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      Glass Transition of Disentangled and Entangled Polymer Melts: Single-Chain-Nanoparticles Approach

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          Abstract

          We study the effect of entanglements on the glass transition of high molecular weight polymers, by the comparison of single-chain nanoparticles (SCNPs) and equilibrated melts of high-molecular weight polystyrene of identical molecular weight. SCNPs were prepared by electrospraying technique and characterized using scanning electron microscopy and atomic force microscopy techniques. Differential scanning calorimetry, Brillouin light spectroscopy, and rheological experiments around the glass transition were compared. In parallel, entangled and disentangled polymer melts were also compared under cooling from molecular dynamics simulations based on a bead-spring polymer model. While experiments suggest a small decrease in the glass transition temperature of films of nanoparticles in comparison to entangled melts, simulations do not observe any significant difference, despite rather different chain conformations.

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          Rheology and microscopic topology of entangled polymeric liquids.

          The viscoelastic properties of high molecular weight polymeric liquids are dominated by topological constraints on a molecular scale. In a manner similar to that of entangled ropes, polymer chains can slide past but not through each other. Tube models of polymer dynamics and rheology are based on the idea that entanglements confine a chain to small fluctuations around a primitive path that follows the coarse-grained chain contour. Here we provide a microscopic foundation for these highly successful phenomenological models. We analyze the topological state of polymeric liquids in terms of primitive paths and obtain parameter-free, quantitative predictions for the plateau modulus, which agree with experiment for all major classes of synthetic polymers.
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            Unconventional face-on texture and exceptional in-plane order of a high mobility n-type polymer.

            Substantial in-plane crystallinity and dominant face-on stacking are observed in thin films of a high-mobility n-type rylene-thiophene copolymer. Spun films of the polymer, previously thought to have little or no order are found to exhibit an ordered microstructure at both interfaces, and in the bulk. The implications of this type of packing and crystalline morphology are discussed as they relate to thin-film transistors.
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              The glass temperature and related properties of polystyrene. Influence of molecular weight

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                Author and article information

                Journal
                Macromolecules
                Macromolecules
                ma
                mamobx
                Macromolecules
                American Chemical Society
                0024-9297
                1520-5835
                20 August 2020
                08 September 2020
                : 53
                : 17
                : 7312-7321
                Affiliations
                Max Planck Institute for Polymer Research , Ackermannweg 10, D-55128 Mainz, Germany
                Author notes
                Article
                10.1021/acs.macromol.0c00550
                7482400
                Copyright © 2020 American Chemical Society

                This is an open access article published under a Creative Commons Attribution (CC-BY) License, which permits unrestricted use, distribution and reproduction in any medium, provided the author and source are cited.

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                Custom metadata
                ma0c00550
                ma0c00550

                Polymer chemistry

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