Modulation of furanic-sulfonated isophthalic copolyesters properties through diols units control

Abstract

A series of furanic sulfonated copolyesters containing 20mol.% of sodium sulfoisophthalate units were synthesized via a two-step melt polycondensation process from (5,5′-isopropylidene-bis(ethyl 2-furoate)) and (dimethyl 5-sodiosulfoisophthalate) with different diols: alkyl (1,2-ethanediol, 1,4-butanediol, 1,6-hexanediol) or ether (diethylene glycol and triethylene glycol). Structural characterization of copolyesters was deeply investigated by 1H and 13C (1D and 2D) NMR spectroscopy and by SEC. The results showed that the final structures not only depend on the initial monomers composition but also on the process which can induce at high temperature etherification and decarboxylation side reactions. For the alkyldiols series low molecular weights were obtained when side reactions occurred and when the monomer excess was difficult to remove from the reaction medium. Finally, it has been displayed that the modulation of diols composition allows for tuning copolyesters properties. Thus the copolyesters are amorphous with Tg ranging from 19 to 66°C whereas their liquid water sorption and hydrolytic degradation resistance are in relation with the flexibility of the chain and their water accessibility to the ester linkages.