Interfacial liquid crystalline mesophase domain on carbon nanofillers in aromatic thermosetting copolyester matrix

Abstract

This work presents the formation process and thermophysical characteristics of preferentially oriented interfacial liquid crystalline (LC) mesophase domain emerging around graphene nanoplatelet (GNP) particles within an amorphous aromatic thermosetting copolyester (ATSP) matrix. Acetoxy-and carboxylic acid-capped matched oligomers of ATSP interact with oxygen-bearing functional groups on the GNPs during the thermal polymerization process which tethers the nanofillers to the crosslinked polymer backbone. Upon curing, a nematic phase LC network develops at the nanoparticle and matrix interface via the crystalline carbonaceous structure induced local ordering effects. The LC region exhibits a thermally reversible phase transition characteristic; attains an isotropic morphology through a heating cycle and reverses to the nematic form following a subsequent cooling cycle. Solid-state nuclear magnetic resonance spectroscopy analysis reveals the presence of a robust interfacial attachment between the GNPs and ATSP backbone. The strong covalent conjugation induces a marked upshift in the glass transition temperature (T g ) in the ATSP-GNP nanocomposites. Introduction of an LC interlayer region surrounding the nanofillers facilitated by a strong interfacial attachment mechanism could help to optimize the performance of polymer nanocomposites. V C 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46584.

Glass transition broadening via nanofiller‐contiguous polymer network in aromatic thermosetting copolyester nanocomposites

“…Furthermore, the GNP particles, being homogeneously distributed within the nanocomposite morphology, marginally slowed thermal degradation processes on the ATSP backbone chains, for which higher thermal stability of the GNP sheets shielded the polymer chains against further bond scissions (see Fig. S20 for thermogravimetric analysis results) …”