Poly(acrylic acid)/nylon6 and polystyrene/nylon6 blends were prepared using supercrifical CO2 as substrate-swelling agent and monomer/initiator carrier. Both supercritical CO2/nylon6 binary system and SC CO2/monomer/nylon6 ternary system were studied. Virgin nylon6 and synthesized blends were characterized through differential scanning calorimetry, infrared spectroscopy, and polarizing microscopy. Supercritical CO2-induced crystallization was found in modified nylon6. (C) 2003 Elsevier Ltd. All rights reserved.