Controlling Nanowear in a Polymer by Confining Segmental Relaxation

• Published in: Nano letters Vol. 6; no. 2; pp. 296 - 300
• Main Authors: Gotsmann, Bernd, Duerig, Urs T, Sills, Scott, Frommer, Jane, Hawker, Craig J
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01.02.2006
• Subjects: Applied sciences; Condensed matter: structure, mechanical and thermal properties; Electronics; Exact sciences and technology; Hardness; Mechanical and acoustical properties of condensed matter; Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology; Mechanical properties of solids; Metals. Metallurgy; Micro- and nanoelectromechanical devices (mems/nems); Microscopy, Atomic Force - methods; Molecular Structure; Nanotubes - chemistry; Particle Size; Physics; Polycyclic Compounds - chemistry; Polymers - chemistry; Polystyrenes - chemistry; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Sensitivity and Specificity; Surface Properties; Tribology and hardness; Atomic force microscopy; Confinement; Mechanical properties; Nanoelectromechanical device; Copolymer; Hardness; Experimental study; Molecular relaxation; Nanotechnology; Organic compounds; Styrene copolymer
• ISSN: 1530-6984; 1530-6992
• DOI: 10.1021/nl0520563

Molecular relaxation of a copolymer designed for nano-electromechanical systems was chemically confined by varying the spacing between cross-links, δc. A critical cross-link spacing of 1−3 nm marks a transition in the nano-mechanical properties evaluated by atomic force microscopy. The transition reveals an interplay between the cross-link spacing and the length scale for backbone relaxation, ξα, in cooperatively rearranging regions. For δc ≫ ξα, the natural backbone relaxation process is relatively unaffected by the cross-links and a ductile, low hardness behavior results. For δc < ξα, the cross-links directly interfere with backbone relaxation and confine segmental mobility, leading to a brittle, high hardness response.