Dynamics of Functional Polymers with Reversible Bonds: The Role of Associating Group Aggregates

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NON-TECHNICAL SUMMARY:Associating polymers formed by reversible chemical bonds between polymer molecules have unique macroscopic properties and functionalities not achievable in other materials, including self-healing and time-programmable functions. Moreover, they form recyclable plastic materials critical for sustainability. However, detailed quantitative understanding of how to control macroscopic properties of these novel polymeric materials remains a challenge. The proposed research addresses this challenge by combining a broad range of experimental techniques with development and testing of new theoretical model approaches connecting molecular-scale processes to macroscopic properties. The knowledge developed in this research will be central to the rational design of novel recyclable polymers with unique, self-healing, and stimuli-responsive properties. It will have strong impact on various fields of science and engineering, including materials science, physics, chemistry and biophysics. A significant focus of the project is integration with education through active involvement of graduate and undergraduate students in research. The project also promotes active collaborations with national user facilities and international collaborations. TECHNICAL SUMMARY:Associating polymers, formed by reversible intermolecular interactions, include a wide spectrum of fundamentally and technologically important materials with better recyclability than traditional polymers. Rational design, synthesis, and fabrication of novel associating polymers require a deep fundamental understanding of how the local reversible interactions and phase separation of the associating groups affect the macroscopic properties of these materials. Despite extensive attention and efforts in the past, detailed quantitative understanding of dynamics in the melts of associating polymers remains limited. This hinders development of novel functional materials with desired properties. The main goal of the planned research is to deepen the fundamental understanding of dynamics in associating polymers on different time and length scales with special focus on the role of associating group aggregates. In this research, the chain and segmental dynamics and the viscoelastic properties of associating polymers will be studied by a combination of rheology, dielectric spectroscopy, differential scanning calorimetry, and light- and neutron scattering spectroscopies. It will be complemented by analysis of structure using small angle X-ray and neutron scattering, and will provide broad-based experimental tests of existing theories. The proposed research will deepen fundamental understanding of microscopic parameters controlling macroscopic properties of associating polymers, especially the role of intrinsic heterogeneities. This will be instrumental for a rational design of materials with unique viscoelastic and self-healing properties, as well as for design of novel functional materials with tunable time programmed and stimuli-responsive properties. From a broader perspective, it might also have strong impact on understanding of many biological materials where reversible bonding and interactions play a critical role..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.