Surface Characterization of Block Copolymers with Water-soluble Block by using Sum-Frequency Generation Spectroscopy

A series of amphiphilic block copolymers containing poly[oligo(ethylene glycol) methacrylate] segments and the corresponding poly[methyl ethers of oligo(ethylene glycol) methacrylate] block copolymer surfaces are investigated by using sum-frequency generation (SFG) vibrational spectroscopy. The terminal moiety on the oligo(ethylene glycol) side chain played an important role in determining the surface structure of the block copolymer films. Due to the amphiphilic character of the methoxy oligo(ethylene glycol) side chain, the PME3MA block exposes the terminal methyl group to the surface and reduces the surface tension in air or vacuum, and it is possible that configurational entropy may also favor the presence of side chains at the surface. The molecular orientation of the block copolymer at the surface is modified due to the multilayered structures of the block copolymers.