Decomposition of adhesive thin polydopamine films by alkaline solutions: influence on nano-topography and zeta potential

Thin films of auto-oxidized dopamine, the so-called polydopamine (PDA), have been introduced as universal bio-inspired “green” adhesion promoter for a variety of applications. This study investigates the effect of different alkaline solutions on PDA films on polyethylene fibers over a time ranging from 1 h to 67 days. On one hand, this supports the application of adhesive PDA films in alkaline media such as cementitious matrices. On the other hand, a controlled chemical decomposition or degradation can be used to reverse adhesion and separate the components of PDA-mediated composite materials for re-use and recycling. The effect of the surface modification and the alkaline treatments was studied using atomic force microscopy, electrokinetic measurements, and spectroscopic techniques. Depending on the composition of the alkaline solution, a progressive dissolution or depolymerization of PDA aggregates was observed. Zeta potential measurements detected, however, acidic groups on the fiber surface even after alkaline treatment for 67 days, indicating that the PDA film was not fully removed. • Alkaline treatment of polydopamine films on polyethylene fibers. • Study of time-dependent degradation over 67 days. • Detachment of polydopamine aggregates in KOH solution. • Depolymerization and dissolution in 3-ionic solution. • Reversal of acid-base properties of residual film.