Semi-interpenetrating polymer network (s-IPN) hydrogels composed of poly(vinyl alcohol) (PVA), and poly(2-acrylamido-2-methylpropylsulfonic acid) (PAMPS) were prepared by radical polymerization using PEG6000 as pore-forming agent during the reaction process. Fourier-transform infrared (FT-IR) spectroscopy was used to confirm the chemical structure of the s-IPN hydrogels, in which the peak of C—O stretching flows to low wave numbers. This was attributed to the formation of strong hydrogen bond between PVA and PAMPS. The crystallinity properties of s-IPN hydrogels were investigated by X-ray diffraction spectrography (XRD). The results show that the s-IPN structure of the hydrogels becomes inhomogeneous when the dosage of PVA is high because of the crystallization of PVA. SEM macrographs revealed that a macroporous structure was formed with the addition of pore-forming agent PEG6000. The swelling properties of the s-IPN hydrogels were studied, showing that the equilibrium swelling ratio of the s-IPN hydrogels ranges from 116 to 320. The swelling speed of the s-IPN hydrogels increased significantly with the addition of PEG6000, and the hydrogel could reach its equilibrium swelling ratio within 240 min. Stress strength of the s-IPN hydrogels was also studied, showing that when the content of PVA was 9.1% (w), the hydrogel reached its maximum stress strength (12.0 MPa). However the stress strength of the hydrogels decreased with increasing the dosage of PEG. This s-IPN hydrogel exhibits significant electrical sensitivity, when a piece of deionized water swollen hydrogel was placed in 0.2 mol•L－1 NaCl solution under an applied voltage, the hydrogel bent toward the anode quickly. Further investigation shows that both the bending speed and the maximum bending angle of the s-IPN hydrogels were influenced by the dosage of PVA and PEG.

Key words: hydrogel, semi-interpenetrating polymer network, stress strength, electrical sensitivity