摘要
采用7Li-NMR对正丁基锂(n-BuLi)与不同摩尔比叔丁醇钾(t-BuOK)的混合物在四氢呋喃与环己烷溶液中的体系进行了分析.继而以1,1-二苯基己基锂作为引发剂,分别采用苯酚锂、叔丁醇钠以及t-BuOK作为副反应抑制剂,进行了甲基丙烯酸正丁酯(BMA)和甲基丙烯酸甲酯(MMA)的负离子嵌段共聚合,并用GPC、1H-NMR对聚合物的结构进行了表征.结果发现n-BuLi与t-BuOK会产生Li与K交换的反应,形成不具备引发活性的t-BuOLi,以及以K为反离子的活性种.其对MMA类极性单体嵌段聚合的副反应有着极为有效的抑制作用.过量的t-BuOK,将进一步提高对副反应的抑制作用.在体系中nt-BuOK/nn-BuL≥20后,即便聚合温度升高至40℃,BMA与MMA极性单体嵌段聚合的总产率也可达到100%,且分子量分布仅为1.40,呈单峰分布.实测的Mn与设定的Mn非常接近;采用1H-NMR实测的nMMA/nBMA也与原料十分接近.从而为MMA类极性单体嵌段聚合的工业化奠定了基础.
7Li-NMR was used to characterize the mixed system of n-butyl lithium（ n-Bu Li） and potassium t-butoxide（ t-Bu Ok） with different molar ratios in THF and cyclohexane. The anionic block-copolymerization of butyl methacrylate（ BMA） and methyl methacrylate（ MMA） was initiated by 1,1-diphenyl hexyl lithium and using phenol lithium,sodium t-butoxide and t-Bu Ok as the side reaction inhibitors. GPC and1H-NMR were used to characterize the structure of the block copolymers. It was found that the exchange reaction of Li in n-Bu Li and K in t-Bu OK could be generated,in which the inactive lithium t-butoxide and active species with K as the counterion formed. The new species had admirable impact on inhibiting the side reaction in the anionic polymerization of the polar monomers,such as MMA. The surplus t-Bu OK in the system could further promote the inhibition effect. When the mole ratio of nt-Bu OK/ nn-Bu Liwas not lower than 20,the total yield of the block copolymerization of BMA and MMA could reach up to 100% and the molecular weight distribution was only1. 40 with unimodal distribution even when the copolymerization temperature was up to 40 ℃. Mndetermined by GPC well coincided with the calculated theoretically data. The value of nMMA/ nBMAin copolymer determined by1H-NMR was also well close to that of raw material. The results could lay an industrial foundation for the block copolymerization of polar monomers,such as MMA.
出处
《高分子学报》
SCIE
CAS
CSCD
北大核心
2015年第7期835-844,共10页
Acta Polymerica Sinica
基金
国家自然科学基金(基金号50933002
51373052)
国家高技术研究发展计划(863计划
项目号2012AA040306)资助项目
