Résumé
Copolymers of N-( isopropylacrylamide) (NIPAM, 90 mol%) and N-L-valine acrylamide (Val, 10 mol%), as well as their hydrophobically-modified copolymers, namely a copolymer of NIPAM, Val, and N-n-octadecylacrylamide (PNIPAM-Val-C-18, 1 mol%) and a copolymer of NIPAM, Val, and N-[4-( 1-pyrenyl)butyl]-N-n-octadecylacrylamide (PNIPAM-Val-C18Py, 1 mol%) were prepared by free radical copolymerization of the respective monomers. Studies by turbidimetry, microcalorimetry, dynamic light scattering, and fluorescence spectroscopy indicated that the hydrophobically-modified copolymers form polymeric micelles in water (effective hydrodynamic diameter: 25 nm +/- 5 nm). Solutions of all the copolymers underwent pH-dependent phase separation upon heating, but the pH- or temperature-stimulated coil-to-globule collapse/chain expansion did not result in complete disruption of the hydrophobic microdomains.