PMSE 484 |
| Investigations of the crystallization behavior of a series of chlorine containing polyethylenes (PEs) with either a random or an exact placement of the Cl atom reveal drastic differences in the development of their crystalline state. Sequence selection rules packing for the random systems, while polyethylenes with precise Cl substitution on each and every 21st, 19th, 15th or 9th carbon, crystallize as homopolymers. Solid-state 13C NMR give evidence for equivalence in the concentration of Cl atoms between crystalline and non-crystalline regions of the precision systems. In contrast the Cl atoms are partially discriminated against entering the crystals in the randomly distributed polymers. The orthorhombic lattice is maintained in the random up to 4.8mol% Cl while all precision Cl containing PEs pack in crystallographic cells that differ from those found in the linear or random systems. In packing long chain segments in precision chlorinated PEs, the accommodation of a larger number of Cl cause lattice distortions to the point that correlated symmetry is found within a different lattice. Implications of studying model systems in understanding the ordering of statistical branched polyolefins with relatively high conomoner content will be pointed out. |
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50 Years after the Discovery of Polymer Single Crystals: A Look Back, Current Discoveries and Future Opportunities
1:30 PM-5:20 PM, Wednesday, August 22, 2007 Westin Boston Waterfront -- Alcott, Oral
Division of Polymeric Materials: Science & Engineering |