Phase separation, thermally induced

Human osteoblast-like MG63 cells were cultured on the macroporous chitosan scaffolds reinforced with hydroxyapatite or calcium phosphate invert glass were fabricated using a thermally induced phase separation technique. 

In order to further understand the nature of this thermally-induced phase separation of NiO(lll) films, we have carried out a detailed XPS and AES investigation of this surface. Both the XPS 0(ls) and the AES O(KLL) features show a significant decrease in intensity (about a factor of 3) upon heating the NiO(l 11) film to 800 K, with the onset of the decrease starting at about 525 K. Considering the limited escape depth of the O Is electrons and the AES O(KLL) electrons (-10 A) [26], the attenuation in the XPS and AES intensities could be attributed to the formation of NiO(lOO) islands which are sufficiently thick that the escape probability of the XPS and AES electrons is reduced [25]. 

The model PBZT/ABPBI molecular composite system is limited since the rod and the matrix do not possess glass transition temperatures for subsequent post form consolidation. In an effort to improve the processability for molecular composites, thermoplastics were used as the host matrix. Processing from acidic solvents requires the thermoplastic host to be soluble and stable in meth-anesulfonic add. Thermoplastic matrices were investigated including both amorphous and semicrystalline nylons [71,72], polyphenylquinoxaline (PPQ) [73] and polyetheretherketone (PEEK) [74], Table 5 shows the mechanical properties obtained for various processed PBZT thermoplastic molecular composite systems. As an example, the PBZT/Nylon systems showed 50-300% improvement over uniaxially aligned chopped fiber composite of comparable compositions. However, the thermally-induced phase separation during consol-... 

Microcellular foams can be produced by thermally induced phase separation (TIPS) [47, 74, 76], The induced spinodal decomposition can be optimized to generate, e.g., polylactide scaffolds with the porous morphology and physicomechanical characteristics of a foam. Interesting materials can be constructed in a simple process. These materials exhibited bundles of channels with a diameter of 400 pm. The internal walls of the tubular macropores have a porous substructure with pore diameters of " 10 pm. It appears to be remarkable that the channels have a preferential... 

Fig. 17a-c. Phase morphologies resulting from thermally induced phase separation of PPTA/PA-6 blends, a 25/75, b 40/60 c 60/40... 

Several main synthesis methods widely applied to produce carbon nanotube-polyurethane nanocomposites were summarized above. In addition, latex technology (27), thermally induced phase separation (28), electrospinning (29,30) and many other methods also show their own advantages and promises, however, these methods will not be discussed here. 

Asymmetric membranes are usually produced by phase inversion techniques. In these techniques, an initially homogeneous polymer solution becomes thermodynamically unstable due to different external effects and the phase separates into polymer-lean and polymer-rich phases. The polymer-rich phase forms the matrix of the membrane, while the polymer-lean phase, rich in solvents and nonsolvents, fills the pores. Four main techniques exist to induce phase inversion and thus to prepare asymmetric porous membranes [85] (a) thermally induced phase separation (TIPS), (b) immersion precipitation (wet casting), (c) vapor-induced phase separation (VIPS), and (d) dry (air) casting. 

Thermally Induced Phase Separation In the TIPS process, an initially homogeneous solution consisting of a polymer and solvent(s) phase separates due to a decrease in the solvent quality when the temperature of the casting solution is decreased. After demixing is induced, the solvent is removed by extraction, evaporation, or freeze drying. 

The only single phase, miscible IPNs reported are homopolymer IPNs, in which both networks are composed of the same polymer, and IPNs based on poly (2,6-dime thy Iphenylene oxide) (PPO) and polystyrene (PS) (18). The corresponding blend of the latter system is miscible and does not undergo thermally induced phase separation below its degradation temperature (19). 

Matsuyama H, Berghmans S, and Loyd DR. Formation of hydrophilic microporous membranes via thermally induced phase separation. J. Membr. Sci. 1998 142 213-224. 

DeMeuse and Jaffe. In another chapter, Brostow et al. discuss the phase behavior of binary and ternary mixtures containing an LCP component. The kinetics of thermally induced phase separation of an HBA/PET LCP blended with poly(ether imide) are described by Zheng and Kyu. 

We have demonstrated miscible blends of PET-PHB/PEI can be formed by rapid solvent casting from the mixed solvent of phenol and tetrachloroethane. The miscibility was confirmed by the systematic movement of Tg in the DSC studies. However, the blend is unstable and undergoes thermally induced phase separation with a miscibility window reminiscent of LCST. The dynamics of spinodal decomposition is non-linear in character and obeys the power law with kinetic exponents of -1/3 and 1 in accordance with the cluster dynamics of Binder and Stauffer as well as of Furukawa. In the temporal scaling analysis, the structure function exhibits universality with time, suggesting temporal self-similarity of the system. 

Thermally-Induced Phase Separation (TIPS). Thermally-induced phase separation (Tl PS) results from cooling a liquid crystal/ thermoplastic melt. The liquid crystal and thermoplastic are chosen to... 

Thermally induced phase separation [33, 37] High porosities ( 95%) Highly interconnected pore structures Anisotropic and tubular pores possible Control of structure and pore size by varying preparation conditions Long time to sublime solvent (48 h) Shrinkage issues Small scale production Use of organic solvents... 

As mentioned, the classical description of a polymer/solvent system uses a ternary diagram with a nonsolvent as the third component. This representation is valid at a constant temperature. In the case of thermally Induced phase separation, this description is... 

Since the deGennes-Pincus analysis was developed for blends in which the two components are the same molecular weight, we made a scaling modification of their theory to account for the fact that our experimental blends have different PS and PVME molecular weights. Thermally induced phase separation was followed in the same manner as previously [9] for 10% and 50% PS blends of both molecular weights. It is significant to note that excimer fluorescence is a more sensitive measure of phase separation at short times because films annealed for about one minute showed no visual signs of opalescence while R increased between 10 and 50% for the different blends. 

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