Large macroscopic size changes in chemomechanical polymers with binding sites for metal ions

A flexible polymer based on the reaction of polyacrylate with diethylenetriamine shows, under the control of transition metal ions in the external aqueous medium, size expansion or contraction by up to 200% (corresponding to 400% volume change); the macroscopic movements, which are fully reversible, show a distinct maximum at a certain metal salt concentration, and vary significantly with the addition of second effector compounds such as sodium chloride or benzoate.