Engineering of Adhesion at Metal-Poly(lactic acid) Interfaces by Poly(dopamine): The Effect of the Annealing Temperature

Georgios Kafkopoulos; Ezgi Karakurt; Ricardo P Martinho; Joost Duvigneau; G Julius Vancso

doi:10.1021/acsapm.3c00672

Engineering of Adhesion at Metal-Poly(lactic acid) Interfaces by Poly(dopamine): The Effect of the Annealing Temperature

ACS Appl Polym Mater. 2023 Jul 6;5(7):5370-5380. doi: 10.1021/acsapm.3c00672. eCollection 2023 Jul 14.

Authors

Georgios Kafkopoulos¹, Ezgi Karakurt¹, Ricardo P Martinho², Joost Duvigneau¹, G Julius Vancso¹

Affiliations

¹ Department of Materials Science and Technology (MTP) of Polymers and Sustainable Polymer Chemistry (SPC), University of Twente, Enschede 7522 NB, The Netherlands.
² Department of Molecules and Materials, MESA+ Institute for Nanotechnology, Faculty of Science and Technology, University of Twente, Enschede 7500 AE, The Netherlands.

Abstract

Control over adhesion at interfaces from strong bonding to release between thermoplastic polymers (TPs) and metal oxides is highly significant for polymer composites. In this work, we showcase a simple and inexpensive method to tune adhesion between a TP of growing interest, poly(lactic acid) (PLA), and two commercial metal alloys, based on titanium and stainless steel. This is realized by coating titanium and stainless steel wires with polydopamine (PDA), thermally treating them under vacuum at temperatures ranging from 25 to 250 °C, and then comolding them with PLA to form pullout specimens for adhesion tests. Pullout results indicate that PDA coatings treated at low temperatures up to a given threshold significantly improve adhesion between PLA and the metals. Conversely, at higher PDA annealing temperatures beyond the threshold, interfacial bonding gradually declines. The excellent control over interfacial adhesion is attributed to the thermally induced transformation of PDA. In this work, we show using thermogravimetric analysis, X-ray photoelectron spectroscopy, Fourier transform infrared, and ¹³C solid-state NMR that the extent of the thermal transformation is dependent on the annealing temperature. By selecting the annealing temperature, we vary the concentration of primary amine and hydroxyl groups in PDA, which influences adhesion at the metal/PLA interface. We believe that these findings contribute to optimizing and broadening the applications of PDA in composite materials.