(807f) Charged Block Copolymer Assemblies Driven By Complex Coacervation

Priftis, D., University of Chicago
Perry, S. L., UMass Amherst
Leon, L., Argonne National Laboratory
Kade, M., University of Chicago
Tirrell, M., University of Chicago

A variety of materials with diverse structures and properties can be formed as a result of electrostatic interactions between oppositely charged macromolecules. Under defined conditions,  complexation between oppositely charged polyelectrolytes can lead to a phase separation phenomenon, referred to as complex coacervation. Complex coacervation is initially seen in the form of polyelectrolyte-rich fluid droplets (1-100 μm in size) displaying a unique combination of physical properties. Using polypeptides as a model system we identified the external parameters that affect coacervation,1 explored the thermodynamics of coacervate formation,2 and studied the rheological3 and interfacial properties4 of polypeptide coacervates.

Building on this work, we are currently exploring how complex coacervation can be used for the development of other polyelectrolyte self-assembly structures. More complex molecular design can be utilized whereby a polyelectrolyte domain is connected to a neutral polymer block. These neutral domains stabilize microphase separation of the coacervate phase. Here, we present the self-assembly of charged block copolymers driven by complex coacervation. We prepared ABA triblock copolymers with a water-soluble polymer (PEG) as the B block and a positively charged polymer (polypeptide) as the A block. Mixing of the triblock copolymer with an oppositely charged polypeptide homopolymer resulted in the formation of nanometer-sized micelles with a coacervate core. The formation of a hydrogel network generated from linked coacervate core domains was observed when the concentration of the polymers was increased (typically greater than about 5 wt % polymer). A series of experimental techniques, including TEM, rheology, SAXS and light scattering, were used for the characterization of the resulting self-assembled structures.

1. Priftis D., Tirrell M., Soft Mater 2012, 8, 9396-9405.                                                                                                

2. Priftis D., Laugel N., Tirrell M., Langmuir 2012, 28, 15947-15957.                                                                        

3. Priftis D., Megley K., Laugel N., Tirrell M., J. of Colloid and Interface Sci. 2013, 398, 39-50.                                    

4. Priftis D., Farina R., Tirrell M., Langmuir 2012, 28, 8721-8729.