Using a bioderived CO2-responsive polymer as an easily removed pressure sensitive adhesive

Pressure sensitive adhesives (PSAs) are used extensively in industry for adhering labels onto substrates. These labels are expected to adhere to the desired substrate during use but be easily removed after serving their purpose. However, strong PSAs can be difficult to remove and can cause significant frustration to consumers and the recycling industry. These conflicting properties of excellent adhesion during use but easy removal at the end-of-life require the material to switch its properties. We have developed a bioderived CO2-responsive adhesive synthesized from a castor oil derivative. The inclusion of CO2-responsive groups allows the bioderived polymer to be readily dissolved into carbonated water. Removal of CO2 and water produces a PSA which displays excellent adhesion comparable to that of commercial cellophane tapes. This new PSA adheres to many common packaging materials such as plastics, metals, and wood. The PSA displays excellent water resistance even after 5 days submerged in neutral water, with no observable loss in adhesive performance. However, exposure to carbonated water causes the PSA to separate easily from the substrate. This bioderived CO2-responsive PSA potentially offers practical advantages in many applications including facilitating the removal of labels from used containers before recycling.