Crystallinity and reversibility in injectable pva/peg hydrogels

Statement of Purpose: Poly(vinyl alcohol) (PVA) is a widely used polymer with impressive physical properties, leading for its use in hydrogel-based implants for a variety of load-bearing applications. In hydrogels, regions with high polymer concentrations naturally occur, leading to crystallinity in the gel network. Current studies utilize methods such as freeze-thawing to induce crystallinity in order to increase the mechanical strength of implants. These studies also detail that crystallinity can be quantified using wide-angle x-ray diffraction (WAXD) and identified with a peak at approximately 19°. However, while crystallinity is vital to the mechanical properties of a hydrogel being surgically implanted, crystallinity adversely affects the potential of this hydrogel to be directly injected into the implantation site during a surgical procedure. In this study, the crystallinity of aged samples is investigated in order to quantify changes to the gel network over time. It is hypothesized that crystallinity will increase proportionally with time. In addition, the potential to reverse crystallinity in these hydrogels after heating at temperatures above the melting point for an extended period of time is investigated. It is hypothesized that this process will reverse crystallinity and reestablish the amorphous properties (i.e. no crystallinity) of the gel. This study is crucial in developing a surgical procedure that utilizes injectable hydrogels, as it can help to establish information about the hydrogel’s shelf-life.