Preparation of Poly(styrene)‑<i>b</i>‑poly(acrylic acid)-Coupled Carbon Dots and Their\nApplications

Abstract

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