柔性间隔基对于香豆素取代二乙炔LB膜聚合及手性形成的影响

THE EFFECT OF FLEXIBLE SPACER ON THE PHOTOPOLYMERIZATION AND CHIRALITY FORMATION OF THE COUMARIN-SUBSTITUED DIACETYLENE LB FILMS

设计合成了2种香豆素取代二乙炔单体,7-(10,12-二十三双炔酰氧基)-香豆素(CODA)和7-(10,12-二十三双炔酰氧乙氧基)-香豆素(CO2DA),研究了柔性间隔基对香豆素取代二乙炔单体在气-液界面的组装、单体LB膜的聚合以及聚二乙炔主链螺旋结构形成的影响.利用Langmui-Blodgett(LB)技术,以纯水为亚相,膜压在35 mN/m时沉积制备了香豆素取代二乙炔单体LB膜.尽管CODA是非手性的,但其LB膜均表现出明显的宏观手性信号.这是由于在压缩过程中香豆素基团间强烈的π-π堆积,形成了螺旋排列,显示出超分子手性.而CO2DA LB膜无明显CD信号.经254 nm紫外光辐照,CODA LB膜聚合成蓝相,聚二乙炔主链表现出明显的宏观手性.而CO2DA LB膜聚合后无明显的CD信号.薄膜中香豆素功能基团的不规则排列不利于二乙炔单体的固态聚合以及聚二乙炔主链螺旋结构的形成.

Two kinds of coumarin substituted diacetylene monomers, named as CODA and CO2DA, were designed and synthesized. The effect of the flexible spacer on their interfacial behavior,photo-polymerization of their resulting LB films and the chirality formation of polydiacetylene （PDA） backbone was investigated and discussed in detail. LB films of coumarin substituted diacetylene monomer could be prepared at 35 mN/m on water subphase through LB technique. Although the above CODA monomers were achiral,the CODA LB films exhibited obvious CD signal, which should be ascribed to the overcrowded packing of coumarin units upon compression. As for CO2DA sample, no obvious CD signal could be observed. Strong collective noncovalent interaction （or-or stacking） was believed to be responsible for the formation of the chiral supramolecular assemblies. When exposed to UV irradiation with 254 nm light, LB films derived from CODA could be polymerized into blue phase and yield obvious chirality for PDA chain although CODA monomer was achiral. However,no obvious CD signal could be observed for the films derived from CO2DA PDA backbone. It was demonstrated that the intermolecular irregular arrangement of the coumarin groups in the LB films was not favorable for the topo-polymerization and chirality formation of PDA backbone.