Development of a starch-based mussel-mimetic adhesive polymer

Jeffrey Kazimir de Kozlowski, Purdue University


Mussel-mimetic adhesive polymers have gained lots of attention for their strong adhesive strength, moisture resistance, and unique ability to crosslink. These properties are mainly attributed to the high content of catecholic 3,4-dihydroxyphenylalanine (DOPA) in mussel adhesive proteins. While there has been success in creating mussel-mimetic synthetic polymers, less effort has been given to create a renewable, green, biocompatible counterpart. This thesis explores the possibilities of starch-based mussel-mimetic adhesives. Carboxymethyl starch of various molecular weights and degree of substitution was synthesized and subsequent conjugation of dopamine to these polymers by 1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide was investigated. The polymers suffered from very low substitution (DScatechol < 0.02) and easily precipitated from solution as an insoluble product. The cause of precipitation was investigated and was shown to be unrelated to autooxidation of conjugated dopamine by O2 and pH. Instead, EDC seemed to be somehow responsible for the precipitation and most likely also for the very low DScatechol due to competing reactions and instability of EDC intermediates. Lap-shear strengths of the CMS-dopamine conjugates failed to exceed those of unmodified CMS. In search of another path to starch-catechol conjugates with higher DScatechol, 1,1'-carbonyldiimidazole was employed for direct conjugation of bis-O-protected 3,4-dihydroxybenzoic acid to unmodified starch. High DS was achieved with 3,4-dimethoxybenzoic acid, but demethylation techniques were incompatible with starch and its esters. Phenylboronic acid was then employed as an easily removable diol protecting group for DHBA, but the complex was apparently not stable enough in solution for selective activation of the carboxylic acid group of PBA-DHBA by either CDI or TosCl. Further screening of different protecting groups or a new coupling chemistry is needed to fully assess the possibilities of starch-catechol conjugates of high DScatechol.




Tao, Purdue University.

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