Water methanol hydrogen-bond affinity

This IPN membrane would be best-suited for the dehydration of THF, as it is much less fragUe than a pure PVP membrane, although when PVA/PVP IPN membranes were used to separate a THF/methanol mixture the membranes appeared to he less selective. Moreover, the selectivity was decreased when the PVP content was increased. The sharp decrease in membrane selectivity at a PVP content of about 20 wt% was attributed to the fact that PVP shows not only a lower affinity towards methanol compared to water, but that it also exhibits hydrogen-bond interactions with PVA and blocks PVA crystallization. As a result, the THF molecules can penetrate more easily into the membrane, which in turn leads to a lower membrane selectivity. 

To understand how the BF3 affinity depends on self-association, the hydrogen-bonded solvents formamide, methanol and water were also studied as bulk liquids. The results [46] are -AH°(3.10) = 115.32 0.90,109.20 0.44 and 104.40 0.36 kJ mol , respectively. There are two obvious terms in these enthalpies (i) the enthalpy of complexation of BF3 and (ii) the enthalpy due to other interactions and to the reorganization of the liquid structure. It would be necessary to correct for the latter terms to isolate the BF3 affinity of these self-associated compounds. 

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