Synthesis of a renewable polyamine from canola oil by photocatalyzed thiol‐ene addition of cysteamine under green conditions

Abstract

A renewable polyamine was obtained by the photocatalyzed thiol-ene addition of cysteamine hydrochloride (CAHC) to canola oil under mild conditions, using green solvents, a simple reaction system and a low-power 365 UV lamp. A comparison of four different solvents was performed and the effect of onestep and stepwise addition of CAHC to the reaction mixture was investigated. The solubilities of CAHC and oil in the solvent played a crucial role in the conversion of double bonds due to diffusion limitations and also due to changes in the opacity of the reaction mixture. Isopropanol showed a good solubility balance, dissolving well the oil and at the same time partially dissolving CAHC. During the one-step addition of CAHC, the maximum conversions achieved were of 38.2% and 69% (in 24 h) with ethanol and isopropanol as solvents, respectively. The selectivity to the thiol-ene product was very high with both solvents (i.e., 88%–90% at 4 h). The stepwise addition of CAHC significantly improved the double bond conversion (i.e., 93% at 24 h) using isopropanol as solvent. Finally, the polyamine was used as a comonomer in the aminolysis of a fatty cyclic carbonate affording a fully biobased elastomeric polyhydroxyurethane (PHU).