Partially bio-based aromatic poly(ether sulfone)s bearing pendant furyl groups: synthesis, characterization and thermo-reversible cross-linking with a bismaleimide

Abstract

A fully bio-based bisphenol bearing pendant furyl group, viz., 4,4′-(furan-2-ylmethylene)bis(2-methoxyphenol) (BPF) was synthesized by base-catalyzed condensation of furfural with guaiacol. New partially bio-based (co)poly(ether sulfone)s bearing pendant furyl groups were synthesized via aromatic nucleophilic substitution polycondensation of BPF and various mixtures of BPF and bisphenol-A with bis(4-fluorophenyl) sulfone in N,N-dimethylacetamide as a solvent. (Co)poly(ether sulfone)s showed inherent viscosities in the range 0.92–1.47 dL g⁻¹ and number average molecular weights , obtained from GPC, were in the range 91 300–131 000 g mol⁻¹. (Co)poly(ether sulfone)s could be cast into tough, transparent and flexible films from chloroform solutions. (Co)poly(ether sulfone)s showed 10% weight loss in the temperature range 431–481 °C and DSC showed T_g in the range 179–190 °C. Tensile strength, Young's modulus and elongation at break, obtained from tensile testing of (co)poly(ether sulfone)s containing pendant furyl groups, were in the range 76.7–83.8 MPa, 1.02–1.18 GPa and 21.4–89.7%, respectively. Most interestingly, pendant furyl groups in (co)poly(ether sulfone)s provide reactive sites for click modification and cross-linking via Diels–Alder reaction with maleimides and bismaleimides, respectively. Cross-linked (co)poly(ether sulfone) was prepared via Diels–Alder reaction of a representative (co)poly(ether sulfone) containing pendant furyl groups with 1,1′-(methylenedi-1,4-phenylene)bismaleimide (BMI) at 60 °C. The formation of cross-linked poly(ether sulfone) was demonstrated by gelation tests, solubility tests and DSC. The cross-linked copoly(ether sulfone) prepared using BMI showed enhanced tensile strength and Young's modulus compared to parent copoly(ether sulfone) and was recycled two times with retention of mechanical properties.