Renewable Aliphatic Polyesters from Fatty Dienes by Acyclic Diene Metathesis Polycondensation

Abstract

AbstractThree renewable, linear, aliphatic polyesters were prepared by Acyclic diene metathesis (ADMET) polymerization of α,ω‐dienes derived from fatty acids. Condensation of 9‐decenoic acid with allyl 9‐decenoate, ethylene glycol, and 9‐decen‐1‐ol proceeded in high conversion (≥94%) and purity (>99%) to give α,ω‐dienes suitable for subsequent polycondensation. Polymerization was achieved using 1.0 mol% Hoveyda‐Grubbs second‐generation metathesis catalyst in combination with 2.0 mol% 2,6‐dichloro‐1,4‐benzoquinone as an isomerization inhibitor under vacuum to drive equilibria toward polymer formation via ethene removal. Polymerization in the presence of solvent promoted ring‐closing metathesis (RCM) at the expense of polymer, with cyclization increasing as the concentration of monomer decreased. Thus, ADMET polymerizations were performed in bulk to mitigate RCM. The resulting polymers with M n and Ð that ranged from 6.6 to 8.9 kDa and 1.75–2.14, respectively, contained 76% or more of renewable carbon content and exhibited atom and carbon economies of greater than 84%. Melt (T m) and crystallization (T c) temperatures were 20.8–48.4 °C and 3.8–37.6 °C, respectively, and increased as ester density decreased within polymer structures. Sub‐ambient glass transitions ranged from −10.3 to −50.0 °C. Lastly, the polymers were thermally stable below 320 °C, as 10% mass loss (T10) occurred above 340 °C, which indicated that they existed as liquids for at least 319 °C (T10 − T m) before decomposing.