Induction time for cold crystallization in semi-rigid polymers: PEN and PEEK

The appearance of long range density fluctuations in two isotropic semi-rig id polymers (PEN and PEEK), during the induction period prior to crystalliz ation, when heating above the glass transition temperature, T-g, has been d emonstrated by simultaneous wide- and small-angle X-ray scattering techniqu es. The parallel use of dielectric spectroscopy, to characterize the segmen tal dynamics of the amorphous polymers polymer above T-g, and of X-ray scat tering, to estimate the induction period for cold crystallization, reveals that segmental mobility of the supercooled melt is a key factor in controll ing the development of the pre-crystalline nanostructures. (C) 2001 Elsevie r Science Ltd. All rights reserved.