P(AM-NVP-DMDA)疏水缔合水溶性共聚物的研究

采用自由基水溶液共聚合法制备了Ｐ（ＡＭ－ＮＶＰ－ＤＭＤＡ）疏水缔合水溶性共聚物。对共聚物的溶液性能进行了研究,包括盐效应、粘温关系、流变性能、热稳定性、与碱、表面活性剂的相互作用、稀溶液性质等。共聚物分子中由于引入了较多的疏水基团而具有较强的疏水缔合效应,在聚合物浓度较低时具有较高粘度。ＮＶＰ结构单元的引入可适当提高共聚物溶液的热稳定性。对共聚物溶液的电镜分析结果表明,在其水溶液中存在着微相分离结构,它对共聚物溶液的增粘起着重要作用。     

疏水缔合水溶性聚合物AO的溶液粘度行为研究

研究了稀溶液中疏水链链长、无机电解质NaCl和CaCl2对疏水缔合水溶性丙烯酰胺／甲基丙烯酰氨乙基-二甲基烷基溴化铵／丙烯酸钠共聚物(AO)在水溶液中的特性粘数和Huggins常数的影响，以及聚合物AO-8的特性粘数和Huggins常数随温度的变化。结果表明：在稀溶液中，无机电解质离子强度增大，共聚物AO在NaCl和CaCl2溶液中的特性粘数减小，Huggins常数增大。在亚浓溶液范围对聚合物质量分数、温度、剪切速率及NaCl含量对聚合物的水溶液表现粘度的影响进行了研究，观察到疏水缔合聚合物盐水溶液在NaCl含量提高的情况下，出现的增粘现象。     

疏水缔合聚合物重均分子量的测定

采用毛细管法和荧光探针法研究了疏水缔合聚合物在不同甲酰胺浓度和盐浓度的溶剂中的特性黏数和疏水缔合作用强度.找到可以消除缔合作用和聚电解质效应的溶剂条件,用静态光散射法测定疏水缔合聚合物的重均分子量.结果表明,NaCl能够有效的屏蔽聚电解质效应,但是不能消除缔合作用,而且由于NaCl增加了溶液的极性,会进一步促进疏水缔合作用,疏水缔合聚合物以聚集体形态存在溶液中,因此,在NaCl溶剂中测得的疏水缔合聚合物的重均分子量不是真实分子量;而甲酰胺可以完全破坏疏水缔合作用,使聚合物分子以单分子态分散在溶液中,进而测得疏水缔合聚合物的真实分子量.当溶剂中的NaCl浓度为0.2 mol/L、甲酰胺体积分数为50%时,可准确测定疏水缔合聚合物的重均分子量.当缔合作用消除后再改变甲酰胺浓度,测得的重均分子量不再变化;聚电解质效应消除后,盐离子浓度的变化不会再改变测得的重均分子量结果.     

疏水改性聚丙烯酰胺溶液的分子模拟

设计了几种不同的非离子型改性聚丙烯酰胺(HM-PAM)和阴离子型改性聚丙烯酰胺(HM-HPAM). 通过分子动力学模拟(MD)方法研究了在聚合物链上加入不同疏水改性单体对提高聚丙烯酰胺耐盐性的影响, 考察了盐浓度对疏水改性聚丙烯酰胺的回旋半径(R_g)、 特性黏数([η])、 径向分布函数(RDF)和均方位移(MSD)的影响以及聚合物的微观结构与特性黏数之间的关系. 研究结果表明, 引入疏水改性单体后, 改性聚丙烯酰胺具有较好的耐盐性. 通过研究非键作用与氢键相互作用可知, 体系中溶质和溶剂间的相互作用及氢键作用越弱, 溶液的特性黏数越大. O-H原子对的RDF结果表明, 聚合物链的伸展与聚合物链及官能团间的相互作用有关. 当RDF峰较弱时, 聚合物链与水的作用越弱, 越有利于聚合物链保持舒展状态, 溶液的特性黏数也就越大. 另外, 从聚合物链的MSD曲线发现, 聚合链的移动性与特性黏数呈负相关.     

疏水缔合聚合物分子量分布曲线的测定

在体积百分浓度为50%1,3-丙二醇、0.2 mol/L Na Cl和水溶剂条件下,消除疏水缔合聚合物(HAWSP)溶液中疏水缔合作用,屏蔽溶液中的聚电解质效应,使HAWSP分子在稀溶液中处于单分子分散状态.然后利用膜孔径分离原理,选择不同孔径的微孔滤膜,用微孔滤膜流动实验装置对疏水缔合聚合物进行分级,将不同分子量的聚合物分离开来.用二次方程拟合滤出液质量-过滤时间关系曲线得到各级分聚合物溶液的质量,以分光光度法测定各级分聚合物溶液的浓度,根据质量和浓度计算得到各级分的累积百分含量.结合静态光散射和毛细管法标定了疏水缔合聚合物Mark-Houwink方程[η]=0.182M~(0.586),用于准确测定疏水缔合聚合物各个级分的分子量.选择四参数方程曲线,根据各级分的分子量M和累积百分含量W,得到分子量的分布曲线.与动态光散射分析进行比较的结果表明,两种方法测试结果一致.     

粘度法研究疏水改性聚丙烯酸与Np7.5的相互作用

研究了氟基团改性和氟碳、碳氢基团同时改性的聚丙烯酸（HM－PAA）以及参与聚合物（PAA）与非离子表面活性剂Np7.5分别在稀溶液和亚浓溶液下的相互作用对特性粘数和Brookfield表观粘度的影响。结果表明,PAA与Np7.5无明显作用,而M－PAA在Np7.5达到一定浓度后,由于Np7.5参与了疏水缔合,特性粘数和表观粘度发生了明显变化。稀溶液中,氟碳基团较多的聚合物出现了链构象的伸展。亚浓溶液中,疏水改性聚合物的粘度都有先上升后下降的变化,但氟碳含量较多的变化更强烈。     

新型疏水缔合丙烯酰胺/2-苯氧乙基丙烯酸酯共聚物的合成与性质

采用胶束共聚方法合成了一种新型的疏水缔合共聚物 ,它由丙烯酰胺 (AM)和少量的 2 苯氧乙基丙烯酸酯 (POEA) (<1 0mol% )组成 ,具有良好的水溶性 .当溶液浓度超过一定值c 后 ,由于分子间的疏水缔合 ,产生很大的增粘作用 .研究了不同聚合条件下包括单体浓度、投料比和SMR值对聚合物的结构和性能的影响 .实验结果表明 ,聚合物的粘度性质和缔合行为取决于其分子量的大小、疏水单体含量及其嵌段的长度和分布 .     

疏水缔合聚丙烯酰胺与双子表面活性剂的相互作用

制备了一种脂肪酸酯双磺酸盐型双子表面活性剂, 利用粘度法、界面张力法和原子力显微镜研究了疏水缔合聚丙烯酰胺与双子表面活性剂在溶液中的相互作用. 实验结果表明: 疏水缔合聚丙烯酰胺在溶液中能够通过自组装形成疏水微区并发展成网络结构, 疏水微区与表面活性剂在溶液中能形成混合胶束; 当一定量的表面活性剂加入时, 对疏水缔合聚丙烯酰胺的自组装起促进作用, 而过多双子表面活性剂的加入又会对聚合物分子的自组装起抑制作用, 从而显著影响疏水缔合聚丙烯酰胺的溶液性质, 随着表面活性剂浓度的增加, 聚合物溶液粘度先增加、再降低; 同时, 疏水缔合聚丙烯酰胺对双子表面活性剂的界面性能也有较大影响, 聚合物的加入使双子表面活性剂降低油/水界面张力的能力下降, 油/水界面张力达到平衡所需时间延长.     

疏水改性聚丙烯酸溶液的流变特性研究

本文通过沉淀聚合制备了具有不同主链结构的疏水改性聚丙烯酸(HMPA),由Huggins方程确定了HMPA在溶液(水,盐/水,醇/水)中的特性粘数[η]和Huggins常数KH,采用流变学法研究了HMPA溶液的疏水缔合行为和流变特性.研究表明,HMPA溶液具有典型的剪切变稀行为,主链结构对HMPA溶液的缔合行为和流变特性有显著影响.主链含有疏水链段的HMPA在乙二醇/水溶液中形成类似弹性体的凝胶网络结构,具有较大的活化能,其表观粘度具有明显的温度敏感性.     

疏水改性水溶性聚合物/表面活性剂溶液性质

表面张力;疏水改性水溶性聚合物/表面活性剂溶液性质     

壳聚糖在稀溶液中的分子构象及其影响因素

结合国内外对壳聚糖在溶液性质方面的研究进展,从壳聚糖的分子量、乙酰度和溶液的离子强度三个方面,探讨了它们对壳聚糖在稀溶液中的分子构象所产生的影响,并从分子间和分子内相互作用力(主要是范德华力、氢键、疏水作用和静电作用)的角度对这种构象转变进行了理论解释。     

Viscometric properties of dilute polystyrene/dioctyl phthalate solutions

We report viscometric data collected in a Couette rheometry on dilute, single‐solvent polystyrene (PS)/dioctyl phthalate (DOP) solutions over a variety of polymer molecular weights (5.5 × 10⁵ ≤ M_w ≤ 3.0 × 10⁶ Da) and system temperatures (288 K ≤ T ≤ 318 K). In view of the essential viscometric features, the current data may be classified into three categories: The first concerns all the investigated solutions at low shear rates, where the solution properties are found to agree excellently with the Zimm model predictions. The second includes all sample solutions, except for high‐molecular‐weight PS samples (M_w ≥ 2.0 × 10⁶ Da), where excellent time–temperature superposition is observed for the steady‐state polymer viscosity at constant polymer molecular weights. No similar superposition applies at a constant temperature but varied polymer molecular weights, however. The third appears to be characteristic of dilute high‐molecular‐weight polymer solutions, for which the effects of temperature on the viscosity curve are further complicated at high shear rates. The implications concerning the relative importance of hydrodynamic interactions, segmental interactions, and chain extensibility with increasing polymer molecular weight, system temperature, and shear rate are discussed. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 787–794, 2006     

Circular dichroism induced by the helical conformations of acylated chitosan derivatives bearing cinnamate chromophores

Through regioselective modifications, some acylated chitosan derivatives, O‐cinnamoyl chitosans with degree of substitution (DS) varying from 0.8 to 2.0 and N‐fatty acyl‐O‐dicinnamoyl chitosans with different fatty acyl chain lengths (C₂–C₁₂), were prepared, and their chiroptical properties in dilute solutions were investigated by circular dichroism (CD). Exciton coupling between two vicinal cinnamoyl chromophores appended to the helical mainchains gave rise to bisignate Cotton effects (CEs), which were used to deduce the absolute sense of the twisting structures in solution phase. It was found that the absolute helicities vary with DS, length of the fatty chain, and solvent property, but are nearly independent of thermal stimulus. The molecular interactions (hydrogen bonding and hydrophobic interaction) involved possibly in the self‐assembled ordered structures were discussed. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1354–1364, 2005     

环糊精包合作用对疏水缔合聚合物流变调节与应用

近年来,利用超分子作用力调节体系流变行为备受人们关注,已在多领域中展现出广泛的应用前景。而环糊精包合作用是一类重要的超分子作用力,向缔合聚合物水溶液中加入环糊精,将拆散缔合结构,引起粘度和粘弹性急剧下降;竞争客体或酶的加入又会诱导分子间发生新的组装行为,使体系流变性得到恢复。本文综述了基于环糊精包合作用的分子组装与流变调节在理论及应用方面的研究现状,重点介绍了环糊精对不同缔合聚合物溶液的流变影响规律和外加物质对体系流变恢复的调节。     

Amphiphilic urethane acrylate hydrogels having heterophasic gel structure: swelling behaviors and mechanical properties

 Amphiphilic urethane acrylate hydrogels containing ionic group (dimethylopropionic acid, DMPA) were prepared by varying the molecular weight of the soft segment (polyether type, PTMG) and type of diisocyanate, and their swelling behaviors and mechanical properties were examined. They showed amphiphilic property due to the hydrophilic ionic groups and hydrophobic polyethers comprising the urethane acrylate network. Heterophasic gel structure could be found for the hydrogels prepared in water, but not for the hydrogels in organic solvent (1,4-dioxane), through scanning electron microscopy. Because of this heterophasic gel structure, they were able to take in a large amount of water as well. The hydrophobic interaction generated by the polyether soft segments between urethane acrylate network chains decreased the degree of swelling, however, increased reversibly the tensile strengths at equilibrium swelling state. MDI-based hydrogel showed low swelling ratio and high tensile strength because of its ordered hard domain structure. These amphiphilic urethane acrylate hydrogels showed salt- and pH-dependent swelling behaviors. Received: 26 September 1997 Accepted: 24 December 1997     

Effect of hydrophobic units of polycarboxylate superplasticizer on the flow behavior of cement paste

For the tuning of conformation of polycarboxylate (PCE) superplasticizers, hydrophobic groups of different stiffness were incorporated, including styrene (St), methyl methacrylate (MMA), ethyl acrylate (EA), and n-butyl acrylate (n-BA) units. The effect of these hydrophobic groups on the dispersing performance, adsorption process and, rheology of cement paste were investigated. Investigation on the solution conformation and adsorption layer thickness indicated the action mechanism of these groups. High backbone stiffness resulted in a lower extent of conformation condensation from pure aqueous solution to pore solution, and therefore more carboxylic groups could be accessible for adsorption. However, the conformation change after adsorption might also be limited and the size of single molecule after adsorption should be small. Hydrophobic groups always resulted in a coiled PCE conformation in salt solution, which indicated a lower adsorption affinity and thinner adsorption layer for these PCE molecules.     

丙烯腈-衣康酸共聚物稀溶液的粘度行为

采用乌氏粘度计研究了丙烯腈-衣康酸共聚物稀溶液的粘度行为,探讨了羧基含量对聚丙烯腈稀溶液偏离Huggins方程的异常行为的影响.结果表明:随着羧基含量增加,溶液粘度偏离Huggins方程越严重,要准确测定聚丙烯腈树脂的分子量,必需适当提高其溶液浓度,避开偏离区域.     

Rheological measurements and light-scattering experiments of dilute solutions of high molecular polystyrene. Light-scattering of flowing polymer solutions

We describe the behavior of dilute polymer solutions by means of light-scattering under shear flow. Solution properties of polystyrene in benzene over a wide range of molecular weight has been studied to determine the coefficientsa andK of the Mark-Houwink relationship and to estimate the rheological conditions with regard to light-scattering experiments of flowing polymer solutions. The investigations were carried out to measure the shear-rate dependence of macromolecules in solution, e.g., to observe an orientation and changing of the mean-square radius of gyration.     

Dimeric (gemini) surfactants: effect of the spacer group on the association behavior in aqueous solution

Dimeric (gemini) surfactants are made up of two amphiphilic moieties connected at the level of, or very close to, the head groups by a spacer group of varying nature: hydrophilic or hydrophobic, rigid or flexible. These surfactants represent a new class of surfactants that is finding its way into surfactant-based formulations. The nature of the spacer group (length, flexibility, chemical structure) has been shown to be of the utmost importance in determining the solution properties of aqueous dimeric surfactants. This paper reviews the effect of the nature of the spacer on some of these properties. The behavior of dimeric surfactants in the submicellar range of concentration, at interfaces, in dilute solution (solubility in water, Krafft temperature, critical micellization concentration, thermodynamics of micelle formation, micelle ionization degree, size, polydispersity, micropolarity and microviscosity, microstructure and rheology of the solutions, solubilization, micelle dynamics, and interaction with polymers) and in concentrated solution (phase behavior) are successively reviewed. Selected results concerning trimeric and tetrameric surfactants are also reviewed.