Role of polymer-clay interactions and nano-clay dispersion on the viscoelastic response of supercritical CO2 dispersed polyvinylmethylether (PVME)-Clay nanocomposites

Mihai Manitiu, Steven Horsch, Esin Gulari, Rangaramanujam M. Kannan

Research output: Contribution to journalArticle

Abstract

Clay dispersion and polymer-clay interactions play a key role in producing property enhancements in nanocomposites; yet characterizing them in complex polymer-clay systems is often a challenge. Rheology can offer insights into clay dispersion and clay-polymer interactions. We have investigated the viscoelastic response for a series of supercritical CO2 (scCO2) processed polyvinylmethylether (PVME)/clay nanocomposites with varying polymer-clay interactions and nano-clay dispersion. PVME is used in this study because it is highly swellable in scCO2, thereby enabling processing of PVME/clay mixtures without the presence of a co-solvent. Since PVME and natural clay are water-soluble, highly dispersed PVME-clay nanocomposites were prepared using water, followed by lyophilization in the presence of polymer. In this 'weakly interacting', but highly dispersed systems, with clay loadings above the percolation threshold, terminal behavior was observed in the linear viscoelastic moduli (i.e. no low frequency plateau is observed). When the nanocomposites were processed in scCO2, with 15 wt% of 30B and I.30P, the WAXD patterns of the resultant nanocomposites were largely comparable, indicating partial dispersion, with intercalation peaks. However, the rheology of these two nanocomposites were significantly different despite similar inorganic volume loading (4 vol%). Even with less dispersion compared to the water-based system, the low-frequency moduli were significantly more enhanced, accompanied by a plateau, and a cross-over frequency shift. Neglecting the small differences in the actual clay content between these clays (4-5 vol% of inorganic matter), this suggests that rheology may be sensitive to strong interactions between the clay surfactant and the polymer. Therefore, polymer-clay interactions and clay-clay interactions may both be important in the ability to sustain a "so-called" percolated network, rather than just clay dispersion.

Original languageEnglish (US)
Pages (from-to)3786-3796
Number of pages11
JournalPolymer
Volume50
Issue number15
DOIs
StatePublished - Jul 17 2009
Externally publishedYes

Keywords

  • Dispersed polymer-clay nanocomposites
  • Rheology
  • Supercritical CO processing

ASJC Scopus subject areas

  • Organic Chemistry
  • Polymers and Plastics
  • Materials Chemistry

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