Influence of crosslinking degree of soluble β-cyclodextrin polymer on the fluorescence of 3-hydroxy-2-naphthoic acid and its ER properties

Six soluble β-cyclodextrin polymers were prepared by the modified method of Renard. Using 3-hydroxy-2-naphthoic acid as a fluorescence probe, the relationship of the crosslinking degree (CLD) of the polymer with the stability of supramolecular complex and the fluorescence properties was investigated, respectively. The results showed that the formation constant increased with the enhancement of CLD as well as the relative fluorescence intensity. And also, a straight-line relationship was observed between the increment of the relative fluorescence intensity and CLD, indicating that CLD had strong influence on the fluorescence properties. The polymers and their complex particles in silicone oil were investigated under DC electric fields, respectively. It was found that these ER fluids exhibited good ER effects. The yield stress increased with the increase of CLD for the pure β-cyclodextrin polymers. The supramolecular complex ER fluids displayed a higher ER effect than the polymer, but the yield stress increased firstly and then decreased with the increase of CLD. This was well confirmed by the measurement of the dielectric properties of these ER fluids.