Aiwei Tian1, David A. Christian1, Dennis E. Discher2, and Tobias Baumgart3. (1) Chemical & Biomolecular Engineering, University of Pennsylvania, Philadelphia, PA 19104-6391, (2) Chemical and Biomolecular Engineering, University of Pennsylvania, Room 129 Towne Building, 220 South 33rd Street, Philadelphia, PA 19104-6393, (3) Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104
Polymersomes made of neutral poly(ethylene oxide)-polybutadiene (PEO-PBD) and negatively charged poly(acrylic acid)-polybutadiene (PAA-PBD) diblock copolymers can laterally segregate into coexisting domains in a certain pH range by calcium cross-bridging between PAA-PBD chains. The phase diagram for phase separation reveals that domain formation occurs in a surprisingly small region of pH and calcium concentration. The sensitivity of these domains to solution conditions after their formation was investigated by varying pH and calcium concentration. 3D images of polymersomes were recorded via confocal fluorescence microcopy imaging, which allowed to obtain domain area fractions using a 2D mapping algorithm. We furthermore studied the effect of temperature on polymersome phase separation as well as the mechanical properties of pure PAA-PBD polymersomes.