CAREER: Dynamics and structure of comb polymer elastomers

非技术摘要：由支链聚合物结构(侧链连接到线性主干的聚合物)组成的聚合物网络可用于独立调整材料的硬度和弹性。超软和超弹性无溶剂材料为可拉伸电子和生物材料的新兴应用提供了潜在的变革性机会。然而，由于与基础支化聚合物体系结构相关的合成限制，控制网络属性仍然是一个巨大的挑战。这项研究项目将通过开发合成方法来精确控制支链长度、支链之间的间距以及将支链连接在一起的化学物质，直接研究网络结构、力学和支链聚合物结构之间的关系。光散射和流变学表征技术将被用来测量在不同溶液和本体条件下的网络性质。从这项研究中获得的见解将解决在理解拓扑复杂的聚合物网络的力学性质方面的一个关键知识缺口，包括那些依赖于变形历史的网络。该项目的结果有望为可调材料的设计提供参考，这些材料具有更高的加工效率和可预测的机械性能，适用于使用薄膜、纤维和泡沫的应用。将开展外联工作，通过创建以社区大学教师和学生为重点的创新研讨会，以及学术界、产业界和国家实验室之间的跨部门合作，来增加知识多样性和软物质研究中代表性不足的科学家的数量。技术综述：支化聚合物弹性体的分子设计为合成网络提供了一条潜在的变革性途径，具有凝胶般的柔软性、高弹性和增强的应变自适应刚性，适用于从可拉伸电子设备到仿生组织的各种应用。这些材料的功效取决于交联网络的基本聚合物拓扑结构(即线型、梳型和瓶刷型聚合物)。例如，梳子和瓶刷弹性体具有前所未有的机械性能，因为可以通过改变侧链长度、侧链间距和交联链间距来分离刚性和弹性。然而，由于合成的限制，交联链和侧链的均匀性和间距在精确控制和实验表征方面具有挑战性。因此，仍然迫切需要一个能够精确控制交联链和侧链间距的实验平台，以阐明支化聚合物弹性体的结构-功能关系。这个职业项目将通过研究具有精确拓扑参数的模型梳状聚合物来解决这些突出的挑战，以加深对交联度和侧链均匀度对弹性体形成、力学性能和结构的影响的基本了解，从而建立弹性体设计的新范式。将整合聚合物合成、X射线/中子散射、溶液动力学和STEM扩展方面的专业知识，以解决三个研究目标和一个教育目标：(1)确定梳状聚合物拓扑结构对弹性体形成和动力学的作用，(2)了解梳状聚合物拓扑结构对弹性体力学的影响，(3)表征梳状聚合物拓扑结构对弹性体结构的影响。以及(4)为本科生建立新的研讨会和研究机会，以增加知识多样性，并支持软物质研究中未被充分代表的科学家。该奖项反映了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。

NON-TECHNICAL SUMMARY:Polymer networks consisting of branch polymer architectures (polymers with sidechains attached to linear backbones) can be used to independently tune material stiffness and elasticity. Supersoft and hyper-elastic solvent-free materials offer potentially transformative opportunities for emerging applications in stretchable electronics and biomaterials. Controlling network properties, however, remains a significant challenge due to synthetic limitations associated with the underlying branch polymer architecture. This research project will directly investigate the relationship between network structure, mechanics, and branch polymer architecture by developing synthetic methods to precisely control branch length, spacing between branches, and the chemistry that links branches together. Light scattering and rheological characterization techniques will be used to measure network properties under varying solution and bulk conditions. The insights gained from this research will address a critical knowledge gap in understanding the mechanical properties of topologically complex polymer networks, including those that depend on deformation history. The results from this project are expected to inform design of tunable materials with enhanced processing efficiency and predictable mechanical properties for applications that use films, fibers, and foams. Outreach efforts will be developed to increase intellectual diversity and the number of underrepresented scientists in soft matter research by creating innovative symposia focused on community college teachers and students and on cross-sector collaboration between academia, industry, and national laboratories. TECHNICAL SUMMARY:The molecular design of branch polymer elastomers offers a potentially transformative route towards synthetic networks with gel-like softness, high elasticity, and enhanced strain-adaptive stiffening for applications ranging from stretchable electronics to biomimetic tissues. The efficacy of these materials is dependent on the underlying polymer topology (i.e., linear, comb, and bottlebrush polymers) of the cross-linked network. For example, comb and bottlebrush elastomers have unprecedented mechanical properties because stiffness and elasticity can be decoupled by varying sidechain length, sidechain spacing, and cross-link spacing. Due to synthetic limitations, however, the cross-link and sidechain uniformity and spacing are challenging to control precisely and characterize experimentally. Thus, there remains a critical need for an experimental platform with precise control of cross-link and sidechain spacing to elucidate structure-function relationships in branch polymer elastomers. This CAREER project will address these outstanding challenges through investigation of model comb polymers with precise topological parameters to develop a fundamental understanding of the effects of cross-link and sidechain uniformity on elastomer formation, mechanical properties, and structure, thus establishing a new paradigm in elastomer design. Expertise in polymer synthesis, X-ray/neutron scattering, solution dynamics, and STEM outreach will be integrated to address three research aims and one educational aim: (1) determine the role of comb polymer topology on elastomer formation and dynamics, (2) understand the effects of comb polymer topology on elastomer mechanics, (3) characterize the effects of comb polymer topology on elastomer structure, and (4) establish new symposia and research opportunities for undergraduates to increase intellectual diversity and support underrepresented scientists in soft matter research..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.