氧化硼对苯乙烯原子转移自由基聚合的加速作用

Rate-accelerating of Boric Oxide for Atom Transfer Radical Polymerization of Styrene

以2-溴丙酸乙酯为引发剂,溴化亚铜为催化剂,N,N,N′,N″,N″-五甲基二乙基三胺为配体,以氧化硼为加速剂,进行了苯乙烯原子转移自由基聚合的加速研究.发现氧化硼与引发剂比例为4时,加速效果最为明显,且对分子量的控制效果较好.在85℃时,添加该比例的氧化硼,苯乙烯在6 h的聚合转化率达到78.5%.在65,75及85℃条件下,加入氧化硼时体系的聚合反应动力学为一级反应,苯乙烯聚合速率分别为空白体系的1.82,1.54和1.5倍;聚合物的分子量可控,分子量分布窄,体系呈现明显的活性聚合特征.通过核磁共振谱对聚合物的结构进行了表征,证明氧化硼在整个聚合过程中只起加速作用,并不影响聚合机理和聚苯乙烯的结构.氧化硼价廉,有利于实现原子转移聚合的工业化.

The polymerization of styrene was mediated by copper （ Ⅰ ） bromide/pentramethyltriamine （PMDETA） using ethyl 2-bromopropionate（EBP） as an initiator and boric oxide（BO） as a rate-accelerating additive. BO was found to be effective to accelerate ATRP of styrene, and the conversions were improved to 78.5% during 6 h at 85 ℃. An optimal molar ratio of BO/EBP for the polymerization of styrene was 4： 1. First-order kinetics, increase of Mn with respect to conversion, and the relatively narrow polydispersity demonstrate that the polymerization of styrene in the presence of BO proceeds in a living fashion. The apparent rate constant of polymerization was improved by a factor of 1.82, 1.54 and 1.5 at 65, 75 and 85 ℃ respectively. NMR spectra study indicates that no influence occurred on the structure of polystyrene when BO was added as promoter. BO is likely to solve the slow polymerization rate of ATRP and promote its industrial application.