Engineering Aliphatic Polyester Triblock Copolymer-Tackifier Blends for Hydrolytically Degradable Pressure Sensitive Adhesives

The design of renewably sourced and readily degradable pressure-sensitive adhesives (PSAs) that exhibit tunable adhesion properties addresses sustainability concerns associated with traditional, fossil fuel-derived incumbents. Here, aliphatic polyester triblock copolymers of poly(l-lactide)-block-poly(γ-methyl-ε-caprolactone)-block-poly(l-lactide) (LML) and associated blends with renewable tackifiers in PSA formulations were explored. We systematically investigated the effects of tackifier, composition, and processing history on the microstructural, thermal, mechanical, and adhesive properties of the PSAs. After solvent casting and thermal annealing, LML-based PSAs showed stable and competitive adhesion properties when compared with commercial PSAs, which we attribute to both microphase separation and crystallinity in the poly(l-lactide) end blocks. For example, PSAs of LML with 33 wt % tackifier showed a peel strength of 2.32 ± 0.10 N cm–1, a loop tack adhesion strength of 1.33 ± 0.22 N cm–1, and no failure in shear resistance experiments for more than 240 h. Importantly, these LML-based PSA formulations are hydrolytically degradable into water-soluble or -dispersible compounds at 45 °C under basic conditions within 30 days, offering the possibility of sustainable end-of-life scenarios, for example, through industrial composting. The combination of properties in LML-based PSAs makes them attractive, sustainable alternatives for current commercial PSAs.