Polymers exhibiting an abnormal thermoresponsive behaviour, in which increase in the polymer concentration in water leads to an increase in the phase transition temperature, are few, and no plausible strategy has been addressed to prepare these polymers. For illuminating a feasible common strategy to prepare polymers with an abnormal thermoresponsive behaviour, in this study, we systematically prepared a series of hyperbranched polyglycerol (HPG) derivatives through a facile esterification reaction between HPG and aliphatic acids having different carbon numbers (X). Turbidimetry measurements demonstrate that thermoresponsive HPGs can be obtained only when HPGs are conjugated with aliphatic units of X ≤ 8. The conjugation of HPG with aliphatic units of X ≤ 4 resulted in thermoresponsive HPGs with a normal thermoresponsive behaviour. For the preparation of thermoresponsive HPGs with an abnormal thermoresponsive behaviour, X should be controlled in the range of 5–8. Fluorescence measurements with nile red as the fluorescent probe demonstrate that the existence of relatively strong hydrophobic interaction is a key factor to ensure that the polymer exhibits an abnormal thermoresponsive behaviour in water. Moreover, turbidimetry and fluorescence techniques are complementary for measuring the phase transition behaviour and suitable for different polymer concentration regions.

中文翻译：

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在水中表现出正常或异常热响应行为的超支化聚甘油衍生物：简便的制备方法以及比浊法和荧光技术的研究

表现出异常的热响应行为的聚合物很少，其中水中聚合物浓度的增加导致相变温度的增加，并且尚未提出任何可行的策略来制备这些聚合物。为了阐明制备具有异常热响应性行为的聚合物的可行通用策略，在本研究中，我们通过HPG和具有不同碳原子数（X）的脂族酸之间的简便酯化反应，系统地制备了一系列超支化聚甘油（HPG）衍生物。比浊法测量表明，当HPG中与的脂族单元共轭热响应的HPG可以仅获得X ≤8. HPG的具有脂族单元的缀合X≤4导致具有正常热响应行为的热响应HPG。为了制备具有异常热响应行为的热响应HPG，应将X控制在5–8的范围内。用尼罗红作为荧光探针的荧光测量表明，存在较强的疏水相互作用是确保该聚合物在水中表现出异常的热响应行为的关键因素。此外，比浊法和荧光技术是用于测量相变行为的补充，适用于不同的聚合物浓度区域。