Roger Spitz

A Study of the Dispersity of Catalytic Sites in Ethylene/Propylene Copolymerization Through Computer-Assisted 13C NMR Analysis

Abstract A series of ethylene(E)/propylene(P) copolymers covering a large range of compositions is obtained by a new solution copolymerization process. The catalyst system consists of a high-activity, high-regioselectivity and high-stereospecificity Ti complex supported on MgCl2. The cocatalyst is triethylaluminum treated with diphenyldimethoxysilane. The polymers are studied by 13C NMR, and the E- and P-centered triads analyzed via the computer-assisted analytical approach. Through a systematic analysis, one can determine the minimum number of components that are needed to fit the data. Each component would correspond to a family of similar catalytic sites. The reactivity ratios (rE and rP ) of each family of active sites and the component weight factor (related to the catalytic activity) are also determined.

13C-NMR of Anionic Low-Molecular-Weight Stat-Poly(Ethylene Oxide-Co-Propylene Oxide): Correlation with Monte Carlo Simulation

Abstract Low-molecular-weight stat-poly(ethylene oxide-co-propylene oxide) copolymers have been prepared by anionic way using a new heterogeneous catalytic process. After checking the reactivity ratios of the system, the new resonance peaks due to low-molecular-weight chains (end groups) have been assigned and the copolymers were fully characterized by 13C-NMR in terms of triads centered in ethylene oxide units. Finally, signal areas have been successfully compared with computer simulation based on the Monte Carlo method, taking into account the chain length distribution resulting from anionic polymerization.

Synthesis of heterogeneous catalysts for gas phase olefin polymerization : Ziegler-Natta catalysts modified with indenyl ligands

A Ziegler-Natta catalyst was first prepared by reacting a silica/magnesium chloride support with Z r Cl 4 in the gas phase, then modified by contacting the supported zirconium with one equivalent of indenyl lithium salt. This new catalyst exhibits high activity when activated with methylaluminoxane both in slurry and gas phase homo- and copolymerizations; the polyethylene produced possesses a narrow molar mass distribution. The behavior of such a heterogeneous catalyst has been investigated under different expiremental conditions, and its behavior in gas phase copolymerization (with butene) has been compared to that of Ind 2 ZrCl 2 .