Renewable co‐polymers derived from castor oil and limonene*

Biobased monomers derived from castor oil as well as from limonene suitable for thiol–ene copolymerization were synthesized. Di‐10‐undecenylether 2 was obtained via GaBr3‐catalyzed reduction of 10‐undecenyl 10‐undecenoate 1. Diene ether 2 and (R)‐limonene 5 were reacted in two steps using radical thiol–ene addition reactions to dithiol ether 4 and dithiol 7, respectively. Diene ether 2 and dithiols 4 and 7 were copolymerized using thermal initiation with AIBN and photochemically initiated thiol–ene reaction, respectively. DSC characterization revealed that these monomers can be used to synthesize polyether polysulfides with good and adjustable thermal properties. Moreover, the synthesized polymers P1 and P2 have successfully been transformed into polyether polysulfones P3 and P4 by oxidation with H2O2. An increase of the melting transition of 40–50°C was observed after oxidation.