Molecular Design and Synthesis of Linear and Star-shaped π-conjugated Oligoanilines with reversible optoelectrochemical properties.

Today every single step toward green chemistry is a high priority to avoid global warming and environmental contaminations. In this regard, conductive, asymmetric star‐shaped, bio‐based structures, comprising tetramers of aniline (SSB‐TA) was synthesized from bio‐sourced resin using microwave irradiation. The hydroxyl‐functional SSB‐TA was characterized by FT‐IR, 1H‐NMR, 13C‐NMR, and the thermal, mechanical and electrical properties of oligomer and its hybrid with poly (hydroxyethyl methacrylate), (HEMA) were measured by TGA, DMTA and four probe conductometer. Results show that SSB‐TA is highly thermal‐stable conductive biobased oligomer (T50% = 452°C [higher than tetraniline] and σ = 8.9 × 10−4 S cm−1) and 2.5% SSB‐TA is the optimum content to improve thermal properties up to 62% and enhance the level of electrical conductivity of poly (HEMA) 12 times. This functional structure can be considered as a suitable candidate to be employed in tissue engineering and biobased adhesives contributing into the self‐assembly process, post treatment reactions as well as additive in not only HEMA but also star‐shaped lactic acid–based systems.

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.

No abstract