Direct microbalance techniques, polymer

Our approach to this problem involves a detailed mechanistic study of model systems, in order to identify the (electro)chemical parameters and the physicochemical processes of importance. This approach takes advantage of one of the major developments in electrochemical science over the last two decades, namely the simultaneous application of /ton-electrochemical techniques to study interfaces maintained under electrochemical control [3-5]. In general terms, spectroscopic methods have provided insight into the detailed structure at a variety of levels, from atomic to morphological, of surface-bound films. Other in situ methods, such as ellipsometry [6], neutron reflectivity [7] and the electrochemical quartz crystal microbalance (EQCM) [8-10], have provided insight into the overall penetration of mobile species (ions, solvent and other small molecules) into polymer films, along with spatial distributions of these mobile species and of the polymer itself. Of these techniques, the one upon which we rely directly here is the EQCM, whose operation and capability we now briefly review. 

Quartz crystal microbalance (QCM) is a well-established technique for monitoring surface deposition as the natural frequency of quartz decreases when mass is deposited onto the chip. This frequency change can be directly related to film formation and can be monitored in real time. The QCM experiment in Figure 15b depicts this phenomenon and indicates that polymer is rapidly adsorbed onto SAMs with the selectively expected from the DAP-Thy recognition dyad. These data also provide a method for determining the varying contributions of adsorption from nonspecific or specific interactions. Any frequency change in the case of A -methylated SAM 17 is due to nonspecific adsorption and can be subtracted from the response observed with SAM 16 to isolate the contribution of specific adsorption processes. 

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