CAREER: Morphological Control in Polymer Blends Using Polymeric Surfactants

摘要-0448845动态：共混不相容聚合物是获得具有特殊性能材料的有效且高效的策略。通常，只有当共混物具有特定的形态时，才能实现所需的性能，例如，扩散阻挡材料要求低扩散系数组分呈片层或小片的形式。因此，控制形态的能力对于设计新的聚合物材料至关重要。这一建议的假设是，不相容的聚合物共混物的形态可以通过添加聚合物表面活性剂来控制。具体地说，我们建议利用界面流动和表面活性剂浓度之间的耦合来操纵形貌。研究建议：两相共混操作得到的结构是共混引起的流体动应力和界面张力引起的界面应力相互作用的结果。后者使得在共混物中获得小尺度的各向异性形态变得困难。添加表面活性剂的一个众所周知的效果是通过降低不相容相间的平衡界面张力来降低这些界面应力。较不明显的是，界面上的流量和表面活性剂浓度之间的耦合导致界面张力偏离其平衡值，以及界面张力梯度。这一提议的重点是量化这些非平衡表面活性剂效应，并利用它们来控制结构演变。该方法的关键元素是有助于突出界面现象的简单材料和流场，以及通过界面耦合反应产生的表面活性剂。后者确保大多数表面活性剂留在界面上，很少溶解在主体中。一项关键的创新是使用了荧光标记的表面活性剂，它允许通过共聚焦激光扫描显微镜定位混合物中的表面活性剂，并测量局部界面张力。表面活性剂可以实现特殊形态的机理将被阐明，如分散的板状、分散的带状或双相连续。我们将探索确定表面活性剂界面粘弹性的流变学方法。教育计划：该计划解决了将本科化学工程课程转向化学产品设计的需要。教育的中心目标是在整个课程中介绍产品设计理念，而不仅仅是作为一门附加的产品设计课程。可以融入化学工程现有课程的短小模块将被设计成便于在整个课程范围内介绍化学产品设计。这些将在最新开发的化学产品设计课程中达到顶峰。在模块和课程中，将选择所有案例研究来强调核心的化学工程学科，如运输现象和热力学。智力优势：聚合物表面活性剂(通常被称为“相容剂”)通常被用来促进不相容聚合物的混合。这一建议是基于这样的想法，即同样的表面活性剂也可以用来操纵形态。与过去在这一领域的研究相比，这一领域的主要科学进展是，结构的各向异性以及流动与界面上表面活性剂之间的耦合将首次被量化。这项研究将为多相流的流体力学提供基本的见解，并将为在不相容的聚合物混合物中使用表面活性剂控制结构奠定基础。广泛影响：虽然研究将在聚合物体系中进行，但结果适用于所有含有表面活性剂的液-液乳液，如食品、个人护理产品或石油行业中遇到的那些。本研究获得的流变特性将指导聚合物共混物加工设备的设计。很大一部分研究将由本科生完成。产品设计模块将提供给各地的教师，可能会影响其他化学工程系的产品设计教学。可行性：PI在这里涵盖的研究主题中拥有广泛的知识和实验技能。所有必要的实验资源要么是可用的，要么将在本研究期间购买。教育署全力支持教育计划所建议的课程改革。

ABSTRACT - 0448845Motivation: Blending of immiscible polymers is an effective and efficient strategy to obtain materials with unusual properties. Often the desired properties are realized only if the blend has a specific morphology, e.g. a diffusion-barrier material requires that the low-diffusivity component be in the form of lamellae or platelets. An ability to control the morphology is therefore crucial for design of new polymeric materials. The hypothesis of this proposal is that the morphology of immiscible polymer blends can be controlled by addition of polymeric surfactants. Specifically, we propose to exploit the coupling between interfacial flow and surfactant concentration to manipulate the morphology. Research Proposal: The structure obtained from a two-phase blending operation is a result of the interplay between hydrodynamic stresses due to blending, and interfacial stresses due to interfacial tension. The latter make it difficult to obtain small-scale anisotropic morphologies in blends. A well-known effect of added surfactant is to reduce these interfacial stresses by decreasing the equilibrium interfacial tension between the immiscible phases. Less obviously, a coupling between the flow and the concentration of the surfactant on the interface causes deviations of the interfacial tension from its equilibrium value, as well as interfacial tension gradients, along the interface. The focus of this proposal is to quantify these nonequilibrium surfactant effects, and exploit them to control structural evolution. Key elements of the methodology are simple materials and flow fields to help highlight interfacial phenomena, and a surfactant that is generated by an interfacial coupling reaction. The latter ensures that most of the surfactant remains at the interface, and very little dissolves in the bulk. A crucial innovation is the use of fluorescently-tagged surfactants, which allows locating the surfactant in the blend, and measuring the local interfacial tension, by confocal laser scanning microscopy. The mechanisms by which surfactants can achieve unusual morphologies such as dispersed plates, dispersed ribbons, or dual-phase continuity, will be elucidated. Rheological methods to determine the viscoelastic properties of surfactant-laden interfaces will be explored. Education Plan: The education plan addresses the need to shift the undergraduate Chemical Engineering curriculum towards Chemical Product Design. The central educational goal is to introduce product design ideas throughout the curriculum, and not only as an add-on Product Design course. Short modules that can be incorporated into existing classes in Chemical Engineering will be designed to facilitate a curriculum-wide introduction to Chemical Product Design. These will culminate in a newly developed capstone course on Chemical Product Design. In the modules as well as in the course, all case studies will be chosen to emphasize core Chemical Engineering disciplines such as Transport Phenomena and Thermodynamics. Intellectual merit: Polymeric surfactants, (more commonly referred to as "compatibilizers") are routinely used to facilitate blending of immiscible polymers. This proposal is based on the idea that the same surfactants can also be used to manipulate the morphology. The chief scientific advances over past research in this area are that the anisotropy of the structure, and the coupling between the flow and the surfactant on the interface, will be quantified for the first time. This research will offer fundamental insights into the fluid mechanics of multiphase flow and will lay guidelines for using surfactants to control structure in immiscible polymer blends.Broader impact: While the research will be conducted on polymeric systems, the results are applicable to all liquid-liquid emulsions with surfactants, such as those encountered in the foods, personal care products, or oil industries. The rheological properties obtained in this research will guide the design of processing equipment for polymer blends. A significant portion of the research will be performed by undergraduate students. The product design modules, to be made available to instructors everywhere, is likely to influence the pedagogy of product design in other Chemical Engineering departments.Feasibility: The PI has extensive knowledge and experimental skills in the research topics covered here. All necessary experimental resources are either available, or will be purchased during this research. The Department whole-heartedly supports the curricular changes proposed in the education plan.