Polymer-Mediated Adhesion: Nanoscale Surface Morphology and Failure Mechanisms

Alberto Baggioli,Mosè Casalegno,Marta Pasquini,Alessio David,Guido Raos

doi:10.1021/acs.macromol.0c02343

Alberto Baggioli, Mosè Casalegno + Show 3 more

Open Access

https://doi.org/10.1021/acs.macromol.0c02343

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Journal: Macromolecules	Publication Date: Dec 29, 2020
Citations: 4	License type: CC BY 4.0

Affiliation: Politecnico di Milano

Abstract

We present coarse-grained molecular dynamics simulations of polymer-mediated adhesion between chemically heterogeneous surfaces. Our surface models exhibit weakly and strongly absorbing sites in 1:1 proportion but are characterized by different degrees of segregation among these sites. When the surfaces are pulled apart, we observe systematic variations in the stress–strain curves, indicating a significant weakening of the adhesive layer on moving from finely interdispersed to more segregated morphologies. In our model systems, the macroscopic failure of the sandwiched polymer films always appears to be cohesive but, at the nanoscale, there is, in fact, a gradual transition from a cohesive to a mixed cohesive–adhesive mechanism.

Highlights

Adhesion phenomena involving polymers and other soft materials are relevant for many technologies, and they provide a wealth of fascinating observations and challenging problems.[1]
Stresses are relatively low in this case, but the practical work of adhesion the integral of the stress− strain curve is still much larger than any estimate based on intermolecular forces and equilibrium thermodynamics
Our molecular dynamics (MD) simulations on a simple model system provide a clear demonstration of the effect of surface morphology on the adhesive properties of polymer films

Summary

■ INTRODUCTION

Adhesion phenomena involving polymers and other soft materials are relevant for many technologies, and they provide a wealth of fascinating observations and challenging problems.[1]. When the adhesive is a rubbery polymer, as is the case in pressure-sensitive adhesives (PSAs), large deformations and viscoelasticity become relevant.[12,13] The combination of surface chemistry and roughness, polymer microstructure and morphology, film thickness, temperature, and deformation speed produces a wide range of scenarios.[14] In a typical “tack test”, two surfaces (adherends) are first brought together and equilibrated, with a polymer adhesive in between They are separated at a constant speed and the stress is measured until complete detachment.

■ RESULTS

■ CONCLUSIONS

■ REFERENCES