The use of the atomic force microscope (AFM) as a local probe for elastohydrodynamic lubrication is discussed. Compliances are measured with a modified AFM that allows application of ac and dc forcedisplacement curves on end-grafted poly(styrene) chains in good (toluene) and poor (water) solvents. In toluene, the chains form a stretched brush whose elastic modulus is an order of magnitude larger than that of the collapsed layer in water. The dc force-displacement curves are compared to those previously obtained on similar systems with the surface forces apparatus.

The 29Si NMR spectra of FAU framework (X and Y) zeolites exhibit a well-resolved splitting into five major bands Si(nAl), where n is the number of first shell aluminum neighbors about silicon. It is well-established that the intensities Si(nA1) reflect the local order resulting from "Al-A1 avoidance" in the placement of first-shell (Loewenstein's rule) and second-shell ("Dempsey's rule") aluminum neighbors. Study of framework metals ordering in FAU materials has been limited by the information content of the intensities Si(nA1) and by the range of SUA1 compositions available by direct synthesis. Recent synthetic advances have greatly increased the composition range of available materials. In this paper we report 29Si NMR spectra of 15 directly synthesized FAU zeolites ranging in SQA1 ratios from -1.3 to -5.3. Careful study of the 29Si NMR spectra reveals considerable information beyond the intensities Si(nAl), manifested in the complex compositional dependence of the band positions and heterogeneous band shapes. The basic premise of this paper is that the 29Si NMR spectra of FAU zeolites are superpositions of many components arising from the multiple local environments for a silicon atom, these local environments differing in the number and types of first-and second-shell A1 substituents. Compositional dependence arises because the relative populations of these local environments are afunction of composition. This paper discusses the process by which this additional information has been retrieved and its implications concerning the building units involved in FAU crystallization. The major conclusion is that the immediate precursor to the FAU lattice is the hexagonal prism tertiary building unit and that the secondary unit is the single 4-ring.

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The norbornyl cation is a fluxional species capable of rearranging to as many as 7! X 11! degenerate configurations. The process has an associated entropy, depending on how many distinguishable structures [those not involving the interchange of identical atoms or groups] are attainable under experimental conditions and this markedly affects the position of hydride-transfer equilibria observable in solution. The equilibration of norbornane with the Zeri-butyl cation has been observed to be endothermic by 9.6 kcal/mol and be driven toward the formation of the fluxional ion by an entropy change of 34.4 gibbs/mol in the 50-deg span from 193 to 243 K.