# Gelation impairs small molecule migration in polymer mixtures

## TL;DR

This study investigates how gelation affects small molecule migration in polymer mixtures, revealing that network elasticity in gels significantly reduces surface migration and slows phase separation, aiding in designing better polymer/gel-oligomer systems.

## Contribution

It demonstrates that gelation impairs surface migration and alters phase separation dynamics in polymer mixtures through computational simulations.

## Key findings

- Surface migration is significantly reduced in oligomer-gel systems due to network elasticity.
- Phase separation is slowed in gels, modifying the Lifshitz-Slyozov-Wagner law.
- The work enables rational design of polymer/gel-oligomer mixtures with predictable segregation.

## Abstract

Surface segregation of the low-molecular weight component in a polymeric mixture leads to degradation of industrial formulations. We report a simultaneous phase separation and surface migration phenomena in oligomer-polymer and oligomer-gel systems following a temperature quench. We compute equilibrium and time varying migrant density profiles and wetting layer thickness using coarse grained molecular dynamics and mesoscale hydrodynamics simulations to demonstrate that surface migration in oligomer-gel systems is significantly reduced due to network elasticity. Further, phase separation processes are significantly slowed in gels, modifying the Lifshitz-Slyozov-Wagner (LSW) law $\ell(\tau) \sim \tau^{1/3}$. Our work allows for rational design of polymer/gel-oligomer mixtures with predictable surface segregation characteristics.