1. Institute of Advanced Biomedical Engineering and Science, Tokyo Women's Medical University (TWIns), 8‐1 Kawadacho, Shinjuku, Tokyo 162‐8666, Japan;2. Department of Applied Chemistry, Waseda University, 3‐4‐1 Ohkubo, Shinjuku, Tokyo 169‐8555, Japan
Abstract:
During characterization of a temperature‐responsive poly(N‐isopropylacrylamide) (PIPAAm) layer grafted onto a Si(100) substrate, atomic force microscopy (AFM) is able to probe the interactions between the microscope tip and the polymer. The modification of the AFM tip surface with octadecyltrichlorosilane (OTS) changes the interaction between the PIPAAm surface and the tip. Although a repulsive interaction is observed between a commercially available Si tip and the PIPAAm surface, a strong attractive interaction between the OTS‐modified Si tip and the surface is observed. Adhesion‐force analysis shows changes in the hydrophilic/hydrophobic character of ultrathin PIPAAm surfaces immediately after a change in temperature. The PIPAAm surface becomes hydrophobic less than 30 min after temperature increase, but requires 120 min to become hydrophilic after temperature reduction.
