Degradable Microgel Wet-Strength Adhesives: A Route to Enhanced Paper Recycling

Demonstrated is a new approach to cellulose fiber-based materials that are strong when wet, yet can be recycled after exposure to a weak reducing agent. Poly(N-isopropylacrylamide-co-acrylic acid) microgels were transformed into wet cellulose adhesives by incorporation of hydrazide groups that can form hydrazone linkages to oxidized cellulose. Reductant responsivity was obtained by introducing cleavable disulfide linkages, either in the chains tethering the adhesive hydrazide groups, or by using disulfide cross-links in the microgels. Both types of disulfide derivatives gave about 75% reduction in cellulose wet adhesion after exposure to a reductant. Truly sustainable wood-fiber replacements for plastic packaging must be insensitive to water while being fully recyclable; this work demonstrates two routes to reversible wet cellulose adhesives, facilitating recycling.