Copolyester/layered silicate nanocomposites: The effect of the molecular size and molecular structure of the intercalant on the structure and viscoelastic properties of the nanocomposites

摘要

The preparation of poly(ethylene glycol-co-cyclohexane-1,4-dimethanol terephthalate)/layered silicate nanocomposites via a melt-intercalation technique is reported. Layered silicates modified with different alkyl ammonium intercalants have been used for this purpose. A comparison is made between carefully chosen pairs of the nanocomposites, the choice depending on the cation-exchange capacity or the intercalant concentration of the organically modified montmorillonite, to study the effects of the molecular size and molecular structure of the intercalant. The structure of the nanocomposites is characterized with wide-angle X-ray diffraction. The presence of well-defined diffraction peaks and an observed increase in the interlayer spacing in the nanocomposites imply the formation of an intercalated hybrid. To investigate the viscoelastic behavior, these nanocomposites are also subjected to dynamic mechanical analysis. The dynamic mechanical properties show an increase in the storage modulus of the nanocomposites over the entire temperature range studied (except in the transition region from 68 to 78 degreesC) in comparison with that of the pristine polymer. The size of the intercalant molecule and the presence of functional groups capable of forming favorable interactions with the polymer govern the amount of polymer infiltrating the clay gallery space and control the increase in the modulus of the nanocomposite. The tan 5 peak signifying the glass-transition temperature shifts to lower temperatures in the nanocomposites. Interestingly, the nanocomposites show less damping than the pristine polymer. This behavior is understood in terms of the confinement of the polymer chains in the clay interlayer. (C) 2003 Wiley Periodicals, Inc. [References: 31]