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X-ray diffraction and infrared, Raman and nuclear magnetic resonance spectroscopic studies, as well as thermal gravimetric analysis were done to characterize the formation of a new class of layered, microcrystalline polymers from the hydrolysis of n-octadecyltrichlorosilane. The results revealed that the polymeric condensate is composed of periodic layers, each bearing a monomolecular layer of intercalated water, separated by crystalline assemblies of alkyl chains.

Many NMR experiments have been designed to measure homonuclear or heteronuclear distances, and often generate time-domain dipolar signals that need to be analysed to extract the relevant dipolar coupling constants. These constants yield internuclear distances directly, and therefore an accurate and easily understandable extraction of these couplings from potentially noisy data is a major concern. Several dipolar signals will be considered in this work, including those obtained from the REDOR, MELODRAMA, and SEDOR experiments, and a new series form for the C7 and DCP signals. A review and discussion of an existing transformbased method for dipolar signal analysis is presented here, along with two new generalized methods for the extraction of coupling constants. One of the new methods is a fast procedure based on asymptotic signal forms, while the other is a regularization method specifically formulated to account for experimental noise, and shows significant performance gains over other methods when applied to noisy time-domain REDOR signals. In addition to its noisehandling ability, the second method also has wide application to many other types of dipolar signals currently available in NMR experiments, and is the only method of those discussed that can effectively yield a C7/DCP 'transform'. The explanation of the methods given here includes fundamental analogies to the 'dePaking' process that has been used to remove broadening effects from static solid-state NMR spectra of 2H nuclei. [ABSTRACT FROM AUTHOR]

Thetwo-dimensional phase-adjusted spinning sidebands (2D PASS) experiment is a useful technique for simplifying magic-angle spinning (MAS) NMR spectra that contain overlapping or complicated spinning sideband manifolds. The pulse sequence separates spinning sidebands by their order in a two-dimensional experiment. The result is an isotropic/anisotropic correlation experiment, in which a sheared projection of the 2D spectrum effectively yields an isotropic spectrum with no sidebands. The original 2D PASS experiment works best at lower MAS speeds (1-5 kHz). At higher spinning speeds (8-12 kHz) the experiment requires higher RF power levels so that the pulses do not overlap. In the case of nuclei such as (207)Pb, a large chemical shift anisotropy often yields too many spinning sidebands to be handled by a reasonable 2D PASS experiment unless higher spinning speeds are used. Performing the experiment at these speeds requires fewer 2D rows and a correspondingly shorter experimental time. Therefore, we have implemented PASS pulse sequences that occupy multiple MAS rotor cycles, thereby avoiding pulse overlap. These multiple-rotor-cycle 2D PASS sequences are intended for use in high-speed MAS situations such as those required by (207)Pb. A version of the multiple-rotor-cycle 2D PASS sequence that uses composite pulses to suppress spectral artifacts is also presented. These sequences are demonstrated on (207)Pb test samples, including lead zirconate, a perovskite-phase compound that is representative of a large class of interesting materials., (Copyright 2000 Academic Press.)