The Interplay of Modulus, Strength, and Ductility in Adhesive Design Using Biomimetic Polymer Chemistry

High‐performance adhesives require mechanical properties tuned to demands of the surroundings. A mismatch in stiffness between substrate and adhesive leads to stress concentrations and fracture when the bonding is subjected to mechanical load. Balancing material strength versus ductility, as well as...

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Bibliographic Details
Published in:Advanced functional materials 2015-08, Vol.25 (31), p.5057-5065
Main Authors: Meredith, Heather J., Wilker, Jonathan J.
Format: Article
Language:English
Subjects:
adhesion
Adhesive bonding
Adhesive strength
Biomimetics
biomimetics, catechols
catechols
Ductility
Glycols
Monomers
poly(ethylene glycol)
polymers
Strength
Terpolymers
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Summary:High‐performance adhesives require mechanical properties tuned to demands of the surroundings. A mismatch in stiffness between substrate and adhesive leads to stress concentrations and fracture when the bonding is subjected to mechanical load. Balancing material strength versus ductility, as well as considering the relationship between adhesive modulus and substrate modulus, creates stronger joints. However, a detailed understanding of how these properties interplay is lacking. Here, a biomimetic terpolymer is altered systematically to identify regions of optimal bonding. Mechanical properties of these terpolymers are tailored by controlling the amount of a methyl methacrylate stiff monomer versus a similar monomer containing flexible poly(ethylene glycol) chains. Dopamine methacrylamide, the cross‐linking monomer, is a catechol moiety analogous to 3,4‐dihydroxyphenylalanine, a key component in the adhesive proteins of marine mussels. Bulk adhesion of this family of terpolymers is tested on metal and plastic substrates. Incorporating higher amounts of poly(ethylene glycol) into the terpolymer introduces flexibility and ductility. By taking a systematic approach to polymer design, the region in which material strength and ductility are balanced in relation to the substrate modulus is found, thereby yielding the most robust joints. A mussel mimicking adhesive terpolymer is synthetically tuned to identify the composition at which the material becomes toughened. The way the strength, ductility, and modulus of an adhesive interact to create the most robust joints between plastic and metal substrates is shown in this systematic study.
ISSN:1616-301X
1616-3028
DOI:10.1002/adfm.201501880