Melanin Upcycling: Creation of Polymeric Materials from Melanin Decomposition Products

Melanin is a widely occurring biopolymer and has been the subject of much research, especially in dermatology. However, from a resource perspective, melanin is still an unutilized biomass because of its complex three-dimensional cross-linked structure, which makes it challenging to handle. Here, we demonstrate melanin upcycling by decomposing melanin and preparing polymeric materials from its products. A detailed study of the chemical decomposition products of artificial melanin, i.e., polydopamine, reveals that the melanin decomposition products are mainly oligomeric pyrrole derivatives containing carboxylic acids. Furthermore, decomposition experiments using natural melanin extracted from cuttlefish ink revealed that the composition of melanin decomposition products is almost identical regardless of the melanin source. We proposed a melanin decomposition mechanism and demonstrated the preparation of biobased polymer films and particles from melanin decomposition products. The use of melanin decomposition products as building blocks for material preparation is expected to lead to the development of new biodegradable polymers from biomass.