Rheo-optical FTIR Investigation of Tacicity effects in Semi-syndiotactic Polypropylenes
Abstract
With metallocene-catalyst technology, it has become possible to synthesize polymers with well-defined tacticity, thereby providing materials with a wide range of properties, with the same monomer. However, understanding the role of tacticity on the crystallization, mechanical, and flow behavior has been a challenge. We are studying semi-syndiotactic polypropylenes (ss-PP) with varying degrees of syndiotacticity, ranging from nearly atactic to nearly syndiotactic. These materials have been custom-synthesized using asymmetric, bridged cyclopentafluorenyl catalysts, and characterized using NMR, modulated DSC, mechanical testing, rheology, and rheo-optical FTIR spectroscopy. In contrast to what is seen in traditional isotactic polypropylenes, our DSC and rheological results indicate that these materials may possess a unique crystal morphology that melts at around 70°C. Rheology, flow birefringence and FTIR spectroscopy are especially sensitive to the onset and evolution of the slow crystallization process. This unique mesophase plays a critical role in the mechanical and the orientation behavior. Using rheo-optical FTIR spectroscopy, we are currently studying the distinct contributions of the mesophase and the amorphous regions in these elastomeric materials.
- Publication:
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APS March Meeting Abstracts
- Pub Date:
- March 2002
- Bibcode:
- 2002APS..MARF10010K