The IR and 1H-MAS NMR spectroscopy of zeolite H-b in interaction with is described. Two families of strong CD 3 CN Si(OH)Al sites have been clearly distinguished : a Ðrst BrÊnsted family, characterized by an NMR signal at 4.4 ppm and an IR peak at 3614 cm-1 (isolated bridged hydroxys) and a second family, characterized by a broad band in the 3-7 ppm NMR range and in the 3600-3200 cm-1 IR range, due to bridged hydroxys which are perturbed by H-bond interactions with the zeolitic framework. This last family of hydroxys form weaker adducts with acetonitrile.

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Amorphous (1) and semicrystalline (2) samples of poly(ethylene naphthalene‐2,6‐dicarboxylate) (PEN) have been investigated by cross‐polarization/magic angle spinning (CP/MAS) 13C NMR at 26°C (1 and 2), 100°C (1) and 120°C (2) in order to study the phase structure and the local motion of polymer chain segments at temperatures below and close to Tg (120°C). The lineshape of the ethylene unit 13C signal in sample 2 is consistent with the presence of two components which were assigned to trans and gauche conformations. The first component arises mainly from the crystalline regions and the second one from the amorphous part. Cross‐polarization curves were traced by changing the contact time between carbon and proton reservoirs. TCH (cross relaxation time) and proton T1p (spin‐lattice relaxation time in the rotating frame) values were obtained as best fit parameters by fitting calculated curves to the experimental data. All 13C NMR data are consistent with the presence of highly rigid ethylene units in both semicrystalline and amorphous samples within the temperature range (T) investigated. This result is in disagreement with the 1H NMR wide line spectra which showed a noticeable narrowing of the linewidth with increasing temperature in the same range, hence indicating a great mobility of the chain segments. To account for this discrepancy a qualitative model based on the existence of two distinct dynamic regions, one where motion is highly restricted and the other one where large reorientations of ethylene group torsional angles take place, is suggested. The NMR results led to the conclusion that three structural phases are present in PEN: crystalline, very rigid amorphous, and very mobile amorphous. © 1995 John Wiley & Sons, Inc.

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Solid‐State 1H‐NMR measurements of T1 relaxation times performed on polycarbonate‐poly(ethyleneterephthalate) (PC–PET) blends point out the presence of two separate domains with apparent dimensions of about 80 nm. The variation of PET domain relaxation time with the increase of PC content is explained in terms of an interface in which parts of the PC molecules are finely dispersed into the PET matrix. Relaxation parameters and compositions match very well an equation that quantitatively describes a three‐phase model formed by two domains separated by an interface of mixed components. Micrographs obtained by transmission electron microscopy (TEM) clearly reveal the presence of two separate domains with a phase inversion at 40/60 wt% composition. PET domains, although larger than expected from NMR analysis, are characterized by a dispersion of small PC particles that are considered responsible for the observed diffusion of magnetization from PET to PC domains. The partial miscibility seems to be physical in nature rather than due to transesterification processes between the components, as stem from 1H‐NMR spectra in solution of PET and PC–PET blends. T1 relaxation times measured in the same way on totally immiscible PC–PA‐6 blends, support, by contrast, the NMR interpretation of PC–PET results. The mechanical properties of PC–PET blends exhibit ductile behavior throughout the entire range of composition. This indicates that PC and PET are mechanically compatible. This is also in agreement with the isothermal crystallization data for PET at various compositions of PC–PET. These results are in agreement with the existence of a partial miscibility between PET and PC. © 1994 John Wiley & Sons, Inc.