A Pair of Homochiral Polyamides with Opposite Optical Activity
Optically active polyamides have received considerable attention in recent years1-2 while few reports to characterize the chirality of the polyamides in solid state.Furthermore, the developments of the polymer with desired chiraliy through intruducing chiral atoms into the backbone are very limited,especially aliphatic linear polymers.The linear aliphatic polyamides of PA11LAT and PA11DAT were prepared by using L-2,3-di-O-acetyl-tartaric acid(L-ATA), D-2,3-di-O-acetyl-tartaric acid(D-ATA) and 1,11-undecanediamine as building blocks via interfacial polycondensation strategy (Scheme 1).The number-average molecular weight (Mn) of PA11LAT and PA11DAT is 50,100 and 51,300 g/mol respectively and the polydispersity indexes of them are under 3.4.The specific optical rotation of PA11LAT is-13.0° in DMSO (c=1.0g/100mL) at 20℃ and PA11DAT is +12.8°.Both of PA11LAT and PA11DAT exhibit intense Cotton effect and display negative and positive mirror CD spectra images in solution and even in solid state (Figure 1).Interestingly, the CD spectra of the polyamides in solid state vary clearly from that in solution state.Figure 1 shows that the CD signals of the polyamides in solid film state display clear splits observed with crossovers at 215nm and 197nm while a weak split with a crossover at 199nm was observed in solution.Furthermore, the negative ellipticities in film state are much more intense than that in ethanol when the similar UV absorption was measured.In fact, the split of the CD signal is related to the interaction between the adjacent chromophores3.In our case, the chiral pools of ATA segments induced the neighbor amide group to a chiral chromophore4.The weak split in dilute ethanol is due to the less intermolecular aggregation and less ordered conformation.And the enlarged optical activity in solid state results from the induced chiral amide groups which display highly enantiopure for the same twisted direct of the amide groups in the backbone.The results indicate that PA11LAT and PA11DAT adopt oppositely chiral conformation, especially, in solid state.
Lingli Zhang Zhe Cui Peng Fu Minying Lin Xinchang Pang Qingxiang Zhao
School of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450001, China;Departmen School of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450001, China
国际会议
9th International Symposium on High-Tech Polymer Materials(第9届国际高技术高分子材料学术会议)(HTPM-9)
郑州
英文
115-116
2016-07-11（万方平台首次上网日期，不代表论文的发表时间）