Halloysite (HNT) is a natural mineral which exhibits a characteristic tubular structure at the nanometric scale. Its surface chemistry presents aluminol groups at the inner surface and silanol ones at the outer surface. This asymmetry of surface composition leads to differences of reactivity which allows selective modification of the halloysite particles to be performed 1,2. In this work, internal surface of halloysite was selectively modified using styrene/(methacryloyloxy)methyl phosphonic acid copolymer (P(S-co-MAPC1(OH)2)) , which was previously synthesized in our laboratory. FTIR, TGA, Py-GC/MS and solvents dispersion tests were used to evidence this surface modification of halloysite. Then, the hybrid nanoparticles were incorporated at various percentages (3 and 10 wt%) in co-continuous polystyrene/polyamide 11 (60/40) blends, using a twin-screw mini-extruder. SEM micrographs showed the preferential localization of halloysite nanotubes at the interface after functionalization, with some nanotubes also in the polystyrene phase. This presence of modified HNT in the PS phase was also evidenced by TGA, where improvements in terms of thermal stability were observed. Rheological measurements were carried out to study the influence of the surface modification of HNT on the morphology of the systems. A gel-like behavior was observed for all HNT reinforced compositions that was enhanced in the case of 10% of functionalized halloysite. References (1) Yah, W. O.; Takahara, A.; Lvov, Y. M. J. Am. Chem. Soc. 2012, 134 (111), 1853. (2) Yah, W. O.; Xu, H.; Soejima, H.; Ma, W.; Lvov, Y.; Takahara, A. J. Am. Chem. Soc. 2012, 134, 12134.