Forecasting molecular dynamics energetics of polymers in solution from supervised machine learning.

Machine learning techniques including neural networks are popular tools for chemical, physical and materials applications searching for viable alternative methods in the analysis of structure and energetics of systems ranging from crystals to biomolecules. Efforts are less abundant for prediction of kinetics and dynamics. Here we explore the ability of three well established recurrent neural network architectures for reproducing and forecasting the energetics of a liquid solution of ethyl acetate containing a macromolecular polymer-lipid aggregate at ambient conditions.

Distinctive Formation of PEG-Lipid Nanopatches onto Solid Polymer Surfaces Interfacing Solvents from Atomistic Simulation.

The interface between solid poly(lactic acid--glycolic acid), PLGA, and solvents is described by large-scale atomistic simulations for water, ethyl acetate, and the mixture of them at ambient conditions. Interactions at the interface are dominated by Coulomb forces for water and become overwhelmingly dispersive for the other two solvents. This effect drives a neat liquid-phase separation of the mixed solvent, with ethyl acetate covering the PLGA surface and water being segregated away from it.

Solutions and Condensed Phases of PEG from All-Atom Molecular Dynamics.

Extensive all-atom molecular dynamics studies of polyethylene glycol (PEG) when solvated and in the polymer bulk condensed phases were performed across a wide temperature range. We proposed two modified all-atom force field and observed the fate of the PEG macromolecule when solvated in water, water with 4% ethanol, and ethyl acetate. In aqueous solutions, the macromolecule collapsed into a prolate spheroidal ball-like structure while adopting a rather elongated coiled structure in ethyl acetate.

Modeling oxidised polypyrrole in the condensed phase with a novel force field.

A novel model potential is developed for simulating oxidised oligopyrroles in condensed phases. The force field is a coarse grained model that represents the pyrrole monomers as planar rigid bodies with fixed charge and dipole moment and the chlorine dopants as point atomic charges. The analytic function contains 17 adjustable parameters that are initially fitted on a database of small structures calculated within all-electron density functional theory.

Exploring with Molecular Dynamics the Structural Fate of PLGA Oligomers in Various Solvents.

This study focuses on the solvent effects that promote preferred solvated structures of polylactic--glycolic acid (PLGA) oligomers of molecular weight 278, 668, and 1449 u in ethyl acetate, water, and a mixture of both solvents. Our methodology consists of all-atom, explicit solvent molecular dynamics simulations for inspection of the solvated oligomer structures at ambient conditions. Parameters for the generalized Amber force field are developed in this work for the ethyl acetate liquid and the PLGA oligomers.