Thermal and Structural Properties of Polyzwitterions, with Research Opportunities for Deaf and Hard of Hearing Interns

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PART 1: NON-TECHNICAL SUMMARYThis research is on a class of polymeric materials called "polyzwitterions". They consist of long chains of chemical units that carry both positive and negative charges. A number of new polyzwitterions will be designed and made in the laboratory with different chemical structures, and then studied to find the best ones for technological applications. They will be tested for heat stability, mechanical strength, and ability to absorb or reject water. The studies will provide a knowledge base which is needed to more rationally develop new materials for a range of applications. It is expected that the proposed research on polyzwitterions will benefit society in important ways. Polyzwitterions may be useful for biomedical uses such as hydrogels or wound dressings. In the field of water purification, polyzwitterions may improve the properties of filtration membranes leading to better water treatment systems. How polyzwitterion molecules interact with each other in the presence of water or salts will be important information for the field of energy technology, leading to new batteries for energy storage. Societal benefit will also be derived from increasing participation in STEM fields of persons from under-represented groups, such as women, minorities, and persons with disabilities (with particular emphasis on a program aimed at deaf and hard-of-hearing undergraduates). PART 2: TECHNICAL SUMMARYAdvanced methods of thermal analysis, such as temperature modulated and fast scanning chip calorimetry, will be used for fundamental studies of thermo-physical properties of polyzwitterions (PZIs) featuring sulfobetaine-type zwitterionic moieties. Thermal measurements will be augmented with structural characterization. The technical objectives are to: 1. synthesize an array of polyzwitterions and investigate fundamental thermal properties of cast films in relationship to variations of chemical chain structure and content of salt; 2. measure fundamental thermal properties of PZIs using fast scanning calorimetry to minimize effects of degradation; 3. investigate the structure of PZIs with respect to formation of intra- and interchain cross-linking as functions of salt content, which can mediate this cross-linking. High precision, high accuracy heat capacity measurements will be made to quantify the solid and liquid states, and their dependence upon bound water and salt content. Specifically, the role of LiCl salt will be investigated as to its impact on the thermal and structural properties of PZIs. Temperature modulated differential scanning calorimetry will be performed on PZI cast films to provide fundamental thermal properties such as the solid state heat capacity. Differential fast scanning chip calorimetry will be used to study these materials at 2000 K/s to avoid degradation, to obtain the dry-state glass transition temperature, liquid-state heat capacity, and heat capacity increment at the glass transition. Glass forming ability will be studied for PZIs in the presence or absence of added salt. Structure of the materials will be evaluated using wide and small angle X-ray analysis and Fourier Transform infrared spectroscopy. Educational and outreach activities will include a summer internship program for deaf and hard-of-hearing interns..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.