How the Aliphatic Glycol Chain Length Determines the Pseudoeutectic Composition in Biodegradable Isodimorphic poly(alkylene succinate--caprolactone) Random Copolyesters.

We synthesize four series of novel biodegradable poly(alkylene succinate--caprolactone) random copolyesters using a two-step ring-opening/transesterification and polycondensation process with ε-caprolactone (PCL) as a common comonomer. The second comonomers are succinic acid derivatives, with variations in the number of methylene groups () in the glycol segment, = 2, 4, 8, and 12. The obtained copolyesters were poly(ethylene succinate--PCL) (ESCL), poly(butylene succinate--PCL) (BSCL), poly(octamethylene succinate--PCL) (OSCL), and poly(dodecylene succinate--PCL) (DSCL). We discovered a new mixed isodimorphic/comonomer exclusion crystallization in ESCL copolymers. The BSCL, OSCL, and DSCL copolymers display isodimorphic behavior. Our findings revealed a significant variation in the pseudoeutectic point position, from mixed isodimorphism/comonomer exclusion crystallization to isodimorphism with pseudoeutectic point variation from 54% to up to 90%. Moreover, we established a link between the melting temperature depression slope variation and the comonomer inclusion/exclusion balance, providing valuable insights into the complex topic of isodimorphic random copolymers.