A general method for functionalisation of microgel particles with primary amines using click chemistry

In this study we introduce a general method for functionalising microgel particles with primary amine groups using a one-step copper catalysed azide-alkyne cycloaddition (CuAAC) reaction. Three different families of microgels containing copolymerised propargyl acrylate (PA) were prepared and then reacted with 2-azido-1-ethylamine (AEA) using CuAAC. The microgels contained poly(ethyl acrylate) (PEA), poly(2-vinylpyridine) (PVP) or poly(N-isopropylacrylamide) (PNP). The functionalisation of the microgels containing PA (i.e., PX-PA) by AEA to give primary amine functionalised particles (PX-PA-AEA) was assessed by elemental analysis and FTIR. The reaction of AEA with PA was quantitative for each of the PX-PA-AEA microgels (X = EA, VP and NP). The PX-PA-AEA systems generally showed larger pH-triggered swelling and zeta potentials than the non-clicked PX-PA particles. The results also showed that PA restricted swelling of the PX-PA and PX-PA-AEA particles by acting as a crosslinker. Of the three microgel systems studied, PVP-PA-AEA had the best combination of high AEA incorporation and pH-triggered swelling.