title: Cationic poly(N-isopropylacrylamide) block copolymer adsorption investigated by dual polarization interferometry and lattice mean-field theory.
abstract: A series of cationic diblock copolymers, poly(N-isopropylacrylamide)(48)-block-poly((3-acrylamidopropyl)trimethylammonium chloride)(X), abbreviated as PNIPAAM(48)-b-PAMPTMA(+)(X) (X = 0, 6, 10, 14, and 20), has been synthesized, and their adsorption onto silicon oxynitride from aqueous solution has been investigated using dual polarization interferometry. The polymer adsorption was modeled by using a lattice mean-field theory, and a satisfactory consistency between theory and experiments was found in terms of surface excess and layer thickness. Both theory and experiments show that the adsorption is limited by steric repulsion for X < X(max) and by electrostatic interactions for X > X(max). Modeling demonstrates that significant surface charge regulation occurs due to adsorption. Both the nonionic and cationic block exhibit nonelectrostatic affinity to silicon oxynitride and thus contribute to the driving force for adsorption, and modeling is used for clarifying how changes in the nonelectrostatic affinity affects the surface excess. The segments of the nonionic and cationic blocks seem less segregated when both have a nonelectrostatic affinity for the surface compared to the case where the segments had no surface affinity. Adsorption kinetics was investigated experimentally. Two kinetic regimes were observed: the adsorption rate is initially controlled by the mass transfer rate to the surface and at higher coverage is limited by the attachment rate.
authors.affiliation: Department of Chemistry, Surface and Corrosion Science, School of Chemical Science and Engineering, KTH Royal Institute of Technology, Stockholm, Sweden.
authors.forename: Alexander
authors.initials: A
authors.lastname: Shovsky
authors.forename: Stefan
authors.initials: S
authors.lastname: Knohl
authors.forename: Andra
authors.initials: A
authors.lastname: Dedinaite
authors.forename: Kaizheng
authors.initials: K
authors.lastname: Zhu
authors.forename: Anna-Lena
authors.initials: AL
authors.lastname: Kjøniksen
authors.forename: Bo
authors.initials: B
authors.lastname: Nyström
authors.forename: Per
authors.initials: P
authors.lastname: Linse
authors.forename: Per M
authors.initials: PM
authors.lastname: Claesson
mesh_terms: D000178:Acrylamides / Q000138:chemical synthesis / Q000737:chemistry*; D000180:Acrylic Resins; D000327:Adsorption; D002412:Cations / Q000737:chemistry; D007700:Kinetics; D015394:Molecular Structure; D011108:Polymers / Q000138:chemical synthesis / Q000737:chemistry*; D017655:Silicon Compounds / Q000737:chemistry*; D013499:Surface Properties
chemical_list: D000178:Acrylamides; D000180:Acrylic Resins; D002412:Cations; D011108:Polymers; D017655:Silicon Compounds; C052970:poly-N-isopropylacrylamide; C032734:silicon nitride