No Strain, No Gain? Enzymatic Ring-Opening Polymerization of Strainless Aliphatic Macrolactones.

Starting from readily available oleic and erucic acid, macrocyclic nonadecalactone (C19 ) and tricosalactone (C23 ) can be synthesized in polymerization grade purity in a four-step reaction sequence. Ring-opening polymerization (ROP) of these strainless macrolactones can be performed utilizing an enzyme as a catalyst. Despite the missing ring-strain as key driving force for smaller (strained) lactones, high molar masses (Mn ≈ 105 g mol-1 ) can be accessed in an entropically driven ROP. Polyester-19 and polyester-23 prepared feature melting temperatures well above 100 °C. Further analysis of the mechanical properties of these materials displays the resemblance to polyethylene. For example, Young's moduli on the order of 600 MPa are observed as a result of the high crystallinity of the polymer.