Salt-Induced Control of the Grafting Density in Poly(ethylene glycol) Brush Layers by a Grafting-to Approach

Publication year: 2018
Authors: Ortiz R. 1, Olsen S. 2, Thormann E. 1

1 - Department of Chemistry, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
2 - Hempel A/S, 2800 Kgs. Lyngby, Denmark

Published in: Langmuir, 2018, Vol. 34(15), p. 4455-4464
doi: 10.1021/acs.langmuir.8b00030

In this work, a method to obtain control of the grafting density during the formation of polymer brush layers by the grafting-to method of thiolated poly(ethylene glycol) onto gold is presented. The grafting density of the polymer chains was adjusted by adding Na2SO4 in concentrations between 0.2 and 0.9 M to the aqueous polymer solution during the grafting process. The obtained grafting densities ranged from 0.26 to 1.60 chains nm-2, as determined by surface plasmon resonance. The kinetics of the grafting process were studied in situ by a quartz crystal microbalance with dissipation, and a mushroom to brush conformational transition was observed when the polymer was grafted in the presence of Na2SO4. The transition from mushroom to brush was only observed for long periods of grafting, highlighting the importance of time to obtain high grafting densities. Finally, the prepared brush layer with the highest grafting density showed high resistance to the adsorption of bovine serum albumin, while layers with a lower grafting density showed only limited resistance.

MP-SPR keywords: anti-fouling coating, bound mass, BSA adsorption, film thickness, grafting density, PEG brushes, polymer characterization