聚紫精-脂肪酸盐表面活性剂复合物的组装合成及相行为研究

通过Menshutkin反应合成聚(对亚二甲苯基-4,4'-联吡啶二溴)(PXV)半刚性链聚紫精,采用等量混合法将聚紫精与系列不同碳链长度的阴离子表面活性剂脂肪酸钠Cn-1COONa(n=10,12,14,16,18)组装制备聚电解质-表面活性剂(PXV-Cn)复合物,运用DSC,TGA,XRD,FTIR等表征手段初步考察复合物的超分子结构及相行为.基于FTIR谱学分析特征、小角与广角变温XRD数据以及DSC热分析焓变的定量计算结果,表明半刚性主链聚紫精和脂肪酸盐极性头基组成的极性层与侧链烷烃非极性层交替排列形成层状超分子结构,其中烷烃链靠近极性端约8个亚甲基处于无定型态,其余碳链则形成结晶相.最短的PXV-C10形成少量规整度较低的三斜晶βT,n≥16以上的长碳链复合物则以六方相αH为主,其它中等长度侧链脂肪酸盐复合物则为多种结晶形式共存.随着碳链长度n的增加,侧链结晶熔点Tm升高,n≥16的长碳链复合物表现出随温度变化的可逆结晶相态变化.且这类聚紫精-表面活性剂复合物表现出高于200℃的热稳定性.

SELF-ASSEMBLY SYNTHESES AND MESOMORPHIC STRUCTURES INVESTIGATION OF POLYVIOLOGEN-ALIPHATATE SURFACTANT COMPLEXES

A kind of semi-rigid main-chain polyelectrolyte,poly(p-xylylene-4,4′-bipyridinium dibromide)(PXV) was synthesized by Menshutkin reaction,then a series of novel polyelectrolyte-surfactant(PXV-Cn) complexes were produced by electrostatic self-assembly through stoichiometric mixing of PXV with various anionic surfactants of sodium aliphatate(Cn-1COONa,n= 10,12,14,16,18).The supramolecular structure and mesomorphic phase behavior of thus assembled PXV-Cn complexes were preliminarily investigated by DSC,TGA,XRD,and FTIR.Based on the FTIR spectroscopic evidence,variant temperature XRD data and thermal analysis enthalpic quantitative calculation,a lamellar mesomorphic supramolecular structure was suggested with the polar head groups of the aliphatate surfactants and the polyelectrolyte PXV composing the polar layer while the alkyl side chains constructing the apolar layer.Furthermore,it was found that the alkyl side chains in the PXV-Cn complexes formed an end-to-end bilayer structure with about eight methylene groups near the head group in the amorphous state and others in the crystalline structure.Among them PXV-C10 with the shortest surfactant alkyl group only possessed the least ordered triclinic crystal phase βT,while the most ordered hexagonal crystal αH dominated in those complexes with n≥16,and variant crystalline polymorphs coexisted in those with intermediate n=12 or 14.The melting points Tm increased with increasing n,the complexes with longer alkyl chains of n≥16 exhibited almost reversible crystalline phase changes in the heating-cooling thermal cycles.This kind of polyviologen-surfactant complexes also showed better thermal stability without any remarkable weight loss below 200℃.The employment of the polyelectrolyte-polyviologen possessing redox properties made it a promising functional polyelectrolyte-surfactant complex for electrochromism and photochromism applications.