Adhesion Engineering in Polymer-Metal Comolded Joints with Biomimetic Polydopamine

Area of Science:

• Materials Science
• Polymer Science
• Surface Chemistry

Background:

• Thermoplastic polymer matrix (TPM)-metal joints are crucial for various applications.
• Interfacial strength significantly impacts the performance of these composite materials.
• Surface modification of metals is a key strategy to enhance TPM-metal adhesion.

Purpose of the Study:

• To investigate a novel surface modification strategy for enhancing interfacial adhesion in TPM-metal comolded joints.
• To evaluate the synergistic effect of a polydopamine (PDA) layer and a poly(methyl methacrylate-co-methacrylic acid) (P(MMA-co-MAA)) copolymer on titanium-PMMA interfaces.
• To optimize the copolymer composition for maximum interfacial strength.

Main Methods:

• Comolding of a model system: poly(methyl methacrylate) (PMMA) and titanium.
• Surface modification of titanium with sequential layers of PDA and P(MMA-co-MAA).
• Quantification of interfacial adhesion using wire pullout experiments.

Main Results:

• Unmodified titanium-PMMA joints exhibited low adhesion (work of adhesion, Ga = 3.8 J m⁻²).
• A combined PDA and P(MMA-co-MAA) coating resulted in a 40-fold increase in adhesion (Ga = 155 J m⁻²).
• Adhesion was maximized at 24% methacrylic acid (MAA) content in the copolymer, with higher MAA hindering bonding.

Conclusions:

• A synergistic effect between PDA and P(MMA-co-MAA) layers significantly enhances TPM-metal interfacial strength.
• The MMA-to-MAA ratio in the copolymer is critical for optimizing adhesion.
• This study provides design principles for robust thermoplastic-metal comolded joints.