A comparative study on switchable adhesion between thermoresponsive polymer brushes on flat and rough surfaces

We report a comparative study of switchable adhesion between different thermoresponsive polymer brushes grafted onto flat and microstructured substrates and bare or brush-modified microparticle probes. The adhesion behaviour is investigated in situ using atomic force microscopy measurements in aqueous environment at different temperatures. It was found that the adhesion force is higher in the case of flat modified brush substrates than in the case of the corresponding microstructured ones. This effect is due to a reduced contact area between the spherical probe and the rough surface. It is also found that the adhesion force decreases in the sequence PNIPAM, P(OEGMA-MEO2MA), P(OEGMA-OPGMA) when probed by a bare spherical bead. On the other hand, adhesion between the flat surface with grafted thermoresponsive brush and the particle probe modified by the thermoresponsive brush of the same kind decreases in the different sequence: PNIPAM, P(OEGMA-OPGMA) and P(OEGMA-MEO2MA). This difference in adhesion properties is explained by the specific chemical architecture of the brushes.