Preparation of Poly(styrene)-b-poly(acrylic acid)-Coupled Carbon Dots and Their Applications

Carbon dots (CDs) are covalently coupled to the poly(acrylic acid) (PAA) block of polystyrene-b-poly(acrylic acid) (PS-b-PAA). The produced amphiphilic PS-b-PAA-CD shows excellent solubility and micellar formation in selective solvents. Transmission electron microscopy study shows that the micelle of PS-b-PAA-CD in water (a PAA-selective solvent) has a strawberry-like shape with the CDs as patches on the PAA corona surface although that in toluene (a PS-selective solvent) has a reversed shape with the CDs in the core. The fluorescence intensity of PS-b-PAA-CD in water is approximately twice that in toluene because the close contacts between the CDs in the core of the micelle lead to decreased fluorescence intensity due to π-π interactions. Thus, PS-b-PAA-CD can be used in sensors via fluorescence quenching through morphology control of micelle by solvent selectivity. The PS-b-PAA-CD aqueous solution is successfully used as an fluorescent ink for inkjet printing and fluorescent fillers for poly(methyl methacrylate) (PMMA) composites. The quantum yields of the CDs in pure CD, PS-b-PAA-CD, and a PMMA/PS-b-PAA-CD composite were almost the same (∼41%). Because of its good solubility in organic solvents and self-assembly property in solution, the application scope of PS-b-PAA-CD can be further expanded in the future.