(542c) Design of Tropoelastin-Mimetic Polyesters That Stick like Mussels

Creating materials that transcend the confined layer of water and efficiently adhere to substrates underwater remains an enduring challenge. Historically, the contact between moisture and water was prevented at least until the curing of the adhesive. However, the recent advancements in tissue engineering and robotics demand adhesives that can stick in the presence of water for their implementation in unprecedented environments. Interestingly, in nature, aquatic organisms such as mussels and sandcastle worms possess adhesive strategies to sustain their life cycle underwater. Emerging reports show that these bioadhesives are a protein-based cocktail of post-translationally modified polymers that undergo liquid-liquid phase separation (LLPS). It is thought that the LLPS helps the effortless delivery of insoluble adhesives underwater and the post-translational modifications provide strong interfacial and cohesive interactions.

Inspired by the modular adhesive strategy found in bioadhesion, in this study, we created polymers that undergo lower critical solution temperature (LCST)-driven LLPS in water. Above LCST, these polymers form polymer-rich and polymer-poor phases known as dense and dilute phases, respectively. The dense phase formed from LLPS has a density higher than water, viscosity lower than dry polymer, and low underwater interfacial tension. We then introduced mussel-inspired functional groups in the phase separating polymers to provide strong interfacial and cohesive interactions to create functional underwater adhesives. These bioinspired adhesive formulations showed stronger adhesion than mussel adhesives underwater. Compared to most synthetic LLPS systems which rely on the complexation of oppositely charged polymers, our model polymers are “charge-free”. Therefore, our system is less toxic and more stable towards changes in pH and ionic strength and demonstrates the potential for tissue adhesive applications where changes in water content, pH, and salt are expected.