Crystallization of Biobased Long-Chain Aliphatic Polyesters as Sustainable Polymers: Effects of the Diol Structure in the Monomer Unit

Biobased polyesters, recyclable sustainable polymers derived from renewable feedstock, are promising alternatives to petroleum-based polymers. The crystallization behavior, crystal structure, and supramolecular structures of a series of biobased long-chain aliphatic polyesters, consisting of a diester of 10-undecenoic acid with isosorbide (IS), isomannide (IM), and butanediol (BD) as the midsegments, were studied by various scattering methods and Raman spectroscopy. Polyesters containing butanediol-type midsegments (C₁₈BD) participated in the crystallization by being incorporated into the orthorhombic polyethylene crystal lamellae. The polyesters containing isosorbide- and isomannide-type midsegments (C₁₈IS, C₁₈IM) were excluded from the crystal lamellae and inhibited the formation of orthorhombic crystals; the lamellar thickness was thus determined by the length of the methylene chains between the midsegments. An introduction of these midsegments (IS, IM) led to formation of some loose structures even in the molten state; acceleration of the nucleation led to a heterogeneous nucleation-like crystallization behavior, and the final spherulite size was finer.