二苯甲酮/一缩二乙二醇光引发丙烯酸丁酯聚合机理

Photopolymerization mechanism of butyl acrylate initiated by benzophenone and diethylene glycol

以二苯甲酮(BP)与一缩二乙二醇(DEG)为光引发剂引发丙烯酸丁酯(BA)聚合,利用核磁共振波谱1H NMR、13C NMR和液相色谱-串联质谱(Q-TOF)对产品结构进行分析。13C NMR结果表明,聚合物链上存在叔碳及季碳原子。Q-TOF分析结果表明,聚合物主要由DEG自由基引发,聚合度主要为6、7的链转移终止的低聚物构成,此外,链自由基可以经歧化及偶合终止。快速链转移反应及叔碳、季碳原子的存在表明聚合物的形成过程可能经历了自由基在DEG分子链上"游走"的机理。自由基在DEG链上的转移及链增长的相互竞争,导致形成多取代的聚合产物。聚合反应存在严重的氧阻聚效应,链自由基与氧气快速反应形成过氧化自由基,经终止反应及分解反应形成多1~3个氧原子的低聚物。

The structure of the products of butyl acrylate photopolymerization initiated by benzophenone and diethylene glycol were characterized by 1H NMR、13C NMR and Q-TOF.The 13C NMR results indicate that there are tertiary and quaternary carbons in the polymer chain.The analysis results of Q-TOF show that the polymers are mainly composed of oligomers initiated by DEG radicals and terminated by chain transfer with polymerization degree of around 6 and 7.In addition,the chain radicals can also be terminated by disproportionation and coupling reaction.The fast chain transfer termination reaction and the presence of tertiary and quaternary carbon atoms indicate that the formation of the polymers may undergo the mechanism of free radicals migration along the DEG molecular chain.The competition between the chain transfer and the chain growth leads to the formation of multi substituted polymer products.The oxygen inhibition effect is significant in the polymerization.The chain radicals react with oxygen rapidly to form peroxide radicals,which undergo the termination and decomposition reactions to form oligomers with one to three oxygen atoms.