Thermoprocessible hydrogels. I. Synthesis and properties of polyacrylamides with perfluoroalkyl side chains

Copolymers composed of acrylamide (AM), N,N-dimethylacrylamide (DMAM), N-is opropylacrylamide (NIPAM) and 2-(N-ethyl-perfluorooctanesulfonamido) acryla mide (FOSA) were synthesized by free radical polymerization. The chemical s tructure of the resulting polymers was characterized with NMR spectroscopy and thermal properties were measured by thermogravimetric analysis (TGA) an d differential scanning calorimetry (DSC). H-1-NMR spectra of the copolymer s of NIPAM with FOSA showed that FOSA was incorporated quantitatively. The glass transition temperature (T-g) of the copolymers and the terpolymers de creased with increasing FOSA content. The T(g)s, however, were higher than predicted for a random copolymer by the Fox equation, which was attributed to microphase separation of the hydrophobic, fluorinated species. Copolymer s of AM and FOSA became discolored above 180 degrees C due to formation of cyclic imide and nitrile moieties through cyclization or dehydration of ami de groups. The equilibrium water sorption of the copolymers decreased with increasing FOSA content, but increasing FOSA suppressed the water desorptio n kinetics. Water sorption and thermal stability were improved by terpolyme rization of AM, NIPAM, DMAM and FOSA.