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.