Building tunable degradation into high-performance poly(acrylate) pressure-sensitive adhesives

Pressure-sensitive adhesives (PSAs) based on poly(acrylate) chemistry are common in a wide variety of applications, but the absence of backbone degradability causes issues with recycling and sustainability. Here, we report a strategy to create degradable poly(acrylate) PSAs using simple, scalable, and functional 1,2-dithiolanes as drop-in replacements for traditional acrylate comonomers. Our key building block is α-lipoic acid, a natural, biocompatible, and commercially available antioxidant found in various consumer supplements. α-Lipoic acid and its derivative ethyl lipoate efficiently copolymerize with n-butyl acrylate under conventional free-radical conditions leading to high–molecular-weight copolymers (Mn > 100 kg mol–1) containing a tunable concentration of degradable disulfide bonds along the backbone. The thermal and viscoelastic properties of these materials are practically indistinguishable from non-degradable poly(acrylate) analogues, but a significant reduction in molecu..., 1H nuclear magnetic resonance spectroscopy: Solution state 1H nuclear magnetic resonance (NMR) spectra were recorded on a Bruker Avance III HD 400 MHz or Bruker Avance NEO 500 MHz. Chemical shifts (δ) are reported in ppm relative to residual protio solvent in CDCl3 (7.26 ppm).
Size-exclusion chromatography instrumentation: Size-exclusion chromatography (SEC) was performed on a Waters instrument using a differential refractive index detector and two Tosoh columns (TSKgel SuperHZM-N, 3 μm polymer, 150 × 4.6 mm) with THF at 35 °C or chloroform containing 0.25% TEA at 35 °C for the mobile phase. Molar masses and molar mass dispersities (Đ) were determined against narrow PS standards (Agilent).
Mechanical analysis: Frequency sweeps and isochronal temperature sweeps were obtained on a TA Instruments ARES G2 in oscillatory shear mode with an 8 mm parallel-plate geometry and a nitrogen-purged forced–convection oven. For all experiments, oscillatory shear was applied within the linear viscoelast..., All uploaded files are .csv and can be opened in Excel or GoogleSheets (free alternative).