FLUORESCENCE STUDIES OF HYDROPHOBIC ASSOCIATION OF FLUOROCARBON-MODIFIED POLY(N-ISOPROPYLACRYLAMIDE)

A series of hydrophobically associating poly(N-isopropylacryamide) (PN IPAM) containing low amounts (0.06-0.88 mol %) of fluorocarbon (CF3(CF 2)(7-)) was prepared by copolymerization of NIPAM and 2-(N-ethylperflu orooctanesulfonamido)ethyl methacrylate. Hydrophobic association of th e copolymers in an aqueous medium was investigated by fluorospectrosco py in which both pyrene (By) and fluorocarbon-substituted pyrene (PyCO R(f)) were used as probes. In comparison with unmodified pyrene, using PyCOR(f) with the same fluorocarbon substituent as in the PNIPAM copo lymers proved to be more informative for monitoring hydrophobic associ ations of the copolymers due to its affinity for the microdomains of t he fluorocarbon chains. Both the monomer emission intensity, I-375, an d the monomer to excimer ratio of intensities, I-375/I-550, Of PyCOR(f ) were good indicators of the dependence of the association on the flu orocarbon content of the copolymers and their concentration.