Effect of monomer composition on structural properties of poly(ethylene-co-propylene) nanofiber by Monte Carlo simulation

Abstract

Structural properties at the bond and molecular level of poly(ethylene-co-atactic propylene) copolymer nanofiber were studied by lattice Monte Carlo simulation. The simulation was performed with a coarse-grained model of these random copolymer chains with the density in the range of 0.753–0.760 g/cm3 at 473 K. The properties of nanofiber were characterized at different monomer fraction. When the ethylene fraction was increased, the relative bead density of nanofibers was increased in the bulk region near the fiber (X) axis and dramatically decreased in the region toward the surface along the radial direction. The interfacial widths of these radial bead density profiles were increased for copolymer with higher ethylene content. End beads of polymer chains became more abundant in the region closer to the vacuum side and the bonds near the surface were more oriented in a parallel direction to the surface with an increase of ethylene content. Molecular size as represented by the radius of gyration (R g ) in the X-component became smaller along the radical direction, while the R g in the Y-Z component was relatively unchanged. There were significant changes in molecular shape (acylindricity) and the size of copolymer (components of the radius of gyration) as a function of ethylene content. Similarly, the largest molecular axis was oriented in a parallel direction to the fiber axis, and changed toward random orientation when the ethylene content was decreased. Open image in new window