title: Tuning the density profile of surface-grafted hyaluronan and the effect of counter-ions.
abstract: The present paper investigates the structure and composition of grafted sodium hyaluronan at a solid-liquid interface using neutron reflection. The solvated polymer at the surface could be described with a density profile that decays exponentially towards the bulk solution. The density profile of the polymer varied depending on the deposition protocol. A single-stage deposition resulted in denser polymer layers, while layers created with a two-stage deposition process were more diffuse and had an overall lower density. Despite the diffuse density profile, two-stage deposition leads to a higher surface excess. Addition of calcium ions causes a strong collapse of the sodium hyaluronan chains, increasing the polymer density near the surface. This effect is more pronounced on the sample prepared by two-stage deposition due to the initial less dense profile. This study provides an understanding at a molecular level of how surface functionalization alters the structure and how surface layers respond to changes in calcium ions in the solvent.
authors.affiliation: Science for Life Laboratory, Department of Chemistry - Ångström Laboratory, Uppsala University, Box 538, 751 21 Uppsala, Sweden. berts@ill.fr
authors.forename: Ida
authors.initials: I
authors.lastname: Berts
authors.forename: Giovanna
authors.initials: G
authors.lastname: Fragneto
authors.forename: Jöns
authors.initials: J
authors.lastname: Hilborn
authors.forename: Adrian R
authors.initials: AR
authors.lastname: Rennie
mesh_terms: D002118:Calcium / Q000737:chemistry*; D006820:Hyaluronic Acid / Q000737:chemistry*; D033363:Neutron Diffraction; D011108:Polymers / Q000138:chemical synthesis / Q000737:chemistry*; D053838:Scattering, Small Angle; D012825:Silicon / Q000737:chemistry; D012997:Solvents / Q000737:chemistry; D013046:Specific Gravity
chemical_list: D011108:Polymers; D012997:Solvents; D006820:Hyaluronic Acid; D002118:Calcium; D012825:Silicon