Solutions and Condensed Phases of PEG₂₀₀₀ from All-Atom Molecular Dynamics

Abstract

Extensive all-atom molecular dynamics studies of polyethylene glycol (PEG 2000 ) 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 2000 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. Inspection of the polymer-condensed phases across the 150−340 K temperature range enabled the atomistic view of the solid glass below the glass transition temperature of 230 K < T g < 250 K and the rubber behavior above T g . Predicted properties include the enthalpy, density, and cohesive energy temperature behavior, the specific heat, thermal expansivity, thermal compressibility, bulk modulus, and Hildebrand solubility parameter both below and above T g . Within the polymer matrix, the PEG 2000 macromolecules were entangled displaying a wide distribution of sizes that persisted when transitioning from the glass to the rubbery phases. Calculated properties agree very well with experiments when available or stand as crucial predictions while awaiting experimental measurement. Understanding the thermodynamics and structure of this useful polymer enables the efficient prediction of its behavior when building novel composite materials for nanomedicine and nanotherapeutics.

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

“…For the solvents considered in this work, water was simulated with the SPC/E model, and EA molecules (CH 3 COOCH 2 CH 3 ) were modeled with GAFF using custom RESP charges from previous calculations. , …”

“…Simulation and modeling provide insight at the atomic scale enabling a level of control and detail unavailable to experiments. PEG(2000) has been studied computationally both in solvents and its condensed phases . Meanwhile, DSPE-PEG has received less attention in the literature, with few examples such as the determination of micelle formation in concentrated aqueous salt solutions simulated using the CHARMM force field to a pileup deposition modeled with the MARTINI coarse-grained force field …”

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

“…Multiple applications of this macromolecule include thermo-sensitive liposomal nanoparticles and in the formation of micelles, disks, vesicles, and bilayers that are commonly assembled for therapeutic drug delivery. [41][42][43][44][45] We term this macromolecule DSPE-PEG and point out that PEG(2000) is a water soluble linear polymer 40 and DSPE is a water insoluble lipid derivative of phosphatidylethanolamine with two long saturated fatty acid chains of stearic acid. Ethyl acetate (EA), C 4 H 8 O 2 , is a non-polar organic solvent commonly used for the fabrication of nanoparticles.…”

“…Ethyl acetate (EA), C 4 H 8 O 2 , is a non-polar organic solvent commonly used for the fabrication of nanoparticles. 26,46,47 Both EA and DSPE-PEG were modeled using the all-atom generalized Amber force eld (GAFF) 48,49 with our custom-calculated restrained electrostatic potential(RESP) atomic charges, 37,39,40 which was combined with the compatible Amber-Lipid17 (ref. 50) force eld for the DSPE portion of the polymer-lipid macromolecule.…”

“…While investigating a substance solubility, researchers have been able to formulate intelligently based on the key insight that solvents, polymers, or solid matter are well characterized by solubility parameters derived from their cohesive energy density. 38 Indeed, based on the Hildebrand solubility parameter of the EA liquid 39 and of the bulk polymer PEG(2000), 40 we have determined that the polymer dissolves in EA at ambient conditions. Most likely, the EA also solvates the DSPE–PEG(2000) bulk solid.…”