Synthesis, characterization and potential applications of 5-hydroxymethylfurfural derivative based poly(β-thioether esters) synthesized via thiol-Michael addition polymerization

Dimethylphenylphosphine was used to efficiently initiate the thiol-Michael addition polymerization to yield 5-hydroxymethylfurfural (HMF) derivative based poly(β-thioether esters) with relatively high molecular weights (over 10 000 g mol−1) under mild conditions. The synthesized linear polymers with hydroxyl groups as side groups could be used as hot melt adhesives. Tests on wood substrates showed an adhesive strength of 1.5 MPa. Additionally, copolymers with various compositions were obtained by adding different ratios of 1,6-hexanedithiol to 1,4-benzenedithiol. 1H NMR analysis revealed that the ratios of these two dithiol monomers present in the copolymers matched well the theoretical ratios. The reversibility of the Diels–Alder reaction between the furan rings and the maleimide groups allowed the poly(β-thioether esters) to be dynamically crosslinked. As the weight ratio of crosslinkers to polymers increased from 1 : 10 to 1 : 2, the storage modulus at room temperature significantly enhanced from 1.5 MPa to 1691 MPa. Additionally, one-pot thiol-Michael polymerization to synthesize HMF derivative based thermoplastic elastomers (TPEs) was investigated. The polymerization reaction was completed within 40 min at room temperature. The maximum elongation at break of TPEs could reach >450%. The use of the Diels–Alder reaction to crosslink TPEs provided an efficient approach to improve their mechanical properties. The HMF derivative based polymers synthesized in this study had a wide range of thermal and mechanical properties. These polymers can be easily synthesized at room temperature via the combination of thiol-Michael and Diels–Alder reactions.