Polymer/Layered Silicate Nanocomposites from Thermally Stable Trialkylimidazolium-Treated Montmorillonite.
Polymer/Layered Silicate Nanocomposites from Thermally
Stable Trialkylimidazolium-Treated Montmorillonite.
Gilman, J. W.; Awad, W. H.; Davis, R. D.; Shields, J.
R.; Harris, R. H., Jr.; Davis, C. H.; Morgan, A. B.;
Sutto, T. E.; Callahan, J.; Trulove, P. C.; DeLong, H.
Chemistry of Materials, Vol. 14, No. 9, 3776-3785,
polymers; nanocomposites; imidazolium; polyamide;
polystyrene; thermal stability
The limited thermal stability of alkylammonium cations
intercalated into smectite minerals (e.g.,
montmorillonite, MMT) and the processing instability of
some polymers [polyamide-6 (PA-6) and polystyrene (PS)]
in the presence of nanodispersed MMT have motivated the
development of improved organophillic treatments for
layered silicates. Success in this regard should enable
the preparation of polymer/layered silicate
nanocomposites from thermoplastic polymers that require
high melt-processing temperatures or long residence
times under high shear and from thermoset resins with
high cure temperatures. Our efforts to address some of
these issues focus on the use of new thermally stable
imidazolium-treated layered silicates for the
preparation of nanocomposites. Several
trialkylimidazolium salt derivatives were prepared with
propyl, butyl, decyl, and hexadecyl alkyl chains
attached to the imidazolium through one of the
nitrogens. These imidazolium salts were used to prepare
the corresponding treated layered silicates. We report
here that the use of 1-alkyl-2,3-dimethylimidazolium
salts to replace the sodium in natural MMT gives
organophillic MMT with a 100 C improvement in thermal
stability (in N2) as compared to the
alkylammonium-treated MMT. The use of
1-alkyl-2,3-dimethylimidazolium salt in fluorinated
synthetic mica (FSM) also gives a 100 C improvement in
thermal stability. The use of
1,2-dimethyl-3-hexadecylimidazolium-treated MMT gives an
exfoliated PA-6 nanocomposite and, depending on
processing conditions, either a partially exfoliated or
an intercalated polystyrene nanocomposite.