Assembly of Polyelectrolyte Star Block Copolymers at the Oil-Water Interface

We present results of coarse-grained molecular dynamics simulations of the assembly of star block copolymers at the oil-water interface. The star block copolymer consist of three arms where each arm is a hydrophilic-hydrophobic block copolymer where the hydrophobic blocks are covalently attached to each other forming the core. The hydrophilic  corona are modeled to become protonated when in contact with the aqueous phase, massively increasing the hydrophilicity of this  block, changing the nature of the star. This results in a conformational change of the star at the interface, significantly stretching the chains comprising the hydrophilic corona into the aqueous phase, while the hyrdrophobic core remains solubilized in the oil phase.  We follow the kinetics of the anchoring and assembly of the star block copolymer at the interface, monitoring their lateral assembly,  and the subsequent reconfiguration of the star and the change in the interfacial tension, as the degree of protonation increases.  At low fractions of protonation, the arm cannot fully anchor to the aqueous side of the interface and interacts with other arms in the oil phase forming a percolated network near the interface.