Polymers from immiscible

Fig. 5. WAXD spectra for (A) BB-loaded PSA, and (B) PNA-loaded PSA. (A) BB loading is (a) 0, (b) 15, (c) 30, and (d) 45. Note that as loading increases, the spectrum shows no change for the PSA crystallinity, but crystals of BB appear, indicating that the solute and polymer are immiscible. (B) PNA loading is (a) 0, (b) 5, (c) 10, and (d) 15. Note that there are no peaks corresponding to PNA as the loading increases, however, the polymer crystallinity decreases with increased loading, indicating polymer/solute compatibility. From Shen et al. (2001a). Reprinted with permission.

Creton, C, Kramer, E. /., Brown, H. R. and Hui, C.-Y Adhesion and Fracture of Interfaces Between Immiscible Polymers From the Molecular to the Continuum Scale. Vol. 156, pp.53-135. 

An excellent review of composite RO and nanofiltration (NF) membranes is available (8). These thin-film, composite membranes consist of a thin polymer barrier layer formed on one or more porous support layers, which is almost always a different polymer from the surface layer. The surface layer determines the flux and separation characteristics of the membrane. The porous backing serves only as a support for the barrier layer and so has almost no effect on membrane transport properties. The barrier layer is extremely thin, thus allowing high water fluxes. The most important thin-film composite membranes are made by interfacial polymerization, a process in which a highly porous membrane, usually polysulfone, is coated with an aqueous solution of a polymer or monomer and then reacts with a cross-linking agent in a water-immiscible solvent. 

The blends of polysulfone with the a-methyl styrene polymers are immiscible, as evidenced by the double glass-transition temperatures in Table II. To improve the miscibility characteristics, polysulfone was modified in two ways. First, 25% of the bisphenol A was replaced by monomer I which contains a pendant ester group and, when no improvement resulted, the whole 50% of the bisphenol A was replaced. Again, the blends remain immiscible as evidenced from Figures 4 and 5 and from Table II. Further, the presence of the pendant ester group in polymer C does not improve the miscibility picture even though one would expect a favorable contribution from the carbonyl group on account of the miscibility of polycarbonate with the a-methyl styrene polymers. 

Adhesion and Fracture of Interfaces Between Immiscible Polymers from the Molecular to the Continuum Scale... 

From the point of view of the mechanical reinforcement it is important to understand how the mechanical strength of the interface varies when the parameter changes (if the two polymers are immiscible) and, more generally, how the fracture toughness of the interface depends on the interfacial width a of the interface [as defined in Eq. (3)]. 

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