scholarly journals Internal and external catalysis in boronic ester networks

2021 ◽  
Author(s):  
Boyeong Kang ◽  
Julia Kalow
Keyword(s):  
Mechanical Properties ◽  
Binding Affinity ◽  
Polymer Networks ◽  
Model Systems ◽  
Self Healing ◽  
Dynamic Materials ◽  
Boronic Ester ◽  
Rate Acceleration ◽  
Exchange Spectroscopy ◽  
Kinetics Of

In dynamic materials, the reversible condensation between boronic acids and diols provides adaptability, self-healing ability, and responsiveness to small molecules and pH. Recent work has shown that the thermodynamics and kinetics of bond exchange determine the mechanical properties of dynamic polymer networks. However, prior studies have focused on how structural and environmental factors influence boronic acid–diol binding affinity, and design rules for tuning the kinetics of this dynamic bond are lacking. In this work, we investigate the effects of diol (or polyol) structure and salt additives on the rate of bond exchange, binding affinity, and the mechanical properties of the corresponding polymer networks. To better mimic the environment of polymer networks in our small-molecule model systems, we incorporated proximal amide groups, which are used to conjugate diols to polymers, and included salts commonly found in buffers. Using one-dimensional selective exchange spectroscopy (1D EXSY), we find that both proximal amides and buffering anions induce significant rate acceleration consistent with internal and external catalysis, respectively. This rate acceleration is reflected in the stress relaxation of gels formed using PEG modified with different alcohols, and in the presence of salts containing acetate or phosphate. These findings contribute to the fundamental understanding of the boronic ester dynamic bond and offer new molecular strategies to tune the macromolecular properties of dynamic materials.

scholarly journals Dynamic Semi IPNs with Duple Dynamic Linkers: Self-Healing, Reprocessing, Welding, and Shape Memory Behaviors

Polymers ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1679
Author(s):  
Yanning Zeng ◽  
Weiming Yang ◽  
Shuxin Liu ◽  
Xiahui Shi ◽  
Aoqian Xi ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Shape Memory ◽  
Material Properties ◽  
Dynamic Properties ◽  
Thermoplastic Polyurethane ◽  
Polymer Networks ◽  
Interpenetrating Polymer Networks ◽  
Diels Alder ◽  
Self Healing ◽  
Boronic Ester

Thermoset polymers show favorable material properties, while bringing about environmental pollution due to non-reprocessing and unrecyclable. Diels–Alder (DA) chemistry or reversible exchange boronic ester bonds have been employed to fabricate recycled polymers with covalent adaptable networks (CANs). Herein, a novel type of CANs with multiple dynamic linkers (DA chemistry and boronic ester bonds) was firstly constructed based on a linear copolymer of styrene and furfuryl methacrylate and boronic ester crosslinker. Thermoplastic polyurethane is introduced into the CANs to give a semi Interpenetrating Polymer Networks (semi IPNs) to enhance the properties of the CANs. We describe the synthesis and dynamic properties of semi IPNs. Because of the DA reaction and transesterification of boronic ester bonds, the topologies of semi IPNs can be altered, contributing to the reprocessing, self-healing, welding, and shape memory behaviors of the produced polymer. Through a microinjection technique, the cut samples of the semi IPNs can be reshaped and mechanical properties of the recycled samples can be well-restored after being remolded at 190 °C for 5 min.

Decoupling of the Chemical and Mechanical Surface Contributions in a Force Curve Measurement with AFM

2003 ◽  
Vol 778 ◽  
Author(s):  
Olivier Noel ◽  
Maurice Brogly ◽  
Gilles Castelein ◽  
Jacques Schultz
Keyword(s):  
Mechanical Properties ◽  
Surface Properties ◽  
Adhesion Force ◽  
Force Measurement ◽  
Mechanical Energy ◽  
Polymer Network ◽  
Polymer Networks ◽  
Model Systems ◽  
Silicon Substrates ◽  
Contact Mode

AbstractAtomic Force Microscope (AFM) was used to perform surface force measurements in contact mode to investigate surface properties of model systems at the nanoscale. Model systems were considered and compared. The first one was related to systems of controlled chemical surface properties with identical mechanical properties (chemically modified silicon substrates with hydroxyl, amine, methyl and ester functional groups). The second one deals with model polymer networks (Cross-linked polydimethylsiloxane or PDMS) of controlled mechanical properties and identical surface chemistry. The third system consists in a model polymer network, whose surface is chemically controlled with the same groups as before with silicon substrates. The results show that the viscoelastic contribution is dominating in the adhesion force measurement. Finally, we propose a relationship (derived from the Gent and Schultz's one), which expresses the AFM adhesion force as a function of mechanical energy dissipated in the contact and the surface properties of the material.

Malleable and Self-Healing Covalent Polymer Networks through Tunable Dynamic Boronic Ester Bonds

2015 ◽  
Vol 137 (20) ◽  
pp. 6492-6495 ◽  
Author(s):  
Olivia R. Cromwell ◽  
Jaeyoon Chung ◽  
Zhibin Guan
Keyword(s):  
Polymer Networks ◽  
Self Healing ◽  
Boronic Ester

scholarly journals Mechanochemically Responsive Viscoelastic Elastomers

2016 ◽  
Vol 83 (7) ◽  
Author(s):  
Mahdi Takaffoli ◽  
Teng Zhang ◽  
David Parks ◽  
Xuanhe Zhao
Keyword(s):  
Time Scales ◽  
Chemical Reactions ◽  
Theoretical Foundation ◽  
Chemical Activation ◽  
Polymer Networks ◽  
Mechanical Forces ◽  
Self Healing ◽  
Proposed Model ◽  
Kinetics Of ◽  
Different Time Scales

Mechanochemically responsive (MCR) polymers have been designed to possess unconventional properties such as changing colors, self-healing, and releasing catalysts under deformation. These properties of MCR polymers stem from a class of molecules, referred to as mechanophores, whose chemical reactions can be controlled by mechanical forces. Although extensive studies have been devoted to the syntheses of MCR polymers by incorporating various mechanophores into polymer networks, the intricate interactions between mechanical forces and chemical reactions in MCR polymers across multiple length and time scales are still not well understood. In this paper, we focus on mechanochemical responses in viscoelastic elastomers and develop a theoretical model to characterize the coupling between viscoelasticity and chemical reactions of MCR elastomers. We show that the kinetics of viscoelasticity and mechanophore reactions introduce different time scales into the MCR elastomers. The model can consistently represent experimental data on both mechanical properties and chemical reactions of MCR viscoelastic elastomers. In particular, we explain recent experimental observations on the increasing chemical activation during stress relaxation of MCR elastomers, which cannot be explained with existing models. The proposed model provides a theoretical foundation for the design of future MCR polymers with desirable properties.

scholarly journals Rosin-Based Epoxy Vitrimers with Dynamic Boronic Ester Bonds

Polymers ◽  
2021 ◽  
Vol 13 (19) ◽  
pp. 3386
Author(s):  
Yanning Zeng ◽  
Jiawei Li ◽  
Shuxin Liu ◽  
Bin Yang
Keyword(s):  
Mechanical Properties ◽  
Mechanical Analysis ◽  
Chemical Degradation ◽  
Self Healing ◽  
Hot Press ◽  
Boronic Ester ◽  
Network Topologies ◽  
Reversible Covalent ◽  
First Time ◽  
Epoxy Groups

Rosin is an abundantly available natural product. In this paper, for the first time, a rosin derivative is employed as the main monomer for preparation of epoxy vitrimers to improve the mechanical properties of vitrimers. Novel epoxy vitrimer networks with dynamic reversible covalent boronic ester bonds are constructed by a reaction between thiols in 2,2′–(1,4–phenylene)–bis (4–mercaptan–1,3,2–dioxaborolane) (BDB) as a curing agent and epoxy groups in the rosin derivative. The rosin-based epoxy vitrimer networks are fully characterized by Fourier transform infrared spectroscopy (FTIR), an equilibrium swelling experiment, and dynamic mechanical analysis (DMA). The obtained rosin-based epoxy vitrimers possess superior thermostability and good mechanical properties. Due to transesterification of boronic ester bonds, rosin epoxy vitrimer network topologies can be altered, giving welding, recycle, self-healing, and shape memory abilities to the fabricated polymer. Besides, the effects of treating time and temperature on welding capability is investigated, and it is found that the welding efficiency of the 20% C-FPAE sample is >93% after treatment for 12 h at 160 °C. Moreover, through a hot press, the pulverized samples of 20% C-FPAE can be reshaped several times and most mechanical properties are restored after reprocessing at 200 °C for 60 min. Finally, chemical degradation is researched for the rosin-based epoxy vitrimers.

Synergy between dynamic covalent boronic ester and boron–nitrogen coordination: strategy for self-healing polyurethane elastomers at room temperature with unprecedented mechanical properties

2021 ◽  
Author(s):  
Kai Song ◽  
Wujin Ye ◽  
Xingchen Gao ◽  
Huagao Fang ◽  
Yaqiong Zhang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Molecular Interactions ◽  
Room Temperature ◽  
Self Healing ◽  
Polyurethane Elastomers ◽  
Coordination Strategy ◽  
Boronic Ester ◽  
Healing Efficiency ◽  
Boron Nitrogen

Boron–nitrogen coordination in polyurethane elastomers enhances the dynamics of the boronic ester while introduces inter- and intra-molecular interactions, leading to mechanical robustness and excellent self-healing efficiency simultaneously.

Self-healing dynamic bond-based rubbers: understanding the mechanisms in ionomeric elastomer model systems

2015 ◽  
Vol 17 (32) ◽  
pp. 21005-21017 ◽  
Author(s):  
N. Hohlbein ◽  
A. Shaaban ◽  
A. R. Bras ◽  
W. Pyckhout-Hintzen ◽  
A. M. Schmidt
Keyword(s):  
Mechanical Properties ◽  
Tensile Tests ◽  
Model System ◽  
Model Systems ◽  
Time Dependent ◽  
Self Healing ◽  
Structure Property ◽  
Healing Efficiency ◽  
Oscillatory Rheology ◽  
Systematic Structure

Systematic structure-property investigations on the time-dependent mechanical properties of an ionomer model system with variation of the ionic fraction and the counter ion as obtained from SAXS, dynamic oscillatory rheology and tensile tests, deliver the prerequisites and tools for property adjustment and optimization of their self-healing efficiency.

Autonomous self-healing polyisoprene elastomers with high modulus and good toughness based on the synergy of dynamic ionic crosslinks and highly disordered crystals

2020 ◽  
Vol 11 (41) ◽  
pp. 6549-6558
Author(s):  
Yohei Miwa ◽  
Mayu Yamada ◽  
Yu Shinke ◽  
Shoichi Kutsumizu
Keyword(s):  
Mechanical Properties ◽  
Room Temperature ◽  
Self Healing ◽  
High Modulus ◽  
Disordered Crystals ◽  
Ionic Crosslinks

We designed a novel polyisoprene elastomer with high mechanical properties and autonomous self-healing capability at room temperature facilitated by the coexistence of dynamic ionic crosslinks and crystalline components that slowly reassembled.

Crosslinker Chemistry Determines the Uptake Potential of Perfluorinated Alkyl Substances by β-Cyclodextrin Polymers

2018 ◽  
Author(s):  
Leilei Xiao ◽  
Casey Ching ◽  
Yuhan Ling ◽  
Mohammadreza Nasiri ◽  
Max Justin Klemes ◽  
...  
Keyword(s):  
Binding Affinity ◽  
Polymer Networks ◽  
Cyclodextrin Polymer ◽  
Perfluorinated Alkyl Substances ◽  
Cyclodextrin Polymers

This work describes several crosslinked β-cyclodextrin polymer networks and correlates the crosslinker chemistry with binding affinity for per- and polyfluorinated alkyl substances (PFASs), including PFOA and PFOS.

Elaboration and Characterization of the Properties of Refractory Cr Base Alloys

2010 ◽  
Vol 72 ◽  
pp. 46-52 ◽  
Author(s):  
Laurent Royer ◽  
Stéphane Mathieu ◽  
Christophe Liebaut ◽  
Pierre Steinmetz
Keyword(s):  
Mechanical Properties ◽  
Melting Point ◽  
Molten Glass ◽  
Energy Production ◽  
Creep Properties ◽  
Refractory Alloys ◽  
Industrial Use ◽  
Kinetics Of ◽  
Selection Of

For energy production and also for the glass industry, finding new refractory alloys which could permit to increase the process temperatures to 1200°C or more is a permanent challenge. Chromium base alloys can be good candidates, considering the melting point of Cr itself, and also its low corrosion rate in molten glass. Two families of alloys have been studied for this purpose, Cr-Mo-W and Cr-Ta-X alloys (X= Mo, Si..). A finer selection of compositions has been done, to optimize their chemical and mechanical properties. Kinetics of HT oxidation by air, of corrosion by molten glass and also creep properties of several alloys have been measured up to 1250°C. The results obtained with the best alloys (Cr-Ta base) give positive indications as regards the possibility of their industrial use.

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