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The influence of regio‐ and stereoirregularities on the crystallization behaviour of isotactic poly(propylene)s prepared with homogeneous group IVa metallocene/methylaluminoxane Ziegler‐Natta catalysts
Author(s) -
Fischer David,
Mülhaupt Rolf
Publication year - 1994
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/macp.1994.021950426
Subject(s) - methylaluminoxane , tacticity , metallocene , polymer chemistry , crystallinity , crystallization , materials science , polymerization , post metallocene catalyst , natta , ziegler–natta catalyst , chemistry , organic chemistry , composite material , polymer
Poly(propylene)s with narrow molecular weight distributions were prepared with various methylaluminoxane‐activated metallocene‐based Ziegler‐Natta catalysts to study the influence of randomly incorporated regio‐ and stereoirregularities on the crystallization behavior. As a function of the metallocene type and the polymerization temperature, the molecular weights varied between 11500 < M n < 63 000, melting temperatures of annealed samples between 125 to 158°C, and the corresponding degrees of crystallinity, as measured by wide‐angle X‐ray scattering, between 49 and 67%. While the virgin poly(propylene)s exhibited exclusively the α‐modification, annealing and melt crystallization favored the development of the γ‐modification. The microstructure analysis by 13 C NMR spectroscopy revealed a linear correlation between the content of the γ‐modification and the average length of the isotactic segments.