Building Tunable Degradation into High-Performance Poly(acrylate) Pressure-Sensitive Adhesives

Area of Science:

• Polymer Chemistry
• Materials Science
• Sustainable Chemistry

Background:

• Poly(acrylate) pressure-sensitive adhesives (PSAs) are widely used but pose recycling and sustainability challenges due to their non-degradable nature.
• Developing environmentally friendly alternatives is crucial for reducing plastic waste and promoting a circular economy in the adhesives industry.

Purpose of the Study:

• To introduce a novel strategy for creating degradable poly(acrylate) PSAs.
• To utilize alpha-lipoic acid and its derivatives as functional, drop-in replacements for conventional acrylate comonomers.
• To demonstrate the recyclability and tunable degradation of the synthesized polymers.

Main Methods:

• Copolymerization of alpha-lipoic acid or ethyl lipoate with n-butyl acrylate using free-radical conditions.
• Characterization of copolymer properties, including molecular weight, thermal behavior, and viscoelasticity.
• Demonstration of reductive degradation using tris(2-carboxyethyl)phosphine and subsequent oxidative repolymerization.

Main Results:

• High-molecular-weight copolymers (M_n > 100 kg mol^-1) with tunable concentrations of degradable disulfide bonds were successfully synthesized.
• The resulting polymers exhibited thermal and viscoelastic properties comparable to non-degradable poly(acrylates).
• Significant molecular weight reduction was achieved upon exposure to reducing agents, with subsequent recyclability demonstrated through oxidative repolymerization.

Conclusions:

• The incorporation of 1,2-dithiolanes enables the creation of degradable and recyclable poly(acrylate) PSAs.
• This approach offers a sustainable pathway for the adhesives industry by transforming persistent polymers into reusable materials.
• The use of alpha-lipoic acid provides a biocompatible and commercially available building block for green polymer chemistry.