Preparation and characterization of high performance Schiff-base liquid crystal diepoxide polymer

Abstract

A novel Schiff-base liquid crystal diepoxide polymer was prepared via a thermal copolymerization of a Schiff-base epoxy monomer (PBMBA) with a diamine co-monomer (MDA). We first proposed that specific effects of highly conjugated Schiff-base moiety on thermal properties of the Schiff-base epoxy polymer (PBMBA/MDA). Thermal degradation behavior of the polymer was characterized using thermogravimetric analysis (TGA) under nitrogen and under air, respectively. Thermogravimetric data obtained from TGA under nitrogen and under air reveal that PBMBA/MDA exhibits higher thermal stability compared with bisphenol-A type epoxy polymer (DGEBA/MDA) and other mesogene-containing epoxy polymer. It is worth pointing out that the outstanding residual char value for the Schiff-base epoxy polymers had been rarely reported. For thermal degradation mechanism of PBMBA/MDA under nitrogen, thermogravimetric analysis/infrared spectrometry (TG-IR) were used to investigate volatile components, and scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) was used to explore morphologies and chemical components of the residual char. The effects of calcination temperature and calcination time on evolution of morphologies and chemical components of the residual char have been studied. It is proposed that the highly π-conjugated Schiff-base moiety is not only involved in a formation of intramolecular hydrogen bonding increasing the onset thermal degradation temperature (Td), but also possesses an effective charring ability retarding a further degradation of polymers. Due to the presence of the specific effects, the thermal stability of the Schiff-base epoxy is improved.