Synthesis and Characterization of Dual-functionalized Laponite Clay for Acrylic Nanocomposites
Originally published in Journal of Applied Polymer Science Volume 106, Issue 3, 5 November 2007, Pages 1496-1506
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Dual-functional laponites were synthesized by a condensation reaction with silane coupling agents followed by cation exchange reaction with quaternary ammonium salts. FTIR and solid state 13C CP/MAS NMR confirmed their structures. Quantitative solid state 29Si DP/MAS NMR spectra indicated that clay silanol groups reacted with silane coupling agents by a decrease in the silanol peak and appearance of a new Si-O-Si peak. Dual-functionalized laponites showed improved dispersion in organic solvents and vinyl monomers. One dual-functional laponite modified with both photosensitizer and coinitiator photo-initiated polymerization of an acrylate (2-phenoxyethyl acrylate, PEA) and a methacrylate (MHMA, methyl α-hydroxymethylacrylate). TEM showed laponite clay sheets were exfoliated in poly(PEA); while a combination of exfoliated, intercalated and tactoid morphologies was found in poly(methyl α-hydroxymethylacrylate). The other dual-functionalized laponite clay with edge-bound methacrylate units copolymerized with methyl methacrylate and led to a high grafting amount and graft efficiency. PMMA nanocomposites showed higher storage modulus both below and above the glass transition temperature compared to the PMMA control. © 2007 Wiley Periodicals, Inc.