OYSTER CEMENT CHEMISTRY FOR BIOMIMETIC COMMERCIAL APPLICATIONS

Oysters are a keystone species found across the world. Oyster reefs can dissipate storm energy, prevent shoreline erosion, are home to various species, and filter seawater. Oysters ability to be pivotal in the ecosystem shows how robust they are as a species. Oysters produce cement that starts from the larval stage when a pediveliger lays down an organic matrix, which later calcifies to form the cement. By understanding how oyster cement works on a chemical level, biomimetic versions will be able to be synthesized and tested. Previous studies have shown that around 10 percent of oyster cement is organic (peptides, carbohydrates and lipids), with the remainder of the cement represented as calcium carbonate (CaCO3). Though exact protein characterization is unknown, peptides in oyster cement are fitted with an abundance of serine residues, which provide good docking ports for post-transitional modifications (PTM). Phosphorylation is a common PTM, and thoughts of phosphorylated proteins could be responsible for the adhesion of oyster cement. Current commercial cement systems utilize hydrophobic polymers in the form of emulsions to increase the properties of cement, known as polymer-modified cement (PMC). This typically increases flexural strength, torsion, chemical resistance, improved hydrophobicity, and others. Polymers in PMC typically have 3 base polymers in the form of acrylate, styrene, or butadiene, and functional groups of these polymers may be modified for improved material functionality. Therefore, the addition of oyster cement chemistry into current PMC systems should improve the adhesion of CaCO3 based systems. The impacts of this research would reduce cure time for cement, and increase the integrity of cement-based repairs. That is the goal of this thesis, to make a biomimetic oyster cement utilizing the theorized peptide chemistry and current PMC polymer backbones to chelate to Ca2+ ions to form an inorganic-based cementous adhesive. Chapter 1 will act as a literature review of biomimetic adhesives, PMC, and how oysters create their adhesive. Chapter 2 will show the overall design of synthesized polymers and the rationale for the synthetic design, including the synthesis and characterization of monomers and polymers. Chapter 2 continues to dive into the mechanical testing and optimization of the cement including the troubleshooting of testing on limestone and aluminum. 21 Chapter 3 will include preliminary results of the effects primary hydroxyl groups play on adhesion. The addition of stoichiometrically increasing the number of hydroxyls should be able to cleave surface-bound water and surface hydroxyls to expose a metal oxide layer which, in theory, should improve adhesion Chapter 4 includes preliminary results of extracting oyster shell protein to isolate pediveliger signaling protein. Chapter 5 will include preliminary results of plant-based adhesive on poison ivy (Toxicodendron radicans). Though the last 2 chapters have nothing to do with oyster adhesive those are projects given to me to do in the first half of my graduate degree and as a fun project respectively.