Catalytic copolymerization of methyl 9,10‐epoxystearate and cyclic anhydrides under neat conditions

Abstract

The solvent‐free copolymerization of methyl 9,10‐epoxystearate 1 with different cyclic anhydrides, such as phthalic anhydride 2, succinic anhydride 3, maleic anhydride 4, or the Diels‐Alder‐adduct 5 of methyl α‐eleostearate and maleic anhydride, using a (salen)CrIIICl‐catalyst and n‐Bu4NCl as co‐catalyst is demonstrated. In this way, polyesters (Mn = 2000–10,000 g/mol) with low glass transition temperatures were formed. The reaction is characterized by sustainable aspects, for instance, the use of starting materials derived from renewable resources (>60%), low catalyst loadings, and no added solvent.Practical applicationsThe alternating ring‐opening copolymerization of epoxides such as methyl 9,10‐epoxystearate with various cyclic acid anhydrides such as phthalic anhydride and succinic anhydride, respectively, afford polyesters of narrow molecular weight distributions using a (salen)CrIIICl catalyst in the presence of n‐Bu4NCl. The pending long chain alkyl groups introduced in the polyesters by the fat derived substrates attribute amorphous properties to the polymers. Various fatty epoxides are easily available and open up the possibility for the synthesis of new highly branched polyestersPolyesters are formed by the copolymerization of methyl 9,10‐epoxystearate with different cyclic anhydrides using a (salen)CrIIICl‐catalyst in the presence of n‐Bu4NCl. The reaction is performed under neat conditions and the resulting alternating copolymers are featured by a high renewable content. In case of phthalic anhydride as co‐monomer, number average molecular weights of up to 10 kDa with narrow dispersities were obtained.