A novel schizophrenic copolymer responsive to pH and temperature change was developed through copolymerization of N-isopropylacrylamid e (NIPAm) and acrylic acid (AA) on chitosan chains by a bio-friendly initiator. The behavior of purified graft copolymer in solution phase was studied in detail by NMR, Zetasizer, TEM, SEM and ATR-FTIR techniques. In dilute aqueous media, two types of reversible nanoparticles can be obtained by changing temperature and pH: positively charged micelles with chitosan-shell in acidic solutions above 33 degrees C and negatively charged micelles with P(NIPAm-co-AA)-shell in alkaline solutions. The transform between these two oppositely charged micelles can be easily controlled by changing pH at human body temperature. The effect of graft degree on the solution behavior was also studied. This novel schizophrenic copolymer has potential applications in drug delivery and other controlled releases. (C) 2010 Elsevier Ltd. All rights reserved.