Assessment of TEMPO as a Thermally Activatable Base Generator and Its Use in Initiation of Thermally-Triggered Thiol-Michael Addition Polymerizations.
Assessment of TEMPO as a Thermally Activatable Base Generator and Its Use in Initiation of Thermally-Triggered Thiol-Michael Addition Polymerizations.
复制标题
DOI：
10.1039/c8py00662h
复制
发表时间：
2018-08
影响因子：
4.6
通讯作者：
Xinpeng Zhang;Sijia Huang;Maciej Podgórski;Xun Han;M. Claudino;C. Bowman
中科院分区：
文献类型：
--
作者：
Xinpeng Zhang;Sijia Huang;Maciej Podgórski;Xun Han;M. Claudino;C. Bowman
我们提出了一种基于温度依赖性硫醇-TEMPO 氧化还原反应引发的热引发硫醇-迈克尔反应。在硫醇存在下，2,2,6,6-四甲基哌啶-1-氧基（TEMPO，pKa = 5.5）在温度依赖性过程中被还原产生更强的碱，即四甲基哌啶（TMP，pKa = 11.4）。这种氧化还原过程在升高的温度下急剧加速，这允许热控制引发碱催化的硫醇-迈克尔加成反应和潜在的其他碱催化反应系统。通过系统改变反应条件（包括溶剂、温度、硫醇类型和浓度），研究了影响 TEMPO 还原产生碱的几个关键因素。这种氧化还原反应的高度依赖于温度的属性在各种基于硫醇-TEMPO的系统中得到了证明，并进一步用于在不同加热条件下热控制硫醇-迈克尔聚合。 TEMPO-硫醇相互作用与高温相结合，在高温下形成强胺类 TMP，能够快速形成基于硫醇-迈克尔的聚合物网络和大规模材料制备，而不会产生通常与高放热聚合相关的任何有害影响。这种开发热引发硫醇-迈克尔聚合物网络的新方法是独特的、通用的和稳健的，在高反应性树脂的轻松处理、散装材料制备、pH敏感材料构建和复合材料/大颗粒合成等应用中具有广泛的实用性。
We present a thermally initiated thiol-Michael reaction based on initiation via the temperature-dependent thiol-TEMPO oxidation-reduction reaction. In the presence of a thiol, 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO, pK a = 5.5) is reduced to produce a much stronger base, i.e., tetramethylpiperidine (TMP, pK a = 11.4) in a temperature dependent process. This oxidation-reduction process is dramatically accelerated at elevated temperature, which allows for thermally controlled initiation of the base-catalyzed thiol-Michael addition reaction and potentially other base-catalyzed reaction systems. Several critical factors that affect base generation from TEMPO reduction were investigated via systematic variation of reaction conditions including the solvent, temperature, and the thiol type and concentration. The highly temperature-dependent attributes of this redox reaction were demonstrated in various thiol-TEMPO based systems and were further utilized to thermally control thiol-Michael polymerizations under different heating conditions. The strong amine species, TMP, formed at elevated temperatures from the TEMPO-thiol interaction combined with high temperature, enables rapid formation of thiol-Michael-based polymer networks and large scale material preparation without any detrimental effects often associated with highly exothermic polymerizations. This novel approach to develop thermally-initiated thiol-Michael polymer networks is unique, versatile and robust, resulting in wide utility in applications such as facile handling of highly reactive resins, bulk material preparation, pH sensitive materials construction, and composite/macro-particle synthesis.