Physics-Based Models of Extraction Kinetics in Solvent-Swollen Polymers: Using Non-Exhaustive Extractions to Estimate...

Leachables from polymeric medical devices can migrate into the body, potentially impacting patient health. Physics-based mass-transport models can estimate patient exposure but require knowledge of the initial leachable amount, $M_0$ . Although $M_0$ can be determined through exhaustive extraction testing, this may be impractical for some solutes due to kinetic or thermodynamic limitations. We developed a free-volume model to estimate $M_0$ from non-exhaustive extractions, accounting for solvent-swelling effects on solute diffusivity, $D$ , in polymers. Based on an analysis of polymer/solvent partition coefficients, we also propose a limiting value for the partition coefficient $K$ . We couple this model to a mass-transport equation to predict $M_0$ . Validation against experimental data demonstrates order-of-magnitude accuracy for both $D$ and $M_0$ . The model is applicable only to rubbery polymers and systems involving relatively hydrophobic polymers, solvents, and solutes. Using the predicted $M_0$ with a transport model for in vivo exposure yields results similar to those obtained when $M_0$ is known a priori. Our work shows that non-exhaustive extractions can be used to infer total extractable quantities and conservatively estimate patient exposure.