Probing friction and adhesion properties of poly(vinyl methylether)homopolymer and blend films under nano-confinement using atomic-force microscopy

摘要

The surface properties of poly(vinyl methylether)(PVME)homopolymer and blend films are characterized by atomic force microscopy(AFM)with the film thickness ranging from 5 nm to 400 nm.When the film thickness is less than 200 nm,lateral force of the PVME films decreases with the decreasing film thickness and has less dependence on the scanning rate.The local adhesion measurements indicate the adhesion force per unit area increases with the decreasing film thickness.These results are consistent to each other showing the increased polymer stiffness and decreased polymer chain mobility due to the confinement in the ultra-thin films.The effects of blending PVME with semicrystalline isotactic polypropylene(i-PP)on the lateral force of the film have also been investigated.Upon blending,both the scale of the lateral forces and their scanning rate dependences exhibit great changes.The lateral force of the blend film has a maximum when the fraction of PVME is around 0.8,similar to that when a polymer goes through the glass-transition.