Solvent-free one-pot sequential synthesis of biobased block copolyesters via melt polycondensation

Biobased block copolyesters were synthesized via a solvent-free, one-pot sequential melt polycondensation of glycerol, levulinic acid, malonic acid, and itaconic acid. Itaconic acid, containing a reactive carbon-carbon double bond, was incorporated to enable the post-polymerization crosslinking with dicumyl peroxide. The effect of the monomer molar ratios on the structure and properties of the block copolyesters was systematically investigated. Malonic acid functioned both as a comonomer and a secondary crosslinking site. This allowed precise tuning of the glass transition temperature, thermal stability, and degradation behavior. Thermogravimetric analysis (TGA) revealed significant enhancements in thermal stability compared to the PGMI homopolyester, which showed the lowest initial degradation temperature (T5% = 154 degrees C) and maximum degradation temperature (Tmax = 362 degrees C). Notably, PGL50M50I achieved the highest T5% of 305 degrees C and Tmax of 394 degrees C. This improvement reflected increased molecular rigidity and denser crosslinked networks with higher malonic acid content. The crosslinked block copolyesters exhibited controlled degradation profiles, which demonstrate their potential for sustainable and biomedical applications.