Influence of the chain microstructure on the properties of metallocene-based thermoplastic elastic polyolefines
FacultiesFakultät für Naturwissenschaften
LicenseStandard (Fassung vom 03.05.2003)
Polymeric materials are unmatched in the diversity of their properties, such as flexibility, stiffness or mechanical strength. One still open point is to tailor these material properties by controlling the molecular architecture. Olefin-based polymers have attracted considerable interest because the development of metallocene catalysts with defined molecular structures and geometries enables the synthesis of polymers with controlled composition and stereoregularity. Certain catalysts are capable of producing low crystalline olefines showing thermoplastic-elastic properties. Since the mechanical properties of elastomers depend on the amount and distribution of crosslinks, one important point in the development of semicrystalline thermoplastic elastomeric polymers is to direct the distribution of crystallizable segments und to study the resulting morphology with respect to the macroscopic properties. In this work the morphology of propene based polymers polymerized by homogeneous transition metal catalysis in a single polymerization step but at various polymerization conditions was explored. Two types of polymers were investigated: Polyketones, which consist of two chemically different phases, propene/ethene/CO, and propene homopolymers. The origin and the nature of the crystalline network are described. The influence of the polymer morphology in the macroscopic properties is explored on different length scales combining various analytical techniques, such as DSC, WAXS and scanning force microscopy. The results obtained clearly show that changing the polymerization conditions can open new possibilities to modify the chain microstructure without any change on the chemical side. The length and the distribution of crystallizable blocks can be varied in such a way that new materials with tailored mechanical properties become available. The incorporation of CO functionalities in the polymer backbone leads to materials with distinct differences in the chemical properties.
Subject HeadingsPolyolefine [GND]
Scanning force microscopy [LCSH]