Tube Dynamics Works for Randomly Entangled Rings

Qin, Jian; Milner, Scott T.

doi:10.1103/physrevlett.116.068307

Cited by 19 publications

(20 citation statements)

References 38 publications

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“…Our TIPS‐PEN segregation to the bottom of the linear PS blend film is a result of the short solvent drying time afforded by ultrasonic spray, which in principle can operate from the wet regime, where the sprayed film is still liquid, to the dry regime, where a powder coating results from complete solvent evaporation before droplets reach the substrate surface 41 . Optimized for device fabrication is the intermediate regime, where a small amount of solvent takes a much shorter time to dry on the coated surface compared with spin or cast coating, thus allowing for multiple coatings without solvent orthogonality.…”

Section: Resultsmentioning

confidence: 99%

“…To manage computational cost, N ~ 65 beads are included in a polymer molecule. Notice that

N ≲ N_{e} \approx 73

, the number of entangled beads, meaning that the model polymer molecule is barely one entangled blob in the tube model 40‐42 . Nevertheless, the small‐scale simulation captures the key differences between the types of PS in the kinetics of individual beads (near joining junctions for branched variants).…”

Section: Resultsmentioning

confidence: 99%

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Phase segregation mechanisms of small molecule‐polymer blends unraveled by varying polymer chain architecture

et al. 2021

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As phase separation between the small‐molecule semiconductor and the polymer binder is the key enabler of blend‐based organic field‐effect transistors (OFETs) fabricated by low‐cost solution processing, it is crucial to understand the underlying phase separation mechanisms that determine the phase morphology, which significantly impacts device performance. Beyond the parameter space investigated in previous work, here we investigate the formation of blends by varying the branch architecture of the polymer binder and by shortening the solvent dry time using ultrasonic spray casting. The phase morphologies of the resulting blend films have been thoroughly characterized with a variety of techniques in three dimensions over multiple length scales, including AFM, energy‐filtered transmission electron microscope, and neutron reflectivity, and have been correlated with electrical transport performance. From the results, we have inferred that the phase morphology is kinetically determined, limited by the inherent slow movement of polymer macromolecules. The kinetic picture, supported by molecular dynamics modeling, not only consistently explains our observations but also resolves inconsistencies in previous works. The achieved mechanistic understanding will guide further optimization of blend‐based organic electronics, such as OFETs and organic photovoltaics.

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Section: Resultsmentioning

confidence: 99%

“…To manage computational cost, N ~ 65 beads are included in a polymer molecule. Notice that

N ≲ N_{e} \approx 73

Section: Resultsmentioning

confidence: 99%

Phase segregation mechanisms of small molecule‐polymer blends unraveled by varying polymer chain architecture

et al. 2021

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“…Both linear and nonlinear viscoelastic behavior of monodisperse linear polymers with high molecular weights have been successfully described by tube-based theories. 3,[5][6][7][8][9] For branched polymers, such as star, H-, comb and Cayley-tree polymers, reptation dynamics is strongly suppressed by the effectively localized branch points. These polymers thus relax in a hierarchical way, starting from the retraction of the outermost branch arms and proceeding to inner layers till the core of the molecules.…”

Section: Introductionmentioning

confidence: 99%

Microscopic Picture of Constraint Release Effects in Entangled Star Polymer Melts

Cao

Wang

2016

Macromolecules

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The constraint release (CR) effect in entangled branched polymers is generally described by the widely accepted Dynamic Tube Dilation (DTD) theory based on the tube model, which predicts the stress relaxation function reasonably well, but not the dielectric or arm end-to-end vector relaxation. The microscopic picture of entanglement dynamics even in the simple case of star polymers is still not fully resolved. In this * To whom correspondence should be addressed entanglements sitting on a target star arm, only those destroyed by the arm free end dominate the arm end-to-end vector relaxation, while the constraint release events produce an accelerated drift of the mean positions of these specific entanglements towards the arm-end, which is an essential mechanism for understanding the relaxation of star polymers in concentrated solutions or melts. Our findings call for an examination of the microscopic foundation of conventional DTD picture and inspire the development of quantitative theories with consideration of more microscopic details.

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“…For examining the assumptions made in different theoretical models and validating their predictions, molecular dynamics (MD) simulations based on bead-spring models have been widely accepted as one of the most suitable candidates because they allow the direct visualization of the conformations and trajectories of individual polymers as well as their topological interactions with neighboring chains, which are essential for understanding the microscopic relaxation mechanisms underlying entanglement dynamics [16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31]. However, the high demand for computational power has limited MD simulations to systems with relatively low polymer molecular weights and smaller system sizes in comparison with real experimental setups.…”

Section: Introductionmentioning

confidence: 99%

Determining Tube Theory Parameters by Slip-Spring Model Simulations of Entangled Star Polymers in Fixed Networks

2019

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Dynamical properties of branched polymer melts are determined by the polymer molecular weights and architectures containing junction points. Relaxation of entangled symmetric star polymers proceeds via arm-retraction and constraint release (CR). In this work, we investigate arm-retraction dynamics in the framework of a single-chain slip-spring model without CR effect where entanglements are treated as binary contacts, conveniently modeled as virtual “slip-links”, each involving two neighboring strands. The model systems are analogous to isolated star polymers confined in a permanent network or a melt of very long linear polymers. We find that the distributions of the effective primitive path lengths are Gaussian, from which the entanglement molecular weight N e , a key tube theory parameter, can be extracted. The procured N e value is in good agreement with that obtained from mapping the middle monomer mean-square displacements of entangled linear chains in slip-spring model to the tube model prediction. Furthermore, the mean first-passage (FP) times of destruction of original tube segments by the retracting arm end are collected in simulations and examined quantitatively using a theory recently developed in our group for describing FP problems of one-dimensional Rouse chains with improbable extensions. The asymptotic values of N e as obtained from the static (primitive path length) and dynamical (FP time) analysis are consistent with each other. Additionally, we manage to determine the tube survival function of star arms μ ( t ) , or equivalently arm end-to-end vector relaxation function ϕ ( t ) , through the mean FP time spectrum τ ( s ) of the tube segments after careful consideration of the inner-most entanglements, which shows reasonably good agreement with experimental data on dielectric relaxation.

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Tube Dynamics Works for Randomly Entangled Rings

Cited by 19 publications

References 38 publications

Phase segregation mechanisms of small molecule‐polymer blends unraveled by varying polymer chain architecture

Phase segregation mechanisms of small molecule‐polymer blends unraveled by varying polymer chain architecture

Microscopic Picture of Constraint Release Effects in Entangled Star Polymer Melts

Determining Tube Theory Parameters by Slip-Spring Model Simulations of Entangled Star Polymers in Fixed Networks

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