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Molecular structure and properties of ethylene‐ co ‐styrene polymers obtained from [norbornane‐7,7‐bis(1‐indenyl)]titanium dichloride catalyst system
Author(s) -
Expósito M. T.,
Vega J. F.,
MartínezSalazar J.
Publication year - 2007
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.26797
Subject(s) - comonomer , norbornane , materials science , copolymer , polymer , polymer chemistry , polymerization , molar mass distribution , styrene , composite material
Ethylene‐ co ‐styrene polymers have been synthesized using the new catalyst system [norbornane‐7,7‐bis(1‐indenyl)]titanium dichloride, and characterized by SEC, 13 C‐NMR, DSC, and dynamic‐mechanical analysis. The copolymers have higher average molecular weights compared with those produced in our group with other single‐site catalysts systems in the same conditions. More specifically, the homopolymers are ultra high molecular weight polyethylenes (molecular weight higher than 10 6 g mol −1 ) and with a narrow molecular weight distribution. All samples have shown an unprecedented homogeneous chemical composition with a random incorporation of the comonomer during the polymerization. The expected relationship between thermal properties and the amount of comomoner related to the exclusion of the phenyl units from the crystalline structure has been found, but the correlation is slightly different from those found in other copolymers. This is likely due to the different molecular features of the copolymers. In addition, intense and narrow mechanical relaxations have been found in the samples tested, pointing towards an extremely homogeneous microstructure. The materials obtained show a conspicuous strain hardening during tensile deformation at high strains, not only related to the constrain imposed by the bulky phenyl group in the amorphous region, but additionally to the extremely high number of entanglements in this region as a consequence of the high molecular mass of the samples. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007