On the formation of inclusion complexes at the solid/liquid interface of anchored temperature-responsive PNIPAAM diblock copolymers with γ-cyclodextrin

Giuseppe Lazzara; Richard A Campbell; Solmaz Bayati; Kaizheng Zhu; Bo Nyström; Tommy Nylander; Karin Schillén

doi:10.1007/s00396-017-4052-6

On the formation of inclusion complexes at the solid/liquid interface of anchored temperature-responsive PNIPAAM diblock copolymers with γ-cyclodextrin

Colloid Polym Sci. 2017;295(8):1327-1341. doi: 10.1007/s00396-017-4052-6. Epub 2017 Mar 22.

Authors

Giuseppe Lazzara^{1

2}, Richard A Campbell³, Solmaz Bayati^{1

4}, Kaizheng Zhu⁵, Bo Nyström⁵, Tommy Nylander¹, Karin Schillén¹

Affiliations

¹ Division of Physical Chemistry, Department of Chemistry, Lund University, P.O. Box 124, SE-221 00 Lund, Sweden.
² Department of Physics and Chemistry, University of Palermo, Viale delle Scienze, 90128 Palermo, IT Italy.
³ Institut Laue-Langevin, 71 avenue des Martyrs, 38042 Grenoble, France.
⁴ Akzo Nobel Surface Chemistry AB, Stenunge Allé 3, SE-444 85 Stenungsund, Sweden.
⁵ Department of Chemistry, University of Oslo, P.O. Box 1033, Blindern, 0315 Oslo, Norway.

Abstract

The thermal responsive behavior of adsorbed layers of diblock copolymers of poly(N-isopropylacrylamide) (PNIPAAM) and poly((3-acrylamidopropyl)trimethylammonium chloride) (PAMPTMA(+)) with γ-cyclodextrin (γ-CD) at the solid/liquid interface has been investigated using three in situ techniques: null ellipsometry, quartz-crystal microbalance with dissipation monitoring, and neutron reflectometry. The measurements provided information about the adsorbed amounts, the layer thickness, hydration and viscoelastic properties, and the interfacial structure and composition. The copolymers adsorb to silica with the cationic PAMPTMA(+) blocks sitting as anchors in a flat conformation and the PNIPAAM chains extending into the solution. The copolymer system alone exhibits reversible collapse above the lower critical solution temperature of PNIPAAM. The addition of γ-CD to pre-adsorbed copolymer layers results in a highly extended conformation as well as some loss of copolymer from the surface, which we discuss in terms of the formation of surface-invoked lateral steric repulsion of formed inclusion complexes.

Keywords: Cyclodextrin; Inclusion complex; Poly(N-isopropylacrylamide); Reflectometry; Solid/liquid interface; Thermoresponsive block copolymer.