Fig. 1. Stimuli-triggered polymersome-to-PICsome transition and concurrent permeability regulation.

For polymersomes self-assembled from amphiphilic diblock and triblock copolymers containing tertiary amine and caged carboxyl moieties in the hydrophobic block, external stimuli including UV light and reductive milieu trigger the decaging of carboxyl functionalities, which transfer protons onto neighboring tertiary amine moieties and render ion-pair interactions. Note that in situ generated PICsomes are highly stable towards extreme pH range, high ionic strength, and elevated temperature due to cooperative ion-pair interactions at high local concentration within pre-organized vesicle bilayers and synergistic contributions from hydrogen bonding interactions of carbamate side linkages. The polymersome-to-PICsome transition is accompanied with the transformation of hydrophobic bilayers into semipermeable membranes and switching of vesicle bilayer permeability. Moreover, sequence structure of the bilayer forming block, A-(B-co-C) vs. A-B-C, could be further utilized to regulate the permselectivity of resultant semipermeable PICsome bilayers.