<p dir="ltr">Water molecules present an obstacle between most synthetic adhesives and surfaces, limiting molecular contact between the glue and substrates. Water can also hydrolyze or swell bulk adhesives, weakening cohesive strength. Nature has solved these challenges for millennia. Marine mussels’ ability to adhere well to wet surfaces stems from an uncommon amino acid, 3,4-dihydroxyphenylalanine (Dopa). The amino acid Dopa contains a catechol moiety that contributes to adhesion and cohesion through hydrogen bonding, metal coordination, and oxidative cross-linking. Hence, biomimetic systems often incorporate catechol groups to provide strong adhesion in both dry and wet environments. In addition to Dopa, mussel adhesive proteins are rich in cationic amino acids lysine and arginine. Previous studies have suggested that cations could displace surface-bound ions, enhancing surface adhesion. However, adhesion performance varied between systems, with no agreement on whether cations are advantageous or disadvantageous. A clear picture of how cations influence underwater adhesion has yet to emerge; therefore, this thesis aims to systematically study these effects.</p><p dir="ltr">In Chapter 2, the synthesis of catechol-containing biomimetic polymers with varying amounts of quaternary ammoniums is presented. Quaternary ammoniums, unlike protonated primary amines, contain non-reactive cations and were used to isolate effects from only charges on adhesion. In Chapter 3, differences between reactive primary amines and quaternary ammoniums were investigated. Structure-function studies have shown how cations influence bulk cohesion versus surface adhesion in dry, under deionized water, and under salt water. The roles of cations in adhesion were complex, with both cohesive and surface bonding relevant in different ways, sometimes even working in opposite directions.</p><p dir="ltr">Furthermore, a styrene-based catechol-containing polymer with excellent underwater adhesion performance is ready to enter the market, but several barriers hinder its industrial implementation. In Chapter 4, new synthetic strategies were developed to scale up and reduce the cost of producing p[vinylcatechol-<i>co-</i>styrene], which are essential for commercialization. This was achieved by selecting cheaper starting materials, switching from anionic to suspension polymerization, and optimizing deprotection reaction conditions. This change also improved adhesion in both dry and underwater conditions. This work is presented as part of our effort to advance the design of adhesives that function in challenging environments.</p>
| Identifer | oai:union.ndltd.org:purdue.edu/oai:figshare.com:article/24645483 |
| Date | 28 November 2023 |
| Creators | Jennifer Marie Garcia Rodriguez (17458722) |
| Source Sets | Purdue University |
| Detected Language | English |
| Type | Text, Thesis |
| Rights | CC BY 4.0 |
| Relation | https://figshare.com/articles/thesis/The_Effects_of_Amine_Moieties_on_Adhesion_and_Cohesion_of_Mussel-Inspired_Polymers/24645483 |
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