Kilambi Harini, Reddy Sirish K, Schneidewind Lauren, Stansbury Jeffrey W, Bowman Christopher N
Department of Chemical and Biological Engineering University of Colorado, Boulder, CO 80309-0424.
Polymer (Guildf). 2007 Mar 23;48(7):2014-2021. doi: 10.1016/j.polymer.2007.02.006.
The copolymerization behavior and the dark polymerization kinetics of highly reactive novel acrylic monomers were compared to traditional acrylate monomers. Copolymerization of thiol functionalities with novel acrylic monomers was characterized, and it was observed that the inclusion of secondary functionalities such as carbamates, carbonates, and cyclic carbonates, in acrylic monomers significantly alters the relative reactivity of the novel acrylates with thiols. While traditional aliphatic acrylates exhibited propagation to chain transfer ratios ranging between 0.8 (± 0.1)-1.5(± 0.2), the novel acrylates characterized by secondary functionalities exhibited much higher propagation to chain transfer ratios ranging from 2.8(± 0.2)-4(± 0.2). In the dark polymerization studies, the kinetics of the novel acrylates were evaluated following cessation of the UV light. The novel acrylates exhibited extensive polymerization in the dark compared to most traditional acrylates and diacrylates. For instance, cyclic carbonate acrylate was observed to attain 35 % additional conversion in the dark when the UV light was extinguished at 35 % conversion, whereas traditional acrylates such as hexyl acrylate attained only 3 % additional conversion when the UV light was extinguished at 35 %, and a diacrylate such as HDDA attained 15 % additional conversion when the UV light was extinguished at 40 % conversion. Also, through choice of appropriate monomers, the dark polymerization studies were performed such that the polymerization rate was approximately the same at the point the light was extinguished for all these monomers. The copolymerization and dark polymerization studies support the hypothesis that the nature of the propagating species in the novel acrylates is altered as compared to traditional acrylic monomers and polymerizations.
将高反应性新型丙烯酸单体的共聚行为和暗聚合动力学与传统丙烯酸酯单体进行了比较。对硫醇官能团与新型丙烯酸单体的共聚进行了表征，观察到丙烯酸单体中包含氨基甲酸酯、碳酸酯和环状碳酸酯等二级官能团会显著改变新型丙烯酸酯与硫醇的相对反应性。传统脂肪族丙烯酸酯的增长与链转移比在0.8（±0.1）-1.5（±0.2）之间，而具有二级官能团的新型丙烯酸酯的增长与链转移比则高得多，在2.8（±0.2）-4（±0.2）之间。在暗聚合研究中，在紫外光停止照射后评估了新型丙烯酸酯的动力学。与大多数传统丙烯酸酯和二丙烯酸酯相比，新型丙烯酸酯在黑暗中表现出广泛的聚合。例如，当在35%转化率时熄灭紫外光，观察到环状碳酸酯丙烯酸酯在黑暗中额外转化率达到35%，而传统丙烯酸酯如丙烯酸己酯在35%转化率时熄灭紫外光时仅额外转化率达到3%，二丙烯酸酯如HDDA在40%转化率时熄灭紫外光时额外转化率达到15%。此外，通过选择合适的单体进行暗聚合研究，使得在所有这些单体的光照熄灭点聚合速率大致相同。共聚和暗聚合研究支持了这样的假设，即与传统丙烯酸单体和聚合相比，新型丙烯酸酯中增长物种的性质发生了改变。
