title: Submicrometric Films of Surface-Attached Polymer Network with Temperature-Responsive Properties.
abstract: Temperature-responsive properties of surface-attached poly(N-isopropylacrylamide) (PNIPAM) network films with well-controlled chemistry are investigated. The synthesis consists of cross-linking and grafting preformed ene-reactive polymer chains through thiol-ene click chemistry. The formation of surface-attached and cross-linked polymer films has the advantage of being well-controlled without any caution of no-oxygen atmosphere or addition of initiators. PNIPAM hydrogel films with same cross-link density are synthesized on a wide range of thickness, from nanometers to micrometers. The swelling-collapse transition with temperature is studied by using ellipsometry, neutron reflectivity, and atomic force microscopy as complementary surface-probing techniques. Sharp and high amplitude temperature-induced phase transition is observed for all submicrometric PNIPAM hydrogel films. For temperature above LCST, surface-attached PNIPAM hydrogels collapse similarly but without complete expulsion of water. For temperature below LCST, the swelling of PNIPAM hydrogels depends on the film thickness. It is shown that the swelling is strongly affected by the surface attachment for ultrathin films below ∼150 nm. For thicker films above 150 nm (to micrometers), surface-attached polymer networks with the same cross-link density swell equally. The density profile of the hydrogel films in the direction normal to the substrate is confronted with in-plane topography of the free surface. It results that the free interface width is much larger than the roughness of the hydrogel film, suggesting pendant chains at the free surface.
authors.affiliation: École Supérieure de Physique et de Chimie Industrielles de la Ville de Paris (ESPCI), ParisTech, PSL Research University, Sciences et Ingénierie de la Matière Molle, CNRS UMR 7615, 10 rue Vauquelin, F-75231 Paris Cedex 05, France .|Sorbonne-Universités , UPMC Univ Paris 06, SIMM, 10 rue Vauquelin, F-75231 Paris Cedex 05, France.
authors.forename: M
authors.initials: M
authors.lastname: Li
authors.affiliation: École Supérieure de Physique et de Chimie Industrielles de la Ville de Paris (ESPCI), ParisTech, PSL Research University, Sciences et Ingénierie de la Matière Molle, CNRS UMR 7615, 10 rue Vauquelin, F-75231 Paris Cedex 05, France .|Sorbonne-Universités , UPMC Univ Paris 06, SIMM, 10 rue Vauquelin, F-75231 Paris Cedex 05, France.
authors.forename: B
authors.initials: B
authors.lastname: Bresson
authors.affiliation: Laboratoire Léon Brillouin, CEA-CNRS, Saclay , 91191 Gif-sur-Yvette Cedex, France.
authors.forename: F
authors.initials: F
authors.lastname: Cousin
authors.affiliation: École Supérieure de Physique et de Chimie Industrielles de la Ville de Paris (ESPCI), ParisTech, PSL Research University, Sciences et Ingénierie de la Matière Molle, CNRS UMR 7615, 10 rue Vauquelin, F-75231 Paris Cedex 05, France .|Sorbonne-Universités , UPMC Univ Paris 06, SIMM, 10 rue Vauquelin, F-75231 Paris Cedex 05, France.
authors.forename: C
authors.initials: C
authors.lastname: Fretigny
authors.affiliation: École Supérieure de Physique et de Chimie Industrielles de la Ville de Paris (ESPCI), ParisTech, PSL Research University, Sciences et Ingénierie de la Matière Molle, CNRS UMR 7615, 10 rue Vauquelin, F-75231 Paris Cedex 05, France .|Sorbonne-Universités , UPMC Univ Paris 06, SIMM, 10 rue Vauquelin, F-75231 Paris Cedex 05, France.
authors.forename: Y
authors.initials: Y
authors.lastname: Tran
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry; D020100:Hydrogels / Q000737:chemistry; D008567:Membranes, Artificial; D011108:Polymers / Q000737:chemistry*; D013499:Surface Properties; D013696:Temperature
chemical_list: D000180:Acrylic Resins; D020100:Hydrogels; D008567:Membranes, Artificial; D011108:Polymers; C052970:poly-N-isopropylacrylamide