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题名 极稀溶液中聚N,N-二乙基丙烯酰胺构象转变机理的研究
姓名 陈勇
院系 化学化工学院
专业 高分子化学与物理
学位名称 理学博士
外文题名 The Research on Mechanism of the Conformational Transition of Poly (N, N-diethylacrylamide) in Extremely Dilute Aqueous Solution
第一导师姓名 柳明珠
关键词 聚N,N-二乙基丙烯酰胺;聚(N,N-二乙基丙烯酰胺-co-N-羟甲基丙烯酰胺);聚(N,N-二乙基丙烯酰胺-co-苯乙烯);构象;温敏性;低临界溶解温度;极稀水溶液;相转变行为;无机盐;脲
外文关键词 poly(N,N-diethylacrylamide);P(DEA-co-NHMAA);poly(N,N-diethylacrylamide-co-styrene);conformation;thermo-sensibility;the lower critical solution temperature;extremely dilute aqueous solution;phase transition behavior;salts;urea
学科 理学
摘要 合成了苊烯(ACE)标记的聚N, N-二乙基丙烯酰胺(PDEA)、N, N-二乙基丙烯酰胺与N-羟甲基丙烯酰胺共聚物(P(DEA-co-NHMAA))和N, N-二乙基丙烯酰胺与苯乙烯共聚物(P(DEA-co-St));利用光物理手段,如荧光强度、荧光淬灭以及荧光各向异性技术,考察了在极稀水溶液中,随着PDEA高分子链亲/疏水结构的变化,以及随着无机盐、脲和甲醇的加入导致溶剂性质的变化;系统地研究了温敏性高分子PDEA的构象变化和导致构象变化的氢键、静电相互作用、疏水缔合以及溶剂化水层的作用机理。 在极稀的PDEA/ACE水溶液中,探讨了无机盐对高分子链构象的影响。结果表明:不同无机盐对非离子型PDEA/ACE的低临界溶解温度(TLCS)的影响与Hofmeister序列相一致;随着NaCl浓度的增加,TLCS线性降低。荧光实验结果表明:当温度低于TLCS时,PDEA/ACE呈伸展的无规线团构象;当温度高于TLCS时,PDEA/ACE发生从无规线团构象到蜷曲球的转变(CGT);完成CGT以后,PDEA/ACE呈致密的蜷曲球构象;在无规线团到蜷曲球构象的转变中,存在着 “熔融”的蜷曲球构象;随着NaCl浓度的增加,上述三种亚稳态的构象变得更为致密。荧光各向异性的研究结果表明:NaCl的加入,只是降低了TLCS,并没有影响CGT过程,表明静电作用仅仅改变了溶剂及溶剂化层中水合作用,并没有直接影响聚合物的构象。
外文摘要 In this thesis, three different polymers, acenaphthylene labeled poly (N,N-diethylacrylamide) (PDEA/ACE), poly(N,N-diethylacrylamide-co-styrene) (P(DEA-co-St)) copolymers, P(N,N-diethylacrylamide-co-N-hydroxymethylacryl- amide) (P(DEA-co-NHMAA)) copolymers, were synthesized by radical solution polymerization. In dilute aqueous solutions, the effects of salts, urea and methanol on the conformation of PDEA/ACE were investigated systematically. The thermo-sensitive properties of hydrophilic or hydrophobic modified PDEA were also investigated by UV-vis and fluorescence spectroscopy technique. In dilute aqueous solution, the PDEA/ACE adopted a loosely coil conformation below its TLCS. PDEA/ACE adopted a compact globular conformation above the temperature at which the coil to globular transition (CGT) was completed. Fluorescence anisotropy investigation suggested a molten globular conformation existed during the CGT of PDEA/ACE solution. In all the above three conformations, the PDEA/ACE was more compact in presence of NaCl than that in absence of any salt. It was demonstrated that the addition of urea increased the openness of conformation and increased the segmental mobility of macromolecules of PDEA/ACE in CGT, resulted in increasing the average diameter of particles. For PDEA and P(DEA-co-NHMAA) aqueous solution, the abrupt transition from coil to globular and the gradual transition from globular to coil may involve different mechanisms.A model has been proposed for the structure of P(DEA-co-NHMAA) formed in dilute aqueous solution. For PDEA/ACE aqueous solution, the abrupt transition from coil to globular due to hydrophobic interaction and the gradual transition from globular to coil may involve different mechanisms. The change of conformation of thermo-sensitivity polymer was clearly associated to the balance between the hydrophobic effect and hydrophilic effect.
研究领域 高分子物理化学
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