ABSTRACT
Well-defined polymer brushes attached to nanoparticles offer an elegant opportunity for surface modification because of their excellent mechanical stability, functional versatility, high graft density as well as controllability of surface properties. This study aimed to prepare hybrid materials with good dispersion in different solvents, and to endow this material with certain fluorescence characteristics. Well-defined diblock copolymers poly (styrene)-b-poly (hydroxyethyl methyl acrylate)-co-poly (hydroxyethyl methyl acrylate- rhodamine B) grafted silica nanoparticles (SNPs-g-PS-b-PHEMA-co-PHEMA-RhB) hybrid materials were synthesized via surface-initiated activators regenerated by electron transfer atom transfer radical polymerization (SI-ARGET ATRP). The SNPs surfaces were modified by 3-aminopropyltriethoxysilane (KH-550) firstly, then the initiators 2-Bromoisobutyryl bromide (BIBB) was attached to SNPs surfaces through the esterification of acyl bromide groups and amidogen groups. The synthetic initiators (SNPs-Br) were further used for the SI-ARGET ATRP of styrene (St), hydroxyethyl methyl acrylate (HEMA) and hydroxyethyl methyl acrylate-rhodamine B (HEMA-RhB). The results indicated that the SI-ARGET ATRP initiator had been immobilized onto SNPs surfaces, the Br atom have located at the end of the main polymer chains, and the polymerization process possessed the characteristic of controlled/"living" polymerization. The SNPs-g-PS-b-PHEMA-co-PHEMA-RhB hybrid materials show good fluorescence performance and good dispersion in water and EtOH but aggregated in THF. This study demonstrates that the SI-ARGET ATRP provided a unique way to tune the polymer brushes structure on silica nanoparticles surface and further broaden the application of SI-ARGET ATRP.
ABSTRACT
Well-defined amphiphilic diblock copolymer poly (methyl methacrylate)-b-poly (N-isopropylacrylamide) grafted hollow spheres (HS-g-PMMA-b-PNIPAM) hybrid materials were synthesized via metal-free surface-initiated atom transfer radical polymerization (SI-ATRP). The ATRP initiators α-Bromoisobutyryl bromide (BIBB) were attached onto hollow sphere surfaces through esterification of acyl bromide groups and hydroxyl groups. The synthetic ATRP initiators (HS-Br) were further used for the metal-free SI-ATRP of methyl methacrylate (MMA) and N-isopropyl acrylamide (NIPAM) using 10-phenylphenothiazine (PTH) as the photocatalyst. The molecular weight of the polymers, structure, morphology, and thermal stability of the hybrid materials were characterized via gel permeation chromatography (GPC), X-ray photoelectron spectroscopy (XPS), ¹H-nuclear magnetic resonance spectroscopy (¹H NMR), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), and thermogravimetric analysis (TGA), respectively. The results indicated that the ATRP initiator had been immobilized onto HS surfaces successfully followed by metal-free SI-ATRP of MMA and NIPAM, the Br atom had located at the end of the main PMMA polymer chain, and the polymerization process possessed the characteristic of controlled/"living" polymerization. The thermal stability of the hybrid materials was increased significantly compared to the pure PMMA and PNIPAM.
ABSTRACT
Amphiphilic copolymers, poly(styrene)-block-Tb complex (PS-b-Tb complex), were synthesized by reversible addition fragmentation chain transfer (RAFT) polymerization. The honeycomb structured porous films were fabricated via dropping the PS-b-Tb complex copolymer solutions on glass substrates by the breath figures method (BFM). The structure and composition of the amphiphilic copolymer PS-b-Tb complex were confirmed by gel permeation chromatography (GPC), Fourier transform infrared spectroscopy (FT-IR) and 1H nuclear magnetic resonance spectroscopy (1H NMR). The surface morphology and elemental mapping of the highly ordered porous films were investigated by field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX) and laser scanning confocal microscopy (LSCM). The results indicated that the solvent type and copolymer concentration can affect the surface morphology of the porous films. The average diameter of the pores in the porous films decreased with the polymer concentration and the molecular weight of the copolymers increased. The FESEM-EDX analysis further verified that the hydrophilic groups (Tb complex groups) were mainly distributed at the pore wall, instead of at the outer surface layer of the films, which was consistent with the LSCM results.
