Solvatochromism and acidochromism of azobenzene-functionalized poly(vinyl amines)

Abstract

Nucleophilic substitution of fluoroaromatics with poly(vinyl amine) (PVAm) is a suitable method for producing various azobenzene-functionalized PVAms. The solubility of the fluoroaromatic reagents in water was mediated by complexation with 2,6-O-dimethyl-β-cyclodextrin (DMCD). The degree of functionalization has been determined using model compounds as reference system. The solvatochromic properties of the polymers and the model compounds have been studied and interpreted using the well-established linear solvation energy relationships (LSER) of Kamlet–Taft and Catalán. The most dominant effect on the solvatochromic behavior is caused by interactions with solvents of a different dipolarity/polarizability. Also the basicity of the solvents is assumed to play an important role in the solvatochromism of the azobenzene-functionalized PVAms which shows the influence of the polymer chains. Furthermore, the UV/vis absorption spectra show a bathochromic shift with increasing acid strength of the medium. The impact of the PVAm backbone on the color of the chromophore bonded is highlighted.