CAREER: Supramolecular engineering of hydrogel forming triblock copolymers

非技术性SUMMARY水凝胶是一种主要由水组成的软材料，因此在卫生、隐形眼镜、医疗植入物和伤口护理产品(到2022年将成为270亿美元的行业)中有广泛的用途。尽管这类材料很重要，但在分子水平上设计新的水凝胶的策略还没有被很好地理解。这项工作的目标是开发一套能够管理和控制水凝胶物理性质的分子设计原则。具有几何定义端基的三嵌段共聚物将被合成。这些聚合物有望在水中自发自组装，以提供水凝胶组合物。水凝胶的纳米和微观结构将被表征，并与水凝胶的物理性质相关联。这一跨学科研究计划位于聚合物科学和超分子化学领域之间，旨在培养这些领域的下一代科学家。这项提议的更广泛的影响包括刺激大学预科和大学生对聚合物科学产生兴趣，以及增加科学家的多样性，特别是来自社会和经济贫困背景的科学家。首席调查员将强调教师培训，以最大限度地发挥该项目更广泛影响的效力。概述的计划包括创建教育模块，向处于学习生涯的K-12、本科生和研究生阶段的学生介绍聚合物科学，以及让弱势群体和代表性不足的群体参与STEM。技术总结合成序列特异性聚合物具有挑战性，管理这些聚合物自组装的设计规则极其复杂。因此，需要开发一种策略来提供分层自组装的合成聚合物，其不依赖于精确的单体序列。这项工作的主要目标是开发一种超分子工程平台，通过在聚合物链的精确位置--如聚合物末端或聚合物嵌段之间的界面--引入超分子官能团来控制这些大分子在水介质中组装成更大、定义明确的系综。中心假设是，几何定义的氢键体系可以在水凝胶形成的三嵌段共聚物的疏水区域内自组装成线性阵列或玫瑰花环，只要相应嵌段的玻璃化转变温度远低于室温。将合成组成为聚(烷基缩水甘油醚)-b-聚乙二醇-b-聚烷基缩水甘油醚的三嵌段共聚物，并在链端官能化，形成阵列氢键基元，如尿素。这些三嵌段共聚物将在水溶液中分级自组装，形成水凝胶。这些材料的粘弹性能将通过流变仪来表征，水凝胶的纳米和微观结构将通过小角度和广角X射线散射来确定。这项基础性研究将提供新的分级组装水凝胶，用于组织工程和药物输送的生物打印，其中水凝胶的物理性质最终可以在分子水平上进行控制。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。

NON-TECHNICAL SUMMARYHydrogels are soft materials that are largely comprised of water, and as such, have found extensive utility in hygiene, contact lens, medical implants, and wound care products (a 27 billion dollar industry by 2022). Despite the importance of this class of materials, molecular-level strategies to design new hydrogels are not well understood. The objective of this work is to develop a set of molecular design principles that can govern and control the physical properties of hydrogels. Triblock copolymers with geometrically defined end-groups will be synthesized. These polymers are expected to spontaneously self-assemble in water to afford hydrogel compositions. The nano- and micro-structure of the hydrogels will be characterized and correlated to the physical properties of the hydrogels. This interdisciplinary research program lies at the interface between the fields of polymer science and supramolecular chemistry, and aims to train the next generation of scientists in these fields. The broader impacts of this proposal include stimulating pre-college and college students to become interested in polymer science, and increasing the diversity of scientists, particularly from societally and economically disadvantaged backgrounds. The Principal Investigator will emphasize teacher training to maximize the effectiveness of the broader impacts of this project. The program outlined includes the creation of educational modules that introduce polymer science to students in K-12, undergraduate, and graduate stages of their learning careers, as well as the engagement of disadvantaged and under-represented groups in STEM. TECHNICAL SUMMARYWholly synthetic sequence-specific polymers are challenging to synthesize, and the design rules that govern the self-assembly of these polymers is incredibly complex. Accordingly, there is a need to develop a strategy to afford hierarchically self-assembled synthetic polymers that does not rely on precise monomer sequences. The primary objective of this work is to develop a platform that supramolecularly engineers block copolymers by introducing supramolecular functionalities at precise locations of a polymer chain--such as at the polymer termini or at the interface between polymer blocks--in order to control the assembly of these macromolecules into larger, well-defined ensembles in aqueous media. The central hypothesis is that geometrically defined hydrogen bonding systems can self-assemble into linear arrays or rosettes within the hydrophobic domain of a hydrogel-forming triblock copolymer, as long as the glass transition temperature of the respective block is far below room temperature. Triblock copolymers with the composition, poly(alkylglycidyl ether)-b-poly(ethylene glycol)-b-poly(alkylglycidyl ether), will be synthesized and functionalized at the chain ends with array-forming hydrogen bonding motifs such as ureas. These triblock copolymers will hierarchically self-assemble in aqueous solution to afford hydrogels. The viscoelastic properties of these materials will be characterized by rheometry and the nano- and microstructure of the hydrogels will be determined by small and wide-angle x-ray scattering. This fundamental study will afford new hierarchically assembling hydrogels for use in bioprinting for tissue engineering and drug delivery, wherein the physical properties of the hydrogel can ultimately be controlled at the molecular level.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.