Porous PVA-PVAc composites

Figure 4 Permeability of porous PVA-PVAc composite film to organic solvents, (a) n-Hexane at 0.5 kg/cm (b) cyclohexane at 0.5 kg/cm (c) benzene at 0.5 kg/cm (d) benzene at 60 kg/cm. ...

Figure 5 Model preparation of porous PVA-PVAc composite film. PVA molecule grafted to PVAc PVA V A PVAc molecule grafted to PVA ID PVAc.

Therefore, the porous film obtained by using the polymerization of VAc in the presence of PVA as a protective colloid is certainly the porous PVA-PVAc composite film. 

If paraffin permeates a white opaque paper, one can read letters through the paper because the paper becomes transparent. This phenomenon is based on the simple principle that micropores in the paper are filled with paraffin, which has a refractive index that is close to that of cellulose. If the porous PVA-PVAc composite film is soaked in organic solvents having the same refractive indices as that of PVA, the porous film is expected to become transparent again, according to the same principle as the phenomenon between paraffin and cellulose. On the basis of this consideration, subsequent experi-... 

The color of the porous PVA-PVAc composite films in organic solvents did not change with the observing... 

There has been a conventional sense that the PVAc latexes prepared in the presence of PVA as a protective colloid contain the graft copolymer of PVA and PVAc, so that PVAc particles in the dried latex film are not extracted at a high ratio with solvents. In this Chapter, it has been defined without an influence by the usual sense that the porous PVA-PVAc composite can be prepared from the PVAc latex film with acetone extraction. The porous film consists of the spherical cells of PVA... 

This principle is applied not only to the PVA-PVAc composites but to other polymer composites. The composite structure does not always need to be porous but may be powders and gels designed for the wettability by solvents and the extension of the surface area in soluble polymers. From this point-of-view, the present work sheds a new light on the research on composite materials related to graft polymers and copolymers. 

Porous membranes with selective permeabiUty to organic solvents have been prepared by the extraction of latex films prepared with moderate ratios of PVA—PVAc graft copolymer fractions. The extracted films are made up of a composite of spherical cells of PVA, PVAc microgel, and PVA—PVAc graft copolymers (113). 

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