Monodisperse hydrogel microspheres were prepared by precipitation polymerization from acrylamide (AAm), methylenebisacrylamide (MBAAm) and methacrylic acid (MAc) in ethanol, and examined their stimuli response by changing pH or temperature. The microsphere was found to contract continuously by heating. The microsphere with a lower-content MBAAm exhibit more pronounced heat-contraction. Also at low pH the microsphere contracted due to the protonation of the carboxyl group in MAc. The internal structure was observed by small angle X-ray scattering (SAXS) and the stimuli-response mechanism was discussed from the view of network chain conformation.
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