Chain conformation of a new class of PEG-based thermoresponsive polymer brushes grafted on silicon as determined by neutron reflectometry

The thermoresponsive PEG-based copolymer poly [2-(2-methoxyethoxy)ethyl methacrylate-co-oligo(ethylene glycol) methacrylate) (P(MEO₂MA-co- OEGMA)] was grafted onto a silicon wafer, and its chain conformation in aqueous solution was studied by neutron reflectometry. The effects of temperature and salt concentration on the polymer's conformation were evaluated. With increasing temperature, it was found that the polymer brushes underwent a transition from an extended state to a compressed state, and eventually a collapsed state above the lower critical solution temperature. The presence of salt significantly affected the well-extended brushes but had little effect on compressed and collapsed brushes. This PEG-based thermoresponsive surface exhibited good protein adsorption resistance. Interestingly, extended and collapsed brushes showed the same level of protein repulsion, something that was not expected.