A quantitative cryoTEM study on crosslinked nanocapsule morphology in RAFT-based vesicle polymerization

The effect of crosslinking on the morphology of nanocapsules synthesized by vesicle-templated reversible addition-fragmentation chain transfer (RAFT) polymerization was investigated and it was found that although crosslinking increases the fraction of protruded capsules, it is not the origin of the protrusions. Starved-feed emulsion polymerization of methyl methacrylate and tert-butyl acrylate with varying amounts of a range of crosslinkers using a seed of cationic vesicles covered by anionic co-oligomers containing a RAFT functional group, results in several different structures, with true spherical capsules and protruded capsules being the main products under the used reaction conditions. Quantitative cryoTEM studies allowed the counting of the different morphologies and it was found that the final fraction of protruded structures strongly depended on the used crosslinker. In the case of using 10 mol% of ethylene glycol dimethacrylate, ∼90% of the observed structures were protruded capsules, whereas this was only ∼4% in the case of 10 mol% ethylene glycol diacrylate. Finally, tomography showed that the protrusions are an integral part of the polymer shell.