Enhanced gold adhesion on sodium alginate films for green electronics: study of the role of oxygenated functional groups

Sodium alginate (SA) is a natural widespread polysaccharide whose constitutional repeating unit is made of alternating mannuronic and guluronic moieties. Transparent, freestanding and flexible films can be obtained from aqueous solutions of SA, making this green polymer very appealing for several uses [1]. When green electronic components are concerned, a thin gold conducting layer with outstanding adhesion can be deposited on SA flexible substrates by sputtering techniques [2]. In fact, as evidenced by a scotch tape test, the adhesion of the metal layer on SA is much stronger than that observed when the thermal evaporation technique is used for Au deposition. To gain insights on the origin of this strong interaction and to understand if it is more of a chemical or physical nature, here we synthesize a series of hydrophobically modified SAs bearing amide or ester groups in place of the carboxyl and/or the hydroxyl groups of the backbone, which are supposed to form complexes with gold. After thoroughly characterization of the polymers, by IR, 1H and 13C NMR spectroscopies, thermogravimetric and elemental analysis, we obtained modified SAs films which were covered whit a thin gold layer by sputtering techniques. [1] X. Guo et al. Int. J. Biol. Macromol. 162 (2020) 618–628. [2] P. Maccagnani et al. Adv. Sustainable Syst. 1900001 (2019).