【作者】 吴强；

【导师】 郑强； 杜淼；

【作者基本信息】 浙江大学 ， 材料加工工程， 2009， 博士

【摘要】 由于在实际应用与理论研究上的重要性，相反电荷聚电解质-表面活性剂复合溶液体系，受到广泛的关注。然而，由于研究手段的限制，已有的研究大多集中在表面活性剂添加聚电解质稀溶液体系，对于聚电解质在缠结溶液中与相反电荷表面活性剂相互作用的研究迄今未见有报道。多相／多组分聚合物体系的流变特性与其组分间的相互作用、相形态密切相关，本文以两种阴离子聚电解质聚丙烯酸（PAA）与羧甲基纤维素钠（NaCMC）为研究对象，在聚电解质的亚浓缠结溶液区间，采用流变学的方法，系统考察了表面活性剂浓度、烷基链长，聚电解质电荷密度、浓度以及温度对聚电解质．表面活性剂复合溶液流变行为的影响，并从聚电解质标度理论与“Sticky Reptation模型”出发，推导出相反电荷表面活性剂在聚电解质亚浓缠结溶液中的动力学标度关系，揭示了复合体系特征流变响应与其形态及组成的对应关系。论文取得了以下主要结果：对阳离子表面活性剂十二烷基三甲基溴化铵(C₁₂TAB)与十六烷基三甲基溴化铵(C₁₆TAB)添加到不同中和度的PAA亚浓缠结溶液体系而言，随着C₁₂TAB和C₁₆TAB浓度(C_surf)增加，PAA溶液的零剪切粘度（η₀）的变化分为两个阶段（对应的临界表面活性剂浓度为C_c）：当C_surf＜C_c时，η₀变化不明显；当C_surf＞C_c时，η₀随C_surf增加显著增高。对于中和度相同的PAA溶液，当C_surf＞C_c时，logη₀～logc_surf曲线所表现出的斜率基本相等，表明PAA-C_nTAB复合体系η₀变化的标度关系与表面活性剂的烷基链长无关。C_c值大于相应体系的临界聚集浓度（CAC），表明体系粘度上升需要吸附一定量的胶束。另外，还发现，中和度较低的PAA-C_nTAB复合溶液的η₀对C_surf更敏感。温度依赖性测试发现，氢键是影响PAA-C_nTAB体系粘度变化的重要因素。采用稳态与动态流变测试方法，考察了C₁₂TAB对不同浓度与取代度的NaCMC亚浓缠结溶液流变行为的影响。稳态与动态测试的结果均表明，随着C_surf增高，NaCMC-C₁₂TAB复合溶液的流变学参数（η₀、松弛时间（τ）、储能模量（G′）），都分为三个阶段(由η₀～C_surf，τ～C_surf与G′～C_surf曲线得到的两个临界浓度分别为C₁，C₂；c₁，c₂与C′₁，C′₂)：当C_surf＜C₁（c₁，C′₁）时，η₀，τ与G′变化不明显；当C₁（c₁，C′₂）＜C_surf＜C₂（c₂，C′₂）时，η₀，τ与G′随C_surf增大显著增加；当C_surf＞C₂（c₂，C′₂）时，η0，τ与G′随C_surf增加，上升的幅度下降。C₁（C₁，C′₁）值大于相应体系的CAC，表明体系粘度上升需要一定量的胶束。c₁，c₂与相应的C′₁，C′₂接近，而低于C₁，C₂，表明松弛时间与动态模量对体系的结构变化更敏感。C₁（c₁，C′₁）与C₂（c₂，C′₂）随着C_surf的增加与取代度的降低而增加，表明NaCMC浓度越高，取代度越低，形成物理网络所需的临界胶束含量就越大，形成完善网络所需的胶束越多。同时，对于NaCMC-C₁₂TAB复合体系而言，随着C_surf的增高，G′～应变（γ）中出现增大的“Payne”效应，G′与损耗模量（G″）对频率（ω）关系曲线在低频区域（终端区域）的斜率减小并逐渐偏离线性粘弹关系，表明体系内物理网络结构逐渐形成与完善。tanδ随C_surf增高而降低，表明复合体系的弹性对C_surf更敏感。此外，Cox-Merz规则对NaCMC-C₁₂TAB复合体系的适用性表明，分子间的长程相互作用随C_surf增高而变化。动力学标度关系是研究聚合物流变学重要的理论工具，通过对PAA-C_nTAB与NaCMC-C₁₂TAB复合体系的研究，我们发现，由于表面活性剂胶束吸附并“桥连”了多条聚电解质分子链，抑制了聚电解质分子链的运动，使得相反电荷聚电解质亚浓溶液的粘度，松弛时间与模量上升，因此，我们从“Sticky Reptation模型”与聚电解质标度关系出发，跟据不同表面活性剂浓度，划分了几个标度区间，推导出相反电荷表面活性剂在聚电解质亚浓缠结溶液中的动力学标度关系，并给出了具体表达式。PAA-C_nTAB与NaCMC-C₁₂TAB的实验结果与该模型理论预测一致，表明该模型的推导是合理的。通过该模型可揭示相反电荷聚电解质-表面活性剂复合体系特征流变响应与其形态及组成的对应关系。更多还原

【Abstract】 The polyelectrolyte and surfactant system with opposite charges has attractedgreat attention both in academic research and commercial application. However, toour knowledge, there were few studies concerning the polyelectrolyte-surfactantinteractions in entangled polyelectrolyte solutions. It is well known that rheologicalbehaviors of multiphase and multicomponent polymer systems are related to thecomponents and phase morphologies. In this dissertation, the rheological behavior ofentangled semidilute solution of anionic polyelectrolyte poly （acrylic acid） （PAA） andsodium carboxymethyl cellulose （NaCMC） containing cationic surfactant wasinvestigated, as a function of surfactant concentration, tail length, polyelectrolyteconcentration, charge density and temperature. Moreover, on the basis of "StickyReptation Model", we modified the polyelectrolyte scaling expression in entangledsemidilute solution. It is found that the relationship between rheological response andstructure of the opposite charged polyelectrolyte and surfactant system can bedescribed by using the modified model.On the other hand, The interactions between anionic polyelectrolyte, poly（acrylicacid） （PAA）, and cationic surfactant, alkyltrimethylammonium bromide （C_nTAB）,were investigated by rheological measurements in PAA entangled semidilute solution.The results reveal that addition of both dodecyl and cetyltrimethylammoniumbromides (C₁₂TAB and C₁₆TAB) into PAA solution could increase its viscosity whenthe surfactant amounts surpassed a critical surfactant concentration （C_c）. The increaseof viscosity is attributed to the surfactant micelles bridging of the polymer chains andconfine the mobility PAA chain. On the other hand, the viscosity increases rapidlywith the adding surfactant into PAA solution with lower neutralization extent, due tolower neutralization extent PAA-C_nTAB complex having more hydrogen bondings.The steady and dynamic rheological behaviors of NaCMC entangled semidilutesolution filled with C₁₂TAB were investigated. Both steady and dynamic rheologicalresults present that the rheological parameters （zero shear rate viscosity （η₀）, relaxation time （τ） and dynamic storage modules （G′）） increase with surfactantconcentration (c_surf), and can be divided in three scaling regions by two criticalC₁₂TAB concentrations (C₁, C₂; c₁, c₂; and C₁′, C₂′are from curves ofη₀～c_surf,τ～c_surfand G′～c_surf, respectively). The presence of two critical C₁₂TAB concentrationsimplies that the structures evolution of NaCMC-C₁₂TAB complex could be exposed tothree states with increase of c_surf, i.e. no network formation, network extentprogressive formation and perfect network formation, respectively. Moreover, c₁, c₂approach C₁′, C₂′, while a little lower than C₁, C₂, indicating that the relaxation timeand dynamic module are more sensitive to detect the structure change of the complex.Both C₁（c₁, C₁′） and C₂（c₂, C₂′） increase with NaCMC concentration increasing andcharge density decreasing. Meanwhile, the dynamic rheological results also revealedthat the decrease of G′at critical strain amplitude, i.e., the so called "Payne Effect", isprominently enhanced upon increasing c_surf. Apart from this phenomenon, as c_surfincreases, the slopes of plotting log G′～logωand log G″～logωdecrease, revealingthat the network extent of NaCMC-C₁₂TAB systems progressively increases as c_surfincreases. It is also found that G′of NaCMC-C₁₂TAB is much more sensitive to c_surfthan that of G″.The experimental results show that the viscosity, relaxation time and moduleincrease with c_surf increasing, which is ascribed to the surfactant micelles bridging ofthe polymer chains and confining of the mobility of polymer chain in entangledsemi-dilute solution. Hence, based on "Sticky Reptation Model", we modify thepolyelectrolyte scaling expression in entangled semidilute solution. And the modelcan be used to explain our experimental results. It is also applied to predict anincrease in viscosity of PAA/C₁₂TAB systems reported in literature. The results are ingood agreement with experimental data, proving our model can be used for examinethe relationship between rheological response and structure of the opposite chargedpolyelectrolyte and surfactant system.更多还原