抄録
Thermosensitive poly(N-isopropylacrylamide) (PNIPAm) brushes grafted on SiO2-coated quartz crystal surface were prepared with a surface-immobilized initiator. By using quartz microbalance with dissipation monitoring (QCM-D) technique, we investigated the collapse and swelling of the brushes in water. Both frequency and dissipation of PNIPAm brushes were found to gradually change with a temperature range between 20-40°C, indicating that PNIPAm brushes undergo a continuous transition in contrast with PNIPAm chains in dilute solution exhibiting a sharp coil-to-globule transition. The nonuniformity and stretching of PNIPAm brushes as well as cooperativity between collapse and dehydration are considered to be responsible for the continuity. A hysteresis was observed in the cooling process. This is not only due to the intrachain and interchain interactions formed in the collapsed state, but also to the nonuniform structure and stretching of the high-density brushes.
