Reconfigurable Polymer Interfaces for Dynamic Interactions and Differentiation of Soft Colloids

第 1 部分：非技术摘要 聚合物材料表面暴露于其环境或与其他材料接触所产生的现象与许多实际应用相关。动态变化的聚合物界面是一类重要的材料，可以根据预编程的场景根据外部刺激调整其特性。该项目旨在开发和研究专门设计的聚合物界面，该界面响应刺激，可以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。排斥和吸引之间的动态切换将被调整并用于颗粒的选择、区分和隔离。这种动态界面能够从饮用水、血液、食品以及商品和特种材料和设备的表面等各种介质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，如果有价值的颗粒与其他成分（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，以及农田和太空任务中的土壤样本）充分稀释，那么这种动态界面将能够区分和提取有价值的颗粒。该项目要解决的主要挑战是了解功能聚合物界面与具有不同特性的各种颗粒相互作用的复杂动态机制，然后应用所获得的知识来正确设计可重构动态界面。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吸引了许多不同背景和培训水平的青年才俊，包括高中生、本科生、研究生和博士后学者，他们关心并感到对强大健康的国民经济、清洁可持续的环境和社会繁荣的发展负有责任。该项目旨在培养他们的技能和经验。 第 2 部分：技术摘要 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，非常缓慢的解吸动力学阻碍了接近平衡。这些性质表现为对各种材料表面的胶体颗粒、液滴、囊泡、蛋白质、微生物等具有强烈的、准不可逆的吸附作用。虽然聚合物界面的这种固有特性有利于粘合剂应用，但这种粘合滞后会导致在多种应用中对复杂混合物中的各种颗粒进行基于亲和力的区分变得复杂。该项目旨在开发一种新的软胶体表面分化和选择性传输机制，该机制是由于动态聚合物表面具有专门设计的功能、微观结构和动态响应。这种机制将通过探索动态振荡聚合物界面来实现，该界面由经历温度驱动相变的微结构聚合物刷的独特的吸引、粘合和排斥微域组成。粘合域将具有共价结合的功能基序，其目标是目标软胶体表面上的互补基序。二维界面将采用各向异性微域图案进行设计。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以促进软胶体的定向传输。该研究的主要挑战在于对微结构聚合物刷界面与具有不同尺寸、弹性和表面官能团组成以及弛豫时间的软胶体之间的动态相互作用有一个基本的了解。将使用软脂质或嵌段共聚物囊泡在专门设计的实验中分析由膨胀的排斥域的渗透压、软颗粒的变形、拉伸的粘合域的熵罚分和互补图案的粘附能控制的附着-脱离动态平衡，并与计算机模拟的结果进行比较。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力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.