Zhijun Liu,Guoming Yuan,Hui Yang,Kunxin Wang,Yanghan Tao,Kun Wu,Jun Shi,Li Yang
Pressure sensitive adhesive (PSA) has great application potential in electronic packaging, flat panel display bonding and other fields. However, the low cohesion strength of these PSAs leads to their inherent low mechanical strength, which seriously hinders their application. In this study, PSA with dual network (DN) structure was prepared. Long chain polyurethane diacrylate (HPA) not only provides covalent cross-linking for linear acrylic polymers, but also provides non-covalent cross-linking of chain entanglements and hydrogen bonds, giving PSA excellent cohesion strength. DN-PSA not only has excellent bonding properties, but also has higher shear strength, its values are 21.9 N/25 mm and 92.5 KPa, respectively, which are increased by 16.5 % and 72.7 % compared with the control group. Although the DN structure reduces the elongation at break of PSA, it greatly increases the tensile strength of PSA, reaching 0.19 MPa. In addition, the PSA also has better heat resistance and higher light transmittance (> 90 %), which indicates that it is suitable for applications requiring high adhesion, cohesion and optical clarity, such as the bonding of flat panel displays.
Ruifen Yang,Ruilin Shang,Jiayan Hu,Zongrui Tong,Lisha Yu,Zhengwei Mao
Marine protein adhesives present robust wet adhesion by mediating interfacial interactions through surface-exposed hydrophobic domains/adhesive groups and maintaining cohesive networks via intrinsically disordered protein structures. Replicating these capabilities in common protein systems remains challenging, especially in stabilizing hydrophobic residues at interface and improving cohesive properties. Here, we developed unfolded protein-based adhesives via a universal strategy of locking with polyelectrolytes that have flexible long chains and high charge density. These polyelectrolytes simultaneously stabilize exposed hydrophobic residues on the unfolded proteins and reinforce cohesion properties via chain entanglement with electrostatic/hydrogen bonding interactions. The unfolded bovine serum albumin (UBSA) and polyacrylic acid (PAA) are integrated to prepare a representative tissue adhesive (UBSA-PAA), exemplifying the polyelectrolyte-locking strategy. The UBSA-PAA adhesive demonstrated interfacial hydrophobicity (water contact angles >90°) and excellent adhesion performance on wet tissue. In severe liver and femoral artery hemorrhage models, this adhesive significantly reduced blood loss compared to commercial fibrin glue, while maintaining comparable biocompatibility. This polyelectrolyte-locking molecular engineering strategy provides a universal framework for designing protein-based adhesives with excellent wet adhesion performance.
Wet adhesion is critical in cases of wound closure, but it is usually deterred by the hydration layer on tissues. Inspired by dopamine-mediated underwater adhesion in mussel foot proteins, wet tissue adhesives containing catechol with 2–3 carbons side chains are reported mostly. To make wet adhesion of this type of adhesives much tougher, catechol derivatives with a long aliphatic side chain (≈10 atoms length) are synthesized. Then, a series of strong wet tissue adhesive hydrogels are prepared through photoinduced copolymerization of acrylic acid with synthetic monomers. The adhesive hydrogel has a high cohesion strength, that is, tensile strength and strain, and toughness of ≈1800 kPa, ≈540%, and ≈4100 kJ m −3 , respectively. Its interfacial toughness on wet and underwater porcine skin is respectively ≈1300 and ≈1100 J m −2 , and its adhesion strength to wet porcine skin is ≈153 kPa. These values are much higher than those of dopamine-based adhesives in the same conditions, demonstrating that the long aliphatic side chain on catechol can greatly improve the wet tissue-adhesion. Additionally, the tough interfacial adhesion can be broken on demand with 5 wt.% aqueous urea solution. This adhesive hydrogel is highly promising in safe wound closure.
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