Polymer microspheres with structured surfaces

Microspheres from polymethyl methacrylate (PMMA) and Eudragit FS 30D (a commercial copolymer of poly(methyl acrylate-co-methyl methacrylate-co-methacrylic acid) 7:3:1) were prepared using microsieve emulsification. A mixture of these polymers in dichloromethane (DCM) was dispersed into water, leading to extraction of DCM in water and the formation of microspheres with a PMMA core and a partially demixed Eudragit shell. With a higher ratio of Eudragit to PMMA, more and bigger pores can be seen on the surface of the microspheres. Eudragit can be removed from the shell of the microspheres under alkaline conditions. Depending on the initial Eudragit to PMMA ratio, PMMA microspheres with different surface morphologies are obtained. At low Eudragit concentrations microspheres with a crumpled surface are formed, while at higher Eudragit concentrations microspheres are formed with a core to which dendritic PMMA structures are attached. At even higher Eudragit concentrations the microspheres obtained after dissolving the Eudragit show a nanorough surface.

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► Core–shell polymer microspheres are prepared with microsieve emulsification.
► The initial ratio of polymers determines the morphology of the microspheres.
► Removal of the shell reveals the different structures of the core surface.