Determination of the rate constant for chain insertion into poly(methyl methacrylate)-block-poly(methacrylic acid) micelles by a fluorescence method
Determination of the rate constant for chain insertion into poly(methyl methacrylate)-block-poly(methacrylic acid) micelles by a fluorescence method
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DOI：
10.1021/ma951338u
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发表时间：
1996-03-11
期刊：
影响因子：
5.5
通讯作者：
Liu, GJ
中科院分区：
文献类型：
--
作者：
Smith, CK;Liu, GJ
已合成并表征了在 PMAA 嵌段末端附着或不附着芘标记的聚（甲基丙烯酸甲酯）-嵌段-聚（甲基丙烯酸）（PMMA-b-PMAA）。当乙酸乙酯体积分数高于80%时，这些聚合物在乙酸乙酯/甲醇混合物中形成以PMAA为核心的胶束。将不带芘标记的PMMA-b-PMAA胶束溶液（即聚合物I）与样品与芘的单聚体溶液（即聚合物II）混合后，芘的荧光强度I-Py(t)随时间增加。这是由于聚合物 II 链的芘基团插入到聚合物 I 胶束的刚性核心中造成的。由于氧气对芘荧光的猝灭减少以及某些非辐射失活途径的可能抑制，在更严格的环境中芘荧光量子产率更高。提出了一个动力学模型来描述链插入过程。使用 I-Py(t) 的导出表达式拟合实验荧光强度数据，可以首次确定二嵌段共聚物链插入胶束的速率常数 k(n)。
Poly(methyl methacrylate)-block-poly(methacrylic acid) (PMMA-b-PMAA) with and without pyrene labels attached to the end of the PMAA block have been synthesized and characterized. These polymers formed micelles with PMAA as the core in ethyl acetate/methanol mixtures when the ethyl acetate volume fraction was higher than 80%. After mixing a micelle solution of PMMA-b-PMAA without pyrene labels, i.e., polymer I, with a unimer solution of the sample with pyrene, i.e., polymer II, the fluorescence intensity I-Py(t) of pyrene increased with time. This was caused by the insertion of the pyrene group of polymer II chains into the rigid core of polymer I micelles. The pyrene fluorescence quantum yield is higher in a more rigid environment due to the reduced quenching of pyrene fluorescence by oxygen and the possible suppression of certain nonradiative deactivation pathways. A kinetic model has been proposed for describing the chain insertion process. Fitting the experimental fluorescence intensity data using the derived expression for I-Py(t) allowed the first determination of the rate constant k(n) for diblock copolymer chain insertion into micelles.