Degradable polymer films: RAFT-mediated emulsion copolymerization of lipoic acid with vinyl monomers

Abstract

The growing drive for sustainable materials has pushed the development of degradable polymers. This work explores the incorporation of α-lipoic acid (LA), a commercially available monomer capable of radical ring-opening polymerization (rROP), into polymer backbones using macroRAFT-mediated emulsion polymerization. A series of poly(butyl acrylate) (PBA) seed latexes with increasing LA content (up to 40 mol%) were synthesized and subsequently chain extended with tert-butyl acrylate (tBA) with up to 40 mol% LA and styrene (St) with up to 10 mol% LA to form diblock copolymers. Degradation studies revealed that thermolysis in DMF to cleave the C–S and S–S bonds was significantly more effective than using tris(2-carboxyethyl)phosphine (TCEP) to selectively target the S–S bonds. Substantial molecular weight reduction was observed from low LA mol% incorporation (<10 mol% LA), with minimal additional reduction with increasing mol% LA. Mechanical testing of PBA-b-PSt films demonstrated that at 5 mol% LA incorporation, minimal impact on mechanical properties was observed, while still enabling effective degradation. These findings highlight the potential of LA-based emulsion polymerization systems for producing scalable, degradable polymeric materials suitable for industrial applications such as coatings and adhesives.