Binary colloidal hetero-coagulation for raspberry-like particles through azide–alkyne click reaction

Abstract

The core–corona hybrid particles with a raspberry-like structure were prepared by a binary colloidal hetero-coagulation through a click reaction between azide group and alkynyl group. The azide functionalized poly(ethylene glycol dimethacrylate-co-2-hydroxyethyl methacrylate) (P(EGDMA-co-HEMA)) microspheres behaved as the core and the alkynyl group modified poly(N,N-methylene diacrylamide-co-methacrylic acid) (P(MBA-co-MAA)) microspheres acted as the corona. In this approach, the azide groups were converted from the hydroxyl groups on P(EGDMA-co-HEMA) microspheres through the successive esterification with α-bromoisobutyryl bromide and the subsequent nucleophilic substitution with sodium azide. The alkynyl groups were endowed onto the P(MBA-co-MAA) microspheres through the amidation between the carboxyl groups and the propargylamine in the presence of dicyclohexylcarbodiimide/4-dimethylamiopryidine (DCC/DMAP) as the dehydrating reagents. The colloidal hetero-coagulation was performed through click reaction between the azide group functionalized P(EGDMA-co-HEMA) microspheres and alkynyl functionalized P(MBA-co-MAA) microspheres via Huisgen 1,3-dipolar cycloaddition with CuBr/PMDETA as catalyst. The coverage of the corona on the core microspheres was tuned through the feed of the corona to the core. The resultant polymer microspheres and raspberry like particles were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM) and Fourier transform spectra (FT-IR).