CAREER: Supramolecular engineering of hydrogel forming triblock copolymers

水凝胶是一种主要由水组成的柔软材料，因此在卫生、隐形眼镜、医疗植入物和伤口护理产品（到2022年将达到270亿美元的产业）中有着广泛的应用。尽管这类材料很重要，但设计新型水凝胶的分子水平策略还没有得到很好的理解。这项工作的目的是发展一套分子设计原则，可以管理和控制水凝胶的物理性质。具有几何定义的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。这个跨学科的研究项目位于聚合物科学和超分子化学领域的交汇处，旨在培养这些领域的下一代科学家。该提案的广泛影响包括刺激大学预科生和大学生对聚合物科学产生兴趣，增加科学家的多样性，特别是来自社会和经济不利背景的科学家。首席研究员将强调对教师的培训，以最大限度地提高该项目的有效性。该计划概述包括创建教育模块，向K-12、本科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：完全合成的序列特异性聚合物的合成具有挑战性，并且控制这些聚合物自组装的设计规则非常复杂。因此，有必要开发一种策略，以提供分层自组装的合成聚合物，而不依赖于精确的单体序列。这项工作的主要目标是开发一个平台，让超分子工程师通过在聚合物链的精确位置（如聚合物末端或聚合物块之间的界面）引入超分子功能来嵌段共聚物，从而控制这些大分子在水介质中组装成更大、定义明确的整体。中心假设是，几何上定义的氢键系统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，只要各自的嵌段的玻璃化转变温度远低于室温。将合成三嵌段共聚物，其组成为聚（烷基缩水甘油酯）-聚（乙二醇）-聚（烷基缩水甘油酯）-聚（烷基缩水甘油酯），并在链端以阵列形成的氢键基序（如脲）功能化。这些三嵌段共聚物将在水溶液中分层自组装，形成水凝胶。这些材料的粘弹性特性将通过流变学来表征，水凝胶的纳米和微观结构将通过小角和广角x射线散射来确定。这项基础研究将为组织工程和药物输送的生物打印提供新的分层组装水凝胶，其中水凝胶的物理性质最终可以在分子水平上进行控制。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值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.