Structure And Properties Of 2,5-Furandicarboxylic Acid-based Copolyesters

In recent years,the renewable biomass resources have great superiority in terms of abundant stock,and wide sources.Therefore,the preparation of bio-based polyester materials using biomass resources instead of traditional petrochemical resources has attracted much attention.The platform compound 2,5-furandicarboxylic acid(FDCA),which can be obtained from lignin,has similar properties to petroleum-based terephthalic acid(PTA)and is expected to be its biobased alternative in the future.Therefore,it is important to investigate structure and properties of FDCA-based copolyesters.In this study,a series of novel FDCA copolymers were successfully synthesized by performing an eco-friendly two-step melt polycondensation method,and their chemical structures and comprehensive properties were characterized and investigated.The main contents and conclusions are as follows:1.Bio-based poly(propylene 2,5-furandicarboxylate-co-propylene2,5-thiophenedicarboxylate)(PPFTFs)were prepared from 2,5-thiophenedicarboxylic acid(TDCA),2,5-furandicarboxylic acid(FDCA),and propylene glycol(PDO).The effect of the amount of TDCA in the copolyester on the final properties of the final product was analyzed and studied.NMR carbon spectra showed that the copolyesters were random copolyesters.Due to the large carboxyl angle(148°)in TDCA and the weak electronegativity of the sulfur atoms in the thiophene ring,the interactions between the molecular chains are small.Therefore,with the increase of TDCA content,the chain flexibility of the copolymers was greatly improved,which led to a gradual decrease of the glass transition temperature of the copolymers.At the same time,the secondary relaxation strength of the copolyester increased with the increase of TDCA.The crystallization ability of poly(propylen 2,5-thiophenedicarboxylate)(PPTF)was significantly better than that of poly(propylene 2,5-furandicarboxylate)(PPF).All copolyesters exhibited good thermal stability.2.Bio-based poly(butylene 2,5-furandicarboxylate-co-butylene2,5-thiophenedicarboxylate)(PBFTFs)were prepared from 2,5-thiophenedicarboxylic acid(TDCA),2,5-furandicarboxylic acid(FDCA),and butanediol(BDO).The effect of the TDCA content in the copolyesters on the final structure and properties were analyzed and studied.By analyzing the IR and NMR spectra of the PBFTFs copolyesters,it was determined that the ideal structure of the copolyesters was successfully synthesized.With increasing TDCA content,the melting temperature of PBFTFs showed a typical V-shape and all copolyesters exhibited heterogeneous homodimeric behavior.The elongation at break of the copolyesters increased due to the introduction of TDCA with larger carbonyl intercalation.3.Poly(decylene terephthalate-co-decylene furandicarboxylate)(PDTFs)were prepared from dimethyl terephthalate(DMT),1,10-decanediol(DDO),and dimethyl2,5-furandicarboxylate(DMFD).The effect of the DMFD content in the copolyester on the final structure and properties were analyzed and studied.Due to the introduction of long chain decanediols,all copolyesters have fast crystallization ability and are semi-crystalline materials.All polymers have a high thermal stability.When the DMFD content exceeds 50%,the copolyesters show a crystal structure similar to that of poly(decylene 2,5-furandicarboxylate)(PDF).Due to having the lowest crystallinity,the intermediate percentage of copolyesters has the highest elongation at break.