Polycaryophyllene as a Promising Plasticizer for Ethylene Propylene Diene Monomer Elastomers

This work focused on the synthesis of polycaryophyllene (Pcar) with controlled molar mass through ring-opening metathesis polymerization of caryophyllene in the presence of styrene as a nonpolar chain transfer agent (CTA). The CTA easily allowed for tuning the molar mass of resulting Pcar from a molar mass of 2 × 104 g mol–1 in the absence of CTA to molar masses ranging between 9 × 102 g mol–1 and 6.5 × 103 depending on the molar ratio of monomer to CTA. As expected, the molar mass decrease affected the glass transition temperature (T g) of styrene end-capped Pcar varying from −36 °C to a range between −40 and −65 °C. The Pcar with a low molar mass (Pcar@Sty#02) emerges as a promising biobased plasticizer candidate for the ethylene propylene diene monomer elastomer (EPDM) because it decreases EPDM T g from −46 to −54 °C. The vulcanized plasticized EPDM with Pcar@Sty#02 showed improved flexibility compared to the one plasticized with the petroleum-based plasticizer or nonplasticized EPDM.