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The glass transition temperatures of binary mixtures of polyamines and polyalcohols are investigated by differential scanning calorimetry (DSC). For all systems, the composition dependence of the glass transition temperature T g shows clear maxima, in stark contrast to those of polyalcohol-polyalcohol mixtures reported previously. A thermodynamic analysis based on the entropy theory is carried out for (1,2-propanediamine) x -(glycerol) 1-x and (1,2-propanediamine) x (1,3-propanediol) 1-x systems. The composition dependence of T g predicted from the entropy theory of regular solutions (regular solution model, RSM) is not able to reproduce the anomalous behavior, and the excess configurational entropies S c E are negative and larger than 20 J K -1 mol -1 in absolute value at the minima. The origin of the large value of S c E is discussed with respect to the change of hydrogen bond network structure on mixing.

Laser-Raman spectra of synthetic apatites containing from zero to 12.4 wt% carbonate ions and enamel apatite are reported. Special attention is paid to the correlation between the intensities of the carbonate, phosphate, and hydroxyl modes and the carbonate content in the apatites. The data presented here indicate that most of the CO2-3 incorporated in the apatite lattice substitutes for PO3-4 and suggest that a small amount of CO2-3 might be located in the OH- position.