Electric-sensitive Properties and Mechanism of P(AMPS-co-BMA) Hydrogels

Electric-sensitive hydrogels[P(AMPS-co-BMA) were prepared by free-radical polymerization with 2-acrylamido-2-methyl propyl sulfonic acid(AMPS) as ionic monomer and(BMA) as non-ionic monomer,using N,N′-methylene bisacrylamide as crosslinking agent,azobisisobutyronitrile as initiator and N,N-dimethyl formamide as solvent,respectively.The swelling properties of hydrogels in deionized water and in NaCl solution were studied in detail.The results show that the swelling rate of the hydrogels increases with the increasing content of AMPS,and the equilibrium swelling ratio of the hydrogels ranges from 236.4 to 298.5.In addition both the deswelling speed and the deswelling extent of the hydrogels decrease with the increasing concentration of polyion in inside of the hydrogels.Moreover,the electrical sensitivity of the hydrogels was studied.The swelling properties of the hydrogels in NaCl solution with an applied voltage were related to the ionic concentration difference between interior hydrogels and exterior NaCl solution.When the concentration of polyion in interior hydrogels is higher than the concentration of NaCl in solution,the hydrogels swells;contrarily,the hydrogels deswells.The bending direction of the hydrogels was also related to the ionic concentration difference between interior hydrogels and exterior NaCl solution.When the concentration of polyion in interior hydrogels is higher than the concentration of NaCl in solution,the hydrogels bend toward cathode;contrarily,the hydrogels bend toward anode.Further investigation shows that the bending speed of the hydrogels also depends on the temperature significantly.