Reconfigurable Polymer Interfaces for Dynamic Interactions and Differentiation of Soft Colloids

聚合材料表面暴露于环境或与其他材料接触所产生的现象与许多实际应用有关。动态变化的聚合物界面是一类重要的材料，根据预先编程的场景，根据外部刺激调整其性能。该项目旨在开发和研究特殊设计的聚合物界面，这些界面可以对刺激做出反应，吸引和排斥微观物体，如胶体、液滴、颗粒、囊泡、病毒或生物细胞。将调整排斥和吸引之间的动态切换，并用于选择，分化和隔离颗粒。这种动态界面可以从各种介质（如饮用水、血液、食物、商品和特种材料和设备表面）中提取和去除有毒有害物质颗粒、土壤颗粒、油滴、细菌和病毒的痕迹。另一方面，这种动态界面将能够区分和提取有价值的颗粒，如果它们在与其他成分的混合物中非常稀释，例如含有贵重和稀有金属的沉积物，某些类型的人类干细胞和其他生物样本，以及农田和太空任务中的土壤样本。该项目面临的主要挑战是了解功能聚合物界面与具有不同性质的各种颗粒相互作用的复杂动态机制，然后将所获得的知识应用于可重构动态界面的适当设计。该项目还提供了一种机制来教育具有创造性和变革性思维的新一代专业人士。先进的高分子科学研究正吸引着众多具有不同背景和培训水平的青年男女，包括高中生、本科生、研究生和博士后学者，他们关心并感到有责任发展强大健康的国民经济，清洁和可持续的环境，以及社会繁荣。这个项目将有助于发展他们的技能和经验。通过吸附-解吸机制与聚合物界面的相互作用受到聚合物的准不可逆吸附特性的限制，即，由于所有吸附段一次脱离的激活自由能很高，因此解吸动力学非常缓慢，阻碍了接近平衡。这些特性表现为对各种材料表面的胶体颗粒、液滴、囊泡、蛋白质、微生物等的强吸附和准不可逆吸附。尽管聚合物界面的这种固有特性对粘合剂的应用是有利的，但这种粘附滞后导致了许多应用中复杂混合物中各种颗粒的亲和性区分的复杂性。该项目旨在通过具有特殊设计的功能、微观结构和动态响应的动态聚合物表面，开发一种新的软胶体表面分化和选择性运输机制。这一机制将通过探索动态振荡的聚合物界面来实现，这些界面由具有独特吸引力、粘性和排斥性的微观结构聚合物刷构成，这些微畴经历温度驱动的相变。粘附结构域将具有共价结合的功能基序，其目标是感兴趣的软胶体表面上的互补基序。二维界面将被设计成微域的各向异性模式。不同的微畴将具有不同的尺寸和特定基序的表面浓度。移动的温度梯度将被应用于软胶体的定向输送。该研究的主要挑战在于对微观结构聚合物-电刷界面与具有不同尺寸、弹性、表面官能团组成以及弛豫时间的软胶体的动态相互作用有一个基本的理解。本文将利用软脂质或嵌段共聚物囊泡进行特别设计的实验，分析由膨胀排斥域渗透压、软颗粒变形、拉伸粘附域熵惩罚和互补基元粘附能控制的附着-分离动态平衡，并与计算机模拟结果进行比较。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

PART 1: NON-TECHNICAL SUMMARY Phenomena derived from the exposure of surfaces of polymeric materials to their environment or in contact with other materials are relevant to many practical applications. Dynamically changing polymer interfaces are an important class of materials that adapt their properties upon external stimuli according to a preprogrammed scenario. This project aims for the development and study of specially designed polymer interfaces which, in response to stimuli, could attract and repel microscopic objects such as colloids, liquid droplets, particles, vesicles, viruses, or biological cells. Dynamic switching between repulsion and attraction will be adjusted and used for selection, differentiation, and isolation of the particulates. Such dynamic interfaces could be able to extract and remove traces of particles of toxic and hazardous materials, soil particles, oil droplets, bacteria, and viruses from various media such as drinking water, blood, food, and surfaces of commodity and specialty materials and devices. On the other side, such dynamic interfaces would be able to differentiate and extract valuable particulates if they are very diluted in mixtures with other ingredients, for example sediments containing noble and rare metals, some types of human stem cells and other biological samples, and samples of soils in agricultural fields and in space missions. The major challenge being addressed in the project is to understand the complex dynamic mechanisms of the interaction of functional polymer interfaces with various particulates possessing different properties and then to apply the obtained knowledge for proper design of the reconfigurable dynamic interfaces. This project also provides a mechanism to educate a new generation of professionals capable of creative and transformative thinking. Advanced polymer science research is attracting many talented young men and women of different backgrounds and training levels, including high school, undergraduate, graduate students and postdoctoral scholars, who care and feel responsible for the development of a strong and healthy national economy, clean and sustainable environment, and societal prosperity. This project will serve the purpose of developing their skills and experience.PART 2: TECHNICAL SUMMARYInteractions with polymer interfaces via adsorption-desorption mechanisms are limited by the quasi-irreversible adsorption character of polymers, i.e., approaching the equilibrium is hampered by very slow desorption kinetics due to a high activation free energy of the detachment of all adsorbed segments at once. These properties are revealed as strong and quasi-irreversible adsorption of colloidal particulates, liquid droplets, vesicles, proteins, microbes, etc. on the surface of various materials. Whereas this inherent property of polymeric interfaces is advantageous for adhesive applications, this adhesion hysteresis causes complications for affinity-based discrimination of various particulates in complex mixtures for numerous applications. This project aims to develop a novel mechanism of surface differentiation and selective transport of soft colloids owing to dynamic polymeric surfaces with specially designed functionality, microstructure, and dynamic response. This mechanism will be realized by exploring dynamically oscillating polymer interfaces made of distinctive attractive, adhesive, and repulsive micro-domains of microstructured polymer brushes that undergo temperature-driven phase transitions. The adhesive domains will have covalently bound functional motifs that target complementary motifs on the surface of soft colloids of interest. The 2D-interfaces will be designed with anisotropic patterns of microdomains. The different microdomains will have variable dimensions and surface concentration of the specific motifs. A traveling temperature gradient will be applied to facilitate directed transport of soft colloids. The key challenges of the study consist in developing a fundamental understanding of the dynamic interaction of the microstructured polymer-brush interfaces with the soft colloids having different dimensions, elasticity, and composition of surface functional groups, as well as relaxation times. The attachment-detachment dynamic equilibrium controlled by osmotic pressure of swollen repulsive domains, deformation of soft particles, entropic penalty of stretched adhesive domains, and adhesion energy of complimentary motifs will be analyzed in specially designed experiments using soft lipid or block-copolymer vesicles and compared with results of computer simulations. .This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.