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Thursday, 27 March 2014

Novel Biomimetic Catechol-Based Coatings for Selected Technological Applications

Nanosfun research group develops robust hydrophobic and oleophobic coatings for textiles waterproofing applications based on a novel approach to the biomimetic polymerization of mussel-inspired catechol derivatives.

Molecules containing catechol (o-dihydroxybenzene) moieties are at the heart of a myriad of key processes and chemicals found throughout nature. Protective coatings and powerful wet adhesives containing this deceptively simple chemical moiety bear witness to its remarkable versatility, and have been a hot source of inspiration for the development of many recently reported biomimetic materials.1 For instance, drawing on P.B. Messersmith’s work on the properties of polydopamine as a universal primer coating, many groups have taken advantage of the residual reactivity of this material to prepare functional coatings by post-deposition derivatization with appropriate side chains or tagging molecules.

The ICN2 Nanostructured Functional Materials group (Nanosfun) has developed an alternative strategy, published recently in two Advanced Materials articles with authors from ICN2, including Dr. Daniel Ruiz, Dr. Javier Saiz (the work is part of his Ph.D. Thesis), Dr. Josep Sedó or Dr. Beatriz Garcia, and co-autohors from the UAB, including Dr. Felix Busque, Dr. Jordi Hernando and Prof. Ramon Alibés. Chosen catechol monomers bearing specific functions or tags are prepared first, such as hydrophobic moieties in the form of long alkyl side chains, or oleophobic perfluorinated side chains, and subsequently polymerized by a general and simple treatment in methanol-ammonia mixtures in the presence of air.

Conceptually speaking, this approach turns upside down the widely-applied biomimetic strategy for the (bio)synthesis of melanin-like materials from catecholamines by focusing on providing a functionality of choice to a catechol moiety, which is later cross-linked with an exogenous source of nucleophilic nitrogen (in this case, ammonia), regardless of the structure of the parent monomer.2

In addition to maximising the relevant functionality of the coating, materials prepared in this fashion were found to be soluble in selected common organic solvents, as opposed to polydopamine and other melanin-like materials. This opened up the possibility of coating substrates in a controlled and optimal way by ex-situ procedures.

As a proof-of-concept of the feasibility of the approach in real-world substrates, polyester and cotton weaves were coated with hydrophobic and oleophobic catechol polymers from dilute solutions, and their performance assessed by contact angle measurements and resistance to wetting tests. The efficacy of the water repellency was evinced by the maintenance of superhydrophobic contact angles of water on these coated textiles, with no wetting apparent even after prolonged exposure (see image).

ICN2 researchers' work with these materials has resulted recently in the publication of two scientific papers in Advanced Materials and a European patent application.3

Publications:

1 Sedo, J; Saiz-Poseu, J; Busque, F; Ruiz-Molina, D. Biomimetics: Catechol-Based Biomimetic Functional Materials. Advanced Materials. 2013,25(5), 653-701 (Issue Back Cover) http://www.ncbi.nlm.nih.gov/pubmed/23180685

2 Saiz-Poseu J, Sedó J, Garcia B, Benaiges C, Parella T, Alibés R, Hernando J, Busqué F, Ruiz-Molina D. Versatile Nanostructured Materials via Direct Reaction of Functionalized Catechols. Advanced Materials. 2013, 25(14), 2066-2070 http://www.ncbi.nlm.nih.gov/pubmed/23418006

Patent:

3 A Process For Preparing A Material Having Hydrophobic And/Or Oleophobic Properties And Material Thus Obtained, Pat. Appl. WO2013064886