Dynamic covalent polymer networks combine intrinsic reversibility with the robustness of covalent bonds, creating chemically stable materials that are responsive to external stimuli.
Although the control of chemical composition and macromolecular architectures of polymer networks is crucial to tailor their properties, the control and characterization of the crosslinking density and defects remains challenging. Therefore, new synthetic approaches are needed, which can, on the one hand dynamically tune the network structure and functionalization, and on the other hand facilitate characterization.The present study explores the combination of nitroxide exchange reaction (NER) and nitroxide mediated polymerization (NMP), in different sequences, to prepare structurally tailored and engineered macromolecular (STEM) networks with controlled strand lengths. The radical nature of the NER enables the precise monitoring of the reaction progress and determination of the defect ratio of the networks in a straightforward manner via electron paramagnetic resonance (EPR) spectroscopy. Additionally, the dynamic nature of the NER permits the disassembly of the networks and the determination of the strand length of the prepared networks by size exclusion chromatography (SEC). The final networks are also characterized by inverse size exclusion chromatography (ISEC) to determine and compare their mesh-size distributions. Thus, this study demonstrates that the combination of NER and NMP offers a versatile approach for the preparation of dynamic polymer networks with controlled and tunable structures. † Electronic supplementary information (ESI) available: Additional synthetic and characterization details (EPR, SEC, ISEC, DSC, NMR, ATR-FTIR, and EI-MS). See
The synthesis and exchange reaction of a rigid, isoindoline-functionalized tetraphenylmethane multi-spin system is described. The exchange reaction was followed using EPR spectroscopy.
Electrografting of diazonium salts containing a protected alkyne moiety was used for the first functionalization of silicon and highly ordered pyrolytic graphite model surfaces. After deprotection with tetrabutylammonium fluoride, further layers were added by the thiol-yne click chemistry. The composition of each layer was characterized via X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry. The same approach was then used to functionalize graphite powder electrodes, which are classically used as negative electrode in lithium-ion batteries. The effect of the coating on the formation of the solid electrolyte layer was investigated electrochemically by cyclovoltammetry and galvanostatic measurements. The modified graphite electrodes showed different reduction peaks in the first cycle, indicating reduced and altered decomposition processes of the components. Most importantly, the electrochemical investigations show a remarkable reduction of irreversible capacity loss of the battery.
We synthesised three different POPs via a nitroxide exchange reaction and modulated their crosslinking degree. That allowed us to investigate the influence of the crosslinking degree and the structure of the molecular components on the porosity.
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