Diblock copolymers of poly(tert-butyl acrylate)-b-poly(azidomethyl styrene) were synthesized and used to modify multiwalled carbon nanotubes. After hydrolysis of the PtBA block, hydrophilic MWCNTs with poly(acrylic acid) brushes (MWCNT-PAA) were obtained and characterized. Then novel polyacrylamide composite hydrogels were prepared by in situ polymerization of acrylamide in presence of MWCNT-PAA. Our results show that the mechanical properties of the composite hydrogels are significantly improved with increasing the content of MWCNT-PAA. For the composite hydrogels, when the content of MWCNTs (weight ratio of MWCNT-PAA/ AM) reached to 1.4 wt%, the tensile strength and the elongation were measured to be 82.7 kPa and 508% respectively, which are at least 3.9 and 3.1 times higher than those of the polyacrylamide hydrogel. Moreover, the swelling property of the hydrogel can be regulated through the content of MWCNT-PAA. Therefore, these hydrogels may have potential applications in biomedical fields without the limitations of water capacity and mechanical properties. (C) 2016 Elsevier Ltd. All rights reserved.