Poly(1-octene) was synthesized by polymerization of 1-octene using high performance MgCl 2 -supported TiCl 4 in combination with triethyl aluminum (TEAl) as cocatalyst in n-hexane for 2 h. Two catalysts, C 1 (diester catalyst) having di-isobutyl phthalate as internal donor and C 2 (monoester catalyst) having ethyl benzoate as internal donor were utilized for the atmospheric polymerizations to evaluate the influence of structurally different internal donors on the productivity, rate of polymerization and molecular weight profiles. The kinetic profile assessed in terms of variation of reaction parameters like temperature, cocatalyst to catalyst molar ratio and monomer concentration was found to be dependent on them. From these kinetic analyses, optimize conditions for polymerizations of 1-octene using diester as well as monoester catalyst were elucidated. The difference in the performance of diester and monoester catalyst system can be explained in terms of stability of active titanium species and chain transfer process. NMR spectroscopy of synthesized poly(1-octene) indicate predominantly isotactic nature.
High performance MgCl 2 supported titanium catalyst having diisobutyl phthalate (DIBP) as internal donor has been synthesized. The organic components present in the catalyst have been studied through FTIR, 1D and 2D NMR spectroscopy. The results indicate presence of diethyl phthalate also in addition to DIBP. WAXD analysis has been done to study the features of MgCl 2 crystallites. Impact of donor components on the catalyst preparation leading to reaction pathways and performance for propylene polymerization has been evaluated.
Polypropylene (PP) blends with various molecular weight and isotacticity were prepared through solution blending and subjected to rapid melt quenching. Structural changes in the PP matrix during mesomorphic phase formation were measured by FTIR spectroscopy and wide-angle X-ray diffraction measurements. The blends with different molecular weight and isotacticity provided the pathway to understand their influence on mesomorphic phase formation. It is observed that low molecular weight PP with low isotacticity forms mesomorphic phase, whereas high molecular weight and low isotactic PP does not lead to the formation of mesomorphic phase.
We carried out deconvolution of the molecular weight distribution curves from gel permeation chromatography for polyolefins into individual active sites considering Flory distribution by an evolutionary-computing-based real-coded genetic algorithm, a nonlinear multivariate optimization algorithm. We applied the deconvolution to homopolymers of 1-octene synthesized using heterogeneous Ziegler-Natta catalysts with different amounts of hydrogen. The molecular weight distribution was deconvoluted in to five Flory distributions, which showed a sensitivity to hydrogen amounts. With no hydrogen presence, the peaks corresponding to high-molecular-weight fractions were intense. As the amount of hydrogen was increased, not only did the intensities of the high-molecular-weight peaks decrease, but also peaks corresponding to low-molecular-weight fractions were observed. The method allowed us to determine the active site distribution of the polymer molecular weight distribution obtained from gel permeation chromatography.
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