Mixing a bis-hydrophilic, cationic miktoarm star polymer with linear poly(styrene sulfonate) PSS at a 1:1 charge-to-charge ratio leads to the formation of unilamellar polymersomes. These consist of an interpolyelectrolyte complex (IPEC) wall sandwiched between poly(ethylene oxide) brushes since the miktoarm stars consist of 3 polycation arms made of quaternized poly(dimethylaminoethyl methacrylate) qPDMAEMA and 1 poly(ethylene oxide) PEO arm. The transmission electron microscopy of vitrified samples (cryogenic TEM) is compared with samples imaged at ambient conditions (in situ TEM). The experimental finding of this rare IPEC morphology is rationalized theoretically: the star architecture forces the assembly into a vesicular shape due to the high entropic penalty for stretching of the insoluble arms in non-planar morphologies.Apart the 1:1 ratio of cationic and anionic polymeric charges, sedimentation velocity analysis was performed by help of Analytical Ultracentrifugation (AUC). As shown by AUC, the IPECs consist of one star per co-assembled structure when having excess star as a host polyelectrolyte. At the same time, the noncentrosymmetric character of miktoarm stars is kept leading to rare Janus-like IPECs.Hence the benefits of using such miktoarm stars are twofold: a) directing the co- and self-assembly into the vesicular morphology with a rather high aggregation number at an equimolar charge-to-charge ratio, b) prevention of aggregation at an excess of miktoarm stars allowing a drastic change in aggregation number in a rather narrow window of charge-to-charge ratios.

Interpolyelectrolyte complexes based on miktoarm stars

248th National Meeting (2014)

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