THE INFLUENCE OF THE EQUILIBRIUM MELTING TEMPERATURE ON THE SUPERMOLECULAR MORPHOLOGY OF SEVERAL POLYMERS

At a constant isothermal crystallization temperature (T(c)), the cryst alline morphologies of several polymers have been found to be a functi on of the melt-liquid temperature (T1). At a constant T(c) below a cri tical crystallization temperature T(c) [about 0.9 T(m)* (K)], a trans ition from a nonspherulitic to a spherulitic morphology occurs when th e melt liquid is heated above a melt-liquid transition temperature, ( T(lt)) [ approximately 1.03 T(m) (K)], where T(m) is the observed melt ing temperature of the sample. The melt-liquid transition temperature, T(lt), which experimentally affects the visible morphology of a semic rystalline polymer, is apparently indistinguishable from the thermodyn amic melting temperature, T(m), determined by the Hoffman-Weeks proce dure. The X-ray powder diffraction patterns of spherulitic and nonsphe rulitic morphologies were identical, independent of the heating-coolin g cycle. This suggests that the transition that occurs at T(lt) does n ot affect the arrangement of polymer molecules in the crystallite, but only the manner in which the crystallites are arranged in the supermo lecular morphology. The evidence suggests, at least for the polymers s tudied, that a residual order exists in the melt until the T(m) or T( lt) of the particular polymer is reached.