Polyesters derived from 4,4’-dixydroxybenzophenone: syntheses and properties

Abstract

To meet polymeric material sustainability requirements of the modern polymer industry, a novel diphenyl-based monomer, dimethyl 2,2’-((carbonylbis(4,1-phenylene))bis(oxy))diacetate (DPBD), was prepared from 4,4'-dixydroxybenzophenone, derived from potentially bio-sourced 4-hydroxybenzoic acid. The diester monomer DPBD was polymerized with either 1,4-butanediol, 1,6-hexanediol, 1,8-octanediol, or 1,4-cyclohexanedimethanol as aliphatic diols to afford aliphatic/aromatic copolyesters (P₁–P₄). The copolyesters were characterized using gel permeation chromatography, differential scanning calorimetry, thermogravimetric analysis, dynamic mechanical analysis, and tensile testing, as well as biodegradation and earthworm acute toxicity assays. The effects of diol carbon chain length and cyclic diol monomers on polyester properties were investigated. From the results, the weight-average molecular weight (M_w) of the polyesters ranged from 37.5 to 45.5 kg/mol, glass transition temperature (T_g) ranged from 65 to 78 °C, initial thermal decomposition temperature (T_d,5%) varied from 324 to 353 °C, yield strength varied from 45 to 56 MPa, and elongation-at-break ranged from 215 to 290%. The properties can be adjusted by tuning the monomer structure, which induced a degradation rate of up to 4.6% after incubation in soil for 30 weeks, in contrast to poly(ethylene terephthalate) (PET) which showed no degradation under the same conditions. The ecotoxicity of the polyesters to earthworms remained low, even at high concentration polymer concentration tested (4000 mg/kg soil), the survival rate was above 82%. Therefore, polyesters offer a good combination of structure-to-property serving as potential alternatives to petroleum-based materials.

Graphical abstract