α-Pinene, the major volatile terpene of pine sap, is an abundant bio-sourced chemical feedstock and a sought-after candidate for the synthesis of new polymeric materials. However, the trisubstituted and sterically congested olefin of α-pinene renders it a notoriously difficult monomer to polymerize through various methods. For this reason, ring opening metathesis polymerization (ROMP) of α-pinene has been largely unsuccessful. Alternatively, δ-pinene is a constitutional isomer of α-pinene that features a disubstituted and more accessible olefin relocated to the neighboring ring position. We synthesized δ-pinene from α-pinene utilizing a three-step and metal-free synthesis and discovered that it undergoes ROMP to high conversion (&gt;95%), high molar mass (70 kDa), and in highly controlled fashion (PDI &lt; 1.2) using Grubbs’ 3rd generation catalyst. Poly(δ-pinene) is a promising amorphous polyolefin with a high glass transition temperature (Tg ≈ 100 °C) and a highly precise microstructure that results from the regioregular propagation of the monomer. This presentation will discuss details of ROMP on δ-pinene along with the characterization and properties of the resulting polymers and its potential use as a segment in block copolymer systems.

Turning pine sap into a precise polyolefin through ring opening metathesis polymerization

ACS Fall 2021

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