title: Poly(N-isopropyl acrylamide) brush topography: dependence on grafting conditions and temperature.
abstract: The topography of poly (N-isopropyl acrylamide) brushes end-grafted from initiator-terminated monolayers was imaged by atomic force microscopy, as a function of the area per chain and of solvent quality. Measurements were done in air and in water, below and above the lower critical solution temperature. At low grafting densities and molecular weights, area-averaged ellipsometry measurements did not detect changes in the volume of water-swollen, end-grafted polymer films above the lower critical solution temperature. However, atomic force microscopy images revealed surface features that suggest the formation of lateral aggregates or "octopus micelles". At high grafting densities and molecular weights, the films collapsed uniformly, as detected by both AFM imaging and ellipsometry. These findings reconcile in part prior results suggesting that some poly(N-isopropyl acrylamide) chains do not collapse in poor solvent, and they also reveal more complex collapse behavior above the lower critical solution temperature than is commonly assumed. This behavior would influence the ability to tune the functional properties of poly(N-isopropyl acrylamide) coatings.
authors.affiliation: Department of Chemical and Biomolecular Engineering, University of Illinois, Urbana, Illinois 61801, United States.
authors.forename: B-C
authors.initials: BC
authors.lastname: Choi
authors.forename: S
authors.initials: S
authors.lastname: Choi
authors.forename: D E
authors.initials: DE
authors.lastname: Leckband
mesh_terms: D000178:Acrylamides / Q000737:chemistry*; D000180:Acrylic Resins; D018625:Microscopy, Atomic Force; D011108:Polymers / Q000737:chemistry*; D013696:Temperature
chemical_list: D000178:Acrylamides; D000180:Acrylic Resins; D011108:Polymers; C052970:poly-N-isopropylacrylamide