A novel hydrophobically modified and cationic flocculant poly(acrylamide-methacryloxyethyltrimethyl ammonium chloride-methacryloxypropyltrimethoxy silane) (P(AM-DMC-MAPMS)) was synthesized by inverse emulsion polymerization. The molecular structure of hydrophobically cationic polyacrylamide (HCPAM) was characterized by FTIR and H-NMR. The effects of DMC and MAPMS feed ratio on intrinsic viscosity and solubility were measured. The effects of hydrophobically cationic flocculants on reactive brilliant red X-3B solution and kaolin suspension were studied. It was found that the introduction of MAPMS could increase the intrinsic viscosities of P(AMDMC-MAPMS) and enhance the flocculation properties to anionic dye solution and kaolin suspension, but reduced their water-solubility. (C) 2008 Wiley Periodicals, Inc. J Appl Polym Sci 111: 1594-1599, 2009