ABSTRACT
Poly(rotaxane)s were synthesised by capping with 2,4-dinitrofluorobenzene the corresponding pseudopoly(rotaxane)s consisting of α-cyclodextrin (α-CD) threaded onto two end-aminated poly(ethyleneglycol) (PEG, Mw 2000 and 3500), with the aim to be used for nanoscale building blocks of facilitated transport membranes. The number of α-CD threaded in poly(rotaxane)s obtained proved to remain constant whatever the initial molar ratio ethylene oxide units: α-CD under our conditions of capping. The resulting polymers had a similar polymolecularity index as the parent PEGs. Thermal properties and light scattering analysis in DMSO showed that inclusion complexation in α-CD stiffens the PEG chains rendering them as semi rod-like macromolecules. A strong tendency to auto-association was observed which is attributed to hydrophobic interactions between the blocking end-groups. Films were prepared by crosslinking poly(vinylalcohol) (PVA) and poly(rotaxane)s with hexamethylenediisocyanate. After removing the end-stoppers under mild alkaline conditions and releasing PEG from the CD cavities, membranes were studied in a water/methanol pertraction system. Large increases in the permeation rate of toluene were observed by replacing α-CD with an α-CD molecular assembly. This effect was interpreted by the cooperativity of CD cavities in the toluene permeation across channels formed inside the membrane.
