Date of Thesis
Traditionally, studies of polymeric organogels focus on the impact of polymer factors (e.g., molecular weight and polymer concentration) 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 different viscosity mineral oils, styrene-ethylene-butylene-styrene (SEBS) triblock copolymer as a gelator, and oleic acid (OA) as a model drug. Samples were formulated to have 6.5, 11.2, and 15.7 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 modulus contribution from the physically crosslinked network, and Ge, the modulus contribution from chain entanglements. Examining the data from these experiments indicates that Gc and Ge only vary 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. 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, which suggests an inverse relationship between diffusion coefficient and solvent viscosity at a constant temperature. The results from these two sets of experiments show that oil viscosity is an underutilized formulation parameter that allows for a higher degree of tunability in terms of gels’ modulus and controlled release than polymer factors alone. The results from this study will be important to those developing transdermal drug delivery devices.
organogels, transport properties, mechanical behavior
Bachelor of Science in Chemical Engineering
Hong, Cameron, "Assessing Solvent Viscosity Impact on the Physical Characteristics of Polymeric Organogels" (2021). Honors Theses. 556.