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将N-异丙基丙烯酰胺(NIPAm)与具有温敏性的大分子单体进行共聚,制得了主链与支链在水溶液中具有不同相转变温度的温敏支化聚合物。经过双重相转变过程后,通过扫描电子显微镜(SEM)可以观察到聚合物链形成的具有较大比表面积的“葡萄串”结构,光散射实验中聚合物粒径大小随着温度升高发生两次突变进一步解释了双重相转变过程中聚合物微观形态的变化。在温敏支化聚合物溶液样品的差示扫描量热法(DSC)曲线中可以观察到35℃与21℃出现两组相对独立的吸热峰,从热力学的角度描述了双重相转变行为。通过使用二维红外相关光谱技术分析了温敏支化聚合物各基团对温度扰动的响应顺序,其结果说明仅存在于支链中的丙烯酸丁酯(BA)结构单元要先于NIPAm结构单元发生变化,对双重相转变行为的机理有了更进一步的说明。“葡萄串”结构的形成有效地提高了温敏聚合物的疏水比表面积,有望应用于生化分离领域。
Copolymerization of N-isopropylacrylamide (NIPAm) with a thermosensitive macromonomer gave a temperature-sensitive branched polymer with different phase transition temperatures in the main chain and the branch chain in aqueous solution. After the double phase transition process, the structure of polymer chains with larger specific surface area was observed by scanning electron microscopy (SEM). The size of the polymer particles in the light scattering experiment was increased with increasing temperature The occurrence of two mutations further explains the changes in the microscopic morphology of the polymer during the double phase transformation. Two sets of relatively independent endothermic peaks at 35 ℃ and 21 ℃ were observed in the differential scanning calorimetry (DSC) curve of the samples of the thermosensitive branched polymer solution, and the dual phase transition behavior was described from the thermodynamic point of view. The sequence of response of the temperature-sensitive branched polymers to temperature perturbations was analyzed by using two-dimensional infrared correlation spectroscopy. The results showed that the butyl acrylate (BA) units present only in the branches were prior to the NIPAm units Changes, the double phase transition behavior of the mechanism has been further explained. The formation of the “grape bunch” structure effectively increases the hydrophobic specific surface area of the thermosensitive polymer and is expected to be applied to the field of biochemical separation.