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Investigation of the stereodefect distribution and conformational behavior of isotactic polypropylene polymerized with different Ziegler–Natta catalysts
Author(s) -
Kang Jian,
Yang Feng,
Wu Tong,
Li Huilin,
Liu Dongming,
Cao Ya,
Xiang Ming
Publication year - 2012
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.36357
Subject(s) - tacticity , ziegler–natta catalyst , polymer chemistry , natta , polymerization , nucleation , polypropylene , materials science , crystallization , crystallography , chemistry , polymer , organic chemistry , composite material
Two isotactic polypropylene (iPP) samples (PP‐A and PP‐B) were obtained by utilizing two different heterogeneous Ziegler–Natta catalysts in a given polymerization system. The molecular structure and conformational behavior of the samples were studied. The results of determination of xylene soluble material (XS) and 13 C NMR showed that the average isotacticity of the samples were nearly same. However, the results of high‐resolution high‐temperature 13 C NMR (HRHT 13 C NMR) and successive self‐nucleation and annealing (SSA) fractionation revealed that the amount of high isotacticity of PP‐B was lower than that of PP‐A, and the amount of relative medium and low isotacticity of PP‐B was higher than PP‐A, indicating that the stereodefect distribution of PP‐B was more uniform than PP‐A. The calculation of average meso sequence length from SSA was found to be in good agreement with that calculated from the results of HRHT 13 C NMR. Moreover, Fourier transformation infrared was utilized to study the influence of stereodefect distribution on the conformational behavior of iPP. The result suggested that the molecular conformation of the PP‐B was more disordered than PP‐A, the regularity of molecular structure for PP‐B was lower than that of PP‐A. The related action mechanism and the influences of which on crystallization behavior were discussed. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012