A neutron reflectometry study of polystyrene network interfaces

Abstract

PACS. 68.35.Ct Interface structure and roughness - 82.70.Gg Gels and sols,

Reptation and interdiffusion in polystyrene networks

“…Swelling of less crosslinked regions is rapid but the relaxation in the approach to equilibrium is slow. This is supported by other measurements on similar polystyrene networks [8,25]. .…”

“…The relaxation of these large-scale heterogeneities will be particularly slow. Similar relaxation behaviour has also been noted in the penetration of a high molecular weight linear polymer into a network [8], as well as the segregation of linear polymer to a vacuum surface from a network [25]. In both cases a two-stage process was observed with slow penetration or segregation following an initial rapid process.…”

“…The Flory-Rehner form can display a slight increase in the interdiffusion coefficient with respect to the melt due to the additional logarithmic term in the free energy (Eq. (8)). This is not the case in the phantom model.…”

“…The synthesis has been described previously [8][9][10][11] and is only briefly summarised here. The reaction is a three-stage process, using a Friedel-Crafts reaction and an exchange reaction to randomly functionalise the polystyrene with an aminomethyl group (NH 2 CH 2 ) and, for the third stage, the crosslinking reaction.…”

“…The diffusion of linear polystyrene into a polystyrene network has been studied by neutron reflectometry (NR) [4], forward recoil spectrometry (FReS) [4,7], and dynamic secondary ion mass spectrometry (d-SIMS) [3]. Another neutron reflection study concentrated on the interface between a homopolymer and network where little or no interdiffusion takes place [8]. One study used d-SIMS to show that the diffusion of linear polymers into a radiation crosslinked network was dependent on the crosslink density of the network, and on the molecular weight of the linear polymer [3].…”