resumo
The functionalization of Laponite RD platelets with different cationic, anionic, and nonionic homo- and copolymers synthesized by reversible addition-fragmentation chain transfer (RAFT) has been investigated. The effective interaction of the macromolecular RAFT agents (macro-RAFTs) with the inorganic particles is known to be of crucial importance for the successful coating of minerals with polymers via RAFT-mediated emulsion polymerization to produce polymer-encapsulated inorganic particles. The macroRAFT agents synthesized in the present work contain carefully selected reinitiating R groups, which bear either ionizable tertiary amine or quaternary ammonium moieties (from 2-(dimethylamino)ethyl methacrylate, DMAEMA), negatively charged acrylic acid (AA) repeat units, or neutral polyethylene glycol (PEG) side chains, and are capable of interacting with Laponite via different adsorption mechanisms. The equilibrium adsorption of these RAFT (co)polymers was investigated by the plotting of adsorption isotherms, and either L-type or H-type curves were obtained. The hydrophobicity of the macroRAFT was shown to promote adsorption, as did the pending configuration of the PEG block. Charge repulsion between AA and the negatively charged surface of Laponite at pH 7.5, on the other hand, was prejudicial for adsorption, while the strong electrostatic interaction between the cationic DMAEMA molecules and the Laponite surface led to high-affinity-type curves.
palavras-chave
POLYMER/LAYERED SILICATE NANOCOMPOSITES; AMPHIPHILIC BLOCK-COPOLYMERS; FREE EMULSION POLYMERIZATION; ANGLE NEUTRON-SCATTERING; NA-MONTMORILLONITE; RADICAL POLYMERIZATION; POLY(ETHYLENE GLYCOL); CARBON NANOTUBES; LATEX-PARTICLES; HYBRID LATEXES
categoria
Chemistry; Materials Science
autores
Chaparro, TD; Silva, RD; Monteiro, IS; Barros-Timmons, A; Giudici, R; dos Santos, AM; Bourgeat-Lami, E
nossos autores
agradecimentos
The authors gratefully acknowledge financial support from the funding agencies FAPESP (2010/19919-6), CNRS, and FCT/MEC from Brazil, France, and Portugal, respectively, and IUPAC for enabling the ENCIRCLE (Polymer Encapsulation of anisotropic inorganic particles by RAFT-mediated emulsion polymerization) project, of which this work was part. The authors thank Juliana Livi Antoniassi from LCT (Poli-USP) for XRD analysis.