Regulation of Phenol-Quinone Equilibrium in Metal-Polyphenolic Network for Initiating Vinyl Monomer Polymerization
Description
In this study, gallium-based MPN was synthesized via ultrasonication of bulk gallium in an aqueous dopamine (DA) suspension. A key novelty lies in our regulation of the phenol-quinone redox equilibrium transition within MPN through a tunable proton-coupled electron transfer (PCET) pathway with coexistence of Ga NPs@PDA and external DA, which enables controlled generation of neutral o-semiquinone radicals (DA•) alongside modulated MPN size growth and colloidal stability decay. This controlled equilibrium was leveraged to develop a one-pot synthesis strategy for functional hydrogel: embedded MPN, Ga-NPs@PDA, and external DA precursors collectively induce vinyl monomer polymerization and crosslinking, yielding multi-functional hydrogels with low hysteresis, tunable pore size, and excellent adhesion. This work establishes a methodology for controlling the phenol-quinone equilibrium, elucidates the mechanisms underlying MPN self-assembly and DA• formation, advances the development of functional MPN nanomaterials, and expands their application potential in functional polymer composites—particularly through the innovative one-pot hydrogel synthesis approach enabled by the newly discovered MPN structural evolution mechanism.
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The Synthesize of MPN Assembly: A 300 mg bulk Ga-LM was immersed in a 10 mL of 1 mg/mL solution of DA and subjected to probe ultrasonication (750 W, 20 kHz and 20% amplitude) using a pulse mode (2 s on, 1 s off) within a 5 to 10 ℃ ice-water alcohol bath. Subsequently, the suspension of Ga-LM nanohybrid particles (Ga-NPs@PDA) and MPN assemblies were acquired. To investigate the transformation mechanism of MPN assembly, extra-DA (e-DA, “e” for extra) were dissolved into the suspension, which was afterward left standing at 4 ℃ for a period of time. Name the obtained sample MPN-LM-Dx. Especially, MPN-Dx was prepared from the supernatant of suspension, where most of the Ga-NPs@PDA was removed by centrifugation. The “LM” refers to Ga-NPs@PDA and the “x” refers to the mass of e-DA per 10 mL suspension. PDA solution was prepared by ultrasonication on 10 mL of 1 mg/mL solution of DA as control group. The Synthesis of MPN Embedded Hydrogel: To prepare the precursors of hydrogel, 1 g NIPAm and 5 mg BIS were dissolved into 10 mL of MPN-LM-Dx suspensions, which were allowed for 8 hours of polymerization at 4 ℃ to afford hydrogels (Ga-NPs@PDA-Dx/HG). Especially, the precursors without the crosslinker BIS were also prepared to investigate the mechanism of FRP of NIPAm, which were denoted as Ga-NPs@PDA-Dx/PNIPAm. The wearable strain sensor was assembled with a 30*10*2 mm hydrogel strip and copper tape. Characterization: Scanning electron microscopy (SEM, Verios G4, FEI), pH meter (PB-10, Sartorius), Ultraviolet-visible spectrophotometer (UV-2800A, Unocal), Laser particle size and ZETA potentiometers (Zeta Sizer NANOZS, Malvern), Fourier transform infrared spectroscopy (FTIR, Tensor 27, Bruker), gel-permeation chromatography (GPC, 1260 Infinity II, PLTK). Fourier digital nuclear magnetic resonance spectrometer (Avance 400 MHz, Bruker) were used. The DA• was indirectly measured through UV-vis spectra by mixing MPN-LM-Dx and MV solution, which were then stored at 4 ℃ for some time and taken the supernatant for characterization. To reveal the phenol-quinone equilibrium in MPN assemblies, the cyclic voltammetry was performed among three electrodes: reference electrode Ag/AgCl, counter electrode Pt, and working electrode. The working electrode MPN/GCE was prepared as follows. 2.5 μL supernatants of MPN-LM-Dx or MPN-Dx were dropped onto the preprocessed glassy carbon electrode (GCE) and dried with nitrogen treatment. Then, the electrode was covered by 0.5 wt% Nafion solution and dried again, which was named MPN/GCE. The analysis was based on the second cycle of CV test. The wearable strain sensor was adhered to the index finger and connected to the electrochemical workstation (PGSTAT M204, Metrohm)，which was used to collect the electrical signals corresponding to the movements of finger.
Institutions
- Northwestern Polytechnical University School of ManagementShaanxi, Xi'an