(712f) Effect of Gel Hydrophobicity on the Dynamics of Small Penetrant Molecules inside Polymeric Networks: A Molecular Simulation Study

Cross-linked polyacrylate is a good candidate material for energy efficient, pervaporation based recovery of alcohol from dilute aqueous solutions resulting from fermentation of cellulosic biomass.  In this work, we use molecular dynamics (MD) simulations with atomistically-detailed models to investigate the effect of hydrophobic and hydrophilic domains in the polymer matrix on the dynamics of water and ethanol molecules.

Polyacrylate systems consisting of butyl acrylate (BA) and 2-hydroxyethyl acrylate (2-HEA) which are hydrophobic and hydrophilic, respectively, are selected for this study.  Also, pentaerythritol tetraacrylate (PETA) is used as the cross-linking agent in order to form the gel network.  The polymerized structures of the gel are built by employing the simulated annealing polymerization technique which allows us to create well-relaxed structures of the system.  Properties of three different systems (pure BA, BA-HEA copolymer and pure HEA gels) are compared.  The dynamics of water and ethanol molecules in these systems is compared by determining their translational and rotational mobility.  Furthermore, intermediate scattering function is also determined which can be used for direct comparison with experimental data on molecule mobility.  Mobility results are discussed in the context of the nanoscale structure of the hydrophobic and hydrophilic groups in the system.