Halloysite nanotubes (HNTs) were grafted with poly(styrene-butyl acrylate-acrylic acid) (P-SBA) via an in situ soap-free emulsion polymerization. To introduce double bonds into the HNTs, N-(beta-aminoethyl)-gamma-aminopropyl trimethoxysilane was first used to modify the HNTs and render amino groups, and then, the double bonds were anchored through an amidation reaction between acryloyl chloride and amino groups. P-SBA chains were grafted onto HNTs because of participating of double bonds in the copolymerization of styrene, butyl acrylate, and acrylic acid. Fourier transforms infrared spectroscopy, transmission electron microscopy, specific surface area measurements, and thermogravimetric analysis were used to characterize the HNTs grafted with P-SBA. The results indicate that 25.21% of P-SBA was grafted onto the outer walls of the HNTs and filled into the inner spaces of the HNTs. The modification dramatically decreased the surface area of the HNTs. The property study of the HNTs grafted with P-SBA focused on the dispersion behavior in the biphase system. The results show that the grafted HNTs dispersed stably in the water/cyclohexane biphase system and were a potential emulsifier. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 117: 3054-3059, 2010