Origins of viscoelastic dissipation in self-assembled organic monolayers
Although self-assembled monolayers (SAMs) are promising candidates for interfacial lubricants in micro-electromechanical systems, the relationship between the monolayer structure and its viscoelastic properties is not understood. Using Acoustic Wave Damping (AWD), the authors have measured the complex shear modulus of linear alkane thiol monolayers, HS(CH{sub 2}){sub n{minus}1}CH{sub 3} denoted as C{sub n}, on Au(111)-textured substrates. The AWD technique measures the elastic energy storage and dissipative loss within a SAM adsorbed onto the electrodes of a quartz crystal microbalance. For C{sub 12}, C{sub 14} and C{sub 18} SAMs, the storage modulus increases with alkane chain length, but the loss modulus exhibits no systematic correlation. To investigate the origins of energy dissipation, the authors used a new, high-sensitivity oscillator circuit to simultaneously monitor the adsorption kinetics and acoustic damping during monolayer growth from the gas phase. For both C{sub 9} and C{sub 12} thiols, the dissipation in the growing monolayer can be correlated with distinct two-dimensional fluid phases and the nucleation and growth of condensed-phase islands.
- Research Organization:
- Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
- Sponsoring Organization:
- USDOE Office of Energy Research, Washington, DC (United States)
- DOE Contract Number:
- AC04-94AL85000
- OSTI ID:
- 658206
- Report Number(s):
- SAND-97-3129C; CONF-980405-; ON: DE98005538; BR: KC0201020; TRN: AHC2DT06%%90
- Resource Relation:
- Conference: Spring meeting of the Materials Research Society, San Francisco, CA (United States), 13-17 Apr 1998; Other Information: PBD: Apr 1998
- Country of Publication:
- United States
- Language:
- English
Similar Records
Structure-Dependent Viscoelastic Properties of C(9)-Alkanethiol Monolayers
Single-monolayer in situ modulus measurements using a SAW device: Photocrosslinking of a diacetylenic thiol-based monolayer