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

Abstract

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.