Suppressed Chain Entanglement Induced by Thickness of Ultrathin Polystyrene Films

The thickness effect on the relaxation behavior and chain entanglements was investigated for thin polystyrene films. By following the time evolution of the wetting ridge at the surface induced by a droplet of ionic liquid, the characteristic time (tau*) at which the ridge height started to change was obtained. Here, we demonstrated experimentally that the characteristic time was associated with the disentanglement time tau(d), tau* similar to tau(d) similar to M-w(3.4)/M-e(1.4), where M-e denotes the entanglement molecular weight. The critical thickness (h(c)) at which tau* started to decrease was approximately 3.3R(g). That is, the M-e increased, or the interchain entanglement density decreased, as the film became thinner than the h(c). This might be explained in terms of the conformational change from spherical to ellipsoidal, leading to a reduction in the pervaded volume (V-p) of chains in the ultrathin films.

Automated summary

The study found that as the thickness of thin polystyrene films decreased, the entanglement molecular weight increased and the interchain entanglement density decreased, resulting in a decrease in the characteristic time of the wetting ridge at the surface.