Shi Tongfei

Swelling Process of Thin Polymer Film Studied via in situ Spectroscopic Ellipsometry

The swelling process of thin polystyrene films in quantity was studied in this paper using the in situ spectroscopic ellipsometry. We systematically investigated the influence of film thickness on the swelling process of thin polystyrene films. The results show that in the case of high Mw polystyrene(Mw=400000), the curve of the swelling degree as a function of time discloses that the relaxation of the long polymer chains accompanies the diffusion of acetone molecules. The swelling process is via the Fickian relaxation mechanism. Both the values of the equilibrium swelling degree and the diffusion coefficient of acetone molecules in the polystyrene film decrease as the film thickness reduces under confinement. However, in the case of low Mw PS(Mw=4100), the dewetting process is so fast before the equilibrium of swelling that the whole swelling process cannot be observed.

Effect of hydrodynamic interaction on flow-induced polymer translocation through a nanotube

We investigated the effect of hydrodynamic interaction(HI) on flow-induced polymer translocation through a nanotube by Brownian dynamics simulations. Whether there is HI in the simulation system is separately controlled by using different diffusion tensors. It is found that HI has no effect on critical velocity flux for long polymer chains due to the competition between more drag force and the hindrance of chain stretching from HI, however, HI broadens the transition interval. In addition, for flow-induced polymer translocation with HI, the critical velocity flux firstly slowly decreases with the increase of chain length and then becomes identical to that of it without HI, that is, the critical velocity flux is independent of chain length. At the same time, HI also accelerates the translocation process and makes the relative variation amplitude of single bead translocation time smaller. In fact, HI can enhance the intrachain cooperativity to make the whole chain obtain more drag force from fluid field and hinder chain stretching, both of which play an important role in translocation process.