Synthesis and biodegradation of aliphatic polyesters from dicarboxylic acids and diols

Poly(butylene succinate) (PBS) and its copolymers, poly(butylene succinate‐co‐adipate) (PBSA) and poly(butylene‐co‐hexylene succinate) (PBHS), were synthesized by direct polyesterification of corresponding diols and dicarboxylic acids. Dimethyl benzene was used as solvent and water‐removing agent. Several catalysts were used to study the esterification of butanediol and succinic acid. Among them, SnCl2 demonstrated superior catalysis behavior. Kinetic behaviors of the synthesis of PBS, PBSA, and PBHS were investigated using SnCl2 as catalyst. By using a water trap containing a 4‐Å molecular sieve, a relatively faster reaction rate was achieved and the molecular weight of some polyesters surpassed 30,000. The variation of molecular weight distribution during the polymerization was monitored by GPC and Mw/Mn demonstrated a trend of decrease with the reaction time. The melting point (Tm) and the glass‐transition temperature (Tg) were measured by DSC technique. The results show that the incorporation of a third monomer unit to PBS lowered Tg and Tm. The biodegradation test was carried out both in the laboratory and in outdoor soil burial. The copolyesters displayed a faster degradation rate than that of PBS.