polymer concentration is large enough for significant overlap necessary for chain entanglement. However, within the intervals studied, neither cellulose concentration nor molecular weight seems to be decisive for if a solution can be electrospun into fibers or not. It is rather the viscosity of the solution that is decisive for electrospinnability, even though the solution is in the entangled semi‐dilute regime. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2303–2310, 2013     

Effect of composition on the solution rheology of stearyl methacrylate‐co‐styrene‐co‐vinyl pyrrolidinone in paraffinic base oil

The rheological behavior of dilute and semi‐dilute solutions of stearyl methacrylate‐co‐styrene‐co‐vinyl pyrrolidinone copolymers (SMA‐S‐VP) was investigated over a wide range of temperatures (20–140°C) under steady shear (0.1–5000 s^?1) and dynamic conditions (0.01–500 rad/s). The solvent used was polyalpha olefin, PAO4 (C20‐C40 fraction), a fully synthetic paraffinic oil normally used as base oil for lubricant oil formulations. The investigation focuses on the effect of the polar comonomer segment content, of the copolymer, on the viscosity‐temperature relationship of the solution. This information provides insight into the effect of polymer microstructure on the viscosity index (VI) behavior of the lubricant. Copolymers with different ratios of stearyl methacrylate, styrene and vinyl pyrrolidinone were synthesized by solution radical polymerization. The microstructure and molecular weight of the copolymers were evaluated by nuclear magnetic resonance spectroscopy (NMR). The molecular weight and polydispersity of the polymers were determined using GPC. The polymer solutions exhibit non‐Newtonian behavior, which is more evident at lower temperatures and higher concentrations. The temperature‐concentration superposition principle developed by Ferry (1) was applied to steady shear data and the resulting master curve was fitted to the Carreau model. A modified Fedors equation for intrinsic viscosity calculation, at low and moderate polymer solution concentrations, was used. The results confirm that the viscosity index improver properties (VII) of the copolymer are superior when the VP content is low. The polymer‐solvent interactions and solvency power of PAO4 were analyzed using an Arrhenius expression. The results show that at low VP content, PAO4 is a better solvent for the copolymer. Polym. Eng. Sci. 44:736–748, 2004. © 2004 Society of Plastics Engineers.     

反应性微凝胶分散液的流变性能

为了在实际应用中更好地利用反应性微凝胶分散液的流变特性,采用自稳定分散聚合的方法合成了带有环氧基或羧基的反应性微凝胶,并研究了其在不同溶剂中的流变性能。结果表明,与相应的线形聚合物相比,当相对分子质量一定时,反应性微凝胶分散液的特性黏度较低,对聚合物相对分子质量依赖性较小;随着反应性微凝胶交联度的增加,特性黏度变小。在二甲苯中,随着反应性微凝胶质量分数的增加,分散液逐渐由牛顿流体转变为非牛顿流体,且随着反应性微凝胶质量分数的增加,假塑性增加。在甲苯、苯乙烯(St)或甲基丙烯酸异冰片酯(IBOMA)稀溶液中,反应性微凝胶的官能团种类对特性黏度的影响较弱,官能团种类对高浓度溶液的流变性能有较大的影响。     

The influence of the solvent upon the low shear viscosity of styrene–acrylonitrile copolymer solutions

This paper describes the results of an experimental investigation concerning the effect of polymer–solvent thermodynamics on low-shear viscosity of copolymer soltions. Thermodynamic parameters and low-shear solution viscosities were measured for solutions of polystyrene homopolymer and styrene–acrylonitrile copolymers in four solvents: benzene, dioxane, methyl ethyl ketone, and dimethylformamide. The thermodynamic quality of a solvent for a polymer is characterized by free-energy-of-mixing parameters. These quantities are: the Flory-Huggins thermodynamic interaction parameter χ, the second virial coefficient (from light scattering), the intrinsic viscosity, and the polymer expansion factor. The thermodynamic interaction between a solvent and a polymer in solution influences the rheological behavior of the system. At low concentrations of polymer in solvent, the low-shear solution viscosity is larger in a good solvent than in a poor solvent. In solutions of higher concentration, the reverse may be true and the viscosity is often significantly larger in a poor solvent than in a good one. These results are not predicted quantitatively by existing theory. The parameters in existing viscosity correlation techniques are found to be solvent dependent. The so-called entanglement concentrations for polymer solutions are not unique for a particular polymer but are related to the free energy of mixing polymer with solvent.     

Electroviscous effect in dilute suspensions of ionic polymer latices

The viscosity of dilute suspensions of ionic polymer latices was measured using a variable-shear capillary viscometer, a rotational viscometer and an Ubbelohde viscometer. The viscosity of the suspension was much larger than the Einstein theoretical value and showed a marked shear-thinning behaviour, due to the electroviscous effect. The dependence of the reduced viscosity of latex suspensions on latex concentration, salt concentration and solvent was essentially the same as that of linear ionic polymer solutions. Counterion effect was also investigated.     

Viscoelasticity of magnesium neutralized telechelic poly(ethylene butylene) ionomer

The associative and mechanical properties of magnesium neutralized telechelic poly(ethylene butylene) ionomer, CTPEB-Mg, in a nonpolar solvent of decalin were studied from very dilute solution up to the bulk in the range of temperature from 15 to 55 °C with rheological methods and dynamic light scattering (DLS) technique. Dilute solution viscometry and DLS revealed that CTPEB-Mg molecules are associated as ring polymer in very dilute solution, followed by linear association of rings above polymer concentration C=1 wt%. The linearly associated rings formed huge polymeric clusters at around C=10 wt%, where the viscosity η of CTPEB-Mg solution increased thirty times over that of an esterified sample of CTPEB. A viscoelastic network was formed around C=15 wt%, above which disengagement of the magnesium dicarboxylate (MDC) ionic bond played a deterministic role for relaxation of the network up to the bulk. In referring to viscosity behaviors of the prepolymer CTPEB as well as esterified samples, changes in dynamic viscoelasticity of the network with increasing C were found to be closely related to corresponding changes in the average size of ionic clusters as well as fractions of elastically effective chains and dangling loops emanating from ionic clusters.     

Expansion-contraction behavior of dilute polymer solutions

Expansion-contraction behavior of capillary jets of dilute polymer solutions has been studied by using small diameter capillary tubes. The test liquids were water, glycerine solution and dilute solutions of polyethylene oxide and guar gum. It has been found that polyethylene oxide molecules degraded considerably at high shear rates; however the molecular degradation had little effect on the observed expansion-contraction behavior of capillary jets. On the other hand, the solvent viscosity had an appreciable effect on the issuing jets and on the final magnitude of the evaluated normal stresses     

Flows of dilute hydrolyzed polyacrylamide solutions in porous media under various solvent conditions

Experimental results on pressure losses of flows of dilute polymer solutions through porous media are summarized. The polymer products employed in this study consisted of partially hydrolyzed polyacrylamides (HPAM) with different degrees of hydrolysis. The effect of the hydrolysis on the pressure drop is investigated in a porous media test section designed to minimize polymer degradation. The investigations were carried out for various solvent conditions, and it is shown that the maximum increase in pressure drop is mainly dependent on the molecular weight of the polymers. The onset of the polymer action is measured for various fluid and solvent properties. Particular attention is given to measurements near θ-conditions. The results stress the importance of the solvent properties on the actions of the polymers and on the resultant pressure drop for porous media flows. The addition of salt ions to solutions of partially hydrolyzed polyacrylamides yields onset behavior previously observed for nonionic polymers. The differences measured between various solvent properties can be explained by the actual hydrodynamic molecule dimensions for a given molecular weight and polymer concentration. To quantify the influences of the solvent properties on the polymers, measurements were carried out in aqueous solutions for various pH values and therefore at various degrees of dissociation. The importance of separating polymer effects caused by their linear dimension in the solution from those that are introduced by and increase in solvent viscosity is shown. Measurements were performed to quantify the effects of solvent viscosity on the polymer action and to separate these effects from those due to changes in molecule dimensions. The implications of the present results are stressed in connection with applications of polymer solutions in tertiary oil recovery, and the positive features of the molecule actions on flow in such applications are described.     

相反电荷强聚电解质复合物盐溶液的粘度研究

合成了高电荷密度的磺酸基强聚电解质,考察了其与阳离子聚电解质聚二烯丙基二甲基氯化铵（PDADMAC）稀溶液复合体系的流动特性。无论外加盐浓度高低,剪切速率高于10s^-1时,复合体系都表现出牛顿流体的行为。在水溶液中,随PDADMAC的增加,复合体系的增比粘度逐渐减小;在高浓度的NaCl溶液中,随PDADMAC的增加,体系的增比粘度基本保持不变。随体系离子强度增大,复合体系增比粘度出现极大值,反映了复合聚集的加强;继续增大离子强度,则复合解离,增比粘度变小直至恒定。