Mechanistic Kinetic Modeling of Thiol-Michael Addition Photopolymerizations via Photocaged "Superbase" Generators: An Analytical Approach.
Mechanistic Kinetic Modeling of Thiol-Michael Addition Photopolymerizations via Photocaged "Superbase" Generators: An Analytical Approach.
复制标题
DOI：
10.1021/acs.macromol.6b01605
复制
发表时间：
2016-11-08
期刊：
影响因子：
5.5
通讯作者：
Bowman CN
中科院分区：
文献类型：
--
作者：
Claudino M;Zhang X;Alim MD;Podgórski M;Bowman CN
提出了涉及光碱发生器的碱介导的硫醇-迈克尔光聚合动力学的动力学机制和相应的数学框架。在这里，模型动力学预测与2-（2-硝基苯基）丙基羰基-1,1,3,3-四甲基胍（nppc - tmg）组成的代表性实验体系非常吻合，该体系作为光碱产生剂用于引发巯基-乙烯基砜的迈克尔加成反应和聚合。从基本机理方案推导出的建模方程表明，总体聚合速率遵循碱和反应物浓度下的准一级动力学过程，由增殖与链转移动力学参数（kp/kCT）之比控制，该参数由限速步骤决定，并控制达到凝胶化所需的时间。当kp/kCT比达到临界值时，凝胶化发生得更早，从此凝胶时间几乎与kp/kCT无关。理论方法允许确定诱导时间对反应动力学的影响，这是由于质子污染物的存在引起的光生碱的初始酸碱中和。对于需要高固化速率的反应系统来说，这种抑制动力学可能是一个挑战，但对于那些需要保持动力学休眠直到被激活的化学系统来说，这种抑制动力学是相关的，尽管最终的代价是降低聚合速率。这种活性聚合的纯阶梯生长特性和所展示的动力学为扩展暗固化反应和均匀材料性能提供了独特的潜力。一般动力学模型适用于光碱引发剂，其中光解遵循单分子裂解过程，释放强碱催化剂，不产生中间自由基。
A kinetic mechanism and the accompanying mathematical framework are presented for base-mediated thiol–Michael photopolymerization kinetics involving a photobase generator. Here, model kinetic predictions demonstrate excellent agreement with a representative experimental system composed of 2-(2-nitrophenyl)propyloxycarbonyl-1,1,3,3-tetramethylguanidine (NPPOC-TMG) as a photobase generator that is used to initiate thiol–vinyl sulfone Michael addition reactions and polymerizations. Modeling equations derived from a basic mechanistic scheme indicate overall polymerization rates that follow a pseudo-first-order kinetic process in the base and coreactant concentrations, controlled by the ratio of the propagation to chain-transfer kinetic parameters (kp/kCT) which is dictated by the rate-limiting step and controls the time necessary to reach gelation. Gelation occurs earlier as the kp/kCT ratio reaches a critical value, wherefrom gel times become nearly independent of kp/kCT. The theoretical approach allowed determining the effect of induction time on the reaction kinetics due to initial acid–base neutralization for the photogenerated base caused by the presence of protic contaminants. Such inhibition kinetics may be challenging for reaction systems that require high curing rates but are relevant for chemical systems that need to remain kinetically dormant until activated although at the ultimate cost of lower polymerization rates. The pure step-growth character of this living polymerization and the exhibited kinetics provide unique potential for extended dark-cure reactions and uniform material properties. The general kinetic model is applicable to photobase initiators where photolysis follows a unimolecular cleavage process releasing a strong base catalyst without cogeneration of intermediate radical species.
登录
查看更多内容
影响因子：
5.5
作者：
Adzima, Brian J.;Aguirre, H. Alan;Kloxin, Christopher J.;Scott, Timothy F.;Bowman, Christopher N.
通讯作者：
Bowman, Christopher N.
影响因子：
--
作者：
Dietliker, K;Jung, TJ;Rist, G
通讯作者：
Rist, G
影响因子：
6.6
作者：
Dietliker, K.;Huesler, R.;Oka, H.
通讯作者：
Oka, H.
影响因子：
3.9
作者：
KUTAL, C;WILLSON, CG
通讯作者：
WILLSON, CG
影响因子：
--
作者：
Khire, Vaibhav S.;Benoit, Danielle S. W.;Bowman, Christopher N.
通讯作者：
Bowman, Christopher N.