| dc.contributor.advisor | Vana, Philipp Prof. Dr. | |
| dc.contributor.author | Primpke, Sebastian | |
| dc.date.accessioned | 2015-02-05T09:27:02Z | |
| dc.date.available | 2015-02-05T09:27:02Z | |
| dc.date.issued | 2015-02-05 | |
| dc.identifier.uri | http://hdl.handle.net/11858/00-1735-0000-0022-5DA6-1 | |
| dc.identifier.uri | http://dx.doi.org/10.53846/goediss-4910 | |
| dc.language.iso | eng | de |
| dc.publisher | Niedersächsische Staats- und Universitätsbibliothek Göttingen | de |
| dc.rights.uri | http://creativecommons.org/licenses/by-nc-nd/3.0/ | |
| dc.subject.ddc | 540 | de |
| dc.title | Mechanism and Kinetics of Catalyzed Chain Growth | de |
| dc.type | doctoralThesis | de |
| dc.contributor.referee | Vana, Philipp Prof. Dr. | |
| dc.date.examination | 2014-12-17 | |
| dc.description.abstracteng | In this work, the activation and polymerization mechanism of Catalyzed Chain Growth (CCG) polymerization of ethylene and styrene was studied. On the basis of two metallocene catalysts (Cp*2ZrCl2 and Cp*2NdCl2Li(OEt2)2) and dibenzyl magnesium (BzMgBz) and n-butyloctyl magnesium (BuMgOct) as co-catalysts the mechanism was determined via a model reaction and afterwards transferred to a typical CCG system.
The model system consisting of Cp*2ZrCl2 and BzMgBz cannot perform beta-hydride elimination and was first studied via Nuclear Magnetic Resonance (NMR). A mechanistic scheme was proposed and kinetic coefficients were successfully derived via modeling in PREDICI. Data analysis was simplified due to direct calculation of the coefficients from NMR data. The analytical toolbox was extended to Ultra-Violet/Visible (UV/Vis) spectroscopic studies. Based on this method the influence of di-n-butyl ether (DBE) on the catalyst/co-catalyst system was studied and a strong lowering of rate coefficients was found.
The co-catalyst was switched to BuMgOct, where beta-hydride elimination of the alkyl chains was found to be fast at 70 °C and dominating the activation mechanism. This hinders the system to perform ethylene polymerization.
The UV/Vis method was applied to the reaction of Cp*2NdCl2Li(OEt2)2 with BzMgBz. Equilibrium constants between a monoalkylated complex and the benzyl brigded bimetallic Nd-Mg complex were determined in dependence of temperature. The reaction turned out to be strongly dependent on the presence of other coordinating molecules like DBE.
The activation mechanism of Cp*2ZrCl2 and BzMgBz was successfully utilized for modeling the polymerization of styrene-d8 by NMR studies. It was found that the basic steps of the exchange reactions are similar to those of activation. The model was successfully extended to the introduction of polymeric species, and kinetic parameters were derived.
The process of monomer addition was found to be chain-length dependent and the
influence of the single rate coefficients on the reaction were screened. It was found that a low catalyst precursor concentration can lead to a rate enhancement. Addition of tetrahydrofurane was found to be disadvantageous for the polymerization reaction. BuMgOct as co-catalyst leads to a process where the termination reaction of the alkyl chains is the main catalyst activation mechanism. Chain growth occurs starting from the
hydride catalyst formed during termination. beta-hydride elimination of the polystyrene chain is much slower than for alkyl chains.
Polymerization of styrene was successfully studied via UV/Vis analysis and a
gravimetric- and Infra-Red (IR)-determination of the conversion. The catalysts Cp*2ZrCl2 and Cp* 2NdCl2Li(OEt2)2 were activated with either BzMgBz or BuMgOct. The influence of DBE on each system was investigated individually. Modeling based on the proposed model was successful. The system of Cp*2ZrCl2 and BuMgOct indicated an additional activation pathway. For the system Cp*2NdCl2Li(OEt2)2 with BzMgBz it was found that the termination reaction via beta-hyrdide elimination and reformation of the active catalyst is the main reaction pathway. The kinetic model was successfully applied to the polymerization of ethylene in a batch reactor and the polymerization was modeled successfully.
As part of a cooperation with Dr. Florian Ehlers and Jan Schwellenbach a new method for the production of PE-b-P3HT block copolymers was found. The formed polymer has combined properties regarding the solubility and viscosity of polyethylene and poly-3-hexyl-thiophene. | de |
| dc.contributor.coReferee | Meyer, Franc Prof. Dr. | |
| dc.subject.eng | Catalyzed Chain Growth | de |
| dc.subject.eng | CCG | de |
| dc.subject.eng | PREDICI | de |
| dc.subject.eng | modeling | de |
| dc.subject.eng | simulation | de |
| dc.subject.eng | polymerization | de |
| dc.subject.eng | kinetics | de |
| dc.subject.eng | reaction mechanism | de |
| dc.identifier.urn | urn:nbn:de:gbv:7-11858/00-1735-0000-0022-5DA6-1-7 | |
| dc.affiliation.institute | Fakultät für Chemie | de |
| dc.subject.gokfull | Chemie (PPN62138352X) | de |
| dc.identifier.ppn | 817544461 | |