Variable Chain Confinement in Polymers With Nanosized Pores and Its Impact on Instability

2015 ◽  
Vol 82 (10) ◽  
Author(s):  
Shan Tang ◽  
Steven M. Greene ◽  
Wing Kam Liu ◽  
Xiang He Peng ◽  
Zaoyang Guo
Keyword(s):  
Polymer Chains ◽  
Simulation Approach ◽  
Free Surfaces ◽  
Nanoporous Polymers ◽  
Instability Modes ◽  
Physical Experiments ◽  
Hyperelastic Model ◽  
Chain Confinement ◽  
Dynamics Simulations ◽  
Pattern Transformation

Recent experiments and molecular dynamics simulations have proven that polymer chains are less confined in layers near the free surfaces of submicron-nanosized pores. A recent model has incorporated this observed variable chain confinement at void surfaces in a mechanism-based hyperelastic model. This work employs that model to do two things: explain the large discrepancy between classical homogenization theories and physical experiments measuring the modulus of nanoporous polymers, and describe the instability behavior (onset and postinstability deformation) of this class of materials. The analysis demonstrates that less confinement of polymer chains near free surfaces of voids inhibits tilting buckling while promoting pattern transformation. The sensitivity of geometric instability modes to void size is also studied in depth, helping lay the foundation for fabricating solids with tunable acoustic and optical properties. The simulation approach outlined provides experimentalists with a practical route to estimate the thickness of the interfacial layer in nanoporous polymers.

A Visco-hyperelastic Model for the Thermo-mechanical Behavior of Polymer Fibers

2010 ◽  
Vol 20 (7) ◽  
pp. 1002-1020 ◽  
Author(s):  
G.P. Potirniche ◽  
A. Pascu ◽  
N. Shoemaker ◽  
P.T. Wang ◽  
M.F. Horstemeyer ◽  
...  
Keyword(s):  
Mechanical Behavior ◽  
Penetration Resistance ◽  
Polymer Chains ◽  
Polymer Fibers ◽  
Deformation Characteristics ◽  
Uniaxial Deformation ◽  
The Finite Element Method ◽  
Dynamic Event ◽  
Hyperelastic Model ◽  
Strain Rate Hardening

A visco-hyperelastic model for the thermo-mechanical behavior of polymer yarns is presented. The model assumes that the stress in a yarn during uniaxial deformation results from the superposition of strain rate hardening effects and the softening caused by filament damage. The filament damage accounts for the fracture of polymer chains and the failure of inter-chain bonds. The constitutive model was implemented in the finite element method as a 1D rope element, and was applied to the study of nylon 6.6 and Kevlar ® 29 behavior. Numerical simulations of fabrics subjected to ballistic impact were performed, and the model is shown to predict the fabric penetration resistance and the deformation characteristics during the dynamic event.

scholarly journals Interface Characteristics of Neat Melts and Binary Mixtures of Polyethylenes from Atomistic Molecular Dynamics Simulations

Polymers ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 1059
Author(s):  
Sanghun Lee ◽  
Curtis W. Frank ◽  
Do Y. Yoon
Keyword(s):  
Molecular Dynamics ◽  
Surface Tension ◽  
Molecular Dynamics Simulations ◽  
Binary Mixtures ◽  
Surface Segregation ◽  
Surface Region ◽  
Polymer Chains ◽  
Methyl Groups ◽  
Free Standing ◽  
Dynamics Simulations

Molecular dynamics simulations of free-standing thin films of neat melts of polyethylene (PE) chains up to C150H302 and their binary mixtures with n-C13H28 are performed employing a united atom model. We estimate the surface tension values of PE melts from the atomic virial tensor over a range of temperatures, which are in good agreement with experimental results. Compared with short n-alkane systems, there is an enhanced surface segregation of methyl chain ends in longer PE chains. Moreover, the methyl groups become more segregated in the surface region with decreasing temperature, leading to the conclusion that the surface-segregation of methyl chain ends mainly arises from the enthalpic origin attributed to the lower cohesive energy density of terminal methyl groups. In the mixtures of two different chain lengths, the shorter chains are more likely to be found in the surface region, and this molecular segregation in moderately asymmetric mixtures in the chain length (C13H28 + C44H90) is dominated by the enthalpic effect of methyl chain ends. Such molecular segregation is further enhanced and dominated by the entropic effect of conformational constraints in the surface for the highly asymmetric mixtures containing long polymer chains (C13H28 + C150H3020). The estimated surface tension values of the mixtures are consistent with the observed molecular segregation characteristics. Despite this molecular segregation, the normalized density of methyl chain ends of the longer chain is more strongly enhanced, as compared with the all-segment density of the longer chain itself, in the surface region of melt mixtures. In addition, the molecular segregation results in higher order parameter of the shorter-chain segments at the surface and deeper persistence of surface-induced segmental order into the film for the longer chains, as compared with those in neat melt films.

A Finite Element-Based Coarse-Grained Model for Cell–Nanomaterial Interactions by Combining Absolute Nodal Coordinate Formula and Brownian Dynamics

2020 ◽  
Vol 88 (4) ◽  
Author(s):  
Teng Ma ◽  
Yuanpeng Liu ◽  
Guochang Lin ◽  
Changguo Wang ◽  
Huifeng Tan
Keyword(s):  
Finite Element ◽  
Brownian Dynamics ◽  
Lipid Membrane ◽  
Contact Region ◽  
Detection Algorithm ◽  
Polymer Chains ◽  
Coarse Grained ◽  
Absolute Nodal Coordinate ◽  
Coarse Grained Model ◽  
Dynamics Simulations

Abstract A fundamental understanding of the interactions between one-dimensional nanomaterials and the cell membrane is of great importance for assessing the hazardous effects of viruses and improving the performance of drug delivery. Here, we propose a finite element-based coarse-grained model to describe the cell entry of nanomaterials based on an absolute nodal coordinate formula and Brownian dynamics. The interactions between nanoparticles and lipid membrane are described by the Lennard–Jones potential, and a contact detection algorithm is used to determine the contact region. Compared with the theoretical and published experimental results, the correctness of the model has been verified. We take two examples to test the robustness of the model: the endocytosis of nanorods grafted with polymer chains and simultaneous entry of multiple nanorods into a lipid membrane. It shows that the model can not only capture the effect of ligand–receptor binding on the penetration but also accurately characterize the cooperative or separate entry of multiple nanorods. This coarse-grained model is computationally highly efficient and will be powerful in combination with molecular dynamics simulations to provide an understanding of cell–nanomaterial interactions.

Molecular insight into the Mullins effect: irreversible disentanglement of polymer chains revealed by molecular dynamics simulations

2017 ◽  
Vol 19 (29) ◽  
pp. 19468-19477 ◽  
Author(s):  
Chi Ma ◽  
Tuo Ji ◽  
Christopher G. Robertson ◽  
R. Rajeshbabu ◽  
Jiahua Zhu ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Molecular Model ◽  
Polymer Chains ◽  
Mullins Effect ◽  
Key Characteristics ◽  
Dynamics Simulations ◽  
First Time ◽  
Insight Into

For the first time, the key characteristics associated with the Mullins effect are captured by a molecular model.

Fabrication and Characterization of RF Plasma Polymerized Thin Films from 3,7-Dimethyl-1,6-octadien-3-ol for Electronic and Biomaterial Applications

2010 ◽  
Vol 123-125 ◽  
pp. 323-326 ◽  
Author(s):  
Kateryna Bazaka ◽  
Mohan V. Jacob ◽  
Robert A. Shanks
Keyword(s):  
Thin Films ◽  
Optical Band Gap ◽  
Energy Gap ◽  
Polymer Chains ◽  
Rf Plasma ◽  
Circuit Boards ◽  
Average Roughness ◽  
Free Surfaces ◽  
Complete Dissociation

Poly(linalool) thin films were fabricated using RF plasma polymerisation. All films were found to be smooth, defect-free surfaces with average roughness of 0.44 nm. The FTIR analysis of the polymer showed a notable reduction in –OH moiety and complete dissociation of C=C unsaturation compared to the monomer, and presence of a ketone band absent from the spectrum of the monomer. Poly(linalool) were characterised by chain branching and a large quantity of short polymer chains. Films were optically transparent, with refractive index and extinction coefficient of 1.55 and 0.001 (at 500 nm) respectively, indicating a potential application as an encapsulating (protective) coating for circuit boards. The optical band gap was calculated to be 2.82 eV, which is in the semiconducting energy gap region.

scholarly journals Development and Testing of an All-Atom Force Field for Diketopyrrolopyrrole Polymers with Conjugated Substituents

2020 ◽  
Author(s):  
Vivek Sundaram ◽  
Alexey V. Lyulin ◽  
Björn Baumeier
Keyword(s):  
Force Field ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Building Blocks ◽  
Variable Number ◽  
Polymer Chains ◽  
Relaxation Processes ◽  
Polymer Backbone ◽  
Dynamics Simulations ◽  
The Individual

We develop an all-atom force field for a series of diketopyrrolopyrrole polymers with two aromatic pyridine substituents and variable number of pi-conjugated thiophene units in the backbone, used as donor material in organic photovoltaic devices. Available intra-fragment parameterizations of the individual fragment building blocks are combined with inter-fragment bonded and non-bonded parameters explicitly derived from density-functional theory calculations. To validate the force field we perform classical molecular dynamics simulations of single polymer chains with 1, 2, and 3 thiophenes in good and bad solvents, and of melts. We observe the expected dependence of the chain conformation on the solvent quality, with the chain collapsing in water, and swelling in chloroform. The glass transition temperature for the polymer melts is found to be in the range of 340K to 370K. Analysis of the mobility of the conjugated segments in the polymer backbone reveals two relaxation processes: a fast one with a characteristic time at room temperature on the order of 10ps associated with nearly harmonic vibrations and a slow one on the order of 100 associated with temperature activated cis-trans transitions.

scholarly journals Molecular structure of azobenzene-containing systems from classical MD simulations

2015 ◽  
Author(s):  
Olga Guskova ◽  
Vladimir Toshchevikov ◽  
Jaroslav Ilnytskyi ◽  
Marina Saphiannikova
Keyword(s):  
Molecular Structure ◽  
Conformational Changes ◽  
Md Simulations ◽  
Chem Phys ◽  
Polymer Chains ◽  
Gyration Radius ◽  
Light Illumination ◽  
Molecular Glasses ◽  
Mesoscopic Level ◽  
Dynamics Simulations

Azobenzene-containing side chain polymers [1,2] and molecular glasses based on propeller-like C3-symmetric azobenzene mesogenes [3] are investigated in classical molecular dynamics simulations. Two length scales are considered: (i) the molecular level with atomistic resolution, where reversible conformational changes of azobenzene chromophores upon light illumination lead to contractions/extensions of low amplitudes due to a limited size of mesogene groups, and (ii) the mesoscopic level, where light-induced molecular movements are observed over larger distances, comparable with the gyration radius of polymer chains. The influence of isomerization and orientation mechanisms on molecular structure and light-induced deformation is elucidated. [1] J. Ilnytskyi et al., J. Chem. Phys. 135, 044901 (2011). [2] M Saphiannikova et al., Proceedings of SPIE "Optical Materials and Biomaterials in Security and Defence Systems Technology X", 8901, 890138 (2013). [3] N.S. Jadavalli et al., Appl. Phys. Lett. 105, 051601 (2014).

scholarly journals An unexpected N-dependence in the viscosity reduction in all-polymer nanocomposite

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Tao Chen ◽  
Huan-Yu Zhao ◽  
Rui Shi ◽  
Wen-Feng Lin ◽  
Xiang-Meng Jia ◽  
...  
Keyword(s):  
Large Scale ◽  
Polymer Melt ◽  
Polymer Nanocomposite ◽  
Underlying Mechanism ◽  
Polymer Chains ◽  
Friction Reduction ◽  
Viscosity Reduction ◽  
Single Chain ◽  
Dynamics Simulations ◽  
Polymer Segment

AbstractAdding small nanoparticles (NPs) into polymer melt can lead to a non-Einstein-like decrease in viscosity. However, the underlying mechanism remains a long-standing unsolved puzzle. Here, for an all-polymer nanocomposite formed by linear polystyrene (PS) chains and PS single-chain nanoparticles (SCNPs), we perform large-scale molecular dynamics simulations and experimental rheology measurements. We show that with a fixed (small) loading of the SCNP, viscosity reduction (VR) effect can be largely amplified with an increase in matrix chain length $$N$$N, and that the system with longer polymer chains will have a larger VR. We demonstrate that such $$N$$N-dependent VR can be attributed to the friction reduction experienced by polymer segment blobs which have similar size and interact directly with these SCNPs. A theoretical model is proposed based on the tube model. We demonstrate that it can well describe the friction reduction experienced by melt polymers and the VR effect in these composite systems.

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