INTRODUCTION OF NEGATIVELY CHARGED FUNCTIONALITIES INTO DOPA CONTAINING POLYMER MIMICS

Many sticky denizens of the ocean use unique and effective techniques to stick together and adhere to surfaces underwater. Underwater adhesion is a daunting task that many have set out to solve. One of the key factors of underwater adhesion and focus of this dissertation will be on negative charges and their role in underwater adhesion. Following previous work done on poly[(3,4-dihydroxystyrene)-co-styrene], an adhesive mimic to mussel adhesives, new functional groups were introduced to the same backbone to determine the change in adhesion in underwater and dry conditions. These functional groups were mainly comprised of negatively charged moieties such as sulfonates, phosphates, and phosphonates. Phosphates have been shown to exist in mussel proteins alongside positively charged proteins. A main facet of this dissertation will be focused on the specific synthesis pathways of modified charged synthetic mimics of existing polymer systems both styrene and acrylic based. Synthetic pathways were a challenging aspect of designing these polymers as functionalization can add many steps to the synthesis of polymers which makes the process tedious and lengthy. Characterization of these polymers were also important for determining the successful synthesis of these functionalized polymers. Several reactions conducted from this research have not been used on polymeric species and have been shown primarily in small organic molecules. Early work on poly[(3,4-dihydroxystyrene)-co-styrene]-based sulfonates, phosphates, and phosphonates established a foundation in pre and post functionalization of polymer species. Testing of adhesion, exploration of functionalization and synthesis optimization were the main goals for each type of functionalized polymer. Following the tests of many poly[(3,4-dihydroxystyrene)-co-styrene] based functionalized polymers it was shown that acrylic versions of phosphates performed substantially better for both 16 dry and underwater adhesion, especially on SAE 304 stainless steel. The acrylic phosphate polymers were based on previous DMA/MMA polymer systems that have shown to have excellent adhesive potential. The phosphate monomer MAEP was introduced to the polymer structure, which facilitated increased binding to steel substrates. Despite the acrylics overwhelmingly higher adhesion compared to the functionalized poly[(3,4-dihydroxystyrene)-co-styrene] polymers the phosphonate versions were shown to form a coacervate like material with positive charged poly[(3,4-dihydroxystyrene)-co-styrene] mimics. These “coacervates” had appreciable adhesion, much higher than the negative or positive versions had alone in dry conditions but despite this could not retain their metastable coacervate phase in wet conditions. Further study is underway in determining the role of negative charges in varying systems and determining whether adding negative charge to a polymer system truly helps with underwater adhesion alone.