β-Pinene-Based Polyester from Renewable Feedstock with Elastomeric Behavior

The utilization of biobased feedstocks in the production of polyesters is a promising opportunity as the industry focuses more and more on sustainability. Terpenes are naturally derived and inexpensive feedstocks that do not compete with agricultural land and can be transformed into a variety of biobased polymers. In particular, the bicyclic monoterpenes α-pinene, β-pinene, and 3-carene are promising candidates for high-value polymer materials when incorporating their cyclic unit in the backbone of polymers. In this work, we propose a straightforward synthesis, transforming β-pinene into nopinone lactone (NopL) via ozonolysis followed by a Baeyer–Villiger reaction without further skeletal rearrangement. Ring-opening polymerization of the lactone monomer was achieved using yttrium-bis(phenolate) and indium-salan complexes as catalysts at different monomer-to-catalyst ratios, yielding tunable molecular weights up to 105 kg·mol–1 and maintaining narrow polydispersities. The cyclobutane ring introduced in the polymer main chain induces higher rigidity in the resulting poly(nopinone lactone) (pNopL), yielding a thermally highly stable amorphous polymer with a glass transition temperature above room temperature (Tg = 23 °C). Mechanical studies show elastomeric behavior with a high elongation at break of 559 ± 46%. Incorporation of p(NopL) as a soft building block in triblock polymers (TBPE) with syndio-polyhydroxybutyrate (PHB) was successful, and stress–strain measurements showed the beneficial influence of the terpene-based polyester on the elasticity of ABA-type polymers.