Assessing Solvent Viscosity Impact on the Physical Characteristics of Polymeric Organogels
Cameron Hong ’21
Kenny Mineart, Chemical Engineering
Traditionally, studies of polymeric organogels focus on the impact of polymer factors on the gels’ mechanical and transport properties. Alternatively, this study seeks to assess the impact of altering solvent viscosity, while holding polymer factors constant. The gels in this study were composed of styrene-ethylene-butylene-styrene (SEBS) triblock copolymer, oleic acid (OA), and mineral oil. Samples were formulated at 10, 20, and 30 wt% SEBS copolymer for each mineral oil, varying in viscosity from ~30 mPa*s to ~500 mPa*s. Uniaxial mechanical testing was performed to determine Gc, the contributions of physical crosslinks, i.e., micelles, to stress, and Ge, the contributions of chain entanglements to stress. Modeling the data from these experiments showed that Gc and Ge only varied with polymer concentration. In a separate set of experiments, Fourier Transform Infrared Spectroscopy (FTIR) was used to track the diffusion of OA out of the gel. Through modeling the release of OA with time using a Fickian diffusion model, the diffusion coefficients for formulations at varying solvent viscosities were determined. Notably, the results of the FTIR experiments conform to behavior predicted by the Stokes-Einstein equation. The results from these two sets of experiments allows for a higher degree of tunability than previously available. The results from this study will be of particular use in development of transdermal drug delivery devices.