|Macromolecules 2011, 44, 3062-3072 Macromolecules ARTICLE (7) There is substantial band broadening caused by some factors not well understood at this moment. An in-depth investigation is needed in order to improve TGIC resolution capability.

Summary: Olefin block copolymers produced by chain shuttling catalysis exhibit crystallinity characteristics that are distinct from what would be expected for typical random olefin copolymers with comparable monomer compositions produced from either 'single-site' or heterogeneous catalysis. Olefin block copolymers produced by chain shuttling catalysis have a statistical multiblock architecture. A unique structural feature of olefin-based block copolymers is that the intra-chain distribution of comonomer is segmented (statistically non-random). Fractionating an olefin block copolymer by preparative temperature rising elution fractionation, TREF, results in fractions that have much higher comonomer content than comparable fractions of a random copolymer collected at an equivalent TREF elution temperature. We have developed a ''block index'' methodology which quantifies the deviation from the expected monomer composition versus the analytical temperature rising elution fractionation, ATREF, elution temperature. When interpreted properly, this index indicates the degree to which the intra-chain comonomer distribution is segmented or blocked. The unique crystallization behavior of block copolymers determine the magnitude of the block index values because the highly crystalline segments along an otherwise non-crystalline chain tend to dominate the ATREF (and DSC) temperature distributions.

Summary: High temperature thermal gradient interaction chromatography (HT‐TGIC) is a newly developed technique to analyze comonomer distributions in polyolefins. This paper documents the key differences between crystallization elution fractionation (CEF) and HT‐TGIC, and the advantages of using multiple detectors in HT‐TGIC to provide comprehensive microstructure characterization. A demonstration of the technique using a specifically designed blend, provides comprehensive data in less than 1.5 hours of analysis time by HT‐TGIC. This paper also reports that HT‐TGIC has excellent short term repeatability.