Rheological and Thermal Properties of a Commercial Liquid-Crystalline Polyesteramide z J. M. GONZALEZ, MC EC MUNOZ, M. CORTAZAR, and A. SANTAMARiA, zyxwvut Departamento de Ciencia zyxw y Tecnologia de Polimeros, and J. J. PENA, Departamento de Fisica de Materiales, Universidad del Pais VascolEuskal Herriko Unibertsitatea, Facultad de QuimicalKimika Fakultatea, Apartado 1072, 20.080 San Sebastia'n, Basque Country, Spain Synopsis A commercial main-chain liquid-crystalline, naphthalene-based polyesteramide, was studied by three experimental techniques: extrusion capillary rheometry, dynamic viscoelasticity, and differ- ential scanning calorimetry (DSC) zyxwvu . From capillary rheometry a maximum at 360°C was observed in viscosity temperature curve. This result is compared with literature data for other thermotropics, and the possibility of a transition from a nematic to an isotropic phase is considered. The results obtained from dynamic viscoelasticity and DSC agree, and reveal the existence of a glass transition at 128°C (by DSC) and 137-147°C (by viscoelastic measurements, depending on frequency) as well as melting at 282°C. Annealing below 230°C produces two types of crystals, whereas annealing above this temperature gives rise to only one type of crystal, the melting temperature of which can be, depending on annealing time, as high as 340°C. The results are compiled in a phase diagram with six regions, four of them corresponding to the solid state, one to a liquid mesophase, and one to an isotropic phase. INTRODUCTION Three types of thermotropic liquid-crystalline (LC ) polymers are known: side-chain LC polymers, main-chain LC polymers, and rigid-rod LC polymers. Whereas the third kind of liquid crystalline polymers, mesogenic rods sur- rounded by flexible side chains, has scarcely been treated in the literature, studies on the other two types of liquid crystals have been extensively reported. In general, the literature on side-chain LC polymers deals with the influence of the structure on the type of mesophase, lF2 whereas works on main-chain LC polymers are often dedicated to rheology, processing, and mechanical and ther- mal properties, with emphasis on the technological and practical advantages of these relatively new materials. There are, however, very interesting work^^'^ concerning the relation between the presence of flexible or rigid nonmesogenic spacers and the types of phases formed, their transition temperatures, and the morphology of mesophases. It is generally accepted that Tennessee Eastman's 60% p -hydroxybenzoic acid-40% polyethylene terephthalate ( PET) copolyester, known as X7G, was the first available thermotropic polymer and consequently received great at- tention by a number of researchers. In recent years, intense patent activity has been developed by Hoechst Celanese, Du Pont, Kodak, ICI, and other com- panies. The excellent review by Calundann and Jaffe5summarizes the molecular Journal of Polymer Science: Part B: Polymer Physics, Vol. 28, 1533-1550 (1990) zyx 0 1990 John Wiley & Sons, Inc. CCC 0887-6266/90/0901533-018$04.00