Diffusion-induced phase

Bulte AMW, Mulder MHV, Smolders CA, and Strathmann H. Diffusion induced phase separation with crystallizable nylons. Mass transfer processes for nylon 4,6. J. Membr. Sci. 1996 121 37 9. 

Bulte AMW, FoUters B, Mulder MHV, and Smolders CA. Membranes of semicrystalUne aliphatic polyamide nylon 4,6 Formation by diffusion-induced phase separation. J. Appl. Polym. Sci. 1993 50(l) 13-26. 

The Loeb-Sourirajan process often is referred to as diffusion induced phase separation (DIPS) to reflect the role of diffusion in forming the asymmetric structure. Liquid-liquid phase separation and the resulting asymmetric structure arise from diffusion of a solvent (acetone) out of the film and diffusion of a nonsolvent (water) into the film. This physical interpretation provided the basis for the development of asymmetric membrane manufacturing processes for other polymer - solvent - non-solvent systems. 

Asymmetric membrane structures have been created from these materials using the diffusion induced phase separation process (DIPS) as well as a thermally induced phase separation process (TIPS) [23] that relies on temperature gradients to produce a gradient in phase separated domain size. Moreover, membranes formed by either process can be further modified by stretching or drawing to alter pore size and porosity. 

Ion 4,6 Formation by diffusion-induced phase separation. Journal of Applied Polymer Science 50 (1993) 13. 

CHE2 Cheng, L.-P., Lin, D.-J., Shih, C.-H., Dwan, A.-H., and Gryte, C.C., PVDF membrane formation by diffusion-induced phase separation, J. Polym. Sci. Part B Polym. Phys., 37, 2079, 1999. 

Non-solvent induced phase separation (NIPS), or diffusion-induced phase separation, involves dissolution of the polymer in a good solvent in order to obtain a homogeneous solution, followed by the addition of a non-solvent miscible with the first solvent. This will cause precipitation of the polymer when the non-solvent concentration becomes significant. 

We introduce a simple model to investigate and calculate a diffusion coefficient as a basic quantity describing transport in Section II, and then we visualize resonances to detect the structure of the Arnold web and overlapped resonances in Section III. With the aid of this representation, to clarify the relevance of Arnold diffusion and diffusion induced by resonance overlap to global transport in the phase space, we compute transition diagrams in the frequency space in Section IV. In Section V, we extend the resonance overlap criterion to multidimensional systems to identify the pathway for fast transport, and in Section VI we revisit the diffusion coefficient to ensure fast transport affecting the global diffusion. A brief summary is given in Section VII. 

Figure 3.4.25 Generation and diffusion of crystal phase boundary in mass-induced phase transition in the single crystal. The cases of smooth guest diffusion (a) and not smooth (b) are shown. This can explain the pressure selective on-off adsorption shown in Fig. 3.4.24.

Since increasing temperature leads to increased fluidity and thus to a faster probe diffusion, pyrene Hpids have been frequently used to study phase transition in membranes [161,162]. Phospholipid phase separation increases the local concentration of dye labeled Hpids and can, therefore, be investigated via the characterization of exdmer formation. The binding of proteins or ions, however, may induce phase separation as well as decreasing lateral lipid diffusion. Since these two effects are opposing in terms of excimer formation, the binding of such proteins or ions cannot be studied by the (Ex/Mo)-ratio. The time-resolved analysis of the monomer fluorescence of the labeled lipid, however, allows for the separation of... 

In the bulk phase-separation approach, an organic solution of a polymer dissolved in a water-miscible solvent is injected into the tissue defect. After injection, the solvent diffuses away from the injection site, resulting in precipitation of the water-insoluble polymer. Selection of an appropriate solvent, which must be non-cytotoxic and not harmful to host tissue, is a key factor for success of the bulk phase-separation system. Two solvents that meet these criteria are N-methyl-2-pyrrolidone (NMP) and dimethyl sulfoxide (DMSO). In recent years, improved strategies for removal of the solvent and release of growth factors have been active areas of investigation. However, the requirement of a solvent to induce phase separation of the polymer limits the scale at which this approach can be applied in vivo. Even for relatively biocompatible solvents such as NMP and DMSO, injection of large volumes is anticipated to adversely affect host tissue, as well as the ability to eliminate the solvent from the body. 

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