In order to improve the mechanical and oxygen barrier properties of poly­(butylene succinate) (PBS), two series of sugar-containing PBS copolyesters with different molecular stiffness were synthesized and comparatively investigated, in which a cyclic alditol, isosorbide (Is) or 2,3-O-isopropylidene-l-threitol (ITh) was, respectively, used as a comonomer. Both cyclic alditols were easily available from biomass feedstock, such that Is is a bicyclic compound derived from d-glucose, and ITh is a monocyclic acetalized compound coming from naturally occurring l-tartaric acid. All these copolyesters containing up to 30 mol % of sugar-based units had satisfactory number-average molecular weights in the 16 000–83 000 g mol–1 range, and presented a random microstructure together with excellent thermal stability. The sugar-containing copolyesters were all semicrystalline and still possessed the monoclinic crystal structure of PBS. The incorporation of either Is or ITh units with rigid cyclic structure into PBS chain decreased the crystallinity and crystallization rate of PBS, while it enhanced its glass transition temperature. In addition, the partial replacement of 1,4-butanediol by sugar-based units endowed PBS with steadily enhanced hydrophilicity. Depending on the type and content of sugar units, the copolyesters show different oxygen barriers and mechanical properties. It was found that copolyester with bicyclic Is sugar units exhibited a better oxygen barrier and mechanical property than that with monocyclic ITh units.

During combustion, 2π + π cycloaddition between phenylmaleimide moieties occurred as cross-linking reaction, which enhanced the char yield to achieve flame retardance and anti-dripping of the copolyester.

A series of phosphorus-containing copolyester prepolymers were first sythesized from dimethyl terephthalate (DMT), ethylene glycol (EG), and 2-carboxyethyl (phenyl)phosphinic acid (CEPPA) by molten transesterification and polycondensation, and then solid-state polymerization (SSP) was conducted for different reaction times (t SSP) so as to prepare higher molecular weight copolymers. The intrinsic viscosity was increased with the increase of t ssp, but decreased with the increase of CEPPA content. The sequence distribution of resultant copolyesters was analyzed by 1H NMR. It was found that the randomness of copolyesters was decreased after SSP, and the transesterification occurred mainly at the ester bonds formed by CEPPA and EG, resulting in the chain growth. DSC results showed that SSP treatment was favorable to enhance the crystallization ability of the obtained copolyesters.

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