scholarly journals Side Chains and the Insufficient Lubrication of Water in Polyacrylamide Hydrogel—A New Insight

Polymers ◽  
2019 ◽  
Vol 11 (11) ◽  
pp. 1845 ◽  
Author(s):  
Lei ◽  
Zhou ◽  
Liu
Keyword(s):  
Mechanical Properties ◽  
Volume Fraction ◽  
Polymer Network ◽  
Polymer Chains ◽  
Side Chain ◽  
Side Chains ◽  
Polyacrylamide Hydrogels ◽  
Young’S Moduli ◽  
Property Changes ◽  
Dynamics Simulations

Existing theories cannot predict the mechanical property changes of polyacrylamide hydrogels with different water content because of the absence of side chains. In this study, polyacrylamide hydrogels are prepared and tested to investigate the side chain effect on their mechanical properties. First, the comparison between the effective chain density and total chain density provides proof of the large amount of side chains in the polymer network of PAAm hydrogel. We propose a practical chain density fraction to measure the side chain fraction. Then, the abnormal Young’s moduli-polymer volume fraction relationship reveals that side chains affect the mechanical properties of hydrogel through the insufficient lubrication of water. Water confined in narrow space within a molecular-level size can bear shear force to provide extra deformation resistance. A constitutive mode considering the effect of the insufficient lubrication of water is proposed. Combining this constitutive model with experimental results, we find that this insufficient lubrication of water exists even in equilibrium PAAm hydrogel. Molecular dynamics simulations reveal that this insufficient lubrication of water comes from the constraint of polymer chains. It also demonstrates that when there is insufficient lubrication, the rearrangement of water molecules leads to the persistent energy dissipation in the Mullins effect of PAAm hydrogel.

Influence of Flexible Side-Chains on the Breathing Phase Transition of Pillared Layer MOFs: A Force Field Investigation

2020 ◽  
Author(s):  
Julian Keupp ◽  
Johannes P. Dürholt ◽  
Rochus Schmid
Keyword(s):  
First Principles ◽  
Good Accuracy ◽  
Field Investigation ◽  
Square Lattice ◽  
Side Chain ◽  
Second Step ◽  
Side Chains ◽  
Dynamics Simulations ◽  
Complex Phenomena ◽  
Closed Pore

The prototypical pillared layer MOFs, formed by a square lattice of paddle-<br>wheel units and connected by dinitrogen pillars, can undergo a breathing phase<br>transition by a “wine-rack” type motion of the square lattice. We studied this not<br>yet fully understood behavior using an accurate first principles parameterized force<br>field (MOF-FF) for larger nanocrystallites on the example of Zn 2 (bdc) 2 (dabco) [bdc:<br>benzenedicarboxylate, dabco: (1,4-diazabicyclo[2.2.2]octane)] and found clear indi-<br>cations for an interface between a closed and an open pore phase traveling through<br>the system during the phase transformation [Adv. Theory Simul. 2019, 2, 11]. In<br>conventional simulations in small supercells this mechanism is prevented by periodic<br>boundary conditions (PBC), enforcing a synchronous transformation of the entire<br>crystal. Here, we extend this investigation to pillared layer MOFs with flexible<br>side-chains, attached to the linker. Such functionalized (fu-)MOFs are experimen-<br>tally known to have different properties with the side-chains acting as fixed guest<br>molecules. First, in order to extend the parameterization for such flexible groups,<br>1a new parametrization strategy for MOF-FF had to be developed, using a multi-<br>structure force based fit method. The resulting parametrization for a library of<br>fu-MOFs is then validated with respect to a set of reference systems and shows very<br>good accuracy. In the second step, a series of fu-MOFs with increasing side-chain<br>length is studied with respect to the influence of the side-chains on the breathing<br>behavior. For small supercells in PBC a systematic trend of the closed pore volume<br>with the chain length is observed. However, for a nanocrystallite model a distinct<br>interface between a closed and an open pore phase is visible only for the short chain<br>length, whereas for longer chains the interface broadens and a nearly concerted trans-<br>formation is observed. Only by molecular dynamics simulations using accurate force<br>fields such complex phenomena can be studied on a molecular level.

scholarly journals The role of side chains in the interaction of new antitumor pyrimidoacridinetriones with DNA: molecular dynamics simulations.

2000 ◽  
Vol 47 (1) ◽  
pp. 47-57 ◽  
Author(s):  
J Mazerski ◽  
I Antonini ◽  
S Martelli
Keyword(s):  
Molecular Dynamics ◽  
Rational Design ◽  
Md Simulations ◽  
Ring System ◽  
Side Chain ◽  
Side Chains ◽  
Intercalation Complex ◽  
Highly Active ◽  
Simulation Techniques ◽  
Dynamics Simulations

Pyrimidoacridinetriones (PATs) are a new group of highly active antitumor compounds. It seems reasonable to assume that, like for some other acridine derivatives, intercalation into DNA is a necessary, however not a sufficient condition for antitumor activity of these compounds. Rational design of new compounds of this chemotype requires knowledge about the structure of the intercalation complex, as well as about interactions responsible for its stability. Computer simulation techniques such as molecular dynamics (MD) may provide valuable information about these problems. The results of MD simulations performed for three rationally selected PATs are presented in this paper. The compounds differ in the number and position of side chains. Each of the compounds was simulated in two systems: i) in water, and ii) in the intercalation complex with the dodecamer duplex d(GCGCGCGCGCGC)2. The orientation of the side chain in relation to the ring system is determined by the position of its attachment. Orientation of the ring system inside the intercalation cavity depends on the number and position of side chain(s). The conformations of the side chain(s) of all PATs studied in the intercalation complex were found to be very similar to those observed in water.

Biomimetic composites inspired by venous leaf

2017 ◽  
Vol 52 (3) ◽  
pp. 361-372 ◽  
Author(s):  
Gongdai Liu ◽  
R Ghosh ◽  
A Vaziri ◽  
A Hossieni ◽  
D Mousanezhad ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Yield Stress ◽  
Poisson’S Ratio ◽  
Composite Structures ◽  
Volume Fraction ◽  
Matrix Material ◽  
Poisson's Ratio ◽  
Fiber Volume ◽  
Young’S Moduli

A typical plant leaf can be idealized as a composite having three principal fibers: the central mid-fiber corresponding to the mid-rib, straight parallel secondary fibers attached to the mid-fiber representing the secondary veins, and then another set of parallel fibers emanating from the secondary fibers mimicking the tertiary fibers embedded in a matrix material. This paper introduces a biomimetic composite design inspired by the morphology of venous leafs and investigates the effects of venation morphologies on the in-plane mechanical properties of the biomimetic composites using finite element method. The mechanical properties such as Young’s moduli, Poisson’s ratio, and yield stress under uniaxial loading of the resultant composite structures was studied and the effect of different fiber architectures on these properties was investigated. To this end, two broad types of architectures were used both having similar central main fiber but differing in either having only secondary fibers or additional tertiary fibers. The fiber and matrix volume fractions were kept constant and a comparative parametric study was carried out by varying the inclination of the secondary fibers. The results show that the elastic modulus of composite in the direction of main fiber increases linearly with increasing the angle of the secondary fibers. Furthermore, the elastic modulus is enhanced if the secondary fibers are closed, which mimics composites with closed cellular fibers. In contrast, the elastic modulus of composites normal to the main fiber ( x direction) exponentially decreases with the increase of the angle of the secondary fibers and it is little affected by having secondary fibers closed. Similar results were obtained for the yield stress of the composites. The results also indicate that Poisson’s ratio linearly increases with the secondary fiber angle. The results also show that for a constant fiber volume fraction, addition of various tertiary fibers may not significantly enhance the mechanical properties of the composites. The mechanical properties of the composites are mainly dominated by the secondary fibers. Finally, a simple model was proposed to predict these behaviors.

scholarly journals Connective Tissue Mechanics of Metridium Senile

1971 ◽  
Vol 55 (3) ◽  
pp. 775-795
Author(s):  
JOHN M. GOSLINE
Keyword(s):  
Mechanical Properties ◽  
Electrostatic Interactions ◽  
Amorphous Polymer ◽  
Polymer Network ◽  
Inorganic Ions ◽  
Tissue Mechanics ◽  
Polymer Chains ◽  
Metridium Senile ◽  
The Matrix ◽  
Elastic Mechanism

1. The mechanical properties of the mesogloea of the sea anemone Metridium senile were investigated. An amorphous polymer network in the matrix was found to play a major role in determining the mechanical properties of the tissue. 2. The matrix network provides an elastic mechanism based on ‘rubber elasticity’ of the folded matrix molecules. The properties of the matrix network alone account for the extensibility and elasticity of mesogloea. 3. The collagen acts as a reinforcing filler providing short-term rigidity to the flimsy polymer network. 4. The collagen fibres are not directly cross-linked to one another but are tied together through the amorphous matrix. 5. The extensibility and elasticity of the tissue appear to be dependent on a very low degree of cross-linking in the mesogloeal system. Inorganic ions mask ionized groups on the collagen and matrix polymer chains and block electrostatic interactions which could cross-link the system.

The Effect of Tacticity and Side Chain Structure on the Coil Dimensions of Polyolefins

2018 ◽  
Author(s):  
Mohammad Atif Faiz Afzal ◽  
Jarod M. Younker ◽  
George Rodriguez
Keyword(s):  
High Throughput Screening ◽  
Waste Water Treatment ◽  
Chain Structure ◽  
Polymer Chains ◽  
Side Chain ◽  
Radius Of Gyration ◽  
Structure Property ◽  
Engine Oils ◽  
Structure Property Relationships ◽  
Dynamics Simulations

<pre>The key to the discovery of materials with targeted properties lies in the understanding of structure-property relationships. In this work, we evaluate the relationship between the polymer structure and their coil dimensions, and explore new polymers based on these relations. Coil dimensions are important features of polymers which affect their performance in various applications, including drug delivery, waste-water treatment, and engine oils. Coil dimensions of the polyolefins are dependent on the number, size, and stereo orientation of side chains along the backbone. Thus, controlling these attributes allows us to tailor the coil dimensions of polyolefins. In the proposed scheme, we calculate the radius of gyration (<i>R<sub>g</sub></i>) of polyolefin chains using molecular dynamics simulations and validate against experimental results. Simulated annealing is implemented to ensure the capture of different configurations. This model affords the ability to quantify the effect tacticity has on the coil dimensions of polyolefins. The results show the suppression of tacticity effects when the polymer chains transition to bottlebrush structures, demonstrating that the side chain steric hindrance plays an important role in the rigidity of the chain backbone. Further, the model is used to evaluate the compositional effects by determining the rigidity of propylene and 1-hexene copolymers. Combining our model with virtual high-throughput screening techniques, we evaluated the coiling behavior of hundreds of new polymers. Using the screening results, we established correlations between the structure of the side chain and the coil dimensions of polymers.</pre><pre>The supplementary material accompanying this paper includes the library of 275 polymers and their corresponding <i>K<sub>s</sub></i> values.<br></pre>

Effects of conformational symmetry in conjugated side chains on intermolecular packing of conjugated polymers and photovoltaic properties

RSC Advances ◽  
2015 ◽  
Vol 5 (128) ◽  
pp. 106044-106052 ◽  
Author(s):  
Jisoo Shin ◽  
Min Kim ◽  
Jaewon Lee ◽  
Donghun Sin ◽  
Heung Gyu Kim ◽  
...  
Keyword(s):  
Charge Carrier ◽  
Conjugated Polymers ◽  
Carrier Mobility ◽  
Light Harvesting ◽  
Charge Carrier Mobility ◽  
Polymer Chains ◽  
Side Chain ◽  
Side Chains ◽  
Photovoltaic Properties

Introduction of the symmetric conjugated side chain to the conjugated backbone of the polymer was found to improve both the light-harvesting ability of the polymer and its charge carrier mobility, apparently by increasing the packing between the polymer chains.

Effect of interphase zone on the overall elastic properties of nanoparticle-reinforced polymer nanocomposites

2018 ◽  
Vol 53 (9) ◽  
pp. 1261-1274 ◽  
Author(s):  
Jafar Amraei ◽  
Jafar E Jam ◽  
Behrouz Arab ◽  
Roohollah D Firouz-Abadi
Keyword(s):  
Mechanical Properties ◽  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Polymer Nanocomposites ◽  
Volume Fraction ◽  
Finite Size ◽  
Radial Distance ◽  
Shear Moduli ◽  
Wide Range ◽  
Dynamics Simulations

In the current work, the effect of interphase region on the mechanical properties of polymer nanocomposites reinforced with nanoparticles is studied. For this purpose, a closed-form interphase model as a function of radial distance based on finite-size representative volume element is suggested to estimate the mechanical properties of particle-reinforced nanocomposites. The effective Young’s and shear moduli of thermoplastic polycarbonate-based nanocomposites for a wide range of sizes and volume fractions of silicon carbide nanoparticles are investigated using the proposed interphase model and molecular dynamics simulations. In order to investigate the effect of particle size, several unit cells of the same volume fraction, but with different particle radii have been considered. The micromechanics-based homogenization results are in good agreement with the results of molecular dynamics simulations for all models. This study demonstrates that the suggested micromechanical interphase model has the capacity to estimate effective mechanical properties of polymer-based nanocomposites reinforced with spherical inclusions.

Tailoring of Mechanical Properties of Diisocyanate Crosslinked Gelatin-Based Hydrogels

2013 ◽  
Vol 1569 ◽  
pp. 3-8 ◽  
Author(s):  
Axel T. Neffe ◽  
Tim Gebauer ◽  
Andreas Lendlein
Keyword(s):  
Mechanical Properties ◽  
Network Formation ◽  
Polymer Network ◽  
Polymeric Materials ◽  
Toluene Diisocyanate ◽  
Crosslinking Reaction ◽  
Young’S Moduli ◽  
Physical Interactions ◽  
Reaction In Water ◽  
Full Conversion

ABSTRACTPolymer network formation is an important tool for tailoring mechanical properties of polymeric materials. One option to synthesize a network is the addition of bivalent crosslinkers reacting with functional groups present in a polymer. In case of polymer network syntheses based on biopolymers, performing such a crosslinking reaction in water is sometimes necessary in view of the solubility of the biopolymer, such as gelatin, and can be beneficial to avoid potential contamination of the formed material with organic solvents in view of applications in biomedicine. In the case of applying diisocyanates for the crosslinking in water, it is necessary to show that the low molecular weight bifunctional crosslinker has fully reacted, while tailoring of the mechanical properties of the resulting hydrogels is possible despite the complex reaction mechanism. Here, the formation of gelatin-based hydrogel networks with the diisocyanates 2,4-toluene diisocyanate, 1,4-butane diisocyanate, and isophorone diisocyanate is presented. It is shown that extensive washing of materials is required to ensure full conversion of the diisocyanates. The use of different diisocyanates gives hydrogels covering a large range of Young’s moduli (12-450 kPa). The elongations at break (up to 83%) as well as the maximum tensile strengths (up to 410 kPa) of the hydrogels described here are much higher than for lysine diisocyanate ethyl ester crosslinked gelatin reported before. Rheological investigations suggest that the network formation in some cases is due to physical interactions and entanglements rather than covalent crosslink formation.

The Effect of Tacticity and Side Chain Structure on the Coil Dimensions of Polyolefins

2018 ◽  
Author(s):  
Mohammad Atif Faiz Afzal ◽  
Jarod M. Younker ◽  
George Rodriguez
Keyword(s):  
High Throughput Screening ◽  
Waste Water Treatment ◽  
Chain Structure ◽  
Polymer Chains ◽  
Side Chain ◽  
Radius Of Gyration ◽  
Structure Property ◽  
Engine Oils ◽  
Structure Property Relationships ◽  
Dynamics Simulations

<pre>The key to the discovery of materials with targeted properties lies in the understanding of structure-property relationships. In this work, we evaluate the relationship between the polymer structure and their coil dimensions, and explore new polymers based on these relations. Coil dimensions are important features of polymers which affect their performance in various applications, including drug delivery, waste-water treatment, and engine oils. Coil dimensions of the polyolefins are dependent on the number, size, and stereo orientation of side chains along the backbone. Thus, controlling these attributes allows us to tailor the coil dimensions of polyolefins. In the proposed scheme, we calculate the radius of gyration (<i>R<sub>g</sub></i>) of polyolefin chains using molecular dynamics simulations and validate against experimental results. Simulated annealing is implemented to ensure the capture of different configurations. This model affords the ability to quantify the effect tacticity has on the coil dimensions of polyolefins. The results show the suppression of tacticity effects when the polymer chains transition to bottlebrush structures, demonstrating that the side chain steric hindrance plays an important role in the rigidity of the chain backbone. Further, the model is used to evaluate the compositional effects by determining the rigidity of propylene and 1-hexene copolymers. Combining our model with virtual high-throughput screening techniques, we evaluated the coiling behavior of hundreds of new polymers. Using the screening results, we established correlations between the structure of the side chain and the coil dimensions of polymers.</pre><pre>The supplementary material accompanying this paper includes the library of 275 polymers and their corresponding <i>K<sub>s</sub></i> values.<br></pre>

scholarly journals The Mechanical Properties of Defective Graphyne

Crystals ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 465 ◽  
Author(s):  
Shuting Lei ◽  
Qiang Cao ◽  
Xiao Geng ◽  
Yang Yang ◽  
Sheng Liu ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Strain Rate ◽  
Young’S Modulus ◽  
Point Defects ◽  
Young's Modulus ◽  
Carbon Allotrope ◽  
Young’S Moduli ◽  
Potential Applications ◽  
Dynamics Simulations

Graphyne is a two-dimensional carbon allotrope with superior one-dimensional electronic properties to the “wonder material” graphene. In this study, via molecular dynamics simulations, we investigated the mechanical properties of α-, β-, δ-, and γ-graphynes with various type of point defects and cracks with regard to their promising applications in carbon-based electronic devices. The Young’s modulus and the tensile strength of the four kinds of graphyne were remarkably high, though still lower than graphene. Their Young’s moduli were insensitive to various types of point defects, in contrast to the tensile strength. When a crack slit was present, both the Young’s modulus and tensile strength dropped significantly. Furthermore, the Young’s modulus was hardly affected by the strain rate, indicating potential applications in some contexts where the strain rate is unstable, such as the installation of membranes.

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