ISSN:
0887-6266
Keywords:
macromolecular complexes
;
poly(ethylene oxide)
;
rare earth metal compounds
;
x-ray analysis
;
thermal analysis
;
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
The solubility, complexation, and morphology in the Nd(NO3)3-PEO and Nd(Dpm)3-PEO systems were investigated using the FTIR, DSC, TGA, WAXD, and SAXS techniques. In both systems, dissolution was verified by the absence of features characteristic of the bulk-phase dopants detectable with WAXD and DSC, and complexation was evident from the FTIR spectral shifts involving the stretching motions of the EO unit. The extent of the Nd3+-EO interaction was found to be much stronger with Nd(NO3)3 than Nd(Dpm)3. As a consequence, a Tg elevation from 222K in pure PEO to 335K at an EO/Nd3+ ratio (defined as n) of between 4.0 and 5.6 was observed in the Nd(NO3)3-PEO system. Moreover, completely dry and amorphous complexes were obtained at n ≥ 5.6, while residual moisture accompanying complexes at n ≤ 4 was found to persist upon prolonged vacuum drying. Being intrinsically hygroscopic at all doping levels, the Nd(NO3)3-PEO system was found to absorb moisture from the atmosphere resulting in wet amorphous complexes, although precipitation of Nd(NO3)3)·6H2O was observed at n ≤ 4. It was proposed that moisture present in the Nd(NO3)3-PEO system be classified into two categories. One is tightly bound to Nd3+ to satisfy its coordination requirement, which was determined to be 11. The other is loosely bound, which is capable of being removed by heating and returning upon exposure to the atmosphere. It is the latter that can be readily quantified by the TGA technique and that lowers Tg via plasticization. In addition to the observed minor FTIR spectral shifts, a relatively weak Nd3+-EO interaction in the Nd(Dpm)3-PEO system resulted in a lack of the Tg elevation for PEO, persistence of the crystalline portion of PEO at all doping levels, and the formation of new crystalline phases as revealed by the WAXD patterns and the DSC thermograms. The short-range order in PEO does not appear to be perturbed, but the SAXS data suggest that the long range-order is disrupted by the presence of Nd(Dpm)3 at an extremely low doping level (i.e., n ≥ 60). © 1994 John Wiley & Sons, Inc.
Additional Material:
10 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/polb.1994.090320316
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