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

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.