Synthesis of multitask star‐shaped oligoaniline: Introducing a novel, efficient epoxy hardener

Abstract

AbstractMultitask star‐shaped oligoaniline (S‐TAH) was synthesized using microwave irradiation in three steps: preparation of phthalic acid‐ capped tetra‐aniline (as the arm), synthesis of a tetrafunctional biobased core, and subsequently, coupling arms to the core, using a divergent approach. A biobased core was synthesized through a direct condensation reaction of pentaerythritol, with l‐lactic acid. The chemical structures were extensively characterized using Fourier‐transform infrared and proton nuclear magnetic resonance spectroscopy. The performance of S‐TAH, as a multitask hardener for bisphenol A‐based epoxy resin (EP), was evaluated using differential scanning calorimetry, thermal gravimetric analysis, dynamic thermomechanical analyses (DMTA), and four‐prob conductometry. Peaks of cure exotherms for S‐TAH/EP (1:1) systems appear at 135°C with a tail‐like peak around 175°C. Compared to conventional amine‐cured EP, the thermal stability of the S‐TAH/EP cured was significantly higher, that is, ~ 40°C enhancement in half weight loss temperature (T50). A three‐fold improvement in char yield was observed. From DMTA, the material cured with S‐TAH displays representative storage moduli in glassy (9.4 GPa) and rubbery (5.2 GPa) states reflecting a uniform network and viscoelastic behavior. The electrical conductivities (σ) of the pure S‐TAH and the epoxy systems cured with S‐TAH/EP are 4.3 × 10−4, and 2.65 × 10−4, respectively. T star‐shaped oligoaniline is a promising multitask hardener—functioning as hardener, thermal stabilizer, electrically conductive and toughening agents—which can be versatilely applied in thermal resistance anticorrosive coatings and conductive adhesives.