pH-Switchable supramolecular sliding'' gels based on polyrotaxanes of polyethyleneimine-block-poly(ethylene oxide)-block-polyethyleneimine block copolymer and alpha-cyclodextrin: synthesis and swelling behaviour

A new type of pH-switchable supramolecular sliding gel has been synthesized, based on polyrotaxanes of polyethyleneimine-block-poly(ethylene oxide)-block-polyethyleneimine block copolymer and alpha-cyclodextrin. The three dimensional supramolecular network was obtained by an inter-molecular crosslinking reaction between CDs belonging to two different polyrotaxanes via 1,1'-carbonyldiimidazole. Higher gel equilibrium swelling has been observed in acidic medium than in basic medium. This behaviour is explained by the ionization of EI units leading to electrostatic repulsion of the PEI blocks.