Associating Structure and Rheology of Bacterial Polysaccharides

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Nontechnical: This award by the Biomaterials program in the Division of Materials Research to University of Michigan Ann Arbor is cofunded by the Mechanics of Materials program in the Division of Civil, Mechanical, and Manufacturing Innovation (ENG). This research is to understand the fundamental water-borne properties of polymers, and will impact the development of natural and sustainable materials that use water as a solvent. The new knowledge about aqueous polymer stability and flow will be useful in areas in which these polymers are found or consumed. For example, aqueous polymers generally, and bacterial polysaccharides in particular, are relevant to the proliferation and control of bacterial biofilms in hospitals, in wastewater treatment plants, and in industrial facilities. The stability, structure, and mechanics of bacterial polysaccharides are also important for producing foods in which they are present or added. The accompanying educational plan will advance the national interest in STEM training by modeling the use of mentoring plans as a mechanism to increase the probability of doctoral completion of all students. The project researcher's engagement in a summer research experience program for undergraduates will increase the participation of students from groups underrepresented in science and engineering. The project's development of a new module about polysaccharide food additives will engage middle school girls in science and engineering, and thereby foster their interest in STEM areas.Technical: Bacterial polysaccharides are an important class of aqueous soluble polymer found in a range of natural environments and industrial contexts. The chemical structure and properties of bacterial polysaccharides are extremely diverse. Yet, the functional rheological properties of these materials are broadly mediated by the interplay between the bacterial polysaccharide's properties as a polymer and as an associating species. At the same time, genetic engineering and chemical substitution make bacterial polysaccharides useful polymers for fundamental study because of their controllable charge, hydrogen bonding, and hydrophobicity. Thus, the connection between the associative structure and rheology of all aqueous soluble polymers can be better understood by fundamental study of bacterial polysaccharides. This project will generate this new understanding through three research aims that involve light scattering, microrheology, and constitutive modeling. This research will be accompanied by an educational plan that involves graduate student training and mentoring. The participation of the PI in a summer research opportunities program and in outreach activities that engage middle school girls in science and engineering is part of this award.