Density Fluctuations as Precursors of Crystallization in a Thermoplastic Polyimide

The present report is part of a general study aiming to investigate the possible evidence of electron density fiuctuations as precursors of crystallization in polymers with different chain stiffness. The present experiments on the thermoplastic polyimide (New-TPI) with varying induction times, studied by small- and wide-angle X-ray scattering (SAXS and WAXS), reveal the onset of long-range ordering prior to crystal growth. Slow crystallization, slightly above Tg indicates the development of well resolved SAXS patterns associated with long range order before the development of crystalline peaks in the WAXS region. The experimental results suggest that density fiuctuations control at sufficiently low temperatures the precrystallization mechanisms during the embryonic period.