Experimental and Theoretical Studies of Shear-Thickening in Associating Polymer Solutions

小行星9870128 本研究的目的是发展一个基本的了解剪切增稠和流动诱导凝胶化缔合聚合物溶液。 提出了一种协调的，三管齐下的方法，其中包括新的官能化聚合物的合成，流变和剪切引起的结构变化的测量，和理论。 将合成具有明确分子量的高度单分散聚合物，并将用旨在促进聚合物之间缔合的官能团定量封端。 官能团将以四种构型之一放置：（1）在每条链的一端或（2）在链的两端或（3）沿链的主链的沿着一半或（4）在两端和沿链长的沿着一半。 物理交联处的支化度将使用具有不同配位数的金属离子来控制。 缔合的程度（或缔合的寿命）将通过添加用作缔合基团的“毒物”的共溶剂来控制。 除了广泛的剪切和法向应力的流变学测量，在原位直接测量的关联程度将作为剪切速率的函数，使用紫外/维斯吸收光谱。 将使用双折射进行聚合物的流动诱导排列的原位测量。 静态结构因子S（q）作为剪切速率的函数的小角度和大角度光散射测量将用于跟踪流动引起的结构变化。 剪切流下的剪切诱导凝胶的生长将使用新开发的光散射显微镜技术。 实验工作将与密集的理论研究计划密切协调。 理论和实验研究将开始工作的模型聚合物的解决方案，其中每个链包含一个单一的，终端连接的贴纸和进展更复杂的贴纸的位置，以及网络形成和凝胶化的问题。 缔合聚合物溶液在工业应用中广泛用作粘度调节剂、防雾剂或防飞溅剂、涂料中的凝结剂和采油中的封闭剂。 这些体系的实用性源于许多重要的物理性质，包括它们在加入非常少量的聚合物的情况下显著提高溶液粘度的能力，它们控制甚至逆转粘度随温度降低的能力（这种能力对于许多润滑剂来说很重要），它们抑制雾化和飞溅的能力，以及它们在一定条件下胶凝的能力。 该研究计划的目的是了解决定这些系统物理特性的分子因素，以便将这些系统设计用于实际工业应用。 ***

9870128 Pine The objective of this research is to develop a fundamental understanding of shear thickening and flow-induced gelation in associating polymer solutions. A coordinated, three-pronged approach is proposed which involves the synthesis of new functionalized polymers, measurements of rheological and shear- induced structural changes, and theory. Highly monodisperse polymers, with well defined molecular weights, will be synthesized and will be quantitatively end-capped with functional groups designed to promote associations between polymers. The functional groups will be placed in one of four configurations: (1) at one end of each chain or (2) at both ends of the chains or (3) halfway along the backbone of the chains or (4) at both ends and halfway along the chain length. The degree of branching at the physical crosslinks will be controlled using metal ions with different coordination numbers. The degree of the association (or lifetime of associations) will be controlled by the addition of cosolvents which serve as "poisons" for the associating groups. In addition to extensive rheological measurements of shear and normal stresses, in situ direct measurements of the degree of association will be performed as a function of shear rate using uv/vis absorption spectroscopy. In situ measurements of flow-induced alignment of polymers will be performed using birefringence. Small and large angle light scattering measurements of the static structure factor S(q) as a function of shear rate will be used to follow flow-induced structural changes. The growth of the shear-induced gel under shear flow will be followed using the newly developed light scattering microscopy technique. The experimental work will be closely coordinated with an intensive program of theoretical research. Theoretical and experimental studies will commence with work on a model polymer solution in which each chain contains a single, terminally-attached sticker and progress towards more complex sticker placement as well as issues of network formation and gelation. %%% Associating polymer solutions find wide use in industrial applications as viscosity modifiers, anti-misting or anti- splatter agents, coagulants in coatings, and blocking agents in oil recovery. The utility of these systems stems from a number of important physical properties, including their ability to significantly enhance solution viscosity with the addition of very small amounts of polymer, their ability to control and even reverse the reduction of viscosity with temperature (this capability is important for many lubricants), their ability to suppress misting and splatter, and their ability to gel under certain conditions. The purpose of this research program is to develop an understanding of the molecular factors which determine the physical properties of these systems in order to engineer these systems for practical industrial applications. ***