Molecular Dynamics Simulation of Sub-Transition for Polyethersulfone

Abstract

Molecular dynamics (MD) simulations of a polyethersulfone (PES) chain are carried out in the amorphous state by using the Dreiding 2.21 force field at four temperatures. Two types of molecular motion, i.e. rotations of phenylene rings and torsions of large segments containing two oxygen atoms, two sulfur atoms, and five phenylene rings on the backbone, are simulated. The modeling results show that the successive phenylene rings should be in‐phase cooperative rotations, whereas the successive large segments should be out‐of‐phase cooperative torsions. By calculating the diffusion coefficient for the phenylene ring rotations, it is found that this rotation contributes to the β‐transition of PES.

Permeation of CO2 and N2 through glassy poly(dimethyl phenylene) oxide under steady‐ and presteady‐state conditions

“…Therefore, it appears that the dual mode solubility and diffusivity Experimentally, it is observed that the volume of polymers decreases more slowly with decreasing temperature below the glass transition temperature than above it. [14][15] The difference between the glassy volume and a hypothetical rubbery volume at that temperature is defined as the excess free volume. Using positron annihilation lifetime spectroscopy (PALS), the excess free volume is shown to appear as an increase in magnitude of both the FFV and the FVE size in pristine glassy polymers.…”

“…13 A major difference between rubbery and glassy polymers is the presence of excess fractional free volume (FFV) in the glassy state due to kinetically trapped molecular chains. [14][15] While FFV exists in all materials, [16][17][18] the excess FFV is proposed to play a special role in sorption and diffusion within glassy polymer materials. 19 An increase in FFV has been shown to correlate with an increase in permeability and diffusion coefficients across a wide variety of glassy polymer compositions.…”

Fouling Characteristics of Microcrystalline Cellulose Duringcross-Flow Microfiltration: Insights from Fluid Dynamicgauging and Molecular Dynamics Simulations

“…3b) using AVOGADRO software [65] . Previous studies by Ahn et al [66] and Shi et al [67] have shown that a polymer with 60 repeating units effectively represents the characteristics of the polymer. As in Ahn et al [66], one end of the polymer chain was terminated with a hydrogen atom while the other end was closed with a phenyl group.…”