Radical copolymerizations of N-isopropylacrylamide (NIPAm) with acrylic acid (AA) initiated by azobisisobutyronitrile in supercritical carbon dioxide (scCO(2), 55 degrees C, 27.6 MPa) were compared with those performed in MeOH at 55 degrees C. The AA compositions of the copolymers in scCO(2) were lower than those of the copolymers in MeOH and they increased upon decreasing the pressure of scCO(2) from 27.6 to 13.8 MPa. The glass transition temperatures of these copolymers deviated positively from those of respective homopolymers prepared in both media, with the copolymer obtained at a 50/50 feed ratio exhibiting the highest value of T-g. FTIR spectroscopy revealed enhanced H-bonding between the amide group of the NIPAm and the carboxyl group of the AA in the copolymers in scCO(2), suggesting that the much higher values of T-g of these copolymers, relative to those in MeOH, arose presumably from the more highly alternating sequences of their NIPAm and AA units.