Synthesis of azide/alkyne-terminal polymers and application for surface functionalisation through a [2 + 3] Huisgen cycloaddition process, “click chemistry”

Abstract

Living radical polymerization of methyl methacrylate (MMA) and a fluorescent comonomer with 2-bromo-2-methylpropionic acid 3-azidopropyl ester and 2-bromo-2-methylhept-6-yn-3-one as initiators has been successfully employed for the synthesis of fluorescently tagged azide and alkyne terminated PMMA with M_n close to that predicted, PDI < 1.20, and good first order kinetics as expected for a living polymerisation. Cotton and organic resin surfaces have been functionalised with alkyne groups using a condensation with 4-chlorocarbonylbutyric acid prop-2-ynyl ester. The surfaces have been further modified using a Huisgen [2 + 3] cycloaddition (“click”) reaction of polymeric and small molecule azides. Different functional azides, mono azido-PEG and a new fluorescent hostasol derivative have been prepared and tested as model substrates for cotton surface modification. FTIR, tensiometry, FE-SEM and confocal spectroscopy have been used to characterize the modified surfaces. Tensiometry shows an increase in the hydrophobicity of the surface; verified by FE-SEM which shows a change in surface morphology. The use of the fluorescence label allows fluorescent and confocal microscopy to demonstrate the surface reactions. This approach is shown to be very general allowing soft and hard surfaces with different geometries to be modified. In particular it is an excellent method to alter the nature of organic resins allowing the incorporation of many different functionalities.