UC Riverside

Polymers are essential, ubiquitous materials in modern society, and their use has led to many industrial and scientific advances. However, many polymers are made using toxic solvents and precursors or are difficult to naturally degrade. This results in polymer waste accumulating in natural spaces, harming those ecosystems. Much of current polymer research focuses on replacing synthetic polymers with natural ones and creating new biodegradable polymers from natural materials, and using more benign synthesis processes. This dissertation investigates the structure-processing-properties-performance relationships of three polymers to better understand how eco-friendly polymers can be designed as replacements for synthetic polymers in select applications.Polyacrylonitrile (PAN) is the industry standard precursor for carbon fiber, but its synthesis uses toxic solvents and reactants. The oxidative stabilization step of PAN-based carbon fiber production is studied using Nuclear Magnetic Resonance (NMR) spectroscopy and Wide-Angle X-ray Scattering (WAXS) to identify key structural elements of PAN that natural alternatives should include. Although a direct transition from PAN crystals to graphite crystals was hypothesized, the data collected suggests a delayed transition but underscore the importance of this transition. Spider silk is investigated as a natural alternative carbon fiber precursor, and the crystallinity, graphite content, and mechanical properties of spider silk carbon fiber are compared to those of PAN-based carbon fiber. These properties are measured using Fourier Transform Infrared spectroscopy, Raman spectroscopy, Scanning Electron Microscopy, WAXS, and tensile testing. Spider silk carbon fiber has comparable strength and lower stiffness than PAN-based carbon fiber. As hydrogen-bonding elements in the silk proteins are combusted, the crystals within silk lose their alignment, resulting in unaligned graphite crystals. In contrast, graphite crystals in annealed PAN retain their alignment along the long axis of the fiber. Finally, biodegradable, biocompatible salicylic acid-based poly(anhydride ester)s (SAPAE)s were studied using NMR, UV-Visible Spectroscopy, and controlled degradation experiments for use as coatings for bone implants and drug delivery systems with tunable release rates. SAPAEs with different chemical compositions were used to form microspheres and encapsulate a model protein. Significant protein release occurred within hours or days based on the SAPAE used, offering a variety of potential applications.