Spinodal phase separation structure

Fig. 4.7 Confocal scanning microscope image of (top) a spinodal phase separation structure Ti02 thin film, and (bottom) the cross-sectional height profile of the above picture across the solid line. Reproduced with permission from Ref. [100].

Mori R, Takahashi M, Yoko T (2005) Photoelectrochemical and photocatalytic properties of multilayered Ti02 thin films with a spinodal phase separation structure prepared by a sol-gel process. J Mater Res 20 121-127... 

An example of an application to polysiloxane elastomers is the characterization of binodal and spinodal phase-separated structures occurring in model PDMS networks.310-312... 

Viers, B. D. Mark, J. E., Atomic Force Microscopy Investigations of Binodal and Spinodal Phase Separated Structures in Model PDMS Elastomers. Polym. Preprints 1998, 39(1), 520-521. 

The bilayer morphology of thin asymmetric films of may be unstable. A regularly corrugated surface structure of the films was ascribed to spinodal transition into a laterally phase separated structure, where the surface morphology depended on the polymer incompatibility and the interfacial interactions [347, 348]. Recently, the phase separation and dewetting of thin films of a weakly incompatible blend of deuterated PS and poly(p-methylstyrene) have been monitored by SFM [349, 350]. Starting from a bilayer structure, after 454 h at T= 154 °C the film came to the final dewetting state where mesoscopic drops of... 

A more sophisticated DIA was proposed for the studies of sphemlite formation and phase separation in polymer blends [Tanaka, 1986 Tanaka and Nishi, 1987]. With a different computer vision, shape features of phase-separated structure was obtained [Gur et al., 1989]. The digitalization gives the possibility of two-dimensional Fourier transformation. A power spectrum of the two-dimensional Fourier transformation was given for the structure developed by spinodal decomposition [Tanaka et al., 1986]. In the real space, one cannot see the order in the image clearly, whereas the characteristic wavelength and the distribution can be seen in the reciprocal space representation. 

Various terms are u in the literature for the development of a network structure ageing, annealing and maturation. In many cases network formation is clearly time dependent. In other cases network formation seems to be instantaneous and a time dependence cannot be observed. In physical networks this may be the result of a sudden temperature decrease, resulting in a spinodal phase separation. During network formation the increase in the storage modulus may be of the order of 10 or more. It is clear that a horizontal plateau... 

In all the above examples the mechanical property enhancement is a consequence of spinodal decomposition of an initially homogeneous mixture to form a co-continuous phase separated structure. 

Phase-Separated Networks. There are two basic morphologies of phase separation which could, at least in principle, produce a network structure. Firstly, a phase separation may occur which results in a localized polymer-rich region, possibly by a nucleation and growth process. This could act as a junction zone. The growth of this rich phase may be limited by geometric constraints, such as entanglements or the copolymeric nature of the molecule. Secondly, the polymer-rich phase may not be localized but form a continuous network. This is more likely to be the case when the nucleation density is high or when spinodal phase separation occurs. 

The dynamics and pattern formation during phase separation processes have been a subject of many experimental and theoretical studies over the past decades as a fascinating example of nonlinear, nonequilibrium phenomena [1,2]. If a binary mixture is rapidly quenched from the single-phase region to the spinodal region of the phase diagram by changing thermodynamic variables, such as temperature and pressure, the mixture becomes thermodynamically unstable and separates, via spinodal decomposition (SD), into two phases. If the volume fraction of one of the phases is close to 0.5 ( isometric case ), the phase-separated structure is implied to be periodic and bicontinuous with the aid of theories [50], experiments [51, 52], and computer simulations [53-56]. 

The mechanism of formation of morphology structures in iPP-E-plastomers blends via shear-dependent mixing and demixing was investigated by optical microscopy and electron microscopy. A single-phase stmcture is formed under high shear condition in injection machine after injection, namely under zero-shear environments, spinodal decomposition proceeds and leads to the formation of a bicontinuous phase stmcture. The velocity of spinodal decomposition and the phase separation depend on the molecular stmcture of iPP and E-plastomer components. 

Wood Hill (1991b) induced phase-separation in the clear glasses by heating them at temperatures above their transition temperatures. They found evidence for amorphous phase-separation (APS) prior to the formation of crystallites. Below the first exotherm, APS appeared to take place by spinodal decomposition so that the glass had an intercoimected structure (Cahn, 1961). At higher temperatures the microstructure consisted of distinct droplets in a matrix phase. 

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