Crosslinked poly(chitosan-N-isopropylacrylamide) [poly(NIPAAM-chitosan)] complex particles were successfully synthesized with the method of soapless dispersion polymerization. The anionic initiator ammonium persulfate (A-PS) and the cationic initiator 2,2'-azobis(2-methylpropionamidine) dihydrochloride (AIBA) were used to initiate the copolymerization. The poly(NIPAAM-chitosan) copolymer particles synthesized with APS as the initiator had a homogeneous morphology, whereas the copolymer particles synthesized with AIBA as the initiator showed a core-Shell morphology. In addition, various variables such as the particle size, reaction rate, and potential were taken into account. (C) 2003 Wiley Periodicals, Inc.