A facile grafting-onto strategy has been exploited to prepare a smart pH-controlled drug delivery system (P-B) via surface-grafting of the preformed silane modified with PMAA [poly(methylacrylic acid)] onto the surface of BMMs (bimodal mesoporous silicas). Accordingly, the PMAA acted as the pH-sensitive component, and the silane provided an anchor with the surface OH group of BMMs. Thereby, a series of P-B with different mass ratio of BMMs to PMAA have been synthesized. Meanwhile, ibuprofen (IBU) was applied as a model drug to investigate the influences of different pH values on drug release. The results showed that the obtained P-B presented a flexible control over drug release by adjusting the grafted amount of PMAA. Moreover, the drug release amount of the drug-loaded samples was pH dependent and increased with the increasing of pH value, implying that the P-B are promising drug-carriers in application of pH-responsive controlled drug delivery systems. (C) 2014 Elsevier Ltd. All rights reserved.