Synthesis and Characterization of Dual-Functionalized Laponite Clay for Acrylic Nanocomposites

Junzuo Wang
Paul A. Wheeler
William L. Jarrett, University of Southern Mississippi
Lon J. Mathias

Abstract

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 C-13 CP/MAS NMR confirmed their structures. Quantitative solid state Si-29 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 alpha-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 alpha-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. (C) 2007 Wiley Periodicals, Inc.