1 e-Polymers 2008, no. 074 http://www.e-polymers.org ISSN 1618-7229 Modification of poly(butylene terephthalate) by reaction with 1,4-butane sultone; synthesis and thermal characterization of new telechelic PBT ionomers Corrado Berti, Annamaria Celli, Elisabetta Marianucci, * Micaela Vannini Dipartimento di Chimica Applicata e Scienza dei Materiali, Università di Bologna, Viale Risorgimento 2, 40136 Bologna, Italy; fax: +39 051 2093220; email: elisabetta.marianucci@mail.ing.unibo.it (Received: 11 January, 2008; published: 15 June, 2008) Abstract: New telechelic poly(butylene terephthalate) (PBT) ionomers, characterized by the presence of some aliphatic sulfonated chain ends, were prepared by reaction with the 1,4-butane sultone. Two methods of synthesis were compared and the final polymers, containing different percentages of ionic groups, were characterized, with particular attention to the thermal properties. Thermogravimetric analysis shows that the presence of ionic groups does not modify the thermal stability of PBT. The differential scanning calorimetry indicates that the crystalline phase and the crystallinity degree of PBT do not change in the presence of ionic chain ends, whereas the crystallization rate was found to be strongly modified. The ionomers crystallize at very high rate, due to the nucleating effect of the ionic aggregations formed in the melt. Keywords: Ionomers; 1,4-butane sultone; PBT; Thermal properties Introduction Ionomers are an important class of polymers characterized by the presence of low concentrations, less than 10 mol%, of covalently bonded ionic substituents which have consistent effects on the final physical and rheological properties [1-5]. Indeed, with respect to the nonionic analogues, ionomers exhibit notable improvements in thermal and mechanical performance, generally attributed to the formation of ionic aggregates, which retard the translation mobility of polymeric chains and cause an increment in melt viscosity. Most investigations have focused on random ionomers, in which ionic groups are randomly distributed as pendant groups along the polymer chains. The morphology of these materials is characterized by a multiphase structure, not perfectly controlled, where ionic regions in the form of multiplets or larger aggregates (clusters) are present. However, the ionic associations tend to be prevented by entanglements of the main polymeric backbone and thus the characterization of the supermolecular architecture and the structure-property relationships are sometimes a little ambiguous. On the other hand, there are significantly few studies concerning telechelic ionomers, which are characterized by ionic groups located only at the polymer chain ends [6-8]. In this case, the ionic associations, occurring only at the terminals, are not impeded by entanglements of the main chains and give rise to an electrostatic chain extension: thus, the microstructure is found to be better defined. As a result, the correlation between structure and properties is simplified.