One-Pot Preparation of Autonomously Self-Healable
Elastomeric Hydrogel from Boric Acid and Random Copolymer Bearing
Hydroxyl Groups
- Publication date
- Publisher
Abstract
Self-healable
hydrogels based on the dynamically reversible boronate
ester or borate ester bonds are usually prepared by reacting boronic
acid or boric acid with diol compounds or polymer-like poly(vinyl
alcohol) bearing a hydroxyl group in each monomer unit. Herein, we
report a finding that not only facilitates the preparation but also
extends the range of self-healable hydrogels of this kind. By simply
copolymerizing commercially available <i>N</i>,<i>N</i>-dimethylacrylamide and 2-hydroxyethyl acrylate (8:2 weight ratio)
in the presence of boric acid in a one-pot fashion, the resulting
random copolymer can gel in aqueous solution at pH = 9, giving rise
to a solid hydrogel (tensile strength >0.5 MPa at water content
of
30%) that, on the one hand, can autonomously self-heal (near 100%
fracture stress recovery within 48 h in air at room temperature) and,
on the other hand, shows the characteristics of elastomer (little
stress relaxation under loading and small residual deformation after
unloading upon repeated 300% elongation cycles). The results reveal
that it can be sufficient to have a random copolymer with comonomer
units bearing hydroxyl groups for reacting with boric acid to generate
dynamically reversible borate ester bonds. This finding thus points
out a general, facile, and cost-effective method to obtain and explore
new borate ester bond-based self-healable hydrogels