Underwater Bonding with Polymer Mimics of Mussel Adhesive Proteins

When it comes to underwater adhesion, shellfish are the true experts. Mussels, barnacles, and oysters attach to rocks with apparent ease. Yet our man-made glues often fail miserably when trying to stick in wet environments. Results described herein focus on poly[(3,4-dihydroxystyrene)-co-styrene], a polymer mimic of mussel adhesive proteins. Underwater bonding was examined as a function of several parameters including polymer molecular weight and composition. In doing so, several surprising results emerged. Poly[(3,4-dihydroxystyrene)- co-styrene] may be the strongest underwater adhesive found to date. Bonding even exceeded that of the reference biological system, live mussels. Adhesion was also found to be stronger under salt water versus deionized water. Such unexpected findings may contradict earlier proposals in which charged amino acids were thought to be key for mussel adhesive function. Taken together, these discoveries are helping us to both understand biological adhesion as well as develop new materials with properties not accessed previously. Reducing the mussel adhesive proteins to the simplest level revealed exciting results for underwater adhesion. Building off of this success, additional components of the mussel adhesive system where selected to be incorporated into the polymer mimic. Charged groups have been incorporated into poly[(3,4-dihydroxystyrene)- co-styrene] before, however, the route was six steps that involved multiple protection/deprotection steps. This synthetic burden has been reduced to three steps with the final step being still being optimized for complete deprotection. Having achieved significant bonding in underwater environments with poly[(3,4-dihydroxystyrene)- co-styrene] attempts were made to bring this system out of the laboratory and into the real world. Drawing inspiration from existing commercial products in addition to mussels and squids a delivery system was designed and tested which would allow for better commercial applicability. Testing has revealed that formulating poly[(3,4-dihydroxystyrene)-co-styrene] for commercial delivery will require several hurdles to be overcome and the groundwork has been well established for further study