Synthesis and characterization of copolyanhydrides of carbohydrate-based galactaric acid and adipic acid

•A series of meso-galactaric acid based copolyanhydrides was polymerized.•Copolyanhydrides consisted of O-acetylated meso-galactaric acid (AGA) and adipic acid moieties.•Thermal properties of the copolymers varied depending on monomer composition.•Increase in the AGA content had clear increasing effect on the Tg and Tm.•Results offer utilization route for meso-galactaric acid producible from pectin-rich industrial side-streams.

A series of copolyanhydrides, consisting of 2,3,4,5-tetra-O-acetylgalactaric acid (AGA) and adipic acid (AA) as monomer units, was polymerized. Synthesis of AGA monomer consisted of two steps. First, O-acetylation of galactaric acid secondary hydroxyl groups was performed using acetic anhydride as a reagent. Acetic anhydride was then further used as a reagent in the synthesis of diacetyl mixed anhydride of AGA. Polymerizations were conducted as bulk condensation polymerization at 150 °C. Thermal properties of the copolymers varied depending on monomer composition. Increase in the AGA content had a clear increasing effect on the Tg. A similar increasing effect was observed in Tm. The degree of crystallinity decreased as AGA content increased. There was a slightly lowering tendency in the molecular weights of the obtained polymers when the AGA content in the polymerization mixtures increased. The described synthesis route shows that bio-based aldaric acid monomers are potential candidates for the adjustment of thermal properties of polyanhydrides.

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