Effect of uniaxial drawing on the structure and glass transition behavior of poly(trimethylene 2,6-naphthalate)/layered clay nanocomposites

The structure-property relationships of poly(trimethylene 2,6-naphthalate)/layered clay nanocomposites are being investigated under uniaxial drawing by using synchrotron wide angle X-ray diffraction, small angle X-ray scattering, transmission electron microscope and dynamic mechanical analyzer. The cold crystallization at 110 °C of PTN and nanocomposites samples under drawing induced the α-crystal form with the chain axis (c-axis) aligned along the drawing direction as well as parallel to the layered clay surface. However, the broad surfaces of the layered clay are oriented and rotated nearly perpendicular to the sample's surface, forming the house of cards type structure. Such structural formation of layered clay in the PTN matrix influenced the thermomechanical properties depending on the extent of confinement and surface interaction effects. The amorphous and crystallized structures of the nanocomposites showed the analogous tendency in which Tg decreased and increased before and after drawing, respectively, relative to the neat PTN. Despite the evolution of free volume after drawing, the nanocomposites exhibited an unusual positive shifting trend in Tg. The deviation of Tg in the PTN nanocomposites system is ascribed to the interplay of two competing effects; (i) the increase in the local free volume owing to the confining effect of intercalation (enhanced the chain mobility) and (ii) entropic constraint imposed by the stronger interfacial interaction due to the physical jamming of layered clay (retarded the chain mobility).