Self-Assembly Behavior of PS-b-P2VP Block Copolymers and Carbon Quantum Dots at Water/Oil Interfaces

The interfacial assembly of polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP) diblock copolymer and carboxylated carbon quantum dots (c-CQDs) at the water/oil interface and the morphology of the resultant assemblies, transferred to a solid substrate, were investigated as a function of pH and the molecular weight of PS-b-P2VP. As expected, the interfacial assembly of PS-b-P2VP and c-CQDs decreased the interfacial tension between the water and toluene. The assembly of the PS-b-P2VP is strongly dependent on pH, that is, the extent of protonation of the P2VP block and, in the presence of the c-CQDs, the extent of interactions between the P2VP block and the c-CQDs. The behavior of the P2VP block also influences the state of the PS block, with the entanglement of the PS block increasing with decreasing pH, since the extension of the PVP block into the aqueous phase increases the packing density of the PS block at the interface. This is reflected in the modulus of the assemblies at the interface where marked changes are observed. The interactions between the CQDs and PS-b-P2VP are found to be sufficiently strong to show the potential of manipulating the structure of the interface with the BCP micelles.