Polymerization of ionic monomers in polar solvents: kinetics and mechanism of the free radical copolymerization of acrylamide/acrylic acid
Polymerization of ionic monomers in polar solvents: kinetics and mechanism of the free radical copolymerization of acrylamide/acrylic acid
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DOI：
10.1016/j.polymer.2005.04.005
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发表时间：
2005-06-17
期刊：
影响因子：
4.6
通讯作者：
Wandrey, C
中科院分区：
文献类型：
--
作者：
Rintoul, I;Wandrey, C
本文给出了在低单体浓度范围内，丙烯酰胺/丙烯酸（AM/AA）自由基共聚动力学与pH、单体总浓度、引发剂浓度和单体比的函数关系。已确定pH和总单体浓度对反应性比有很大影响。当总单体浓度为0.4 mol/l， T=313 K时，AM的反应比由pH 1.8时的0.54增加到pH 12时的3.04。相反，AA的反应性比从1.48降低到0.32。交叉发生在pH接近4.2时。由于AA的电离程度的变化引起的静电效应是影响动力学的主要因素。当总单体浓度从0.2 mol/l增加到0.6 mol/l时，AM和AA的反应率分别从4.01降低到2.13，从0.25提高到0.47。单体总浓度越高，离子强度越高，电离单体AA和部分带电的生长聚合物链端之间的静电斥力就越小，这可以解释这种效应。精确的数据集是在可变单体反应性情况下计算共聚物组成的新方法的先决条件。(c) 2005 Elsevier Ltd版权所有。
A precise data set describing the kinetics of the free radical copolymerization of acrylamide/acrylic acid (AM/AA) in the range of low total monomer concentration as a function of the pH, total monomer concentration, initiator concentration, and comonomer ratio is presented. Strong impact on the reactivity ratios has been identified for the pH and total monomer concentration. Specifically, at constant total monomer concentration of 0.4 mol/l and T=313 K the reactivity ratio of AM increases from 0.54 at pH 1.8 to 3.04 at pH 12. Contrarily, the reactivity ratio of AA decreases from 1.48 to 0.32. The crossover occurs at pH approximate to 4.2. Electrostatic effects due to the variation of the degree of ionization of AA are primarily suggested to influence the kinetics. When the total monomer concentration increases from 0.2 to 0.6 mol/l at constant pH=12, the reactivity ratios of AM and AA decrease from 4.01 to 2.13 and increase from 0.25 to 0.47, respectively. Reduction of electrostatic repulsion between the ionized monomer AA and partially charged growing polymer chain ends due to higher ionic strength at higher total monomer concentration serves as explanation of the effect. The precise data set is the prerequisite for a novel approach to calculate copolymer compositions in case of variable monomer reactivity. (c) 2005 Elsevier Ltd. All rights reserved.