Achieving high molecular weight alternating copolymers of 1-octene with methyl acrylate via Lewis acid catalyzed copolymerization

Abstract

The radical (co)polymerization of long-chain α-olefins (C₄₊) to produce high molecular weight (M_w) polymers is of great importance. However, this process is currently faced with significant challenges due to the presence of less reactive allylic radicals during radical (co)polymerization, leading to oligomers or polymers with extremely low M_w (less than 1 × 10⁴ g mol⁻¹). Using copolymerization of 1-octene with methyl acrylate (MA) as a proof-of-concept for addressing this challenge, we present a feasible method for synthesizing high M_w α-olefin copolymers via scandium trifluoromethanesulfonate (Sc(OTf)₃)-mediated radical copolymerization. In this case, copolymers of 1-octene and MA (poly(1-octene-alt-MA)) with a M_w exceeding 3 × 10⁴ g mol⁻¹ were successfully synthesized in the presence of Sc(OTf)₃. Meanwhile, the presence of alternating 1-octene–MA sequential structures was observed. To further enhance the M_w of poly(1-octene-alt-MA), a difunctional comonomer, 1,7-octadiene, was introduced to copolymerize with 1-octene and MA. The results indicate that the incorporation of difunctional comonomer leads to a significant increase in the M_w of the copolymers synthesized. The addition of 1 mol% of 1,7-octadiene resulted in a copolymer with a remarkably high M_w of up to 13.45 × 10⁴ g mol⁻¹ while still maintaining a high degree of the alternating 1-octene–MA sequence (41%). The influence of polymerization parameters on the molecular weight were also investigated. Increasing the monomer concentration, reducing the dosage of initiator, and lowering the polymerization temperature have been found to be advantageous in enhancing the molecular weight. This approach has also been successfully applied to the synthesis of high molecular weight alternating copolymers of other long-chain α-olefins, including 1-hexene, 1-decene and 1-tetradecane, with methyl acrylate. In summary, this study provides a feasible method for converting “less activated” α-olefins into high M_w olefin copolymers. This approach holds significant potential for the production of value-added polyolefins, thus offering promising prospects for future applications.