Tunable Enthalpic and Entropic Interactions in Blends of Block Copolymers and Polymeric Additives

University Of Tennessee Knoxville, Knoxville TN

Investigators

Abstract

NON-TECHNICAL SUMMARY Block copolymer thermoplastic elastomers (TPEs) are critical components in numerous products across many industries, including medical devices, telecommunications and construction. These materials also show promise as membranes for water purification and fuel cells. However, TPEs are challenged by issues with long-term stability, which limits their service life in established applications and prevents their adoption in clean water and clean air technologies. This research program will lay critical groundwork to address this challenge by tailoring the structure of block copolymer TPEs with a class of interaction-tuned polymer additives, thereby enabling careful studies of the molecular and mesoscale attributes that control the observed mechanical properties. This knowledge will guide the development of high-performance block copolymer TPEs that maintain their mechanical integrity over long timescales. Furthermore, the principles can be extended beyond the model chemistries that are the focus of this research program, thereby facilitating the development of new TPEs based on renewable feedstocks. The collaboration between Stein and Kilbey will provide graduate and undergraduate students with training in polymer synthesis and advanced materials characterization techniques. Laboratory research is complemented by 1) an annual workshop for graduate students at UTK focused on Fundamentals of Polymer Physics; and 2) a new graduate elective that provides training in Computational Tools for Data Analysis, which introduces methods to process, analyze and organize large amounts of experimental data. Undergraduate student involvement is facilitated by the NSF-supported ASPIRE and TLSAMP programs at UTK, which provide funded research opportunities for students from under-represented groups, especially first-generation college students from the Appalachia region. TECHNICAL SUMMARY This research program will examine structure and properties in blends of linear triblock copolymers and interaction-tuned random copolymer (PrC) additives. The enthalpic and entropic driving forces that control miscibility of these constituents will be tailored by changing the composition, molecular weight and architecture of the PrC additives, enabling a systematic interrogation of a large parameter space. Three related research thrusts will test the key hypothesis that PrC additives can enhance macroscopic mechanical properties by modulating the local structure within nanoscopic PS domains. The local structure, as defined in the proposal, includes attributes such as chain conformations, interfacial area per chain, and the spatial distribution of PrC additives. Outcomes of this research will provide a framework that guides the design of miscible polymer additives to enhance specific TPE properties, including tensile strength, ductility, or creep resistance. This will allow for the design of block copolymer membranes that preserve their mechanical properties over long time scales, which is critical for next-generation energy conversion devices and water purification technologies. Although this research program will be implemented with model styrenic materials, the fundamental principles elucidated through the design of PrC additives are envisioned to be directly relatable to other classes of materials that face similar challenges with long-term stability, including those derived from renewable resources. Students will be trained in polymer chemistry, polymer physics, high-throughput analysis of large data sets, and advanced materials characterization. These technical skills are critical for competitiveness in and lifelong contributions to a society dependent on materials science and engineering. Additionally, opportunities provided to and direct mentoring of students from under-represented groups will help to inspire and stimulate young learners, catalyze their success, and ignite curiosity, ultimately fostering the development of a diverse and competitive workforce. . 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.