The effect of thermal treatment on the structure and relaxation processes of olefinic polymers synthesized with metallocene catalysts

The relationships between the structure and properties have been establishe d in several copolymers of ethylene and 1-hexene, synthesized by a metalloc ene catalyst. A dependency with composition and thermal history has been fo und. The branches cannot be incorporated into the orthorhombic crystal latt ice, and consequently, structural parameters such as crystallinity and crys tal lattice constants are considerably affected as 1-hexene content increas es in the copolymer. The beta-relaxation does not appear in the homopolymer . In the copolymers, it is shifted to lower temperature and its intensity i s increased as 1-hexene content raises. On the other hand, the alpha-mechan ism associated to motion within the crystalline regions is also moved to lo wer temperatures but its intensity is diminished as 1-hexene content increa ses in the copolymer. (C) 2000 Elsevier Science Ltd. All rights reserved.