Environmentally Responsive “Hairy” Nanoparticles:  Mixed Homopolymer Brushes on Silica Nanoparticles Synthesized by Living Radical Polymerization Techniques

• Published in: Journal of the American Chemical Society Vol. 127; no. 17; pp. 6248 - 6256
• Main Authors: Li, Dejin, Sheng, Xia, Zhao, Bin
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society 04.05.2005; Amer Chemical Soc
• Subjects: Applied sciences; Chemistry; Chemistry, Multidisciplinary; Colloidal state and disperse state; Exact sciences and technology; General and physical chemistry; Organic polymers; Physical and chemical studies. Granulometry. Electrokinetic phenomena; Physical Sciences; Physicochemistry of polymers; Properties and characterization; Science & Technology; Solution and gel properties; PHASE-SEPARATION; SELF-ASSEMBLED MONOLAYERS; BLOCK-COPOLYMERS; SWITCHABLE MORPHOLOGY; POLY(METHYL METHACRYLATE)/POLYSTYRENE BRUSHES; SURFACE-INITIATED POLYMERIZATION; SELECTIVE SOLVENT; AMBIENT-TEMPERATURE; MULTIWALLED CARBON NANOTUBES; GRAFTING DENSITY; Infrared spectrometry; Organic solvent; Polydispersed polymer; Functionalization; Solution structure; Styrene polymer; NMR spectrometry; Spherical particle; Particle suspension; Silica; Submicron particle; Amphiphilic polymer
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja0422561

This article reports on the preparation of environmentally responsive “hairy” nanoparticles by growth of mixed poly(tert-butyl acrylate) (PtBA)/polystyrene (PS) brushes from silica particles using living radical polymerization techniques and subsequent hydrolysis of PtBA to produce amphiphilic mixed poly(acrylic acid) (PAA)/PS brushes. Silica particles were synthesized by the Stöber process and were functionalized with an asymmetric difunctional initiator-terminated monolayer. Surface-initiated atom transfer radical polymerization of tBA was carried out in the presence of a free initiator. Kinetics study showed that the polymerization was well controlled. By cleaving PtBA off the particles, the molecular weights of the grafted and free polymers were found to be essentially identical. Mixed PtBA/PS brushes were obtained by the nitroxide-mediated radical polymerization of styrene from PtBA particles. The M n of the grafted PS was found to be the same as that of the free PS formed in the solution from the free initiator. Amphiphilic mixed PAA/PS brush-coated nanoparticles were synthesized from mixed PtBA/PS particles by hydrolysis of PtBA with iodotrimethylsilane. Tyndall scattering experiments and 1H NMR study showed that the mixed PAA/PS particles can be dispersed and form a stable suspension in CHCl3, a selective solvent for PS, and also in CH3OH, a selective solvent for PAA, demonstrating the capability of these hairy nanoparticles to undergo chain reorganization in response to environmental changes.