Thermodynamics and Stereochemistry of Diels–Alder Polymer Networks: Role of Crosslinker Flexibility and Crosslinking Density

2021 ◽  
Author(s):  
Qing Zhou ◽  
Zhen Sang ◽  
Kartik Kumar Rajagopalan ◽  
Yelena Sliozberg ◽  
Frank Gardea ◽  
...  
Keyword(s):  
Polymer Networks ◽  
Crosslinking Density ◽  
Diels Alder

scholarly journals Mechanical Response of Two-Dimensional Polymer Networks: Role of Topology, Rate Dependence, and Damage Accumulation

2018 ◽  
Vol 85 (3) ◽  
Author(s):  
Konik Kothari ◽  
Yuhang Hu ◽  
Sahil Gupta ◽  
Ahmed Elbanna
Keyword(s):  
Mechanical Response ◽  
Polymer Networks ◽  
Soft Materials ◽  
Crosslinking Density ◽  
State Theory ◽  
Polymer Chains ◽  
Local Network ◽  
Network Characteristics ◽  
Rate Dependent

The skeleton of many natural and artificial soft materials can be abstracted as networks of fibers/polymers interacting in a nonlinear fashion. Here, we present a numerical model for networks of nonlinear, elastic polymer chains with rate-dependent crosslinkers similar to what is found in gels. The model combines the worm-like chain (WLC) at the polymer level with the transition state theory for crosslinker bond dynamics. We study the damage evolution and the force—displacement response of these networks under uniaxial stretching for different loading rates, network topology, and crosslinking density. Our results suggest a complex nonmonotonic response as the loading rate or the crosslinking density increases. We discuss this in terms of the microscopic deformation mechanisms and suggest a novel framework for increasing toughness and ductility of polymer networks using a bio-inspired sacrificial bonds and hidden length (SBHL) mechanism. This work highlights the role of local network characteristics on macroscopic mechanical observables and opens new pathways for designing tough polymer networks.

scholarly journals Theoretical Insight into the Reversal of Chemoselectivity in Diels-Alder Reactions of α,β-Unsaturated Aldehydes and Ketones Catalyzed by Brønsted and Lewis Acids

Organics ◽  
2021 ◽  
Vol 2 (1) ◽  
pp. 38-49
Author(s):  
Lakhdar Benhamed ◽  
Sidi Mohamed Mekelleche ◽  
Wafaa Benchouk
Keyword(s):  
Lewis Acids ◽  
Major Product ◽  
Diels Alder ◽  
Unsaturated Ketone ◽  
Unsaturated Aldehydes ◽  
Aldehydes And Ketones ◽  
Theoretical Insight ◽  
Insight Into ◽  
Good Agreement

Experimentally, a reversal of chemoselectivity has been observed in catalyzed Diels–Alder reactions of α,β-unsaturated aldehydes (e.g., (2E)-but-2-enal) and ketones (e.g., 2-hexen-4-one) with cyclopentadiene. Indeed, using the triflimidic Brønsted acid Tf2NH as catalyst, the reaction gave a Diels–Alder adduct derived from α,β-unsaturated ketone as a major product. On the other hand, the use of tris(pentafluorophenyl)borane B(C6F5)3 bulky Lewis acid as catalyst gave mainly the cycloadduct of α,β-unsaturated aldehyde as a major product. Our aim in the present work is to put in evidence the role of the catalyst in the reversal of the chemoselectivity of the catalyzed Diels–Alder reactions of (2E)-but-2-enal and 2-Hexen-4-one with cyclopentadiene. The calculations were performed at the ωB97XD/6-311G(d,p) level of theory and the solvent effects of dichloromethane were taken into account using the PCM solvation model. The obtained results are in good agreement with experimental outcomes.

Exploring secondary interactions and the role of temperature in moisture-contaminated polymer networks through molecular simulations

Soft Matter ◽  
2021 ◽  
Vol 17 (10) ◽  
pp. 2942-2956
Author(s):  
Rishabh D. Guha ◽  
Ogheneovo Idolor ◽  
Katherine Berkowitz ◽  
Melissa Pasquinelli ◽  
Landon R. Grace
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Temperature Variation ◽  
Polymer Networks ◽  
Molecular Simulations ◽  
Effect Of Temperature ◽  
Secondary Interactions ◽  
Dynamics Simulations ◽  
Secondary Bonding

We investigated the effect of temperature variation on the secondary bonding interactions between absorbed moisture and epoxies with different morphologies using molecular dynamics simulations.

Converting the role of LiClO4 from salting-in to salting-out in Diels-Alder reactions by solvent manipulation

2003 ◽  
Vol 16 (9) ◽  
pp. 633-635 ◽  
Author(s):  
Suvarna S. Deshpande ◽  
Sanjay S. Pawar ◽  
Usha Phalgune ◽  
Anil Kumar
Keyword(s):  
Diels Alder ◽  
Salting Out

ChemInform Abstract: Switched Role of Fullerene in the Diels-Alder Reaction: Facile Addition of Dienophiles to the Conjugated Fullerene Diene Moiety.

ChemInform ◽  
2009 ◽  
Vol 40 (24) ◽  
Author(s):  
Jiayao Yao ◽  
Zuo Xiao ◽  
Jianxin Zhang ◽  
Xiaobing Yang ◽  
Liangbing Gan ◽  
...  
Keyword(s):  
Alder Reaction ◽  
Diels Alder ◽  
Diels Alder Reaction

Amplified photo-responses in sequentially polymerized azobenzene-containing polymer networks: the role of isomer interconnection

2020 ◽  
Vol 11 (12) ◽  
pp. 1998-2005
Author(s):  
Chenzhe Li ◽  
Hyunsu Kim ◽  
Jongwon An ◽  
Maenghyo Cho
Keyword(s):  
Polymer Networks

Sequentially polymerized azobenzene-containing polymer networks with isomer-interconnected features can greatly enhance photo-actuation responses.

scholarly journals The Role of Non-Rubber Components on Molecular Network of Natural Rubber during Accelerated Storage

Polymers ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 2880
Author(s):  
Huifeng Zhang ◽  
Lu Zhang ◽  
Xu Chen ◽  
Yueqiong Wang ◽  
Fuchun Zhao ◽  
...  
Keyword(s):  
Natural Rubber ◽  
Network Formation ◽  
Crosslinking Density ◽  
Factors Affecting ◽  
Hardening Mechanism ◽  
Accelerated Storage ◽  
Before And After ◽  
The Impact ◽  
Vital Factor

Though the non-rubber components have long been recognized to be a vital factor affecting the network of natural rubber (NR), the authentic role of non-rubber components on the network during accelerated storage has not been fully illuminated. This work attempts to clarify the impact of non-rubber components on the network for NR during accelerated storage. A natural network model for NR was proposed based on the gel content, crosslinking density, and the non-rubber components distribution for NR before and after centrifugation. Furthermore, the effect of non-rubber components on the network was investigated during accelerated storage. The results show that terminal crosslinking induced by non-rubber components and entanglements are primary factors affecting the network formation during accelerated storage. By applying the tube model to analyze the stress-strain curves of NR, we found that the contribution of the entanglements to the network formation is larger than that of terminal crosslinking during accelerated storage. The work highlights the role of non-rubber components on the network during accelerated storage, which is essential for understanding the storage hardening mechanism of NR.

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