De-swelling kinetics of swollen copolymer hydrogels (AA/AMPS

AA/DMAEMA and AMPS/DMAEMA) in metallic ion (Ag+

Cu2+

Fe3+ and Pb2+) solutions was investigated with gravimetry.The copolymer hydrogels showed responsive volumetric shrinking behavior in Ag+

Cu2+

Fe3+ and Pb2+ metallic ion solutions

and the extent of de-swelling increased with increasing metallic ion concentration.By using a decaying exponential first-order function

the volume shrinking process of the hydrogels could be well fitted with the correlation coefficient above 0.98.At a fixed concentration of metallic ion

the equilibrium volume shrink ratios (V∞/V0) of AA/AMPS

AA/DMAEMA and AMPS/DMAEMA hydrogels were in the order Fe3+>Pb2+>Cu2+>Ag+

Cu2+>Fe3+>Pb2+>Ag+

and Pb2+>Fe3+>Cu2+>Ag+

respectively

and so did the de-swelling rate constant.In addition

a mechanism

“lone pairs of electrons-unoccupied orbitals” was proposed for the gel volume shrinking process

in which the energy of activation values of AA/AMPS-Fe3+

AA/DMAEMA-Cu2+

and AMPS/DMAEMA-Pb2+ system were 3.081

1.86

and 1.917 kJ·mol-1

respectively.