pH-responsive molecularly imprinted particles were successfully fabricated by pore-filling poly (acrylic acid) (PAA) gels into bisphenol-A (BPA)-imprinted poly-ethersulfone particles. The adsorbed BPA amount (or rate) decreased aftezr filling the PAA gels both for the imprinted and nonimprinted particles. However, it was confirmed that changing the acidity of the solution reversibly controls the rebinding ability toward BPA and that the BPA uptake of the pore-filled particles exhibited chemical valve behavior at a pH between 3 and 6. This finding can be attributed to the swelling of the PAA gels in the particles. The present methodology provides a simple way to prepare pH-responsive molecularly imprinted materials and is expandable to the imprinting of other hydrophobic molecules, such as dibenzofuran. Also, the results of this work demonstrate the potential of stimuli-responsive molecularly imprinted polymer materials as smart chemicals and as drug-delivery systems. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 113: 916-921, 2009