Procedure for preparation of high-water-content hydrogels using clay and a dendritic molecular binder
Lab/Group: Aida Lab (JST ERATO-SORST and The University of Tokyo)
Related Journal & Article Information
Journal: Nature
Article Title: High-water-content mouldable hydrogels by mixing clay and a dendritic molecular binder
Introduction
This protocol describes a facile, quick and reproducible preparation of hydrogels. The protocol requires four components: water, clay nanosheets (Clay-NS), a dendritic macromolecule (Gn-binder; n = generation number) and sodium polyacrylate (ASAP). Upon mixing with ASAP in water, Clay-NS, which are heavily entangled with one another, are exfoliated and dispersed homogenously because of a possible site-specific wrapping of their positive-charged edge parts with anionic ASAP. Meanwhile, Gn-binder possesses two dendron units, which are decorated with multiple guanidinium ion pendants on their periphery. A previous paper1 reports that a mono-dendron version of Gn-binder interacts strongly with the oxyanionic surface groups of proteins. Upon addition of Gn-binder to the aqueous solution of Clay-NS with ASAP, exfoliated nanosheets of clay are crosslinked kinetically through multivalent salt-bridge formation between the guanidinium ion pendants of Gn-binder and oxyanionic groups on the nanosheet surface. Consequently, the hydrogelation takes place.
Materials
Reagents
Clay-NS (Laponite XLG) was purchased from Rockwood Ltd.
ASAP (sodium polyacrylate) was purchased from Wako Pure Chemical Industries, Ltd.
Gn-binder was synthesized through an adapted synthetic protocol of previous literatures.1,2 For details, see Supplementary Information of the related article in Nature.
Ultrapure-grade water was used for hydrogelation.
Equipment
Magnetic stirrer
Teflon-coated magnetic stirrer bar
Plastic vial
Water purification system (Milli-Q, Nihon Millipore K.K.)
Procedure
A typical example of the hydrogelation with Clay-NS, ASAP, and Gn-binder is given below:
1. Dissolve 3.0 mg of sodium polyacrylate (ASAP) in 1.0 mL of water.
2. Dissolve 7.5 mg of G3-binder in 0.25 mL of water.
3. Suspend 100 mg of Clay-NS to 3.75 mL of water.
4. Stir the suspension of Clay-NS at room temperature such as 20 ˚C.
5. Add 1.0 mL of the aqueous solution of ASAP to the stirred suspension of Clay-NS at room temperature such as 20 ˚C.
6. Stir the ASAP-containing Clay-NS suspension for 10 minutes at room temperature such as 20 ˚C and confirm that it turns into a clear viscous solution.
7. Dropwise add 0.25 mL of the aqueous solution of G3-binder to the vigorously stirred Clay-NS/ASAP solution.
8. Let the resultant solution stand for 3 minutes and obtain a transparent, self-standing gel.
Troubleshooting
Gn-binder is highly adhesive to glass:
a) Leave Gn-binder protected until ready for hydrogelation.
b) Use plastic vials and containers when performing hydrogelation.
c) Powerful and efficient stirring is helpful for accelerating the exfoliation of Clay-NS and hydrogelation. However, air-bubbles occasionally form in the resulting hydrogel.
Critical Steps
Anticipated Results
References
1. Okuro, K., Kinbara, K., Tsumoto, K., Ishii, N. & Aida, T. Molecular glues carrying multiple guanidinium ion pendants via oligoether spacer: stabilization of microtubules against depolymerization. J. Am. Chem. Soc. 131, 1626–1627 (2009).
2. Ihre, H., Padilla De Jesus, O. L. & Fréchet, J. M. J. Fast and convenient divergent synthesis of aliphatic ester dendrimers by anhydride coupling. J. Am. Chem. Soc. 123, 5908–5917 (2001).
Acknowledgements
Keywords
Hydrogel, Clay, Dendrimer, Nanocomposite, Self-healing