DWI-Leibniz-Institute for Interactive Materials, e.V., RWTH-Aachen University, Forckenbeckstraße 50, D-52074, Aachen, Germany.
Department of Physics and Chemistry, Technical University of Cluj-Napoca, 25 G. Baritiu Str, RO-400027, Cluj-Napoca, Romania.
Macromol Rapid Commun. 2017 Oct;38(19). doi: 10.1002/marc.201700362. Epub 2017 Aug 21.
Quantification of the stimuli-responsive phase transition in polymers is topical and important for the understanding and development of novel stimuli-responsive materials. The temperature-induced phase transition of poly(N-isopropylacrylamide) (PNIPAm) with one thiol end group depends on the confinement-free polymer or polymer brush-on the molecular weight and on the nature of the second end. This paper describes the synthesis of heterotelechelic PNIPAm of different molecular weights with a thiol end group-that specifically binds to gold nanorods and a hydrophilic NIPAm end group by reversible addition-fragmentation chain-transfer polymerization. Proton high-resolution magic angle sample spinning NMR spectra are used as an indicator of the polymer chain conformations. The characteristics of phase transition given by the transition temperature, entropy, and width of transition are obtained by a two-state model. The dependence of thermodynamic parameters on molecular weight is compared for hydrophilic and hydrophobic end functional-free polymers and brushes.
定量研究聚合物的刺激响应相转变是当前的研究热点，对于理解和开发新型刺激响应材料具有重要意义。具有一个硫醇端基的聚（N-异丙基丙烯酰胺）（PNIPAm）的温度诱导相转变取决于无约束聚合物或聚合物刷的分子量以及第二端基的性质。本文通过可逆加成-断裂链转移聚合，合成了具有硫醇端基（特异性结合金纳米棒）和亲水性 NIPAm 端基的不同分子量的杂臂 PNIPAm。质子高分辨率魔角样品旋转 NMR 谱被用作聚合物链构象的指示剂。通过两态模型获得了由转变温度、熵和转变宽度给出的相转变特性。比较了亲水性和疏水性端基无规聚合物和刷的热力学参数对分子量的依赖性。
