Rheology of self-assembled monolayers on solid-liquid interface oscillating at MHz frequency

The rheology properties (viscosity and elasticity) of chemisorbed soft matters on a solid-liquid interface oscillating at MHz were investigated using a quartz crystal microbalance (QCM). As a chemisorbed soft matter, we employed the self-assembled monolayers (SAMs) of mercapto oligo(ethylene oxide) methyl ethers, HS(CH2CH2O)nCH3 (n = 5, 11, 12, 19, 27, 35 and 43), where those molecular weights had unity. The systematical analyses on the basis of the Voight model revealed the relationships of η∝Mn0.180 and μ∝Mn0.344, where η and μ are the viscosity and elasticity of the SAM, and Mn is the molecular weight of HS(CH2CH2O)nCH3. As a result, we found that the SAM consisting of the oligomer followed the formula of polymer.