MODIFY · Multi-scale modelling of interfacial phenomena in acrylic adhesives undergoing deformation

In soft nanostructured materials containing polymers (such as acrylic adhesives), interfaces pose specific challenges since they are usually diffuse and can transfer stress through chain entanglements. The equilibrium structure of soft polymer interfaces is well-known, but their mechanical strength remains poorly understood. Yet many new nanostructured materials contain internal interfaces and important applications involve a contact between the soft polymer and a hard substrate. The detailed understanding and modelling of the mechanical response of these interfaces is challenging and currently prevents the use of modelling as a screening tool for new materials in important applications. We will address these problems through a specific example of application where interfaces dominate materials performance: i.e. soft nanostructured adhesives. The objectives of MODIFY is to obtain a fundamental understanding of the complex interfacial structure-related interactions in these materials through sophisticated multi-scale modelling by addressing the following issues: (i) The mechanism(s) of stress transfer at internal interfaces between soft latex particles; this needs to be done at different scales from the molecular entanglement to the finite element level. (ii) The mechanism of stress transfer at hard/soft interfaces between the substrate and the soft adhesive. (iii) The effect of the presence of multiple internal interfaces on the macroscopic rheological properties of the material, and (iv) The respective role played by the polymer rheology and the interfaces in controlling the complex deformation field experienced by the soft adhesive during debonding. If successful, we expect that the economic impact of MODIFY will lie in the design by the industrial partners with knowledge-based methods of advanced adhesives tailored to match specific known and new substrates, and with enhanced recyclability.