Hou Lei, Wu Peiyi
The State Key Laboratory of Molecular Engineering of Polymers, Department of Macromolecular Science, Laboratory of Advanced Materials, Fudan University, Shanghai 200433, China.
Soft Matter. 2014 May 28;10(20):3578-86. doi: 10.1039/c4sm00282b. Epub 2014 Mar 24.
The self-aggregation behavior of poly(N-isopropylacrylamide)-b-poly(N-vinylcaprolactam) (PNIPAM-b-PVCL) during the thermal-induced phase transition in water was explored by a combination of calorimetric, turbidity, dynamic light scattering (DLS) and FTIR measurements. Only one transition can be observed via all detecting methods, revealing the cooperative aggregation of the two distinct temperature-sensitive segments. What is more, the combination of strong hydrophobic interactions among the entire polymer chains and hydrogen bonds of C=O…H-N within PNIPAM segments results in the sharp variations at the LCST and gradual variations above the LCST during the phase transition of PNIPAM-b-PVCL aqueous solution upon heating. Additional analysis by perturbation correlation moving window (PCMW) and two-dimensional correlation spectroscopy (2Dcos) indicates that the hydrophobic C-H groups have an earlier response than the relatively hydrophilic C=O groups during the LCST transition.
通过量热法、浊度法、动态光散射（DLS）和傅里叶变换红外光谱（FTIR）测量相结合的方法，研究了聚（N-异丙基丙烯酰胺）-b-聚（N-乙烯基己内酰胺）（PNIPAM-b-PVCL）在水中热诱导相变过程中的自聚集行为。通过所有检测方法只能观察到一个转变，这揭示了两个不同的温度敏感链段的协同聚集。此外，整个聚合物链之间强烈的疏水相互作用与PNIPAM链段内C=O…H-N氢键的结合，导致了PNIPAM-b-PVCL水溶液加热相变过程中在最低临界溶液温度（LCST）处的急剧变化以及在LCST以上的逐渐变化。通过扰动相关移动窗口（PCMW）和二维相关光谱（2Dcos）进行的额外分析表明，在LCST转变过程中，疏水的C-H基团比相对亲水的C=O基团有更早的响应。
