PECASE: Molecular Design and Nanomechanical Testing of High-Toughness Biomimetic Polymeric Systems

这份职业计划的研究部分涉及仿生的、在分子水平上具有高度可控机械性能的“模块化”聚合物系统的设计和纳米机械测试。提出了一种提高合成大分子分子韧性的一般设计策略，它涉及合成的“主体”聚合物与较小的、纳米尺寸、形状恒定的“客体”的非特异性、非共价键的络合。这项研究将首先研究一个模型体系，该体系涉及聚氧乙烷(PEO)-[CH2-CH2-O]n-与小球状蛋白人血清白蛋白(HSA)的络合。使用一种混合单层技术可以实现PEO链端的化学连接和足够低的链接枝密度，该技术包括单(硫醇)功能化的PEO和自组装的烷基硫醇单分子层(SAM)在金表面的共同化学吸附。PEO底物将在人血清白蛋白溶液中孵育，形成表面固定的大分子络合物。高分辨率力谱将被用来通过非特定的物理吸附相互作用将单个大分子络合物拴在探针尖端，并将在水溶液中测量拉伸纳米力学性能(例如，力F与分离距离D的关系)。为了控制分子的弹性和韧性，将研究各种参数，如主体聚合物的相对分子质量、相邻客体之间主体链段的长度、pH值和离子强度。从长远来看，这项研究项目将扩展到包括树枝状大分子、SAM功能化纳米颗粒和互补低聚物衣物纳米颗粒在内的其他普通“客人”类别。%本职业计划书中描述的教育活动与研究目标紧密结合，将使材料科学专业的学生接触到材料性质和行为的分子起源。第二个目标是向来自不同学科的学生展示纳米技术领域最新、最令人兴奋的科学发现，并鼓励他们从事本科研究项目、申请研究生院，和/或在研究和学术界追求职业生涯。实现这一目标的途径包括：继续开设为期一学期的本科课程“材料和生物材料的纳米力学”；在“自主活动期”开设一门为期4周的特别本科课程“纳米技术科学与工程”；开设为期一周的研究生级别的实验室暑期课程“高分辨率力谱”；以及面向高中教师。

The research component of this CAREER proposal involves the design and nanomechanical testing of biomimetic, "modular" polymeric systems with highly controlled mechanical properties at the molecular level. A general design strategy for improving the molecular toughness of synthetic macromolecules is proposed which involves the nonspecific, noncovalent complexation of a synthetic "host" polymer with smaller, nanometer-size, shape-persistant "guests." The research will begin by studying a model system which involves the well-studied complexation of poly(ethylene oxide) (PEO), -[CH2-CH2-O]n- and the small globular protein, human serum albumin (HSA). Chemical attachment of one PEO chain end to a surface and sufficiently low chain grafting densities will be achieved using a mixed monolayer technique involving the co-chemisorption of mono(thiol)-functionalized PEO and a self-assembling alkanethiol monolayer (SAM) on gold. The PEO substrates will then be incubated in an HSA solution to form surface-immobilized macromolecular complexes. High-resolution force spectroscopy will be employed to tether the individual macromolecular complexes to a probe tip via nonspecific, physisorption interactions and the extensional nanomechanical properties (e.g. force, F, versus separation distance, D) will be measured in aqueous solution. A variety of parameters will be studied in order to control the molecular elasticity and toughness, such as the host polymer molecular weight, the length of host chain segment between two neighboring guests, pH, and ionic strength. In the long-term, this research project will be expanded to include other general classes of "guests" including dendrimers, SAM-functionalized nanoparticles, and complementary oligomer-clothed nanoparticles.%%%The educational activities described in this CAREER proposal are strongly integrated with the research objectives and will expose materials science students to the molecular origins of material properties and behavior. A secondary goal is to show students from a variety of disciplines some of the latest, most exciting scientific discoveries in the field of nanotechnology and to encourage them to take up undergraduate research projects, apply to graduate school, and / or pursue a career in research and academia. This will be achieved through the continuing development of a new semester-long undergraduate course entitled "Nanomechanics of Materials and Biomaterials," the creation of a special 4-week undergraduate course during our "independent activities period" entitled " Nanotechnology Science and Engineering," the creation of a week-long, graduate-level laboratory summer course entitled " High-Resolution Force Spectroscopy," and outreach to high school teachers.