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Langmuir 1999, 15, 4018-4020
Notes On the Formation of Colloidally Dispersed Phase-Separated Poly(N-isopropylacrylamide) Karinne Chan, Robert Pelton,* and Ju Zhang McMaster Centre for Pulp and Paper Research, Department of Chemical Engineering, McMaster University, Hamilton, Ontario, Canada L8S 4L7 Received September 16, 1998. In Final Form: March 11, 1999
Introduction Poly(N-isopropylacrylamide) (polyNIPAM) is a watersoluble polymer with a lower critical solution temperature of 32 °C.1,2 Homopolymers, copolymers, macrogels, and microgels based on N-isopropylacrylamide have been the subject of many publications because of the fascinating temperature-sensitive properties and potential applications of polyNIPAM materials. Heating concentrated aqueous polyNIPAM results in rapid phase separation at the cloud point temperature, giving a macroscopic coacervate phase containing about two bound water molecules per isopropyl group.3 By contrast, with very dilute polyNIPAM solutions it is possible to use light scattering to follow the collapse of individual chains during heating, thus yielding valuable information about the coil-to-globule transition.4-7 These extremely dilute (
