NSF-BSF: Emergent Rheology of Blends Containing Supramolecular Polymers

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NON_TECHNICAL SUMMARY:This collaborative project between Professors Shenhar (Hebrew University, Jerusalem) and Craig (Duke University, USA) will test the hypothesis that a special family of polymers, termed supramolecular polymers, represent a promising and untapped material class for next-generation flow-property modifiers. The flow of polymer melts dictates a wide range of societal impacts, including: the enormous energy consumption associated with polymer processing; the range of polymers that can be efficiently manufactured; the properties and performance of products, including cosmetics, pharmaceuticals, and coatings; and, the recycling of plastics products. As a result, additives are used to influence the flow properties of polymer melts. The global market for these products, termed “rheology modifiers,” currently exceeds $7 billion/yr. Numerous challenges motivate the development of new, generalizable and scalable strategies for rheology modifiers that give enhanced performance at lower loading and can be tailored for a broad range of applications. Drivers include: growing awareness of the potential health and environmental impacts of rheology modifier leaching; increased global focus on energy efficiency; emergence of new manufacturing technologies – especially additive manufacturing – with bespoke rheological requirements; recognition of the need for improved recycling pathways. Supramolecular polymers, in which the molecular units are held together by reversible bonds, combine the softening effects of molecular additives at the high temperatures used for the production of plastics with the typical polymer-like behavior that imparts plastic materials their useful mechanical properties at ambient temperature. This project will combine the structural control of supramolecular polymers developed by Shenhar with the rheological expertise developed by Craig to pursue fundamental principles that will unlock this new class of rheology modifiers. TECHNICAL SUMMARY:This project tackles critical, fundamental questions about the rheological modifications that are possible through the blending of supramolecular polymers into traditional polymer melts. A combination of synthesis and characterization will be used to test and refine quantitative structure-activity relationships for this relatively unexplored set of materials. Supramolecular polymers represent a promising and untapped material class for next-generation rheology modifiers. Supramolecular polymers combine the plasticizing effects of low-molecular weight additives with a rich combination of Newtonian and non-Newtonian rheology that can be tuned through molecular structure. Despite their promise, supramolecular polymers are largely unutilized as rheology modifiers. The research plan seeks to provide new and generalizable principles for the rheology of these new blends of two material classes. The proposed work seeks: (i) to develop a robust understanding of the unique rheology of each supramolecular component, including the heretofore unexplored rheology of their respective melt phases; (ii) to characterize the rheology of blends of supramolecular and covalent components, establishing design principles through which the supramolecular polymer confers unique rheological behavior to the covalent melt; (iii) to explore supramolecular blending as a facilitator of melt extrusion and additive manufacturing (3D printing) of traditionally intractable polymers. .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.