Size-affected crystallization of trans-1,4-polybutadiene

By using different catalyst systems, two trans-1,4-polybutadiene (TPBD) sam ples with different tr trans-content and molecular weight were synthesized. The phase transition of two samples from monoclinic form to hexagonal phas e was revealed by differential calorimeter scanning and X-ray, respectively . The small-angle X-ray scattering measurements showed the remarkable discr epancy of phase transition and melting point between the two samples was at tributed to the different lamellar thickness of crystals: The crystals with different crystalline morphology and lamellar thickness w ere developed by casting different concentration TPBD solutions. Transmissi on electron microscopy morphology observations proved that annealing the sp ecimen at the temperature above the phase transition point for different ti mes resulted in the different lamellae thickening of monoclinic form. It me ans that annealing the TPBD in its hexagonal phase will also slightly favor the increase of both the phase transition temperature and melting point of hexagonal phase. (C) 2001 Elsevier Science Ltd. All rights reserved.