Dynamic Polymer Brush by Segregation of Amphiphilic Copolymers*

A layer of polymer chains tethered by one end to a surface is called polymer brush and known to show various unique properties such as prevention of protein adsorption and anti-fouling activity. The surface segregation phenomena of copolymers with surface-active blocks should be useful for preparing such a brush layer in spontaneous process. We reported hydrophilic polymer brushes formed at the interface between water and hydrophobic polymer matrix by the segregation of amphiphilic diblock copolymers blended in the matrix. In this system, while the hydrophilic block with high surface energy avoids air surface it segregate to cover the interface between hydrophobic PDMS and water. The structures of formed brush layers at D₂O/polymer interfaces were analyzed by neutron reflectivity (NR). The brush density was calculated to be as high as 2 chains/nm², which is surprisingly comparable to the polymer brush fabricated by the “grafting-from” method. Moreover, even if the brush is lost or damage, the remaining block copolymers embedded in the elastomer can segregate again to repair the brush (self-repair). Therefore, the kinetics of dynamic polymer brush growth, which determines the time for self-repair, is very important. The kinetics of dynamic polymer brush formation was investigated using Quartz Crystal Microbalance (QCM), contact angle measurement and time-resolved NR.