Long-chain aliphatic polyesters from plant oils for injection molding, film extrusion and electrospinning

Dicarboxylic acids derived from plant oils are attractive intermediates for the synthesis of polymer materials. Similar to polyethylene, the incorporation of long methylene sequences enables polymer crystallization and renders polyesters hydrophobic. Long-chain aliphatic polyesters that incorporate the full length of the plant oil methylene sequences possess high melting points (Tm > 100 °C) and crystallization temperatures, suitable for thermoplastic processing. This differs from shorter chain analogs. Here, the incorporation of aromatic comonomers such as terephthalic acid is required in order to improve dimensional stability, heat distortion temperature and mechanical properties of aliphatic polyesters. More recently, entirely chemical catalytic conversions of plant oils have complemented the existing approach of biotechnological ω-oxidation as a route to long-chain aliphatic monomers. Self-metathesis generates (after subsequent double bond hydrogenation) a long-chain α,ω-diacid ester along with a stoichiometric amount of linear hydrocarbon as the main products (Scheme 1). In this context, the implementation of a commercial-scale refining of palm oil to chemicals by metathesis with 1-butene is notable. Due to the specifics of the process and of olefin metathesis in general, a significant amount of self-metathesis will occur as a side reaction to yield 1,18-octadecene dioate. A different route has recently been found with isomerizing alkoxycarbonylation (Scheme 1). Other than metathesis, the long-chain methylene sequence of the fatty acid feedstock is fully incorporated into the α,ω-diacid ester product. This is a result of the highly kinetically controlled outcome of the isomerizing carbonylation reaction vs. the equilibrium product distribution from metathesis. Scheme 1 Main products of the isomerizing carbonylation and self metathesis, respectively, of unsaturated fatty acid esters.