You will be shown an abstract from a biomedical research paper. Given this abstract, your task is to extract all unique entities of the following types: ["Chemical"].

Please return the output as a JSON object of the format: {"Chemical": ["Arsenic", ...]}. The keys should be entity types and values should be lists of extracted entities belonging to the corresponding type. If you cannot find entities belonging to a specific type, the value should be [].

Only output the JSON object and do not include any additional text.

Abstract:

Biobased polyesters with composition-dependent thermomechanical properties: synthesis and characterization of poly(butylene succinate-co-butylene azelate). Environmentally friendly poly(butylenesuccinate-co-butyleneazelate) (P(BS-co-BAz)s) aliphatic copolyesters with composition-dependent thermomechanical properties were synthesized from succinic acid (SuA), 1,4-butanediol (BDO), and dimethylazelate (DMAz) through a two-step polycondensation reaction. The molar SuA/AzA ratio was varied from 4:1 to 1:4, and the chemical structure and molecular characteristics of resulting (co)polyesters were characterized by NMR and SEC, whereas thermal properties and crystallinity were studied by differential scanning calorimetry (DSC), dynamic mechanical thermal analyses (DMTA), and X-ray diffraction (XRD). A good agreement between theoretical and experimental SuA/AzA molar ratios in the copolyesters was achieved, together with the recovery of semicrystalline random copolymers of uniform composition along the chains. NMR, DSC, DMTA, and XRD results show that depending on their composition the P(BS-co-BAz) copolyesters might find applications from elastomers to high-impact thermoplastics.
{"Chemical": ["P(BS-co-BAz) copolyesters", "poly(butylenesuccinate-co-butyleneazelate)", "poly(butylene succinate-co-butylene azelate)", "aliphatic copolyesters", "SuA", "P(BS-co-BAz)s", "1,4-butanediol", "AzA", "copolyesters", "polyesters", "succinic acid", "dimethylazelate", "(co)polyesters", "DMAz", "BDO"]}