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Keywords:

  • glass transition;
  • molecular motion;
  • morphology;
  • multiwalled carbon nanotubes;
  • nanocomposites;
  • nanotechnology;
  • polysilsesquioxane

Abstract

Diglycidyl ether of bisphenol A (DGEBA)-bridged polyorganosiloxane precursors have been prepared successfully by reacting diglycidyl ether of bisphenol A epoxy resin with 3-aminopropyltriethoxysilane. Acid-modified and unmodified multiwalled carbon nanotube (MWCNT) were dispersed in the diglycidyl ether of bisphenol A-bridged polyorganosiloxane precursors and cured to prepare the carbon nanotube/diglycidyl ether of bisphenol A-bridged polysilsesquioxane (MWCNT/DGEBA-PSSQ) composites. The molecular motion of MWCNT/DGEBA-PSSQ nanocomposites was studied by high-resolution solid-state 13C NMR. Acid-modification can improve the affinity between MWCNT and the polymer matrix. The molecular motion of the DGEBA-PSSQ decreased with acid-modified MWCNT content. However, when unmodified MWCNT was used, the molecular motion of the DGEBA-PSSQ was increased. SEM and TEM microphotographs confirm that acid-modified MWCNT exhibits better dispersion than unmodified MWCNT in DGBEA-PSSQ. The dynamic mechanical properties of acid-modified MWCNT/DGBEA-PSSQ composites are more favorable than those of unmodified MWCNT. Tg of the DGEBA-PSSQ decreased from 174.0 °C (neat DGEBA-PSSQ) to 159.0 °C (1 wt % unmodified MWCNT) and 156.0 °C (1 wt % acid-modified MWCNT). The storage modulus (at 30 °C) of the DGEBA-PSSQ increased from 1.23 × 109 Pa (neat DGEBA-PSSQ) to 1.65 × 109 Pa (1 wt % acid-modified MWCNT). However, when unmodified MWCNT was used, the storage modulus of the DGEBA-PSSQ decreased to 6.88 × 108 Pa (1 wt % unmodified MWCNT). At high temperature, above 150 °C, storage modulus of nanocomposites was higher than that of neat polymer system. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 472–482, 2008