Collapse and Swelling of Thermally Sensitive Poly(N-isopropylacrylamide) Brushes Monitored with a Quartz Crystal Microbalance

2006-07-18 17:25

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Thermally sensitive poly(N-isopropylacrylamide) (PNIPAM) brushes grafted on SiO2-coated quartz crystal surface were prepared with a surface-immobilized initiator. Using quartz crystal microbalance (QCM), we investigated the collapse and swelling of the brushes in water in real time. Both frequency and dissipation of PNIPAM brushes were found to gradually change throughout a temperature range 20-38 °C, indicating that PNIPAM brushes undergo a continuous collapse transition in contrast with PNIPAM chains free in dilute solution exhibiting a sharp coil-to-globule transition. This result is in accordance with the previous theoretical prediction. The nonuniformity and stretching of PNIPAM brushes as well as the cooperativity between collapse and dehydration transitions are thought to be responsible for the continuity. On the other hand, a hysteresis was also 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.

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Collapse and Swelling of Thermally Sensitive Poly(N-isopropylacrylamide) Brushes Monitored with a Quartz Crystal Microbalance

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Reentrant Behavior of Poly(N-isopropylacrylamide) Brushes in Water-Methanol Mixtures Investigated with a Quartz Crystal Microbalance

对NPL标准物质Inconel 600和黄铜导热性能的高温测试

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