An amphiphilic graft copolymer as a surface-modifying additive for poly(methyl methacrylate)

An amphiphilic graft copolymer was prepared by transesterification of poly(2-ethylhexyl acrylate-co-methyl methacrylate) with poly(ethylene glycol) monomethyl ether (MPEG2000). The grafting reaction was performed in melt at 155°C. The purified graft copolymer was blended into poly(methyl methacrylate) in concentrations of 1.5-30 wt %, either by mixing in chloroform solution or by melt mixing by means of a twin-screw extruder or a Brabender blender. Films of the blends were prepared by solution casting onto glass plates or by hot pressing between polished Al plates. At concentrations up to 20% of the graft copolymer homogeneous blends were obtained. At higher concentrations the blends were heterogeneous, and side-chain crystallinity was detectable by DSC analysis. The surface properties of the films were studied by measurements of water contact angles. The surface accumulation of the graft copolymer was demonstrated as a large increase in the wetting angle hysteresis, and found to depend on the procedure for film preparation as well as the casting substrate. © 1995 John Wiley & Sons, Inc.