摘要
研究了1,8-二氮杂二环十一碳-7-烯(DBU)引发的N-取代甘氨酸-N-硫代羧酸酐(NNTA)开环聚合.聚合通过两性离子开环聚合机理进行,表现出良好的可控性,聚合产率高(>86%),分子量可控(900~7500 g/mol),分子量分布较窄(1.13~1.25).通过^(1)H-NMR、^(13)C-NMR谱图、MALDI-ToF质谱和红外光谱等表征手段,证明所得聚合产物具有环形结构,且聚合物链上带有DBU残基和硫代氨基甲酸酯基团.与苄胺(BA)引发所得的线形聚类肽相比,DBU引发所得的聚类肽具有更小的流体力学体积,进一步证明了其环形结构.扩链反应表明,加入新单体后聚合反应仍可以继续进行,产物分子量显著增加,表明了DBU引发的NNTA聚合具有活性特征.DBU引发的NNTA两性离子开环聚合是一种简便、高效的环形聚类肽合成方法.
The ring-opening polymerizations of N-substituted glycine N-thiocarboxyanhydrides(NNTAs)initiated by 1,8-diazabicycloundec-7-ene(DBU)were investigated.Homo-and co-polymerizations of N-ethylglycine N-thiocarboxyanhydride(NEG-NTA)and N-butylglycine N-thiocarboxyanhydride(NBG-NTA)initiated by DBU were carried out in THF at 60℃,which produced corresponding poly(N-ethylglycine)(PNEG),poly(N-butylglycine)(PNBG)and poly(N-ethylglycine-co-N-butylglycine)(P(NEG-co-NBG))with high yield(>86%)and narrow dispersities(1.13-1.25).By adjusting monomer to initiator feed molar ratios ranging from 10 to 100,the molecular weights of PNEGs could be tuned from 900 g/mol to 7500 g/mol,which showed the good controllability of the polymerizations.1H-NMR and MALDI-ToF mass analyses revealed the structures of cyclic polypeptoids bearing one DBU moiety and one thiocarbamate group.The DBU moiety would be eliminated by potassium trifluoroacetate during the MALDI-ToF analysis and DBU-free cyclic polypeptoids were formed.The existence of thiocarbamate group was further proven by 13C-NMR and FTIR analyses.To further confirm the cyclic structures of the products obtained by using DBU initiator,linear polypeptoids were synthesized as comparisons by benzylamine(BA)-initiated NNTA polymerizations.With the same degree of polymerizations(DPs),polypeptoids obtained by DBU initiator had lower hydrodynamic volumes,which indicated their cyclic structures.The living characteristics of DBU-initiated NNTA polymerizations were finally supported by the chain extension reaction.The polymer chain could continue propagating after the addition of another batch of monomers,and the molecular weight of the product increased significantly while the dispersity kept narrow(Đ=1.23).DBU-initiated NNTA polymerizations went through zwitterionic ring-opening polymerization mechanism.Attack of DBU on NNTA would generate a zwitterionic propagating intermediate,in which DBU cation and thiocarbamate anion interacted strongly with each another by electrostatic interaction.The chain propagation caused by NNTA monomer addition at the thiocarbamate end of zwitterionic propagating intermediate.And then,end-to-end macrocyclization between DBU cation and thiocarbamate anion formed cyclic polypeptoids.Since NNTAs are more stable monomers compared to NNCAs,and DBU is an accessible initiator,DBU-initiated NNTA zwitterionic ring-opening polymerization is a simple and facile method for the synthesis of cyclic polypeptoids.
作者
胡祖佳
颜舒婷
戚家乐
陶鑫峰
林绍梁
Zu-jia Hu;Shu-ting Yan;Jia-le Qi;Xin-feng Tao;Shao-liang Lin(Shanghai Key Laboratory of Advanced Polymeric Materials,School of Materials Science and Engineering,East China University of Science and Technology,Shanghai 200237)
出处
《高分子学报》
SCIE
CAS
CSCD
北大核心
2021年第7期708-716,I0002,共10页
Acta Polymerica Sinica
基金
国家自然科学基金(基金号21901073,52073092)
上海市自然科学基金(基金号19ZR1412100)
上海市晨光计划(项目号18CG32)资助.
关键词
聚类肽
两性离子开环聚合
环形聚合物
N-硫代羧酸酐
有机碱
Polypeptoids
Zwitterionic ring-opening polymerization
Cyclic polymers
N-Thiocarboxyanhydrides
Organic bases
作者简介
通讯联系人:陶鑫峰,E-mail:taoxinfeng@ecust.edu.cn;通讯联系人:林绍梁,E-mail:slin@ecust.edu.cn。
