A novel side-chain ferrocene (Fc)-containing polyelectrolyte was successfully synthesized using controlled ring-opening metathesis polymerization (ROMP) of a water-soluble norbornene-based quaternary ammonium salt functionalized with ferrocenyl units. The polymerization was catalyzed by the third-generation Grubbs catalyst, enabling precise control over molecular weight and degree of polymerization. The resulting homopolymers exhibited well-defined structures confirmed by ¹H NMR, ¹³C NMR, IR, UV-vis spectroscopy, and mass spectrometry. The monomer displayed excellent solubility in both polar and nonpolar solvents, including DMF, DMSO, CH₂Cl₂, THF, methanol, ethanol, benzene, toluene, ethyl acetate, and acetonitrile, while remaining insoluble in petroleum ether and diethyl ether. Polymerization kinetics monitored by in situ ¹H NMR revealed complete conversion within 30 minutes at room temperature, indicating high efficiency and living characteristics of the ROMP process. End-group analysis via ¹H NMR allowed accurate determination of polymerization degrees: 10 ± 1 for 8a, 25 ± 2 for 8b, 50 ± 3 for 8c, and 83 ± 6 for 8d—values closely matching theoretical expectations based on feed ratios.
The polyelectrolyte framework incorporated pendant hydrophilic quaternary ammonium groups that significantly enhanced water compatibility. All homopolymers were obtained as orange powders, displaying good solubility in DMF and DMSO but decreasing solubility in water and other organic solvents as molecular weight increased. Notably, the highest molecular weight sample (8d) showed only partial solubility in water. The redox activity of the Fc units was confirmed through reversible color changes from orange to green upon oxidation with FeCl₃, accompanied by a shift in UV-vis absorption from 436 nm to 633 nm. Reduction with sodium ascorbate restored the original orange color and reappeared peak at 436 nm. Cyclic voltammetry in DMF with NBu₄PF₆ electrolyte showed a single, chemically reversible wave at 0.7 V vs SCE, confirming the electrochemical reversibility of the Fc/Fe(III) redox couple. However, slow electron transfer kinetics were observed due to the bulkiness of the polymer matrix hindering structural rearrangement.
To develop functional hydrogels, covalently cross-linked polyelectrolyte hydrogel (CC-Fc-HG) was fabricated by copolymerizing the Fc-containing monomer with a water-soluble norbornene crosslinker. Scanning electron microscopy revealed a honeycomb-like porous microstructure with average pore size of 120 ± 30 µm.Cyclophilin F Antibody In Vitro Energy-dispersive X-ray spectroscopy confirmed the presence of Fe and Br, verifying successful incorporation of Fc units. The freeze-dried CC-Fc-HG exhibited a water absorption rate (WAR) of 130%, indicating it could absorb 1.3 times its dry weight in water. Thermal analysis via DSC and TGA demonstrated a glass transition temperature (Tg) of 57 °C and three distinct decomposition stages: dehydration (30–120 °C, 1% loss), degradation of polynorbornene network (120–440 °C, 53% loss), and decomposition of Fc moieties (400–800 °C, 9% loss), leaving a residual mass of 38%.CD31 Antibody Description Rheological studies indicated elastic behavior under low strain (≤10%), with G’ > G”; however, mechanical integrity collapsed beyond 110% strain, consistent with network failure.PMID:35090043
Further enhancement in swelling capacity was achieved through supramolecular engineering. Two strategies were employed: (1) soaking CC-Fc-HG in saturated γ-cyclodextrin (γ-CD) solution, forming S-Fc@γ-CD-HG-1; (2) pre-forming a host-guest complex between γ-CD and monomer 7, followed by ROMP with crosslinker to yield S-Fc@γ-CD-HG-2. The formation of the 1:1 inclusion complex was verified by 2D NOESY NMR, showing cross-peaks between γ-CD cavity protons (H3/H5) and Fc Cp protons. The resulting supramolecular hydrogels displayed dramatically improved swelling: S-Fc@γ-CD-HG-1 reached an equilibrium WAR of 400%, while S-Fc@γ-CD-HG-2 achieved up to 500%. SEM imaging confirmed enlarged pore sizes (198 ± 23 µm and 260 ± 30 µm, respectively), directly linked to the increased hydrophilicity introduced by γ-CD/Fc complexes. Thermal stability slightly increased due to stronger intermolecular interactions, with Tg values rising to 61 °C and 63 °C for S-Fc@γ-CD-HG-1 and S-Fc@γ-CD-HG-2, respectively.
Redox-responsive swelling-shrinking behavior was systematically investigated. Upon exposure to H₂O₂, the Fc units oxidized to cationic Fc⁺, increasing hydrophilicity and causing macroscopic expansion—e.g., diameter increase from 20 mm to 23 mm in CC-Fc-HG, with WAR rising from 130% to 240%. Reversal with glutathione reduced Fc⁺ back to neutral Fc, restoring hydrophobicity and inducing shrinkage. Similar cycles were observed in supramolecular systems, where swelling reached 600% (S-Fc@γ-CD-HG-1) and 620% (S-Fc@γ-CD-HG-2), with full reversibility confirmed by SEM and gravimetric analysis. This dynamic response arises from the reversible disassembly/assembly of γ-CD@Fc inclusion complexes triggered by redox cycling. These findings establish a new class of side-chain Fc-containing supramolecular polyelectrolyte hydrogels with tunable, reversible swelling properties, offering promising applications in stimuli-responsive drug delivery, biosensors, and soft actuators.MedChemExpress (MCE) offers a wide range of high-quality research chemicals and biochemicals (novel life-science reagents, reference compounds and natural compounds) for scientific use. We have professionally experienced and friendly staff to meet your needs. We are a competent and trustworthy partner for your research and scientific projects.Related websites: https://www.medchemexpress.com