Estudo fisico-quimico de polietileno glicol com agua e sorventes aromaticos

AUTOR(ES)
DATA DE PUBLICAÇÃO

1993

RESUMO

This work presents results on some physico-chemical properties of low molecular weight polyethylene glycol (PEG) studied by spectophotometric, volumetric and calorimetric methods. These properties can be expressed as function of the number of meros. The dye acridine orange (AO), dissolved in PEG, was used as molecular probe to investigate the hydration process in this polymer. lt was shown that this phenomenum depends on the dye s acid-base equilibrium, i. e., on the water content and on the number of meros which has a monohydrate structure. The excess volume (V) values for PEG with water and benzene are negatives although the volume contraction is larger for the first one. The excess enthalpy (H) diagrams obtained from the literature were compared to the V one. For the water system the diagrams profiles are similar and the values of H are also negatives but positive for the benzene solutions. This indicates different interactions between the mixtures components. For the first time it was observed that low molecular weight PEG shows liquid-liquid phase diagrams with compounds like n-alkyl benzene that can be described by enthalpy and entropy mixture. The imiscibility increases with the number of aliphatic carbon atoms number of the aromatic solvent and with the number of terminal hydroxyl groups in the polymer. The distinct behavior of PEG with water and organic solvents was invetigated by freezing-point depressionof the systems as the molar fraction of one component is increased. For the same solvent the cryoscopic constants, normalized for the mero s number, are independent of the polymer molecular weight.

ASSUNTO(S)

polimeros termoplasticos

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