The crystalline cyclic oligosaccharide γ-cyclodextrin (γCD) is a natural, non-toxic and biodegradable precursor that can be used to prepare innovative polymers. A set of cross-linked γCDs was synthesised from the cross-linking reaction of crystalline γCD with non-toxic PEGDGE in aqueous alkaline solution. All γCPCD cross-linked samples were soluble in water and various organic solvents and exhibited amorphous material properties with Tg values as low as –23 °C. Furthermore, the cross-linked product (γCPCD) was modified by i) curing reaction using additional PEGDGE cross-linker to form an insoluble polymer (Cur-γCPCD) and ii) nitration reaction to give nitrated derivative (γNCPCD) soluble in organic solvents. The cured polymer displayed excellent swelling properties in various solvents (up to 200% in distilled water) and an even lower Tg of –37 °C while the nitrated derivative showed good thermal stability up to 190 °C and Tg at +19 oC.
The study highlighted that γCPCD in its various forms could be developed as a polymeric material in food and pharmaceutical formulations, with the swelling properties of Cur-γCPCD making it particularly interesting as a controlled drug delivery system and the nitrated γNCPCD as active pharmaceutical ingredient. The ability of these systems to solubilise and stabilise a variety of molecules is under investigation foreseeing a synergy of γCD toroid and network morphology. The new polymers are promising materials for the complexation and removal of contaminants from the environment.
E. Dossi, M. Bolton, G. Kister, A. Afsar, Cross-linking of γ-Cyclodextrin Using Non-toxic Polyethylene Glycol Spacer Units, ChemistrySelect 2021, 6, 7727–7731, doi.org/10.1002/slct.202101963