The whole process of phase transition and relaxation of poly(N-isopropylacrylamide) aqueous solution
The whole process of phase transition and relaxation of poly(N-isopropylacrylamide) aqueous solution
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DOI：
10.1039/c3cp43309a
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发表时间：
2013-01-01
影响因子：
3.3
通讯作者：
Katayama, Kenji
中科院分区：
文献类型：
--
作者：
Inoue, Hayato;Kuwahara, Shota;Katayama, Kenji
利用外差瞬态光栅（HD-TG）方法结合激光温度跳跃技术，对聚N-异丙基丙烯酰胺（PNIPAM）水溶液从相变到分子弛豫的全过程进行了观测。对应于线圈到小球构象转变的初始相变以96 +/-7 μ s的时间常数发生。然后，小球分子由于疏水相互作用而聚集，并且当通过加热实现的温度高到足以超过相变温度时，聚集体的尺寸增加到足以散射光（11 +/-1ms）。由于热扩散，聚集体松散，时间常数为44 +/- 5 ms。即使在此之后，释放的小球分子也返回到线圈状态，寿命为1.5-5 s，正如我们在以前的论文中所报道的那样（H. Inoue等人，物理化学化学物理学，2012，14，5620-5627）。
We observed the whole dynamics from the phase transition to the molecular relaxation of a poly(N-isopropylacrylamide) (PNIPAM) aqueous solution using the heterodyne transient grating (HD-TG) method combined with the laser temperature-jump technique. The initial phase transition corresponding to coil to globule conformational transition occurred with a time constant of 96 +/- 7 mu s. Then, the globule molecules aggregated due to hydrophobic interaction, and the size of the aggregates increased sufficiently to scatter light (11 +/- 1 ms) when the temperature achieved by heating was high enough to exceed the phase transition temperature. The aggregates loosened due to thermal diffusion with a time constant of 44 +/- 5 ms. Even after that, the released globule molecules returned back to the coil state with a lifetime of 1.5-5 s, as we reported in a previous paper (H. Inoue et al., Phys. Chem. Chem. Phys., 2012, 14, 5620-5627).