Assessing the contribution of secondary relaxation processes in acrylate polymers to permeate diffusion
Abstract
Amorphous polymers in glassy state undergo secondary or beta (β) relaxations relating to localized segmental motion of the polymer side chains. It is hypothesized that these non-cooperative β relaxations in acrylate polymers affect the diffusion coefficients of permeant molecules. A model to test the hypothesis based on Arrhenius kinetics of β relaxation and Fickian diffusion is proposed. Relaxation kinetics of acrylate polymer films Eudragit NM30D and Poly(methyl methacrylate) were determined from dilelectric analysis and the diffusion coefficients determined from vapor sorption analysis based on long time fourier diffusion model. At isothermal temperatures the frequency dependence of relaxation on the diffusion kinetics of moisture across these polymers was found to be a ratio of their activation energies as predicted from the model. The magnitude of correlation between relaxation and diffusion which is dependent on the ratio of permeant to polymer pathway size also increases as the activation energy for diffusion increases. The influence of β relaxations in acrylate polymers to permeate diffusion may help better understand the physico-chemical properties of various pharmaceutical formulations that use Eudragit polymers as a drug carrier.
Degree
Ph.D.
Advisors
Morris, Purdue University.
Subject Area
Polymer chemistry|Pharmacy sciences|Materials science
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