Development of lignin microcapsules for the controlled delivery of actives

Abstract

Lignin is the most abundant aromatic biopolymer on Earth. Every year, about 70x10(^6) tons of lignin are produced, but its utilization for the production of high added-value materials is not so easy and direct. This is due to the highly complex structure of this material, which also differs depending on the botanical origin. Moreover, the harsh conditions of the industrial extraction processes (from which the so-called “technical lignins” are obtained) contribute to significantly modify its structure making it very dissimilar to the native one. Nonetheless, in the last years several attempts towards lignin valorisation have been made, and uses of this renewable biopolymer in place of less eco-friendly and synthetic materials have increased. In particular, the direct generation of nanostructures from technical lignins is highly attractive because it allows for the exploitation of their peculiar characteristics without the need for time-consuming and costly pre-treatments. In this context, the present Thesis work aims at developing lignin microcapsules for the controlled delivery of lipophilic actives, using ultrasonication as a green and scalable method of synthesis. Time-dependent release of the active and capsule stability at different pH conditions were evaluated, taking into account different lignin/active ratios and the effect of ad hoc prepared additives. Morphological and structural characterisations were carried out as well to extrapolate structure-property relationships.