Telechelic ionomeric poly(butylene terephthalate): Synthesis, characterization and comparison with random ionomers

Telechelic poly(butylene terephthalate) (PBT) ionomers have been prepd. by melt synthesis using a new polycondensation process that involves a pre-reaction of sulfobenzoic acid sodium salt with butanediol. No side reaction occurs and the incorporation of the ionic groups is quant. The addn. of a buffer agent, such as Na3PO4, to the catalyst reduces the THF formation and improves the polycondensation rate. The comparison of the thermo-mech. and phys. properties between random and telechelic ionomers is also reported. The ionic groups act as chain-extension reversible electrostatic links for telechelic ionomers while act as crosslinks in random ionomers. Therefore, random ionomers present a consistently higher melt viscosity compared to telechelic ionomers and to PBT and for this reason high mol. wt. random ionomers cannot be obtained by melt polycondensation. Thermal and hydrolytic stabilities of telechelic ionomers are comparable with those of com. PBT and consistently higher respect to those of random ionomers. The presence of ionic groups decreases the translation mobility of the polymer chains thus lowering the crystn. rate.