Coregulation of Properties of Poly(butylene succinate)-Based Quaternary Copolyesters via Branched and Linear Diol Modification

Abstract Poly(butylene succinate) (PBS), a representative bio-based and biodegradable polymer, exhibits great potential in food packaging and agricultural mulch films. However, its applications are limited by high crystallinity, low toughness, low degradation rate, and poor oxygen barrier properties. To address these issues, PBS was modified by the introduction of both linear diols (C2–C12) and branched diols (1,2-dodecanediol) (1,2-do). First, the quaternary poly(butylene succinate-co-1,12-dodecanediol succinate-co-1,2-dodecanediol succinate) (PBDdS) copolyesters were synthesized by melt polycondensation. Although the branched structure hinders crystallization, the mechanical properties of the copolyesters are significantly improved. The optimum elongation at break reaches 818.1%, which is five times that of PBS. Subsequently, the 1,12-dodecanediol (1,12-Do) segment was replaced by linear diols with carbon chain lengths of 2, 6, 8, and 10. The influence of the carbon length of the main chain and the content of the branched chain on the crystallization, mechanical properties, hydrophilicity, oxygen barrier properties, and degradation properties was investigated. According to the research, polymers containing shorter-chain units, such as 1,2-ethylene glycol (1,2-EG), show higher tensile strength, superior oxygen barrier properties (2.3 times PBS), better hydrophobicity (97.00°), and a shorter degradation cycle. Conversely, polymers containing long-chain units, such as 1,12-dodecanediol, exhibit superior toughness (5.0 times PBS), better oxygen permeability, greater hydrophilicity (78.25°), and a longer degradation cycle. Furthermore, all copolymers exhibit good thermal stability. These results demonstrate an effective strategy for modulating the mechanical, barrier, surface, and degradation properties of PBS-based polyesters.