Bioinspired Nanocomposites

Optimizing the interfacial adhesion between a reinforcing particle and the polymer matrix is critical for proper stress transfer in response to loading. In collaboration with P. Messersmith, we are working towards strengthening the interface in inorganic-organic composites by mimicking the adhesive properties of marine mussels. Mussels have the amazing ability to stick to almost anything even in an aqueous environment (Figure 1). We have synthesized a biomimetic initiator inspired by L-3,4-dihydroxyphenylalanine (DOPA), a key constituent in the adhesive proteins secreted by marine mussels, for use in surface-initiated polymerization (SIP) from metal substrates. We employed this initiator (Figure 2) to graft poly methyl methacrylate (PMMA) polymer coatings from NiTi and Ti-6Al-4V wires by atom transfer radical polymerization (AtrP). We are investigating the interfacial adhesive properties between the SIP-modified alloy wires and bulk polymer system by performing pullout experiments on the wires embedded in PMMA matrix. The polymer chains directly grafted to the surface of the inorganic reinforcement are expected to entangle with the bulk polymer chains leading to a strong interfacial interaction. We have demonstrated a dramatic improvement in adhesion between the reinforcing NiTi wire and polymer matrix when using the DOPA mimetic initiator for AtrP from the metal surface. The treated wires demonstrated an average improvement in interfacial shear strength of 115% when compared to the unmodified system (Figures 3 and 4). Thus, our method is promising for application in both macro- and nanoscale composites. We also speculate that the catechol-anchoring group will provide a strong and water resistant bond between reinforcement and matrix as demonstrated in nature, leading to improved durability of the composite in aqueous environments. The improved adhesion we have demonstrated may be well suited for use in biomedical composites where typical reinforcement modification may break down because of the aqueous environment.

Mussel’s Byssal
Ti6Al4V

We have demonstrated a dramatic improvement in adhesion between the reinforcing NiTi wire and polymer matrix when using the DOPA mimetic initiator for AtrP from the metal surface. The treated wires demonstrated an average improvement in interfacial shear strength of 215% when compared to the unmodified system (Figures 3 and 4). Thus, our method is promising for application in both macro- and nanoscale composites. We also speculate that the catechol-anchoring group will provide a strong and water resistant bond between reinforcement and matrix as demonstrated in nature, leading to improved durability of the composite in aqueous environments. The improved adhesion we have demonstrated may be well suited for use in biomedical composites where typical reinforcement modification may break down because of the aqueous environment.

Pullout curves for NiTi
SEM image

Researcher on this project:

Lesley Meade

Collaborators:

Phil Messersmith

Publications:

L. Hamming, R. Qiao, P. B. Messersmith, and L. C. Brinson, “Effects of a bio-inspired interfacial modification on the properties of polymer matrix nanocomposites”, Composites Science and Technology, 2009, 69, 1880-1886.

L. Hamming, X. Fan, P. B. Messersmith, and L. C. Brinson, “Mimicking mussel adhesion to improve interfacial properties in composites”, Composites Science and Technology, 2008, 68 (9), 2042.



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