Statistical Mechanics of Thermoreversible Gelation

热可逆凝胶化的统计力学

• 批准号: 9624596
• 负责人: Grzegorz Szamel
• 金额: $ 29.7万
• 依托单位: Colorado State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1996
• 资助国家: 美国
• 起止时间: 1996-04-01 至 2001-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9624596&HistoricalAwards=false
• 关键词: Statistical; Mechanics; Thermoreversible; Gelation

Grzegorz Szamel is supported by a Faculty Early Career Development Award in the Theoretical and Computational Chemistry Program to develop a theoretical understanding of thermoreversible polymer gelation and the properties of thermoreversible gels. The specific problems to be studied are: 1) existence and properties of a thermodynamic transition underlying the observed gelation transition; 2) structure of the sol and gel phases; 3) elastic properties of the gel phase; and 4) viscoelastic properties of the sol and gel phases. The method to be used is a generalization of a recent statistical mechanical approach to rubber vulcanization (formation of a permanent polymer network) to the case of reversible crosslinking. Specifically, a statistical mechanical theory of chemical association will be used to describe reversible bonding of specific monomers distributed randomly along polymer chains. A replication approach will be used to facilitate averaging over the positions of specific monomers. Finally, an order parameter field (related to frozen density fluctuations) will be introduced, and an effective free energy functional will be derived. The free energy functional will be analyzed using methods similar to those used in the study of the vulcanization transition. The goal of the education plan is to teach students the value and significance of quantitative reasoning in physical chemistry, and chemistry in general. In particular, recitation classes will be introduced into teaching the physical chemistry courses in order to improve student's ability to solve chemical problems using the relevant mathematical formalism. Moreover, a new course on mathematical and computational methods for chemists will be instituted in order to expose students to the applications of numerical and simulational methods in chemistry. Polymer gels have attracted a lot of interest because of the wealth of their potential practical applications. Examples include drug delivery devices, chemical valves and sensors, and magnetic resonance monitoring agents. Their properties can change drastically in response to external stimuli such as temperature, electric field, or light. Szamel's research concentrates on one class of polymer gels, thermoreversible gels. These gels originate from reversible crosslinking of polymeric systems. These gels are reversible, i.e. they liquify upon heating, and are regenerated upon cooling.

Grzegorz Szamel在理论和计算化学项目中获得了教师早期职业发展奖，以发展对热可逆性聚合物凝胶化和热可逆性凝胶特性的理论理解。需要研究的具体问题有：1)观察到的胶凝转变背后存在热力学转变及其性质；2)溶胶和凝胶相结构；3)凝胶相的弹性性能；4)溶胶相和凝胶相的粘弹性。所使用的方法是对可逆交联情况下橡胶硫化（形成永久聚合物网络）的最新统计力学方法的推广。具体来说，化学结合的统计力学理论将用于描述沿聚合物链随机分布的特定单体的可逆键。一种复制方法将被用来简化对特定单体位置的平均。最后，将引入一个序参量场（与冻结密度波动有关），并推导出有效的自由能泛函。自由能泛函将使用与研究硫化转变类似的方法进行分析。该教育计划的目标是让学生了解定量推理在物理化学和一般化学中的价值和意义。特别是在物理化学课程中引入复习课，提高学生运用相关数学形式解决化学问题的能力。此外，还将开设一门新的化学数学和计算方法课程，使学生接触到数值和模拟方法在化学中的应用。聚合物凝胶由于其丰富的潜在实际应用而引起了人们的极大兴趣。例子包括药物输送装置，化学阀门和传感器，以及磁共振监测剂。它们的性质会随着外界刺激（如温度、电场或光）的变化而急剧变化。Szamel的研究集中在一类聚合物凝胶上，即热可逆凝胶。这些凝胶源于聚合物体系的可逆交联。这些凝胶是可逆的，即加热时液化，冷却时再生。