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Polyolefin blend miscibility: Quantitative investigations of dynamic heterogeneity

Gill, Lance
Scope and Method of Study: Using advanced solid-state NMR to study the microscopic interactions of amorphous polymer blends and the influences of each component to the dynamic heterogeneity of those miscible blends.
Findings and Conclusions: The chain-specific information gained through this experimental approach based on solid-state CODEX NMR experiments reveals that the effective glass transition for each component in a miscible blend may not occur at a common temperature. The slow chain dynamics associated with conformational changes at the chain level have unique central correlation times and correlation time distributions. The quantitative analysis of the CODEX data and methods used in this study produce results that are in good agreement with those produced by other documented methods. Results from the temperature dependent models show a clear sensitivity to the changes that occur upon blend formation when compared to the pure components. Entropy increases that occur upon mixing are detected using the CODEX experimental data. The unique advantage to this approach is that such quantitative data can be obtained without isotopic labeling, electric dipole moment constraints, or introduction of probe molecules. This demonstrates the particular capabilities of the experimental strategy that applies to a wide range of more complex macromolecular systems including polymer nanocomposites, organic/inorganic hybrid materials, biological macromolecules, and block copolymers.