Synthesis of high molecular weight copolymers of isobutylene and bio-renewable β-pinene via cationic polymerization

Abstract

To overcome the environmental and resource constraints of petroleum-based polyisobutylene (PIB), the cationic random copolymerization of isobutylene (IB) with the sustainable and renewable monomer β-pinene (Bp) was systematically investigated using an Al₂Et₃Cl₃/trace water initiation system. Through condition optimization (T = −80 °C, [Al₂Et₃Cl₃] = 1.00 × 10⁻² mol L⁻¹, n_IB : n_Bp = 98 : 2), IB-co-Bp copolymers with high molecular weight (M_n was up to 7.86 × 10⁴ g mol⁻¹) were successfully synthesized. This random copolymer structure and reaction mechanism were elucidated via¹H-NMR and DFT. The structural characteristics, thermal properties and mechanical properties of the copolymer were systematically investigated to clarify its composition-property relationships. More importantly, dynamic mechanical analysis of the vulcanized samples demonstrated that Bp incorporation significantly influenced the copolymer's viscoelastic behavior and network structure. The vulcanization of IB-co-Bp copolymers was shown to effectively enhance its damping performance, thus providing a novel strategy for high molecular weight bio-based PIB and a sustainable pathway for developing advanced elastomers.