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, nIB:nBp = 98:2), IB-co-Bp copolymers with high molecular weight (Mn was up to 7.86×104 g/mol) were successfully synthesized. This random copolymer structure and reaction mechanism were elucidated via 1H-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.