Biomass-derived carbon dots for the initiation of conventional radical and ATRP-based photopolymerization processes.

Abstract

In recent years, there has been increasing interest in using carbon nanodots (CDs) as a component photoinitiator to initiate photopolymerization. These systems support conventional radical photopolymerization and light-mediated atom transfer radical polymerization (photo-ATRP), emphasizing single-component (Type I initiators) and multicomponent systems, which involve at least two reaction partners, specifically, the Type II CD initiator. The latter can function in both photoinduced conventional radical polymerization and photo-ATRP. CDs provide an important advantage by reducing toxicological concerns, as they are nontoxic to cells, and minimizing migration issues typically associated with molecular systems. Here we present two novel photopolymerization methods utilizing biomass-derived CDs as light-sensitive components. The first approach uses biobased furfural to create a Type I CD initiator for photoinduced uncontrolled radical polymerization, which initiates polymerization via homolytic bond cleavage of oxime ester groups attached to the CD surface. The second method employs sodium alginate to generate CDs capable of initiating photoinduced radical polymerization or activating alkyl halides in photo-ATRP processes. Key topics covered in these methods include (1) preparation and characterization of biomass-derived CDs; (2) experimental procedures for CD-assisted photo-induced conventional radical polymerization and photo-ATRP and (3) analysis of the resulting polymers. Preparing and characterizing the CDs takes ~4 d, while photochemical reactions can be conducted within 1 h, depending on requirements. Product separation and analysis take an additional 0.5 h. This protocol is designed for users with experience in polymer chemistry and CD handling.