Hou Lei, Wu Peiyi
State Key Laboratory of Molecular Engineering of Polymers, Collaborative Innovation Center of Polymers and Polymer Composite Materials, Department of Macromolecular Science and Laboratory for Advanced Materials, Fudan University, Shanghai 200433, China.
Soft Matter. 2015 Apr 14;11(14):2771-81. doi: 10.1039/c5sm00026b.
The LCST-transitions of linear, well-defined polymers of N-isopropylacrylamide (NIPAM) and N-vinylcaprolactam (VCL), including a homopolymer mixture, diblock and statistical copolymers, in water are explored and compared by applying turbidity and FTIR measurements in combination with two-dimensional correlation spectroscopy (2Dcos). Only one transition is observed in all polymer systems, suggesting a dependent aggregation of poly(N-isopropylacrylamide) (PNIPAM) and poly(N-vinylcaprolactam) (PVCL) parts in the phase transition processes. With the help of 2Dcos analysis, it is discovered that the hydrophobic interaction among C-H groups is the driving force for simultaneous collapse of the two distinct thermo-responsive segments. Additionally, the delicate differences within the LCST-transitions thereof have been emphasized, where the phase separation temperatures of the homopolymer mixture and the diblock copolymer are close while that of the statistical copolymer is relatively higher. Moreover, both diblock and statistical copolymers exhibit rather sharp phase transitions while the homopolymer mixture demonstrates a moderately continuous one.
通过将浊度和傅里叶变换红外光谱（FTIR）测量与二维相关光谱（2Dcos）相结合，研究并比较了N-异丙基丙烯酰胺（NIPAM）和N-乙烯基己内酰胺（VCL）的线性、结构明确的聚合物（包括均聚物混合物、二嵌段共聚物和无规共聚物）在水中的低临界溶液温度（LCST）转变。在所有聚合物体系中仅观察到一个转变，这表明在相变过程中聚（N-异丙基丙烯酰胺）（PNIPAM）和聚（N-乙烯基己内酰胺）（PVCL）部分存在相关聚集。借助二维相关光谱分析发现，C-H基团之间的疏水相互作用是两个不同的热响应链段同时塌陷的驱动力。此外，还强调了其LCST转变中的细微差异，其中均聚物混合物和二嵌段共聚物的相分离温度相近，而无规共聚物的相分离温度相对较高。而且，二嵌段共聚物和无规共聚物均表现出相当尖锐的相变，而均聚物混合物则表现出适度连续的相变。
