scholarly journals A coarse-grained polymer model for studying the glass transition

2019 ◽  
Vol 150 (9) ◽  
pp. 091101 ◽  
Author(s):  
Hsiao-Ping Hsu ◽  
Kurt Kremer
Keyword(s):  
Glass Transition ◽  
Coarse Grained ◽  
Polymer Model

All-atomistic molecular dynamics study of the glass transition of amorphous polymers

2021 ◽  
Author(s):  
Zhiye Tang ◽  
Susumu Okazaki
Keyword(s):  
Molecular Dynamics ◽  
Glass Transition ◽  
Spatial Scale ◽  
Degrees Of Freedom ◽  
Main Chain ◽  
Polymer Materials ◽  
Coarse Grained ◽  
Mode Analysis ◽  
Radius Of Gyration ◽  
Chemical Structures

Glass transition is an important phenomenon of polymer materials and it has been intensively studied over the past a few decades. However, the influencing factors arising from the chemical structures of the polymers are often ignored due to a continuous or coarse-grained description of the polymer. Here, we approached this phenomenon using all-atomistic molecular dynamics (MD) simulations and two conventionally used polymer materials, polycarbonate (PC) and poly-(methyl methacrylate) (PMMA). We reproduced the glass transition temperatures (Tg) of the two materials reasonably well. Then we characterized and investigated the glass transition process by looking at the changes of potential energy, dihedral transition, and thermal fluctuation of the individual degrees of freedom in the systems, over the entire temperature range of glass transition. As previously reported, the dihedral angles stop their conformational changes gradually at the Tg, especially for the main chain dihedrals, and sidechain rotations immediately rooting from the main chain. The volumetric change during the temperature decrease is confirmed to be because of conformational adjustment, probably due to the tendency of chain stretching for the maintenance of the radius of gyration, and the loss of thermal energy. The strength of motions of single degrees of freedom and polymer chains, and overall slow motions obtained by normal mode analysis (NMA) shows that different motions at different spatial scale may gradually stop at distinct temperature in the MD simulation temporal and spatial scales. Presumably, the small spatial scale do not contribute to the glass transition at the experimental scale since the timescale is much longer than their relaxation time.

scholarly journals Self Assembly of Model Polymers into Biological Random Networks

2020 ◽  
Author(s):  
Matthew Bailey ◽  
Mark Wilson
Keyword(s):  
Network Structure ◽  
Biological Networks ◽  
Self Assembly ◽  
Short Range ◽  
External Pressure ◽  
Coarse Grained ◽  
Random Networks ◽  
Network Structures ◽  
Polymer Model ◽  
Microscope Images

<div>The properties of biological networks, such as those found in the ocular lens capsule, are difficult to study without simplified models.</div><div>Model polymers are developed, inspired by "worm-like'' curve models, that are shown to spontaneously self assemble</div><div>to form networks similar to those observed experimentally in biological systems.</div><div>These highly simplified coarse-grained models allow the self assembly process to be studied on near-realistic time-scales.</div><div>Metrics are developed (using a polygon-based framework)</div><div>which are useful for describing simulated networks and can also be applied to images of real networks.</div><div>These metrics are used to show the range of control that the computational polymer model has over the networks, including the polygon structure and short range order.</div><div>The structure of the simulated networks are compared to previous simulation work and microscope images of real networks. </div><div>The network structure is shown to be a function of the interaction strengths, cooling rates and external pressure. </div><div>In addition, "pre-tangled'' network structures are introduced and shown to significantly influence the subsequent network structure.</div><div>The network structures obtained fit into a region of the network landscape effectively inaccessible to random</div><div>(entropically-driven) networks but which are occupied by experimentally-derived configurations.</div>

Investigation of coarse-grained models across a glass transition

2020 ◽  
Vol 18 (2-3) ◽  
pp. 185-199 ◽  
Author(s):  
Ryan J. Szukalo ◽  
W. G. Noid
Keyword(s):  
Glass Transition ◽  
Coarse Grained

scholarly journals Self Assembly of Model Polymers into Biological Random Networks

2020 ◽  
Author(s):  
Matthew Bailey ◽  
Mark Wilson
Keyword(s):  
Network Structure ◽  
Biological Networks ◽  
Self Assembly ◽  
Short Range ◽  
External Pressure ◽  
Coarse Grained ◽  
Random Networks ◽  
Network Structures ◽  
Polymer Model ◽  
Microscope Images

<div>The properties of biological networks, such as those found in the ocular lens capsule, are difficult to study without simplified models.</div><div>Model polymers are developed, inspired by "worm-like'' curve models, that are shown to spontaneously self assemble</div><div>to form networks similar to those observed experimentally in biological systems.</div><div>These highly simplified coarse-grained models allow the self assembly process to be studied on near-realistic time-scales.</div><div>Metrics are developed (using a polygon-based framework)</div><div>which are useful for describing simulated networks and can also be applied to images of real networks.</div><div>These metrics are used to show the range of control that the computational polymer model has over the networks, including the polygon structure and short range order.</div><div>The structure of the simulated networks are compared to previous simulation work and microscope images of real networks. </div><div>The network structure is shown to be a function of the interaction strengths, cooling rates and external pressure. </div><div>In addition, "pre-tangled'' network structures are introduced and shown to significantly influence the subsequent network structure.</div><div>The network structures obtained fit into a region of the network landscape effectively inaccessible to random</div><div>(entropically-driven) networks but which are occupied by experimentally-derived configurations.</div>

scholarly journals Simulation of defects, flexibility and rupture in biopolymer networks

RSC Advances ◽  
2022 ◽  
Vol 12 (4) ◽  
pp. 2171-2180
Author(s):  
Matthew H. J. Bailey ◽  
Mark Wilson
Keyword(s):  
Simple Graph ◽  
Graph Representation ◽  
Coarse Grained ◽  
Polymer Model

We use a coarse grained polymer model and a simple graph representation to introduce defects into a biopolymer network, then cause them to rupture.

scholarly journals Structural order as a genuine control parameter of dynamics in simple glass formers

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Hua Tong ◽  
Hajime Tanaka
Keyword(s):  
Glass Transition ◽  
Order Parameter ◽  
Liquid Structure ◽  
Coarse Grained ◽  
Glassy Dynamics ◽  
Slowing Down ◽  
Structural Order ◽  
Particle Level ◽  
Complex Structural ◽  
Unified Description

AbstractGlass transition is characterised by drastic dynamical slowing down upon cooling, accompanied by growing spatial heterogeneity. Its rationalisation by subtle changes in the liquid structure has been long debated but remains elusive, due to intrinsic difficulty in detecting the underlying complex structural ordering. Here we report that structural order parameter characterising local packing capability can well describe the glassy dynamics not only macroscopically but also microscopically, no matter whether it is driven by temperature or density. A Vogel-Fulcher-Tammann (VFT)-like relation is universally identified between the structural relaxation time and the order parameter for supercooled liquids with isotropic interactions. More importantly, we find such an intriguing VFT-like relation to be statistically valid even at a particle level, between spatially coarse-grained structural order and microscopic particle-level dynamics. Such a unified description of glassy dynamics based solely on structural order is expected to contribute to the ultimate understanding of the long-standing glass-transition problem.

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