Thermosensitive copolymers poly(NIPAm-co-NNPAm) of N-isopropylacrylamide (NIPAm) with N-n-propylacrylamide (NNPAm) were synthesized by free radical copolymerization using potassium persulfate (KPS) and sodium sulfite (Na2SO3) as initiator. FTIR and H-1 NMR confirmed the structure of the copolymer poly(NIPAm-co-NNPAm). The dynamic mechanical analysis and dynamic contact angle were determined. The lower critical solution temperature (LCST) of copolymers was investigated by DSC. The results indicated the LCST decreased with the higher NNPAm contents. The phase transition of the copolymer solution occurred at body temperature within 30 s and the copolymers changed into soft solids. The copolymer could be used as a new non-adhesive liquid embolism material for the intervenient therapy of the cerebral arterio-venous malformation (AVM). (c) 2005 Elsevier B.V. All rights reserved.