Development of the Biobased Copolyesters of Poly(Isosorbide Terephthalate) With High Biomass Contents Using Dimer Diol and Diacid and a Distannoxane Catalyst

Biobased materials like isosorbide (ISB) reduce carbon emissions but have low reactivity, leading to low molecular weight and composition issues in copolymers, which researchers address by modifying ISB, using high‐temperature/high‐pressure conditions, or adding reactive phenolic solvents like p ‐cresol to enhance reactivity under milder conditions. To further improve this challenge, this study employs poly(isosorbide terephthalate) (PIT), a copolyester synthesized from ISB and dimethyl terephthalate (DMT), as the base polymer. However, due to the inherent brittleness and poor mechanical properties of PIT, it is further copolymerized with two types of long‐alkyl dimers, diol (DO) and diacid (DA), at incorporation levels ranging from 5 to 50 mol%. Furthermore, to address the issue of low reactivity of ISB, two catalysts, 1‐chloro‐3‐hydroxy‐1,1,3,3‐tetrabutyldistannoxane (CHTD) and titanium(IV) butoxide, are compared, and the synthesis strategy is optimized. We found that using the distannoxane catalyst of CHTD, combined with p ‐cresol as a reactive condensation reagent to DMT, resulted in the highest molecular weight and ensured accurate copolymer composition. As a result, both DO and DA series exhibit higher decomposition temperatures (350°C–390°C) and lower glass transition temperatures (90°C–150°C) than those of PIT at 302°C and 174°C, respectively. Mechanically, both series perform well, with 50% DA showing exceptional flexibility and elongation at break up to 600% and 50% DO offering higher stiffness and ultimate tensile strength 1.87 MPa. High‐frequency dielectric measurements at 29 GHz reveal a decreasing dielectric constant ( D k ) and dissipation factor ( D f ) with increased long‐alkyl dimer content, with 50% DO achieving a low D k of 2.53 and a D f of 0.0046. Additionally, 50% DO has a biocontent of 72.0%, positioning it as a strong contender for advanced, biobased insulating materials with superior performance.