Herein we report a new and simple method that has been developed to prepare smart polymeric microgels consisting of temperature-sensitive cores with pH-sensitive shells. The microgels were obtained directly from one step seed polymerization of N-isopropylacrylamide and N,N-methylenebisacrylamide from water-soluble biopolymers containing carboxymethyl groups in supercritical carbon dioxide. The effect of initial concentration of initiator, crosslinker, and carboxymethyl starch (CMS) dose as well as reaction pressures on the yield and morphology of the resulting polymer were investigated. CMS and crosslinker worked effectively as surfactant to some extent. PNIPAM/CMS particles with diameters in 100 nm and narrow particle size distribution were produced in supercritical carbon dioxide, in high yield and in short reaction times. (c) 2006 Elsevier Ltd. All rights reserved.