RUI: Utilization of a Thio-Bromo Substitution Reaction for the Preparation of a New Class of ROMP Hydrogels

水凝胶是一种聚合物网络，不溶于水，但在水存在时会膨胀。由于这一特性，它们在生物医学领域有着广泛的应用。德克萨斯农工大学金斯维尔分校的克里斯托弗·霍布斯教授的团队探索了制备功能性水凝胶的新途径。特别是，他的研究小组开发了一种高效且不含贵金属的反应，用于水凝胶的合成和改性。该项目为许多人数不足的本科生提供跨学科的研究经验，为在科学、技术、工程和数学(STEM)领域的职业生涯提供了重要的垫脚石。此外，霍布斯教授组织了聚合物化学研讨会，在这些研讨会中，高中教师学习可用于在他们的科学课堂上介绍聚合物化学方面的方法和实验，以期招募新一代不同的年轻学生进入STEM领域。该项目侧重于利用硫醇和α-溴酸酯之间的简单、无催化剂的取代反应来制备新类别的水凝胶。该方法利用硫代溴取代反应，将含α-溴代酯的聚降冰片烯和聚(氧杂诺龙烯)S转化为具有已知的向大分子结构注入水膨胀性的官能团(例如，羟基、氨基和离子基)的聚合物。生成的聚合物与二硫醇交联会产生一类新的水凝胶。虽然开环歧化聚合(ROMP)法制备含α-溴代酯的聚降冰片烯和聚(氧杂诺龙烯)S需要使用Ru催化剂，但这些聚合物转化为水凝胶的过程涉及无金属反应，最大限度地减少了贵金属的使用。在NSF大分子、超分子和纳米化学计划的支持下，Hobbs教授的团队进行了研究，以检验这种合成方法的有效性以及水凝胶性能对聚合物主链、侧链基团和交联剂特性的依赖关系。

Hydrogels are polymeric networks that are not soluble in water but instead swell in the presence of water. Because of this property, they have broad applications in the biomedical fields. Professor Christopher Hobbs' group at Texas A&M University-Kingsville explores new routes toward the preparation of functional hydrogels. Specially, his research group develops a highly efficient and precious metal-free reaction for the synthesis and modification of hydrogels. This project provides interdisciplinary research experience to many underrepresented undergraduate students, delivering a vital stepping stone toward careers in fields of science, technology, engineering, and mathematics (STEM). Additionally, Professor Hobbs organizes Polymer Chemistry Workshops, in which high school teachers learn methods and experiments that can be used to introduce aspects of polymer chemistry in their science classes in the hopes of recruiting a new, diverse generation of young students to STEM fields.This project focuses on the utilization of a facile, catalyst-free substitution reaction between thiols and alpha-bromo esters for the preparation of a new class of hydrogels. The process employs thio-bromo substitution reactions to convert alpha-bromoester-containing polynorbornenes and poly(oxanorbornene)s to polymers with functionality (e.g., hydroxyl, amino, and ionic groups) known to instill water-swellability to macromolecular architectures. Cross-linking of the resulting polymers with dithiols produces a new class of hydrogels. While the preparation of alpha-bromoester-containing polynorbornenes and poly(oxanorbornene)s by Ring Opening Metathesis Polymerization (ROMP) requires the use of a ruthenium catalyst, the conversion of these polymers to hydrogels involves metal-free reactions that minimize the use of precious metals. With the support from the NSF Macromolecular, Supramolecular and Nanochemistry Program, Professor Hobbs' group conducts research to examine the effectiveness of this synthetic approach and the dependence of the hydrogel properties on the polymeric backbone, side chain groups, and cross-linker identity.