Aliphatic–Aromatic Polyols by Thiol–Ene Reactions

Abstract

Aliphatic–aromatic polyols were synthesized by thiol–ene reactions (photochemical or thermal) using mercaptanized starting materials from bio-based compounds: limonene dimercaptan, thioglycerol, mercaptanized castor oil and isosorbide (3-mercaptopropyl) ether. Aromatic starting materials were phenols containing double bonds; ortho-allyl phenol (OAP, petrochemical-based) and eugenol (EUG, bio-based). The phenolic hydroxyl groups were blocked by alkoxylation with propylene oxide (PO) or glycidol (GLY) prior to use in thiol–ene reaction. The aromatic rings were attached to the mercaptans by reacting thiol groups with the double bonds of alkoxylated OAP (OAP–PO and OAP–GLY) and alkoxylated EUG (EUG–PO and EUG–GLY). These synthesized aliphatic–aromatic polyols were utilized for preparation of rigid polyurethane foams whose physical–mechanical properties were superior to those made only from bio-based aliphatic polyols. These rigid PU foams can be used in a wide range of applications; such as thermal insulation of freezers, buildings, pipes and storage tanks for food and chemical industries, as wood substitute, packaging materials and flotation materials.