Molecular dynamics study of the adhesion between end-grafted polymer films II -effect of grafting density-

Adhesion between two polymer films consisting of end grafted polymer is studied by coarse-grained molecular dynamics. The grafting density of the polymer film is varied from the dilute mushroom region to dense polymer brush region, and the debonding behavior is studied by varying the temperature. It is shown that below the glass transition temperature, the debonding behavior is mainly determined by grafting density. At low grafting density, fibrils are formed and the stress-strain curve has a plateau region. At high grafting density, the fracture becomes brittle like, and the stress drops sharply after the strain exceeds certain critical values. Above the glass transition temperature, cav ities are formed, and the stress becomes a gradually decreasing function of strain.