Reconfigurable Polymer Interfaces for Dynamic Interactions and Differentiation of Soft Colloids

第1部分：由于聚合物材料表面暴露在其环境中或与其他材料接触而产生的非技术概述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，它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，这种界面可以在受到刺激时吸引和排斥胶体、液滴、颗粒、小泡、病毒或生物细胞等微观物体。将调整排斥和吸引之间的动态切换，并用于颗粒的选择、区分和分离。这种动态界面能够从饮用水、血液、食品以及商品和特殊材料和设备的表面等各种介质中提取和去除有毒和危险物质的颗粒、土壤颗粒、油滴、细菌和病毒的痕迹。另一方面，如果这种动态界面在与其他成分的混合物中被非常稀释，例如含有贵金属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业领域和空间飞行任务中的土壤样本，则这种动态界面将能够区分和提取有价值的颗粒。该项目的主要挑战是了解具有不同性质的各种颗粒与功能聚合物界面相互作用的复杂动力学机制，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，以培养具有创造性和变革性思维的新一代专业人员。先进的聚合物科学研究正在吸引着许多来自不同背景和培训水平的有才华的年轻男女，包括高中、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。这个项目将服务于发展他们的技能和经验的目的。第2部分：技术总结通过吸附-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，由于所有吸附链段同时脱离的高活化自由能，接近平衡受到非常缓慢的解吸动力学的阻碍。这些性质表现为胶体颗粒、液滴、小泡、蛋白质、微生物等在各种材料表面的强吸附和准不可逆吸附。尽管聚合物界面的这种固有属性对粘合剂应用是有利的，但这种粘合滞后导致了基于亲和力区分复杂混合物中的各种颗粒的复杂情况，适用于多种应用。本项目旨在开发一种新的表面分化和软胶体选择性传输的机制，这是由于具有特殊设计的功能、微结构和动态响应的动态聚合物表面。这一机制将通过探索动态振荡的聚合物界面来实现，这些界面由经历温度驱动相变的微结构聚合物刷子的独特的吸引、粘合和排斥微域组成。粘附域将具有共价结合的功能基序，这些功能基序针对感兴趣的软胶体表面的互补基序。2D界面将被设计成具有微区的各向异性图案。不同的微域将具有不同的尺寸和特定基序的表面浓度。将应用移动温度梯度来促进软胶体的定向传输。这项研究的关键挑战在于对微结构聚合物-刷子界面与具有不同尺寸、弹性和表面官能团组成以及松弛时间的软胶体的动态相互作用有一个基本的了解。在特殊设计的实验中，将利用软脂或嵌段共聚囊泡分析由膨胀排斥域渗透压、软颗粒变形、拉伸粘着域的熵惩罚和互补模体的粘着能控制的附着-脱离动态平衡，并与计算机模拟结果进行比较。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.