Batch and Semi-Batch Radical Ring-Opening Emulsion Copolymerization of α-Lipoic Acid and Butyl Acrylate

We report a scalable experimental strategy for the emulsion copolymerization of butyl acrylate (BA) with unmodified (±)-α-lipoic acid (LA) with uniform insertion of breakable bonds. LA is a challenging monomer and its polymerization has been traditionally limited to solution or miniemulsion techniques until recently. Recent advancements have demonstrated that LA can successfully be incorporated into BA-based latexes using conventional batch emulsion polymerization. We here establish the necessary process control in emulsion polymerization conditions to achieve an industrially more relevant solids content of 30 wt % compared to typical laboratory studies and a uniform copolymer production. By employing a water-soluble azo initiator and a semibatch process, we successfully minimize composition drift using a starved-feed conditions. In addition to yielding more homogeneous copolymers, the resulting latex is colloidally stable and uniform particle size distributions are obtained. Importantly, the copolymers obtained by the semibatch process undergo oxidative thermal degradation, yielding oligomers of lower molar masses and narrower size distributions than those obtained via the batch process. Our findings establish a new, scalable platform for producing degradable latex systems, offering significant potential for applications in care chemical and adhesive sectors that require compositionally controlled and environmentally responsive polymer particle dispersions.