Synthesis of Degradable Vinyl Copolymers Based on Lipoic Acid via <i>Ab Initio</i> Emulsion Polymerization
Yasemin Fadil, Dragon Fan, Steven Thompson, Per B. Zetterlund
Abstract
The global problem of plastic pollution is attracting increasing attention; one means of reducing the impact of future plastic waste is the development of degradable polymer materials. The incorporation of degradable comonomers such as α-lipoic acid (LA) into conventional polymers is a promising approach. The present work represents the first time LA has been incorporated into common vinyl polymers such as styrene, acrylates, and methacrylates using aqueous ab initio emulsion polymerization, which is the industrial method of choice for large-scale production of vinyl polymers due to ease of processing (low-viscosity reaction mixture), environmental friendliness due to water being the reaction medium, and straightforward scalability. It is demonstrated that the choice of radical initiator and surfactant is crucial; notably, the arguably most common radical initiator in emulsion polymerization, potassium persulfate (KPS), is incompatible with LA. Stable latexes comprising submicron-sized nanoparticles of high-molecular-weight copolymer were obtained using the initiators VA-044 and VA-057 with the cationic surfactant cetrimonium bromide (CTAB) and anionic sodium dodecyl sulfate (SDS), respectively. The obtained copolymers were degraded successfully to levels close to the theoretical maximum based on the LA content at 100 °C in dimethylformamide under air.