STOICHIOMETRY AND MORPHOLOGY IN TERBIUM NITRATE POLY(ETHYLENE OXIDE) MACROMOLECULAR COMPLEX

The Tb (NO3)3-PEO system was characterized to have a solubility limit equivalent to n congruent-to 6.5 and a coordination number of 12.4 +/- 0.1, compared to 5.0 and 10.9 +/- 0.1 for the Nd(NO3)3-PEO system. Th e greater coordination involving Tb3+ appears to be responsible for th e lower asymptotic glass transition temperature at high doping levels of the Th (NO3)3-PEO complex. In both systems, anhydrous amorphous com plexes were obtained below the respective solubility limits, over whic h apparent solubilities were found to be enhanced by the presence of t ightly bound moisture while retaining the amorphous character of the c omplexes. Whereas partial precipitation was observed in the Tb (NO3)3- PEO system upon exposure to ambient moisture, both complexation and am orphous character were found to persist in the Nd(NO3)3-PEO system in the presence of absorbed moisture. (C) 1994 John Wiley & Sons, Inc.