Morphology-controlled synthesis of porous polymer nanospheres for gas absorption and bioimaging applications

Abstract

This paper reports the development of a simple and effective way to prepare novel soluble porous polymer nanospheres (PPSs) by A₃B₂ catalytic emulsion polymerization using a Suzuki reaction as a one-step, surfactant-free process. The PPSs chemical structures are characterized by Fourier transform infrared spectroscopy, transmission electron microscopy, powder X ray diffraction, dynamical light scattering, and thermogravimetric analysis. The results show that tris(4-bromophenyl)amine (A₃) and benzene-1,4-diboronic acid (B₂) monomers in a dilute Suzuki system (1 : 20 as the ratio of toluene to water) form a A₃ core/B₂ shell nano-size micelle in the oil/water template at the early stage. With the reaction processing, the ∼10 nm nanoparticles precipitate in droplets and move into the water phase. The small individual nanoparticles further aggregate and connect into ∼200 nm porous nanoparticles. The controlled second level of porosity is attributed to the uniform individual nanoparticles’ self-assembly. Its porosity is confirmed by N₂ sorption isotherms at 77 K. Among the PPS series, PPS3 has a high surface area of 2180 m² g⁻¹ and adsorbs up to 2.08 wt% hydrogen by mass at 1.13 bar/77 K. Photoluminescence investigations have shown that PPS copolymers with different concentrations of 4,7-dibromo-2,1,3-benzothiadiazole emit blue, green and yellow light, respectively. Preliminary investigations show that PPS displays a low cytotoxicity and can be used as a fluorescence marker in bioimaging.