Synthesis of Exfoliated PMMA/Na-MMT Nanocomposites via Soap-Free Emulsion Polymerization

PMMA/Na-MMT nanocomposites were synthesized through a soap-free emulsion polymerization of methyl methacrylate (MMA) using 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS). A conventional anionic surfactant, dodecylbenzenesulfonic acid sodium salt (DBS-Na), was also used to compare with AMPS in the interaction with pristine Na-MMT. Both surfactants were intercalated into the layers of the pristine Na-MMT dispersed in water before polymerization. The nanocomposites with AMPS were exfoliated during polymerization because AMPS made the polymer end-tethered on pristine Na-MMT. The nanocomposites were exfoliated up to the 10 wt % content of pristine Na-MMT relative to the amount of MMA. The molecular weight of PMMA obtained from the nanocomposite with AMPS decreased, and the glass transition temperature (Tg) and storage modulus (E′) of the nanocomposites became higher as the amount of Na-MMT increased.