Uncovering the relationship between the structure and acid-base properties for hyperbranched polyester-polyols self-assembled on carbon surfaces

Abstract

The self-assembly of three different generations of hyperbranched polyester-polyol polymers, based on 2,2-bis(methylol)propionic acid units (H20, H30, and H40 Boltorn®), on carbon electrodes was studied. The physico-chemical properties of this family of polymers confined on a surface were explored by electrochemical impedance spectroscopy (EIS) and atomic force microscopy (AFM). Surface pKa of the hyperbranched polymer layers were determined by impedimetric titration by EIS based on the variation in the charge transfer resistance of the electroactive redox probe [Fe(CN)6]4−/[Fe(CN)6]3− at different pH. AFM was used to characterize the surface topography and also its viscoelastic properties by the acquisition of phase images. The relation between structure and acid-base properties can be explained in terms of a rearrangement of the layer due to the effect of intermolecular hydrogen bonds and adsorbate-substrate interactions. In this study, we report a powerful, versatile and yet simple procedure for functionalizing carbon materials surfaces without pre-treatment requirements, which could be useful to generate promising platforms for the development of sensors and drug delivery systems.