Focusing bond tension in bottle-brush macromolecules during spreading

Abstract

The backbone of molecular bottle-brushes undergoes spontaneous degradation upon spreading on a solid substrate. The self-generated tension in the brush backbone is ascribed to steric repulsion between the densely grafted side chains. The paper discusses two approaches for controlling the bond-scission process on the molecular and macroscopic scales, respectively. On the molecular scale, the tension linearly increases with the distance from the backbone ends and attains its maximum value in the middle section of the backbone. When the backbone becomes shorter than the side chains, the tension is focused precisely on the central bond resulting in the predominant mid-chain fracture of the brush backbone. On the macroscopic scale, addition of a linear polymer to a melt of molecular bottle-brushes alters the film pressure and thus allows controllable positioning of the fracture zone within a spreading film.