Long-term operation of hydrogels relies on protective coatings to avoid water swelling or evaporation, but these protections often cause substantial decreases in overall softness and stretchability. Here, a mechanically compatible seal with a coherent interfacial design is developed to encapsulate hydrogels. This seal is made from polybutylene (PIB) and polypropylene-graft-maleic anhydride (PP-g-MAH) blended poly(styrene-isobutylene-styrene) (SIBS). The PIB oligomers soften the SIBS networks, while the MAH groups facilitate covalent bonding between the SIBS and hydrogel. The sealed hydrogel exhibits an elastic modulus of 24 kPa and an elongation at a break of >
1000%, both comparable to those of the pristine hydrogel. The adhesion energy between the seal and hydrogel reached >
140 J m