Molecular Tensile Machines Single macromolecules as probes for pressure and friction in fluid monolayers Sergei S. Sheiko, UNC Chapel Hill, PRF# 46204-AC7 Our research program develops a molecular-level understanding of polymer spreading through imaging of individual molecules as they flow across a solid substrate. To probe the film pressure with ever greater sensitivity, we have designed brush-like macromolecule with a disulfide linker in the middle of the all-carbon polymethacrylate backbone. The designed macromolecules are able to transmit and focus the film tension onto a single covalent bond. In addition to gauging the film pressure, the designed molecules can be used as a miniature tool for mechanical activation of chemical reactions at specific chemical bonds within flowing macromolecules. The applied force can be finely tuned in a broad range from 10 pN to 10 nN by varying the substrate surface energy. This new tool may be also used in combination with other activation stimuli, such as light, temperature, and electric field. Molecular Tensile Machines S-S Adsorption S S Molecular tensile machines. Brush-like macromolecules with a disulfide linker undergo mid-chain fracture during spreading on a substrate. This type of molecular architectures is regarded as molecular tensile machines, wherein the brush section generates tension and transmits it to the disulfide bond. The new molecular tools allow single-bond studies of mechanical activation of various chemical reactions. Macromolecules 42, 1805 (2009).