Fluorescence studies of associative behavior of cationic surfactant moieties covalently linked to poly(acrylamide) at the surfactant head or tail
Fluorescence studies of associative behavior of cationic surfactant moieties covalently linked to poly(acrylamide) at the surfactant head or tail
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DOI：
10.1016/s0032-3861(02)00897-2
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发表时间：
2003-02
期刊：
影响因子：
4.6
通讯作者：
H. Morimoto;A. Hashidzume;Y. Morishima
中科院分区：
文献类型：
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作者：
H. Morimoto;A. Hashidzume;Y. Morishima
比较了在不同相对位置（相对于聚合物主链）具有相同（或相似）疏水和带电基团的疏水改性水溶性聚合物的缔合性质。合成了两种类型的表面活性剂单体（surfmers）;阳离子表面活性剂在表面活性剂带电的头部（二甲基十二烷基-4-乙烯基苄基氯化铵（St-QC 12））或在末端（13-（4-乙烯基苯基）十三烷基三甲基溴化铵（St-C13 Q））连接到苯乙烯的对位。将这些表面活性剂与丙烯酰胺（AAm）进行共聚，并用不同的荧光技术表征了共聚物在水中的缔合行为。AAm/St-QC_（12）和AAm/St-C_（13）Q共聚物中表面活性剂的含量固定在10mol%左右。共聚物中的表面活性剂单元自缔合形成共聚物聚集体。表观临界胶束浓度（CMC）（即表面活性剂单元的互聚物缔合开始的聚合物浓度），其由AAm/St-QC 12的芘探针的激发光谱估计（cmc=2.6×10 - 4g/l）比AAm/St-C13 Q低几倍（cmc=1.3×10 - 3g/l），AAm/St-QC 12中的表面活性剂单元比AAm/St-C13 Q中的表面活性剂单元表现出更强的互聚物缔合倾向。在AAm/St-C13 Q中的p-取代苯乙烯残基（亚苯基）的稳态荧光光谱中存在激基缔合物发射，表明苯环在聚合物聚集体中彼此非常接近。稳态荧光光谱和荧光猝灭的硝酸铊和1-硝基己烷表明，在AAm/St-C13 Q中的亚苯基基团被纳入由表面活性剂的烃链形成的疏水微区，而在AAm/St-QC 12中的亚苯基基团位于聚合物聚集体的表面附近的方式，它们是充分地彼此分开，因此没有激基缔合物形成。
Association properties of hydrophobically modified water-soluble polymers bearing the same (or similar) hydrophobic and charged groups at different relative positions (with respect to the polymer main chain) were compared. Two types of surfactant monomers (surfmers) were synthesized; a cationic surfactant was linked to the p-position of styrene at the surfactant charged head (dimethyldodecyl-4-vinylbenzylammonium chloride (St-QC12)) or at the tail end (13-(4-vinylphenyl)tridecyltrimethylammonium bromide (St-C13Q)). These surfmers were copolymerized with acrylamide (AAm), and the association behavior of the copolymers in water was characterized using different fluorescence techniques. The surfmer contents in the AAm/St-QC12and AAm/St-C13Q copolymers were fixed to more or less 10mol%. The surfmer units in the copolymers self-associate to form multipolymer aggregates. An apparent critical micelle concentration (cmc) (i.e. a polymer concentration for the onset of interpolymer association of the surfmer units) estimated from excitation spectra of pyrene probes for AAm/St-QC12(cmc=2.6×10−4g/l) was several times lower than that for AAm/St-C13Q (cmc=1.3×10−3g/l), surfmer units in AAm/St-QC12showing a stronger tendency for interpolymer association than those in AAm/St-C13Q. The presence of excimer emissions in steady-state fluorescence spectra for the p-substituted styrene residues (phenylene groups) in AAm/St-C13Q indicated that the benzene rings are in close proximity to one another in the polymer aggregates. Steady-state fluorescence spectra and fluorescence quenching by thallium nitrate and 1-nitrohexane indicated that the phenylene groups in AAm/St-C13Q were incorporated in hydrophobic microdomains formed from surfactant hydrocarbon chains, whereas the phenylene groups in AAm/St-QC12are located near the surface of polymer aggregates in a way that they are sufficiently apart from each other and hence no excimer is formed.