Adding the Effect of Topological Defects to the Flory–Rehner and Bray–Merrill Swelling Theories

Rebello, Nathan; Beech, Haley K.; Olsen, Bradley D.

doi:10.1021/acsmacrolett.0c00909

Cited by 21 publications

(23 citation statements)

References 43 publications

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“…where x 1 and x 2 are the fractions of primary and secondary loops per crosslink, respectively. Figure 1b shows that contrary to gels, 11,22,53 for the studied networks, the correction is relatively small. But it clearly emphasizes that compared to exact phantom ANT prediction, the MMT success is a bit fortuitous since the MMT does not account for the effect of the loops on the modulus.…”

Section: ■ Results and Discussionmentioning

confidence: 89%

Molecular Dynamics Study on the Validity of Miller–Macosko Theory for Entanglement and Crosslink Contributions to the Elastic Modulus of End-Linked Polymer Networks

Gusev

Schwarz

2022

Macromolecules

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Stress-relaxation molecular dynamics simulations are performed to obtain estimates of the shear modulus of "real" end-linked poly(dimethylsiloxane) networks with excluded-volume interaction between the strands. Computer microstructures with up to 10 4 identical strands end-linked by tri-or tetrafunctional crosslinks are studied. A representative range of extents of reaction and strand molar masses is considered. It is found that for the entire range, the additivity assumption for the contributions of the chemical crosslinks and entanglements to the modulus is remarkably valid even though the topological factors of the real and their topologically equivalent phantom networks differ very substantially and that for the real networks the affine deformation requirement is not satisfied. It is demonstrated that the classical additive mean-field Miller−Macosko theory, which does not explicitly address the underlying microscopic mechanisms, gives consistently accurate predictions for both real and phantom moduli of studied end-linked polymer networks, and the predictions are achieved using a quick arithmetic calculation.

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Section: ■ Results and Discussionmentioning

confidence: 89%

Molecular Dynamics Study on the Validity of Miller–Macosko Theory for Entanglement and Crosslink Contributions to the Elastic Modulus of End-Linked Polymer Networks

Gusev

Schwarz

2022

Macromolecules

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“…The experimental data for χ in the literature (see Table ) are not really consistent and were measured mainly at temperatures around 100 °C outside of our temperature window for synthesis and analysis. If this is not the case like in ref , the data were computed from swelling measurements and thus may contain a dependence on the model for elasticity and swelling.…”

Section: Resultsmentioning

confidence: 99%

Amphiphilic Model Networks Based on PEG and PCL Tetra-arm Star Polymers with Complementary Reactivity

et al. 2022

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A new approach for the synthesis of model amphiphilic polymer co-networks (ACNs) based on a heterocomplementary coupling reaction of a 2-(4-nitrophenyl)-benzoxazinone terminated tetra-arm polycaprolactone star (tetra-PCL) with an amino-terminated tetra-arm polyethylene glycol star (tetra-PEG) is presented. The reaction conditions (solvent, concentration, and temperature) were varied widely. Reaction kinetics and gelation were analyzed with high-resolution NMR spectroscopy and computer simulations. The results agree with a nearly homogeneous mixture where local composition fluctuations affect kinetics only after most of the molecules are attached to the gel. Viscometry, dynamic light scattering data, and literature data for the solubility parameters were combined to provide estimates for the Flory−Huggins interaction parameter of the two star polymers in toluene, chloroform, and THF as solvents. These estimates allow one to collapse equilibrium swelling data in different solvents on a universal curve. Multiple quantum NMR analysis shows an enhanced formation of double connections between the same pair of stars as compared to preceding work on tetra-PEG gels made by the same cross-linking strategy but with a different coupling reaction. Besides this last observation, the remaining results indicate that the networks possess a near model-like structure with only a small fraction of pending arms as the most relevant type of network defects.

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“…Early investigations focused on controlling the network architecture by cross-linking poly(dimethylsiloxane) chains of narrow dispersity and well-defined molecular weight. The resulting materials enabled a better molecular understanding of mechanical properties like elasticity − and fracture, , but their architectures proved to be heterogeneous on the basis of small-angle scattering. − Networks of poly(butadiene), , poly(urethane), , and poly(ethylene glycol) have been synthesized by using a similar strategy, with the latter ones being the most homogeneous and also affording refinement of molecular models on elasticity, swelling, and fracture . However, synthesizing polymer networks by cross-linking polymer chains requires multiple steps including, at the very least, the synthesis of polymer chains and post-cross-linking in the bulk or concentrated solution.…”

Section: Introductionmentioning

confidence: 99%

Controlling Architecture and Mechanical Properties of Polyether Networks with Organoaluminum Catalysts

et al. 2022

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Soft materials can sustain large, elastic, and reversible deformations, finding widespread use as elastomers and hydrogels. These materials constitute 3-D polymer networks and are typically synthesized by cross-linking polymer chains or copolymerizing monomer and cross-linker. Seminal investigations have enabled control over the network architecture by cross-linking chains of poly(dimethylsiloxane), poly(1,4-butadiene), or tetra-poly(ethylene glycol); however, as soft materials become attractive for robotics, electronics, and prosthetics, codesigning the network architecture, mechanical, and functional properties has become pressing. We investigate the relationship among reaction pathway, network architecture, and mechanical properties in poly(ethyl glycidyl ether) networks synthesized by epoxide ring-opening polymerization with two organoaluminum catalysts. The key result is that uncontrolled polymerizations yield loosely cross-linked, entangled, soft, and extensible networks, whereas more controlled polymerizations, instead, lead to highly cross-linked, stiff, and brittle networks. Such catalytic control over network architecture and mechanical properties could enable design of novel soft, tough, and functional materials.

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Adding the Effect of Topological Defects to the Flory–Rehner and Bray–Merrill Swelling Theories

Cited by 21 publications

References 43 publications

Molecular Dynamics Study on the Validity of Miller–Macosko Theory for Entanglement and Crosslink Contributions to the Elastic Modulus of End-Linked Polymer Networks

Molecular Dynamics Study on the Validity of Miller–Macosko Theory for Entanglement and Crosslink Contributions to the Elastic Modulus of End-Linked Polymer Networks

Amphiphilic Model Networks Based on PEG and PCL Tetra-arm Star Polymers with Complementary Reactivity

Controlling Architecture and Mechanical Properties of Polyether Networks with Organoaluminum Catalysts

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