The assembly of rotaxane-like dye/cyclodextrin/surface complexes on aluminium trihydroxide or goethite

Abstract

Simple azo-dyes carrying phosphonic acid and arsonic acid substituents such as 4-(4′-hydroxyphenyl azo)phenylphosphonic acid (5) and 4-(4′-hydroxyphenylazo)phenylarsonic acid (6) bind more strongly to high surface area oxides such as aluminium trihydroxide and goethite than their carboxylic and sulfonic acid analogues and the phosphonate-functionalized dyes have been shown to have greater humidity fastness when printed onto commercial alumina-coated papers. Adsorption isotherm measurements provide evidence for the formation of ternary dye/cyclodextrin/surface complexes. Dyes which form such ternary complexes show higher light fastness when printed onto alumina coated papers in an ink formulation containing α-cyclodextrin.