(663h) Rapid Predictions of Solute Diffusivity in Polymers Using Molecular Simulations
AIChE Annual Meeting
2020
2020 Virtual AIChE Annual Meeting
Materials Engineering and Sciences Division
Transport Phenomena in Polymer Systems
Friday, November 20, 2020 - 9:00am to 9:15am
Solute diffusion in medical devices comprising polymeric materials may raise public health issues, where toxicological risks may arise via unintended leaching from implanted devices. However, accurately measuring solute diffusion coefficients (D) at physiological temperature is a challenge, both experimentally and with simulations. Although molecular dynamics (MD) simulations can be used to predict D for gases in polymers with great accuracy, it remains challenging to quantify D for larger molecules (molecular weight > 100 g/mol), like plasticizers, dyes, or drugs. Heavier molecules diffuse more slowly, so both experiments and simulations can take months of real time to arrive at an estimate of D [1, 2]. Here, we discuss a method to bypass these time-consuming approaches. We show a link between D and the Debye-Waller factor (u2), a measure of solute âcagingâ between diffusive hops. Using MD, we simulate a variety of polymer/solute combinations across the glass transition. Above the so-called mode-coupling temperature TC, there is an apparently universal linear relation between ln D and 1/u2. Below TC, this relation still provides an upper bound on D, which may be a useful limit when assessing medical device safety in practice. Because u2 can be quantified in very short MD simulations, this suggests a means to rapidly estimate D [2].
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