In situ synthesis of poly(ethylene terephthalate) (PET) in ethylene glycol containing terephthalic acid and functionalized multiwalled carbon nanotubes (MWNTs) as an approach to MWNT/PET nanocomposites

Multiwalled carbon nanotubes (MWNTs) (diameter range, 10-20 nm) were functionalized with 4-methoxybenzoic acid and 4-ethoxybenzoic acid via a Friedel-Crafts reaction in polyphosphoric acid to afford methoxybenzoyl- and ethoxybenzoyl-functionalized MWNTs. As-received MWNT, methoxybenzoyl-functionalized (MeO-MWNT), and ethoxybenzoyl-functionalized (EtO-MWNT) nanotubes were dispersed in ethylene glycol (EG). Because of the structural similarity, the mixture of EtO-MWNT (0.4 wt %) and EG was a homogeneous dispersion, whereas MeO-MWNT and pristine MWNT were dispersed in EG rather heterogeneously at the same loading. In situ polycondensation of EG and terephthalic acid in the presence of pristine MWNT, MeO-MWNT, or EtO-MWNT was carried out to generate the corresponding MWNT/PET, MeO-MWNT/PET, and EtO-MWNT/PET nanocomposites. High molecular weight poly(ethylene terephthalates) (PETs), with intrinsic viscosity range 0.6-0.7 dL/g (o-chlorophenol at 30 +/- 0.1 degrees C), were obtained in all cases. In comparing the images from scanning electron microscopy (SEM) taken at the same magnification for these nanocomposites, it is clear that the MWNT/PET system has poor MWNT dispersion and the MeO-MWNT/PET system has a better dispersion. However, EtO-MWNT in PET matrix is most homogeneously dispersed, and the interfacial boundary between EtO-MWNT and PET matrix is practically nondiscernible.