Bond Tension in Tethered Macromolecules.

The paper presents scaling analysis of mechanical tension generated in densely branched macromolecules tethered to a solid substrate with a short linker. Steric repulsion between branches results in -fold amplification of tension in the linker, where is the number of chain-like arms. At large ~ 100-1000, the generated tension may exceed the strength of covalent bonds and sever the linker. Two types of molecular architectures were considered: polymer stars and polymer "bottlebrushes" tethered to a solid substrate. Depending on the grafting density, one distinguishes the so-called mushroom, loose grafting, and dense grafting regimes. In isolated (mushroom) and loosely tethered bottlebrushes, the linker tension is by a factor of [Formula: see text] smaller than the tension in a tethered star with the same number of arms . In densely tethered stars, the effect of interchain distance () and number of arms () on the magnitude of linker tension is given by ≅ () for stars in a solvent environment and ≅ () for dry stars, where is the Kuhn length and ≅ is intrinsic bond tension. These relations are also valid for tethered bottlebrushes with long side chains. However, unlike molecular stars, bottlebrushes demonstrate variation of tension along the backbone ≅ / as a function of distance from the free end of the backbone. In dense brushes [Formula: see text] with ≅ 1000, the backbone tension increases from ≅ = 1 pN at the free end of the backbone ( ≅ ) to its maximum ≅ ≅ 1 at the linker to the substrate ( ≅ ).