PolySTRAND Model of Flow-Induced Nucleation in Polymers

Read, Daniel J.; McIlroy, Claire; Das, Chinmay; Harlen, Oliver G.; Graham, Richard S.

doi:10.1103/physrevlett.124.147802

Cited by 28 publications

(46 citation statements)

References 35 publications

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“…Protein-based natural materials persistently inspire the development of novel humanmade materials, owing to their biocompatibility, unique combinations of strength and toughness [1][2][3][4], low-energy processing [5] and efficient solvent recycling [6]. While the industrial production of polymer-based fibres is challenged by a highly non-trivial interdependence between the molecular level of bond-orientation-dependent nucleation, and the macroscopic level, where the temperature-dependent rheology generates stretch of entire chain segments [7][8][9][10][11], silk is processed in semi-dilute aqueous conditions [5], where nucleation can be induced through the stretch-induced disruption of the solvation layer [12]. In order to generate sufficient stretch at modest flow rates, the silk protein has evolved to contain 'sticky' patches (which are assumed to be consisting of ionic calcium bridges between the carboxylated side groups of aspartic and glutamic acids) that significantly slow down stretch relaxation in flow [6,13].…”

Section: Introductionmentioning

confidence: 99%

Stretching of Bombyx mori Silk Protein in Flow

et al. 2021

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The flow-induced self-assembly of entangled Bombyx mori silk proteins is hypothesised to be aided by the ‘registration’ of aligned protein chains using intermolecularly interacting ‘sticky’ patches. This suggests that upon chain alignment, a hierarchical network forms that collectively stretches and induces nucleation in a precisely controlled way. Through the lens of polymer physics, we argue that if all chains would stretch to a similar extent, a clear correlation length of the stickers in the direction of the flow emerges, which may indeed favour such a registration effect. Through simulations in both extensional flow and shear, we show that there is, on the other hand, a very broad distribution of protein–chain stretch, which suggests the registration of proteins is not directly coupled to the applied strain, but may be a slow statistical process. This qualitative prediction seems to be consistent with the large strains (i.e., at long time scales) required to induce gelation in our rheological measurements under constant shear. We discuss our perspective of how the flow-induced self-assembly of silk may be addressed by new experiments and model development.

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Section: Introductionmentioning

confidence: 99%

Stretching of Bombyx mori Silk Protein in Flow

et al. 2021

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“…To better understand the coupling between phase separation and crystallization, we apply molecular dynamics (MD) simulations to investigate the crystal nucleation in inhomogeneous polymers. Previous authors have used MD simulations to study the kinetics and the precursors of the quiescent [27][28][29][30][31][32][33] and flow-induced [20][21][22]31,34,35] nucleation and crystallization in homopolymer melts. Computational studies of crystal nucleation in inhomogeneous polymer blends, however, are still lacking.…”

Section: Introductionmentioning

confidence: 99%

Molecular Dynamics Simulations of Crystal Nucleation near Interfaces in Incompatible Polymer Blends

Zhang

Zou

2021

Polymers

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We apply molecular dynamics (MD) simulations to investigate crystal nucleation in incompatible polymer blends under deep supercooling conditions. Simulations of isothermal nucleation are performed for phase-separated blends with different degrees of incompatibility. In weakly segregated blends, slow and incompatible chains in crystallizable polymer domains can significantly hinder the crystal nucleation and growth. When a crystallizable polymer is blended with a more mobile species in interfacial regions, enhanced molecular mobility leads to the fast growth of crystalline order. However, the incubation time remains the same as that in pure samples. By inducing anisotropic alignment near the interfaces of strongly segregated blends, phase separation also promotes crystalline order to grow near interfaces between different polymer domains.

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“…Adding external forces to the chain in our simulations will produce toy-models to aid the understanding of protein folding/unfolding under mechanical forces 33 and flow-induced crystallization in polymers. 34,35 Simulations of the crystallization dynamics [24][25][26][27] and the reaction co-ordinates identified by Leitold et al, 26,27 could be combined with techniques to project high-dimensional barrier crossing simulations onto lowdimensional co-ordinates, 36,37 to produce an analytically tractable model for the crystallization dynamics of this system. Accurate simulations of the free energy landscape, especially at the barrier peak, are a prerequisite for this approach.…”

Section: Discussionmentioning

confidence: 99%

Monte–Carlo simulation of crystallization in single‐chain square‐well homopolymers

Wicks

Wattis

Graham

2020

Polymer Crystallization

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We present Monte-Carlo (MC) simulations of the crystallization transition of single-chain square-well homopolymers, with a continuous description of monomer positions. For long chains with short-ranged interactions this system shows a strong configurational bottleneck, which makes it difficult to explore the whole configuration space. To surmount this problem we combine parallel tempering with a nonstandard choice of tempering levels, a bespoke biasing strategy and a method to map results between different temperatures. We verify that our simulations mix well when simulating chains of 128 and 256 beads. Our simulation approach resolves issues with reproducibility of MC simulations reported in prior work, particularly for the transition region between the expanded coil and crystalline region. We obtain highly reproducible results for both the free energy landscape and the inverse temperature, with low statistical noise. We outline a method to extract the free energy barrier, at any temperature, for any choice of order parameter, illustrating this technique by computing the free energy landscape as a function of the Steinhardt-Nelson order parameter for a range of temperatures.

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PolySTRAND Model of Flow-Induced Nucleation in Polymers

Cited by 28 publications

References 35 publications

Stretching of Bombyx mori Silk Protein in Flow

Stretching of Bombyx mori Silk Protein in Flow

Molecular Dynamics Simulations of Crystal Nucleation near Interfaces in Incompatible Polymer Blends

Monte–Carlo simulation of crystallization in single‐chain square‐well homopolymers

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