Thesis (Ph. D.)--West Virginia University, 2000. / Title from document title page. Document formatted into pages; contains xvii, 289 p. : ill. Includes abstract. Includes bibliographical references.

Thesis (Ph. D.)--University of Missouri-Columbia, 1998. / Typescript. Vita. Includes bibliographical references (leaves 327-343). Also available on the Internet.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1982. / Typescript. Vita. Description based on print version record. Includes bibliographical references.

No description available.

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

The reactions of five trihalomethyl group substituted electron-deficient olefins with electron-rich olefins were studied in order to determine the effect of steric bulk upon the subsequent reactions of the tetramethylene intermediates initially formed. Reactions of β-trihalomethyl group substituted olefins yielded cyclobutane adducts, resulting from a gem dimethyl effect which accelerates the collapse of the tetramethylene intermediate. Reactions of α-trihalomethyl group substituted olefins gave both small molecule and polymeric products. Polymers were produced in reactions where steric interactions between the termini of the tetramethylene intermediates prevented ring formation. Ester substituted electron-deficient olefins reacted with electron-rich olefins to give both cyclobutane and 6-alkoxy-3,4-dihydro-2H-pyran derivatives. A transition from concerted to stepwise reaction was observed, resulting from steric hindrance in the transition state leading to [4+2] cycloaddition. Exploratory studies of ion-radical propagation and chain transfer in polymerization processes were also conducted. The acid catalyzed free radical polymerization of imines was attempted, along with chain transfer studies of zwitterion-radical intermediates.

Heterogeneous Ziegler-Natta catalysts are responsible for most of the industrial production of polyethylene and polypropylene. A unique feature of these catalysts is the presence of more than one active site type, leading to the production of polyolefins with broad distributions of molecular weight (MWD), chemical composition (CCD) and stereoregularity. These distributions influence strongly the mechanical and rheological properties of polyolefins and are ultimately responsible for their performance and final applications. The inherent complexity of multiple-site-type heterogeneous Ziegler-Natta catalysts, where mass and heat transfer limitations are combined with a rather complex chemistry of site activation in the presence of internal and external donors, plus other phenomena such as comonomer rate enhancement, hydrogen effects, and poisoning, makes the fundamental study of these systems a very challenging proposition. In this research project, new mathematical models for the steady-state and dynamic simulation of propylene polymerization with Ziegler-Natta heterogeneous catalysts have been developed. Two different modeling techniques were compared (population balances/method of moments and Monte Carlo simulation) and a new mechanistic step (site transformation by electron donors) were simulated for the first time. Finally, polypropylene tacticity sequence length distributions were also simulated. The model techniques showed a good agreement in terms of polymer properties such as molecular weights and tacticity distribution. Furthermore, the Monte Carlo simulation technique allowed us to have the full molecular weight and tacticity distributions. As a result, the 13C NMR analytical technique was simulated and predicted.

Heterogeneous Ziegler-Natta catalysts are responsible for most of the industrial production of polyethylene and polypropylene. A unique feature of these catalysts is the presence of more than one active site type, leading to the production of polyolefins with broad distributions of molecular weight (MWD), chemical composition (CCD) and stereoregularity. These distributions influence strongly the mechanical and rheological properties of polyolefins and are ultimately responsible for their performance and final applications. The inherent complexity of multiple-site-type heterogeneous Ziegler-Natta catalysts, where mass and heat transfer limitations are combined with a rather complex chemistry of site activation in the presence of internal and external donors, plus other phenomena such as comonomer rate enhancement, hydrogen effects, and poisoning, makes the fundamental study of these systems a very challenging proposition. In this research project, new mathematical models for the steady-state and dynamic simulation of propylene polymerization with Ziegler-Natta heterogeneous catalysts have been developed. Two different modeling techniques were compared (population balances/method of moments and Monte Carlo simulation) and a new mechanistic step (site transformation by electron donors) were simulated for the first time. Finally, polypropylene tacticity sequence length distributions were also simulated. The model techniques showed a good agreement in terms of polymer properties such as molecular weights and tacticity distribution. Furthermore, the Monte Carlo simulation technique allowed us to have the full molecular weight and tacticity distributions. As a result, the 13C NMR analytical technique was simulated and predicted.

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