CAREER: Morphological Control in Polymer Blends Using Polymeric Surfactants

摘要-0448845动机：不混溶聚合物的共混是获得具有不寻常性能的材料的有效和高效的策略。通常，只有当共混物具有特定形态时，才能实现所需的性能，例如，扩散阻挡材料要求低扩散率组分为层状或片状形式。因此，控制形态的能力对于新聚合物材料的设计至关重要。该建议的假设是，不混溶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。具体而言，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态。研究建议：从两相共混操作获得的结构是由于共混引起的流体动力学应力和由于界面张力引起的界面应力之间相互作用的结果。后者使其难以获得小规模的各向异性形态的共混物。添加表面活性剂的一个众所周知的作用是通过降低不混溶相之间的平衡界面张力来降低这些界面应力。不太明显的是，流动和界面上表面活性剂浓度之间的耦合导致界面张力偏离其平衡值，以及沿界面沿着的界面张力梯度。这个建议的重点是量化这些非平衡表面活性剂的影响，并利用它们来控制结构的演变。该方法的关键要素是简单的材料和流场，以帮助突出界面现象，以及由界面耦合反应产生的表面活性剂。后者确保大部分表面活性剂保留在界面处，并且很少溶解在本体中。一个关键的创新是使用荧光标记的表面活性剂，它允许定位的表面活性剂在混合物中，并测量局部界面张力，通过共聚焦激光扫描显微镜。表面活性剂可以实现不寻常的形态，如分散板，分散带，或双相连续性的机制，将得到阐明。流变学方法来确定粘弹性能的表面活性剂负载接口将进行探讨。 教育计划：该教育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。中心教育目标是在整个课程中引入产品设计思想，而不仅仅是作为附加的产品设计课程。短模块，可以纳入现有的类化学工程将被设计，以促进化学产品设计的全学科介绍。这些将最终在一个新开发的顶点课程化学产品设计。在模块以及在过程中，所有的案例研究将被选择强调核心化学工程学科，如传输现象和热力学。智力优点：聚合物表面活性剂（更通常称为“增容剂”）通常用于促进不混溶聚合物的共混。该建议是基于这样的想法，即相同的表面活性剂也可以用于操纵形态。在过去的研究在这一领域的主要科学进展是，结构的各向异性，以及流动和界面上的表面活性剂之间的耦合，将首次量化。这项研究将为多相流的流体力学提供基本的见解，并将为使用表面活性剂控制不混溶聚合物共混物的结构奠定指导方针。更广泛的影响：虽然研究将在聚合物体系中进行，但结果适用于所有含表面活性剂的液-液乳液，例如食品，个人护理产品或石油工业中遇到的那些。本研究所获得的流变特性将指导聚合物共混物加工设备的设计。研究的很大一部分将由本科生进行。产品设计模块，将提供给各地的教师，很可能会影响其他化学工程部门的产品设计教学法。可行性：PI在这里所涵盖的研究课题方面拥有广泛的知识和实验技能。 所有必要的实验资源都是可用的，或将在本研究期间购买。教育署全力支持教育计划中的课程改革建议。

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.