Designer Soft Microparticles for a Changing Environment

摘要直径为数十至数百微米的聚合物颗粒和胶囊，大小与人的头发相似，广泛用于化学或环境敏感活性分子或纳米颗粒的封装和保护，例如用于食品和洗涤剂添加剂，化妆品以及药物输送。在储存和运输过程中，封装剂保护货物，并在期望的位置释放货物，通常是通过一些外部刺激使封装剂破裂或降解。微胶囊，具有薄壳和大空心核的颗粒，特别有价值，因为只需要少量的封装剂就可以保护大量所需的有效载荷。在这个项目中，开发了一种新型微胶囊，其外壳可以在不同的外部刺激下可逆地释放胶囊内容物，而不会破坏外壳，使胶囊完好无损，可以重复使用或反复开关释放。这些胶囊是理想的应用，如在水中的废物清除，在那里他们可以打开收集废物，关闭以清除它，并重新打开以释放废物在适当的存储容器。这些胶囊是从复杂的乳液中获得的，比如水芯油滴，这些油滴是用微流体装置制造的，其通道结构与滴的大小相当。该技术可以精确制造胶囊，控制尺寸，壳厚度和成分，分散性非常低。参与该项目的学生，无论本科生还是研究生，都将接受功能聚合物合成、微流体技术和材料表征方面的培训，为他们提供一套广泛的工具，这些工具对于现代材料科学的多学科研究是必不可少的。技术摘要化学或环境敏感活性分子或纳米颗粒的胶囊化在许多应用中至关重要，从食品添加剂到洗涤剂和药物输送；传统上，牺牲封装剂用于一次性、单向封装和释放设计。该项目的主要目标是开发和制造一种基于功能性聚合物微胶囊的新型动态封装系统，该系统与环境表现出积极和可逆的相互作用。微流控装置用于创建定义明确的多乳液滴的不混溶流体，形成模板的软封装材料。研究了功能材料在复杂乳液中组装的物理过程，以及材料本身的动态功能，以及液体限制对这些过程和性质的影响。该项目的另一个目的是研究这些功能性聚合物微胶囊与溶质、环境和外部刺激的相互作用，以实现胶囊内外的响应性和选择性渗透性。具有这种响应性渗透性的封装系统能够可逆地、按需释放活性物质，并允许通过触发货物的吸收和捕获来补充胶囊内的活性物质。本研究将这种封装剂的应用从单向输送系统扩展到净化和分离的应用。该项目的另一个目标是开发具有控制力学性能的设计多孔介质，以研究多孔介质行为和其中多相流的基本机制。这些模型系统为广泛应用但尚未得到很好理解的过程提供了见解，包括压力冲击导致的多孔介质破裂，以及聚合物溶液对多孔介质中多相流体流动的影响。

Non-technical AbstractPolymeric particles and capsules with diameters of tens to hundreds of micrometers, similar to the size of a human hair, are extensively used for the encapsulation and protection of chemically or environmentally sensitive active molecules or nanoparticles, with uses, for example, for food and detergent additives, for cosmetics, as well as for drug delivery. During storage and delivery, the encapsulant protects the cargo, and releases it at the desired location, often through some external stimulus that breaks or degrades the encapsulant. Microcapsules, particles with thin shells and large hollow cores, are particularly valuable because only small amounts of encapsulant is needed to protect large amounts of the desired payload. In this project, novel microcapsules are developed with shells that release the capsule content reversibly in response to different external stimuli without shell destruction, leaving the capsule intact for reuse or repeated on-off switching of the release. These capsules are ideal for applications such as waste removal in water, where they can be opened to collect the waste, closed to remove it, and reopened to release the waste in appropriate storage containment. These capsules are obtained from complex emulsions, such as water-cored oil drops, that are fabricated using microfluidic devices with channel architectures of comparable size to the drops. This technology enables precise manufacturing of capsules with control over size, shell thickness, and composition with very low dispersity. The students involved in this project, both undergraduates and graduates, are trained in functional polymer synthesis, microfluidic technology, and materials characterization, giving them a broad set of tools that is indispensable for modern multidisciplinary research in materials science. Technical AbstractEncapsulation of chemically or environmentally sensitive active molecules or nanoparticles is crucial in numerous applications, from food additives, to detergents and drug delivery; traditionally sacrificial encapsulants are used in a one-time, one-way encapsulate-and-release design. A primary aim of this project is to develop and fabricate a new class of dynamic encapsulant systems based on functional polymer microcapsules that exhibit active and reversible interactions with their environment. Microfluidic devices are used to create well-defined multiple emulsion drops of immiscible fluids that form templates for soft encapsulation materials. The physics of the assembly of functional materials in complex emulsions, and the dynamic functionalities of the materials themselves, are investigated, as is the influence of liquid confinement on these processes and properties. An additional aim of the project is to investigate the interactions of these functional polymeric microcapsules with solutes, the environment, and external stimuli for responsive and selective permeability in and out of the capsule. Encapsulation systems with such responsive permeability enable the reversible, on-demand release of actives, and allow the replenishment of actives inside the capsules through triggered uptake and trapping of cargo. This research extends the application of such encapsulants from one-way delivery systems to utilization in purification and separation. An additional objective of this project is the development of designer porous media with controlled mechanical properties to study fundamental mechanisms of the behavior of porous media and multiphase flow within it. These model systems provide insight into processes that are widely practiced but not well understood, including the fracturing of porous media due to pressure shocks, and the effects of polymer solutions on multiphase fluid flow in porous media.