Kinetics of bulk photo-initiated copper(i)-catalyzed azide-alkyne cycloaddition (CuAAC) polymerizations.
Kinetics of bulk photo-initiated copper(i)-catalyzed azide-alkyne cycloaddition (CuAAC) polymerizations.
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DOI：
10.1039/c5py01655j
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发表时间：
2016-01-21
影响因子：
4.6
通讯作者：
Bowman CN
中科院分区：
文献类型：
--
作者：
Song HB;Baranek A;Bowman CN
基于铜(i)催化叠氮化物-炔环加成（CuAAC）反应的光引发聚合可以实现时空控制和形成机械坚固、高度玻璃化的光聚合物。在此，我们研究了影响光- cuaac聚合动力学的几个关键因素，通过系统变化的反应条件，如单体的理化性质；铜盐和光引发剂的种类和浓度；光强度;曝光时间和溶剂含量。采用实时傅立叶变换红外光谱（FTIR）原位监测聚合动力学。合成并聚合了六种不同的二官能叠氮化物单体和四种不同的三官能炔单体，它们含有脂肪族、芳香族、醚和/或氨基甲酸酯取代基。在相同的辐照条件下，用醚基取代氨基甲酸酯结构使单体的转化率从65%提高到90%。氨基甲酸酯的结果是更硬的单体和更高的粘度混合物，表明链迁移率和扩散是决定CuAAC网络形成动力学的关键因素。通过改变光还原步骤的各个方面来操纵光引发率；最终，铜催化剂和光引发剂的每个官能团的负载大于3mol %时，对浓度的速率依赖性很小或没有，而负载低于3mol %时，对浓度的速率依赖性为一级。此外，一个由樟醌组成的光引发体系在400-500 nm的75 mW cm−2光照射1分钟后，在黑暗中转化率达到60%，突出了铜(i)的催化寿命和步长聚合的性质相结合所实现的CuAAC光聚合的独特特征。
Photoinitiation of polymerizations based on the copper(i)-catalyzed azide–alkyne cycloaddition (CuAAC) reaction enables spatio-temporal control and the formation of mechanically robust, highly glassy photopolymers. Here, we investigated several critical factors influencing photo-CuAAC polymerization kinetics via systematic variation of reaction conditions such as the physicochemical nature of the monomers; the copper salt and photoinitiator types and concentrations; light intensity; exposure time and solvent content. Real time Fourier transform infrared spectroscopy (FTIR) was used to monitor the polymerization kinetics in situ. Six different di-functional azide monomers and four different tri-functional alkyne monomers containing either aliphatic, aromatic, ether and/or carbamate substituents were synthesized and polymerized. Replacing carbamate structures with ether moieties in the monomers enabled an increase in conversion from 65% to 90% under similar irradiation conditions. The carbamate results in stiffer monomers and higher viscosity mixtures indicating that chain mobility and diffusion are key factors that determine the CuAAC network formation kinetics. Photoinitiation rates were manipulated by altering various aspects of the photo-reduction step; ultimately, a loading above 3 mol% per functional group for both the copper catalyst and the photoinitiator showed little or no rate dependence on concentration while a loading below 3 mol% exhibited 1st order rate dependence. Furthermore, a photoinitiating system consisting of camphorquinone resulted in 60% conversion in the dark after only 1 minute of 75 mW cm−2 light exposure at 400–500 nm, highlighting a unique characteristic of the CuAAC photopolymerization enabled by the combination of the copper(i)’s catalytic lifetime and the nature of the step-growth polymerization.