Molecular Observation of Constraint Release in Polymer Melts

Zamponi, Michaela; Wischnewski, A.; Monkenbusch, M.; Willner, Lutz; Richter, D.; Likhtman, Alexei E.; Káli, György; Faragó, B.

doi:10.1103/physrevlett.96.238302

Cited by 42 publications

(64 citation statements)

References 11 publications

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“…Corresponding experiments have been reported in Ref. [90]. Provided that the matrix chains are short enough relative to the tagged chains, the results are obviously (and not unexpectedly) in favor of the constraint-release effect.…”

Section: (D) Constraint Releasesupporting

confidence: 70%

Molecular Dynamics in Polymers

Kimmich

2012

Principles of Soft-Matter Dynamics

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Suitably modified versions of the Langevin equation introduced in Chap. 2 will be taken as a general basis for analytical explanations of macromolecular-chain motions. The reader will straightforwardly be led from the dynamics of freely draining polymer chains as the simplest case to entangled-chain phenomena and finally to mesoscopic confinement effects. The Langevin equation-based treatments will be supplemented step by step by additional force terms specific for the diverse model scenarios. The restriction to this equation-of-motion strategy is expected to favor the comprehensibility of this demanding field. The relaxation-mode solutions will be expressed in the form of predictions for diverse experimental techniques outlined in Chap. 3. This in particular refers to spin-lattice relaxation, coherent and incoherent neutron scattering, and mechanical relaxation.

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Section: (D) Constraint Releasesupporting

confidence: 70%

Molecular Dynamics in Polymers

Kimmich

2012

Principles of Soft-Matter Dynamics

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“…Apparently, the short chain melt does not simply act as a heat bath but couples to the internal ring relaxation modes and slows them down for longer times. Similar results were found on binary linear polyethylene melts [33].…”

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confidence: 76%

Caught in the Tube

Napolitano

2015

Physics

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Using neutron spin echo spectroscopy, we show that the segmental dynamics of polymer rings immersed in linear chains is completely controlled by the host. This transforms rings into ideal probes for studying the entanglement dynamics of the embedding matrix. As a consequence of the unique ring topology, in long chain matrices the entanglement spacing is directly revealed, unaffected by local reptation of the host molecules beyond this distance. In shorter entangled matrices, where in the time frame of the experiment secondary effects such as contour length fluctuations or constraint release could play a role, the ring motion reveals that the contour length fluctuation is weaker than assumed in state-of-the-art rheology and that the constraint release is negligible. We expect that rings, as topological probes, will also grant direct access to molecular aspects of polymer motion which have been inaccessible until now within chains adhering to more complex architectures. [7]. Furthermore, in the fields of material science and engineering, blends of different polymer architectures including rings are employed aiming to produce polymer materials with emerging properties [8,9]. Recently, simulation science in particular led to new insights into ring dynamics on a coarse grained level [10,11]. In chemistry, novel procedures have enabled the production of appreciable amounts of pure, well-defined rings [12][13][14][15][16] that in turn permit detailed physical investigations of their structure and dynamics.One of the important and fundamental goals of this broad approach is the understanding of entangled polymer dynamics far beyond the state-of-the-art standpoint. For cyclic polymers, reptation as well as the related relaxation through contour length fluctuations (CLFs) and constraint release (CR) are fully suppressed, requiring qualitatively different relaxation behavior in ring melts. The center of mass (c.m.) motion in such melts was found to be subdiffusive, characterized by a t 3=4 power law [17] which was understood in terms of the lattice animal theory [18] as well as in a recent approach of the diffusion of centrality [19]. Very recently the internal dynamics was also successfully addressed experimentally [17]: Rings relax via a combination of free internal loop-motion and loop migration. As a result, the mean-square displacement for internal segment motion follows a weak t 0.3 power law, a finding also supported by simulation [20].The unique ring topology also severely affects the ring structure and dynamics when blended with linear chains. Simulations showed that other than in the ring melts the ring conformation is close to Gaussian and no compaction is visible, at least in the range of ring concentrations below overlap [21]. On the other hand, rheological investigations display a very strong influence of small amounts of linear chains on the rheological response of a ring melt [22]. Threading linear chains through the rings crucially influences the long-range diffusion of rings [23,24], e.g., single-molecul...

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“…We note that such a Rouse behavior of an entangled chain was also observed in studies of the single chain dynamic structure factor from NSE on a long polyethylene chain diluted with short oligomers, from which the Rouse monomeric friction coefficient of the short matrix could be determined. 18 In d-PBO thy80k/PBO 15k the diluted tube diameter becomes comparable with the end-to-end distance of the backbone and this explains the Rouse-like behavior observed for the inactive blend. In the second case d-PBO thy-80k/PBO 5k, due to the low short chains volume fraction, the tube dilution of the entangled backbone is only partial.…”

Section: Figure 10: Storage and Loss Moduli For D-pbo Thy-80k And Pbomentioning

confidence: 70%

Hydrogen Bonding in a Reversible Comb Polymer Architecture: A Microscopic and Macroscopic Investigation

et al. 2016

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Abstract:In this work an investigation of the hydrogen bonding mechanism in a transiently branched comb-like polymer system in the melt is reported. The system under investigation consists of a polybutylene oxide (PBO)-based backbone, randomly functionalized with thymine (thy) groups, in combination with shorter PBO graft chains, end-functionalized with diaminotriazine (DAT) groups. The functional groups are able to associate through hydrogen bonding. The hetero-complementary association of these groups leads to the formation of a transiently branched comb-like polymer system. Since recently virtually exclusive heterocomplementary association could be observed in the supramolecular association of telechelically-modified oligomeric PEG chains, here we aim to extend the supramolecular assembly mechanism towards branched structures. The present work combines Small Angle Neutron Scattering (SANS) experiments on a selectively labeled system with macroscopic dynamics measured in linear rheology response. The association of thy-and DAT-modified components was studied as a function of temperature and composition. The scattering function reveals the formation of a block copolymer and can be exclusively attributed to heterocomplementary association of the hydrogen bonding groups. Scattering functions of nonfunctionalized blends are also reported as references and evidence the change in the microstructure induced by the hetero-complementary association. All scattering profiles were described by means of the Random Phase Approximation (RPA) formalism from which the average aggregation number i.e. comb arm functionality and the equilibrium association constant could be determined directly in the melt state as a function of temperature. On the other hand, rheological measurements were performed in the melt state to study the influence of the reversible bonds on the macroscopic dynamics of the polymer system. The rheology data are in good agreement with the SANS results and confirm the transient comb-like branched architecture. The supramolecular association exhibits characteristic bonding times of the groups in the order of 1 s at -25 °C and therefore makes the thy-DAT pair an ideal candidate for the development of responsive materials that combine permanent and transient linkages for novel applications and self-healing properties.

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Molecular Observation of Constraint Release in Polymer Melts

Cited by 42 publications

References 11 publications

Molecular Dynamics in Polymers

Molecular Dynamics in Polymers

Caught in the Tube

Hydrogen Bonding in a Reversible Comb Polymer Architecture: A Microscopic and Macroscopic Investigation

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