Commercial polyolefins are often produced in grades distinguished by claims of branch content, branch length and even branch-on-branch hierarchies. The description of these complex topologies has often been left to the imagination of catalytic chemists since no clear analytic platform exists to challenge the fairly detailed propositions for branch structure. Rheological characterization coupled with NMR spectroscopy and measures of the hydrodynamic size can give some indication of the richness of branching topologies available in commercial polyolefins but these methods do not fully describe complex polyolefin topologies. In collaboration with LyondellBasell we have recently developed a new approach to understanding branched structure using small-angle scattering of neutrons that can elucidate many complicated topological features such as branch-on-branch structure and new topological descriptions of structure. The technique uses only milligrams of sample and can be carried out in less than one hour at a national user facility.
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