The impact of polymer architecture on polyion complex (PIC) micelles: when topology matters (and when it doesn't)

The influence of homopolymer architecture on the properties of polyion complex micelles is reported. Using a combination of dynamic and static light scattering, the authors show how the architecture is only relevant in kinetically trapped states of micelles formed by the electrostatic assembly of poly(N-isopropyl acrylamide-block-styrene sulfonate) (p(NIPAM-b-SS) and linear, 4-arm, 8-arm star quaternized poly(dimethyl amino ethyl acrylate) (PDMAEA) homopolymers or poly(amidoamine) (PAMAM) dendrimers. Interestingly, the micellar size and the aggregation number in these kinetically arrested states follow a clear trend with the number of arms but differ in the case of dendrimers possibly due to the distinct chemical nature of the monomers. The authors show that if the micelles are prepared in a weak polyelectrolyte pairing regime (i.e., high ionic strength), they all converge into similar structures. The presented findings represent a new way of controlling the properties of polyion complex micelles through kinetically trapped states.