Thermal degradation of poly(sulfobetaines)

Due to their interesting properties, zwitterionic polymers have been extens ively studied; however, only a few reports discuss their thermal degradatio n. The objective of this work was to study the pattern of thermal degradati on of three poly(sulfobetaines) with different lateral chain lengths and th e relationship between structure and degradation mechanism of the polymers. Because the initial decomposition temperatures are not significantly diffe rent in polymers with different ethylene glycol residues, it was possible t o study the thermal behavior of these polymers at the same temperature rang e. The apparent activation energies of the degradation for polymers, calcul ated by the Ozawa method, was different for each poly(sulfobetaine). A deco mposition mechanism is suggested, which included a Hoffman elimination of t he quaternary amine giving vinyl ethers, which in turn, decompose to carbox ylic acids, which can suffer and intramolecular cyclization reaction, and f inally produce a polypropylene like chain. (C) 1999 John Wiley & Sons, Inc.