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SynopsisThe solubility behavior of poly(vinylidene fluoride) (PVDF) in about 50 liquids was investigated. The results were input to a computer program to obtain a three-dimensional representation of the polymer solubility region in the Hansen space; the values of dispersion, hydrogen bonding, and polar components of the total solubility parameter were evaluated. The latter was also estimated from limiting viscosity number data in the eight solvents found. Both experimental methods gave values in very good agreement. Comparisons among our findings, the literature. and calculated results are discussed.[q] = 2.01 X x M:om5(1)

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Gels of a-zirconium phosphate (a-ZrP) in water have been prepared by exfoliation of crystalline a-ZrP induced by intercalation-deintercalation of propylamine. Although these gels are X-ray amorphous, their Raman spectra indicate that the a-type layers of the starting material remain essentially unaltered. Replacement of gel water with water miscible organic solvents has allowed the formation of a-ZrP gels in a great variety of solvents, such as alkanols, N,N-dimethylformamide (DMF), 1-methyl-2-pyrrolidone (NMP), acetone, tetrahydrofuran (THF) and even chloroform. Particular attention has been devoted to a-ZrP gels in DMF. On the basis of the surface area of the dry gels, the average thickness of the particles of exfoliated a-ZrP has been estimated between 25 and 80 nm for a-ZrP percentages in the starting gels between 2.5 and 10 wt%, respectively, in agreement with SEM images. a-ZrP gels in THF have been used for the preparation of polystyrene/ a-ZrP nanocomposites with filler loadings up to 8 wt%. The presence of exfoliated a-ZrP delays the beginning of thermal decomposition of the polymer by a maximum of 45 uC for 4 wt% filler loading. The state of filler exfoliation has been confirmed by transmission electron microscopy.

Porous membranes and dense films were prepared from polysulfone solutions in N-methyl-2-pyrrolidone (NMP) containing different types and amounts of clay. Commercial clays supplied by Southern Clay, either unmodified (Cloisite Na) or organically modified (Cloisite 30B and Cloisite 93A), were used. The clay behavior in the organic solvent was dependent on the presence and type of the organic compatibilizer: Cloisite containing Na ions did not swell in NMP, whereas those with the organic compatibilizer swelled, though to a different degree. Electron microscopy observations were made to examine the clay dispersion in the membrane structure. At variance with Cloisite Na and Cloisite 93A formed microaggregates, Cloisite 30B yielded nanostructures composed of both single sheets and well-ordered multilayer silicate clusters, which were characterized by an interlayer distance higher than that of the neat clay. The increase in the distance between the layers of Cloisite 30B was related to the formation of intercalated nanocomposites, whereas the presence of single sheets well distributed in the polymer matrix supported the occurrence of delaminated nanocomposites. The intercalation of the polymer into clay layers was confirmed with wide-angle Xray diffractometry. The addition of Cloisite 30B to the casting solution influenced the phase-separation process in the coagulation bath. Therefore, by the variation of the layered-silicate concentration in the casting solution, membranes with different morphological structures and ultrafiltration properties were obtained. Cloisite 30B was also found to improve the wettability and mechanical properties of dense films.