Pressure-sensitive adhesives (PSAs) are used for a variety of applications (e.g. packing tape, labels, and sticky notes), but are traditionally derived from fossil fuel and not readily degradable. Here, we report a new approach to generate degradable PSAs through the copolymerization of α-lipoic acid (αLA), ethyl lipoate (ELp), and n-butyl acrylate (nBA). Both αLA and ELp have 1,2 dithiolane rings that under thermal-induced free radical polymerization, can generate disulfide bonds along the copolymer backbone. The disulfide backbone allows for the copolymer to be selectively deconstructed into oligomers with low molar masses (Mn = 1.6 kg mol–1) that are sufficiently small for biodegradation. By tuning the copolymerization conditions, the concentration of disulfides along the backbone can be reduced to generate an adhesive that degrades into oligomers with higher molar masses (Mn = 12 kg mol–1). The larger oligomers can be repolymerized through oxidation of the thiol chain ends to demonstrate a closed-loop cycle. With similar Me and Tg to nBA, ELp is a promising deconstructable additive for acrylic-based PSAs with the resulting copolymer showing comparable thermomechanical and physical properties to traditional PSA formulations.

Designing sustainable pressure-sensitive adhesives

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