作者:Yu Jian、Yong He、Yukun Sun、Haitao Yang、Wantai Yang、Jun Nie
DOI:10.1039/c3tc30360h
日期:——
Thiolâepoxy/thiolâacrylate hybrid networks with systematic variations (100/0, 75/25, 50/50, 25/75, 0/100, w/w) were prepared by free-radical photoinitiator (ITX) and photo-base generator (TBD·HBPh4) induced photopolymerization. The enhanced spectral sensitivity of TBD·HBPh4 at long wavelengths (320â500 nm) with aid of ITX was capable of in situ generation of a strong base (TBD) to achieve the relatively fast and essentially quantitative thiolâepoxy click reaction. The ITX/TBD·HBPh4 photoinitiating system, which generated both the free radicals and the strong base upon UV exposure, could induce thiolâepoxy/thiolâacrylate hybrid polymerizations. The kinetics investigated with real-time IR indicated that the thiolâacrylate reactions were faster and more efficient than the thiolâepoxy reactions (>95% conversion in a matter of seconds and minutes, respectively), and the thiol conversion increased with an increase in the epoxy concentration. The incorporation of the thiolâepoxy reaction offered several advantages: the polymerization shrinkage decreased with the increase in the thiolâepoxy content due to the low shrinkage factor for the thiolâepoxy system (every mole of epoxy group polymerized produces 6.3 mL of shrinkage). The glass transition temperature of the thiolâepoxy/thiolâacrylate hybrid networks progressively increased as a function of the thiolâepoxy content, also resulting in enhanced mechanical and physical properties. This work will be helpful to make optical and electronic devices with low shrinkage and stress, decreased residual monomers, and improved mechanical properties.
通过自由基光引发剂(ITX)和光碱生成剂(TBD·HBPh4)诱导的光聚合,制备了具有系统变化(100/0,75/25,50/50,25/75,0/100,w/w)的硫醇-环氧/硫醇-丙烯酸混合网络。在较长波长(320-500 nm)下,TBD·HBPh4的光谱敏感性提高,配合ITX,能够原位生成强碱(TBD),从而实现相对快速且基本定量的硫醇-环氧点击反应。ITX/TBD·HBPh4光引发系统在UV照射下能够同时生成自由基和强碱,从而诱导硫醇-环氧/硫醇-丙烯酸的聚合。实时红外线研究的动力学表明,硫醇-丙烯酸反应比硫醇-环氧反应更快且效率更高(分别在几秒到几分钟内转换率超过95%),且随着环氧浓度的增加,硫醇的转化率也随之提高。引入硫醇-环氧反应带来了几个优点:由于硫醇-环氧体系的收缩因子较低(每摩尔聚合的环氧基团产生6.3 mL的收缩),聚合收缩随着硫醇-环氧含量的增加而减少。硫醇-环氧/硫醇-丙烯酸混合网络的玻璃转变温度随着硫醇-环氧含量的增加而逐渐升高,同时增强了机械和物理性能。这项工作将有助于制造低收缩和应力、减少残留单体、以及改善机械性能的光学和电子设备。