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

Abstract

Multitask 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 (T 50 ). A threefold 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 Â 10 À4 , and 2.65 Â 10 À4 , 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.