Structure and properties of aromatic naphthalene thermotropic liquid crystal copolyester/MWCNT composites

Aromatic naphthalene thermotropic liquid crystal copolyesters (N-TLCP) have strong intermolecular forces and possess excellent comprehensive properties. In this study, the N-TLCP/MWCNT nanocomposites derived from 6-hydroxy-2-naphthoic acid (HNA), 2,6-naphthalene dicarboxylic acid (NDA), terephthalic acid (TA), 4,4′-dihydroxy biphenyl (BP) and carboxyl MWCNT were prepared via in situ “one-pot” melt polymerization method. The structure and properties of N-TLCP/MWCNT composites were fully analyzed. The interaction between MWCNT and TLCP matrix was confirmed by FTIR, XPS, Raman spectrum and rheometric measurements; and the strong interaction was observed for addition of a small amount of MWCNT (<0.5 wt%), which was attributed to the fact that the functional group COOH on the surface of MWCNTs enhances the dispersion state of the CNTs and molecular interaction through hydrogen bond/chemical covalent bonds. As a result, the glass transition temperature, melting temperature, thermal stability and mechanical properties of the N-TLCP/MWCNT composite was improved. However, more addition of MWCNT would tend to aggregate and impact the molecular weight and structure of the N-TLCP by the chemical reaction between its COOH group and OH group of the N-TLCP, which is not favor for improving the mechanical properties.