Nanofibrous chiral supramolecular assembly-derived self-healing hydrogels with polyethylene glycol

Unique polymer hydrogels with unusual cross-linking networks and self-healing properties have been recently reported. In this study, we fabricated hybrid hydrogels consisting of a chiral supramolecular one-dimensional assembly of glutamide-derived lipids bearing pyridinium head groups (G-Py+) cross-linked with termini-anionised hydrophilic polyethylene glycol polymers (S-PEGn-S). The cationic group-linked G-Py+ forms nanotubular aggregates in water. G-Py+/S-PEGn-S aqueous mixtures formed hydrogels at certain concentrations and ambient temperatures. The terminal anionic sulfate groups play a key role in hydrogel formation, as evidenced by the absence of gelation in G-Py+/PEGn. The negative circular dichroism signal observed for pyridinium exhibited a blue shift upon the addition of S-PEGn-S but maintained its signal intensity even with excess S-PEGn-S, suggesting the chiral orientation of the nanofibrous G-Py+ self-assembly preserved even complexation with S-PEGn-S in hydrogel. The hybrid hydrogel of sulfated polyethylene glycol with nanofibrous chiral supramolecular assembly exhibited self-healing property at a temperature below the gel-to-liquid crystalline phase transition (TC) of G-Py+ aggregates, which was evidenced by the inversion fluid method and viscoelastic measurements.


Synthesis of G-Py +
Synthesis scheme of G-Py + was depicted and the synthesis of each step is described below.
The solution was washed with 1.0 mol/L HCl, 1.0 mol/L NaOH and water.
After cooling to room temperature, a white crystal appeared, and unreacted pyridine was removed by filtration.The white crystals in this step were dried in vacuo: yield 0.22 g (39 %, 0.32 mmol); mp  1H,NH),1H,1H,.FT-IR and 1 H NMR spectra were shown in Figure S1 and S2.

Figure S2
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Synthesis of S-PEGn-S
Synthesis scheme of S-PEG-S was depicted and the synthesis of each step is described below.
S-PEGn-S 20 g of polyethylene glycol (PEGn) (degree of polymerization (n) = 70, 200, 350) was dissolved in 20 mL of dichloromethane, and the solution was cooled in ice bath.Chlorosulfonic acid (10 equiv.) was added the solution under cooling, and the mixture was stirred at room temperature for 20 h.Thereafter, the solution was concentrated and decanted dropwise into diethyl ether.The precipitate was washed several times with diethyl ether, collected by filtration and dried under vacuum to obtain white powder.

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