scholarly journals Theory of Flexible Polymer Networks: Elasticity and Heterogeneities

Polymers ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 767 ◽  
Author(s):  
Sergey Panyukov
Keyword(s):  
Volume Fraction ◽  
Polymer Networks ◽  
Chain Model ◽  
Flexible Polymer ◽  
Classical Models ◽  
Polymer Volume

A review of the main elasticity models of flexible polymer networks is presented. Classical models of phantom networks suggest that the networks have a tree-like structure. The conformations of their strands are described by the model of a combined chain, which consists of the network strand and two virtual chains attached to its ends. The distribution of lengths of virtual chains in real polydisperse networks is calculated using the results of the presented replica model of polymer networks. This model describes actual networks having strongly overlapping and interconnected loops of finite sizes. The conformations of their strands are characterized by the generalized combined chain model. The model of a sliding tube is represented, which describes the general anisotropic deformations of an entangled network in the melt. I propose a generalization of this model to describe the crossover between the entangled and phantom regimes of a swollen network. The obtained dependence of the Mooney-Rivlin parameters C 1 and C 2 on the polymer volume fraction is in agreement with experiments. The main results of the theory of heterogeneities in polymer networks are also discussed.

Theoretical Equilibrium Moduli and Swelling Extents for Elastomers Crosslinked in Solution

1990 ◽  
Vol 63 (1) ◽  
pp. 46-55 ◽  
Author(s):  
J. P. Queslel ◽  
J. E. Mark
Keyword(s):  
Volume Fraction ◽  
Amorphous Polymer ◽  
Polymer Networks ◽  
Deformation Model ◽  
Chain Model ◽  
Swelling Properties ◽  
Plateau Modulus ◽  
Contour Model ◽  
Polymer Volume ◽  
Affine Deformation

Abstract Equilibrium elongation moduli and swelling properties have been calculated for amorphous polymer networks prepared in a diluted reference state of polymer volume fraction υ2C. The three molecular elasticity theories employed are based on (i) an idealized affine deformation model (in which the constraints on junction fluctuations are infinite), (ii) an idealized phantom chain model (in which the constraints are absent), and (iii) the more realistic Flory-Erman theory (in which the constraints vary with crosslinking conditions, degree of swelling, and extent of elongation). A discussion of the dependence of the constraint parameter κ on υ2C is given, and is applied to the calculation of stress-strain isotherms in elongation specifically for cis-polyisoprene cured with dicumyl peroxide. The experimental dependence of κ on υ2C investigated by Erman and Mark was found to be similar to the dependence of the plateau modulus on dilution, and this is consistent with the constrained contour model proposed by Erman and Monnerie.

Estimation of Effective Thermal and Mechanical Properties of Particulate Thermal Interface Materials (TIMs) by a Random Network Model

2017 ◽  
Author(s):  
Pavan Kumar Vaitheeswaran ◽  
Ganesh Subbarayan
Keyword(s):  
Mechanical Properties ◽  
Network Model ◽  
Thermal Stresses ◽  
Volume Fraction ◽  
Random Network ◽  
Thermal Interface Materials ◽  
Thermal And Mechanical Properties ◽  
Thermal Interface ◽  
Classical Models ◽  
Interface Materials

Particulate thermal interface materials (TIMs) are commonly used to transport heat from chip to heat sink. While high thermal conductance is achieved by large volume loadings of highly conducting particles in a compliant matrix, small volume loadings of stiff particles will ensure reduced thermal stresses in the brittle silicon device. Developing numerical models to estimate effective thermal and mechanical properties of TIM systems would help optimize TIM performance with respect to these conflicting requirements. Classical models, often based on single particle solutions or regular arrangement of particles, are insufficient as real-life TIM systems contain a distriubtion of particles at high volume fractions, where classical models are invalid. In our earlier work, a computationally efficient random network model was developed to estimate the effective thermal conductivity of TIM systems [1,2]. This model is extended in this paper to estimate the effective elastic modulus of TIMs. Realistic microstructures are simulated and analyzed using the proposed method. Factors affecting the modulus (volume fraction and particle size distribution) are also studied.

Enrichment of Charged Monomers Explains Non-monotonic Polymer Volume Fraction Profiles of Multi-stimulus Responsive Copolymer Brushes

Langmuir ◽  
2020 ◽  
Vol 36 (42) ◽  
pp. 12460-12472 ◽  
Author(s):  
Edwin C. Johnson ◽  
Joshua D. Willott ◽  
Isaac J. Gresham ◽  
Timothy J. Murdoch ◽  
Ben A. Humphreys ◽  
...  
Keyword(s):  
Volume Fraction ◽  
Stimulus Responsive ◽  
Polymer Volume ◽  
Copolymer Brushes

Bimodality and Increased Amount of Crosslinker Enhances Tensile Properties of the Silicone Networks

e-Polymers ◽  
2007 ◽  
Vol 7 (1) ◽  
Author(s):  
Gul Bali Shah
Keyword(s):  
Elastic Modulus ◽  
Tensile Properties ◽  
Phase Inversion ◽  
Volume Fraction ◽  
Polymer Networks ◽  
Short Chain ◽  
Percent Elongation ◽  
Bimodal Networks ◽  
Crosslinker Concentration ◽  
First Time

AbstractThe effect of bimodality i.e. blending short and long chain (0 to 80 % w/w) silicone prepolymers, and that of concentration of the crosslinker on the tensile properties such as percent elongation at break (%Eb), ultimate tensile strength (UTS), 100 % modulus and elastic modulus (E) has been investigated. It was found out that the greater amount of crosslinker used for crosslinking provide an additional reinforcement to the silicone network whereas bimodality further significantly accentuates this effect. Remarkably, the %Eb of the silicone networks was found to increase to an average of 2.4 times than that of the monomodal network, cured in each of the three series of bimodal networks cured with 3.9, 9.1 and 12.3% of crosslinker. The optimum property in each case was observed at about 70 mol % of P100. The over all order of sensitivity of these properties up to about 70 mol % of short chain prepolymer has been observed to be as: %Eb > UTS > 100% modulus > elastic modulus. It has been shown that in addition to the previously published reports the tensile properties are acutely dependent not only upon the degree of crosslinking and primary molecular weight; but also on bimodality and crosslinker concentration for preparation of the unfilled silicone polymer networks. The concept of phase inversion (or phase transition) associated with the optimum properties in polymer blends has for the first time been applied to the bimodal polymer networks. It has been observed that the maxima in tensile properties generally corresponds to phase inversion which takes place at 0.5 volume fraction (70 mol %) of short chain (P100) prepolymer which is in accordance with the literature for other systems.

scholarly journals Low-Temperature Meltable Elastomers Based on Linear Polydimethylsiloxane Chains Alpha, Omega-Terminated with Mesogenic Groups as Physical Crosslinkers: A Passive Smart Material with Potential as Viscoelastic Coupling. Part I: Synthesis and Phase Behavior

Polymers ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 2476 ◽  
Author(s):  
Sabina Horodecka ◽  
Adam Strachota ◽  
Beata Mossety-Leszczak ◽  
Beata Strachota ◽  
Miroslav Šlouf ◽  
...  
Keyword(s):  
Low Temperature ◽  
Smart Materials ◽  
Self Assembly ◽  
Lamellar Structure ◽  
Volume Fraction ◽  
Polymer Networks ◽  
Polarized Light ◽  
Building Blocks ◽  
Structure Property ◽  
Mechanical Coupling

Physically crosslinked low-temperature elastomers were prepared based on linear polydimethylsiloxane (PDMS) elastic chains terminated on both ends with mesogenic building blocks (LC) of azobenzene type. They are generally (and also structurally) highly different from the well-studied LC polymer networks (light-sensitive actuators). The LC units also make up only a small volume fraction in our materials and they do not generate elastic energy upon irradiation, but they act as physical crosslinkers with thermotropic properties. Our elastomers lack permanent chemical crosslinks—their structure is fully linear. The aggregation of the relatively rare, small, and spatially separated terminal LC units nevertheless proved to be a considerably strong crosslinking mechanism. The most attractive product displays a rubber plateau extending over 100 °C, melts near 8 °C, and is soluble in organic solvents. The self-assembly (via LC aggregation) of the copolymer molecules leads to a distinctly lamellar structure indicated by X-ray diffraction (XRD). This structure persists also in melt (polarized light microscopy, XRD), where 1–2 thermotropic transitions occur. The interesting effects of the properties of this lamellar structure on viscoelastic and rheological properties in the rubbery and in the melt state are discussed in a follow-up paper (“Part II”). The copolymers might be of interest as passive smart materials, especially as temperature-controlled elastic/viscoelastic mechanical coupling. Our study focuses on the comparison of physical properties and structure–property relationships in three systems with elastic PDMS segments of different length (8.6, 16.3, and 64.4 repeat units).

Equilibrium phase diagram of semi-flexible polymer networks with linkers

2013 ◽  
Vol 102 (3) ◽  
pp. 38003 ◽  
Author(s):  
C. J. Cyron ◽  
K. W. Müller ◽  
K. M. Schmoller ◽  
A. R. Bausch ◽  
W. A. Wall ◽  
...  
Keyword(s):  
Phase Diagram ◽  
Polymer Networks ◽  
Equilibrium Phase ◽  
Equilibrium Phase Diagram ◽  
Flexible Polymer ◽  
Semi Flexible Polymer

scholarly journals Computational analysis of morphologies and phase transitions of cross-linked, semi-flexible polymer networks

2015 ◽  
Vol 471 (2182) ◽  
pp. 20150332 ◽  
Author(s):  
Kei W. Müller ◽  
Christian J. Cyron ◽  
Wolfgang A. Wall
Keyword(s):  
Phase Transitions ◽  
Computational Study ◽  
Polymer Networks ◽  
Constitutive Models ◽  
Structural Polymorphism ◽  
Flexible Polymers ◽  
Fibre Network ◽  
Flexible Polymer ◽  
Morphological Differences ◽  
Semi Flexible Polymer

The eukaryotic cytoskeleton is a protein fibre network mainly consisting of the semi-flexible biopolymer F-actin, microtubules and intermediate filaments. It is well known to exhibit a pronounced structural polymorphism, which enables intracellular processes such as cell adhesion, cell motility and cell division. We present a computational study on cross-linked networks of semi-flexible polymers, which offers a detailed analysis of the network structure and phase transitions from one morphology to another. We elaborate the morphological differences, their mechanical implications and the order of the observed phase transitions. Finally, we present a perspective on how the information gained in our simulations can be exploited in order to build both flexible and accurate, microstructurally informed, homogenized constitutive models of the cytoskeleton.

Short Double Stranded DNA Alignment in the Melt of Flexible Polymers

2015 ◽  
Vol 10 (01) ◽  
pp. 59-68
Author(s):  
Zareh A. Grigoryan ◽  
Armen T. Karapetian
Keyword(s):  
Aspect Ratio ◽  
Phase Formation ◽  
Polymer Matrix ◽  
Liquid Crystalline ◽  
Volume Fraction ◽  
Flexible Polymers ◽  
Flexible Polymer ◽  
Double Stranded Dna ◽  
Dna Alignment ◽  
Ratio Energy

It is shown that the molecules of double — stranded DNA form a liquid-crystaline ordered phase, depending on the value of parameter of Flory-Huggins, DNA aspect ratio, energy of attraction between the molecules of DNA and volume fraction of the flexible polymer. Liquid crystalline order formation in double-stranded DNA, immeresed in the polymeric matrix occurs with increase of the volume fraction of the flexible polymer. The orrdered phase formation in double-stranded DNA is governed by volume fraction of DNA and by temperature. The results clearly show the effect of the polymer matrix on the ordering in DNA molecules.

DMAP-based flexible polymer networks formed via Heck coupling as efficient heterogeneous organocatalysts

2016 ◽  
Vol 104 ◽  
pp. 15-21 ◽  
Author(s):  
Wei Xu ◽  
Wu Xia ◽  
Yukun Guan ◽  
Yiming Wang ◽  
Cuifen Lu ◽  
...  
Keyword(s):  
Polymer Networks ◽  
Heck Coupling ◽  
Flexible Polymer
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