N Phase Separator

Nakanishi, K. and Soga, N., Phase-separation in gelling silica organic polymer-solution—Systems containing poly(sodium styrenesulfonate), Journal of the American Ceramic Society 74(10), 2518-2530, 1991. 

Here we have extended the Poole model in order to describe multiple phase separations in cuprates. The free energy of a complex system in which n phase separations are observed, is obtained by adding the term Ay, to the Van der Waals free energy ArDW yielding a total free energy... 

Nakanishi, K. Soga, N. Phase separation in silica sol-gel system containing polyacryUc acid. I. Gel formation behavior and effect of solvent composition. J. Non. Cryst. Sol. 1992,139, 1-13. 

From this calculated phase diagram we observe that at low TMV concentrations a relative polymer concentration (j)p = 0.125 is required to cause I-N phase separation which corresponds in this case to a mass concentration of Cp = 3(f)pM/4TiNARg = 6.4 mg/ml The agreement with experiment should be considered with care since in the theoretical calculation the electrostatic interactions have not been taken into account. 

More extensive measurements on the I-N transition in TMV suspensions with added PEO (M = lOOkDa, Rg = 10 nm) were carried out by Adams and Fraden [26]. They observed at TMV concentrations of 20 mg/ml, at which the pure rod system is in the isotropic phase, the first signs of I-N phase separation at 5 mg/ml added PEO and a more definite transition for 10 mg/ml added PEO. To compare this experimental observation with theory we present in Fig. 6.13 also the theoretical phase diagram for L/D = 17 (TMV virus as before) but now with q = 2Rg/D = 2 -10/18 =1.1, which are the relevant parameters for this mixed TMV-PEO suspension. From this calculated phase diagram we observe that at low TMV concentration a relative polymer concentration phase separation which corresponds in this case to a mass concentration of Cp = 3(j)pM/4nNAR g = 10 mg/ml. This is again in reasonable agreement with theory. As mentioned before the electrostatic interactions that certainly play a role have not been taken into account, and therefore the comparison with experiment should be considered with care. 

MOR Morimoto, S. and Ohtani, N., Phase separation enthalpies of polymer solids in ternary polymer-solvent-nonsolvent systems (Jap.), Kenkyu Hokoku Seni Kobunshi Zairyo Kenkyushu, 119, 35, 1979. 

Miyake N., Wainright J.S., SavineU R.F. Evaluation of a sol-gel derived Nafion/silica hybrid membrane for proton electrolyte membrane fuel cell applications— 1. Proton conductivity and water content. J. Electrochem. Soc. 2001 148(8) A898-A904 Nakanishi K., Komura H., Takahashi R., Soga N. Phase separation in silica sol-gel system containing poly(ethylene oxide). 1. Phase relation and gel morphology. Bull. Chem. Soc. Jpn. 1994 67(5) 1327-1335... 

Figure A2.5.27. The effective coexistence curve exponent P jj = d In v/d In i for a simple mixture N= 1) as a fimction of the temperature parameter i = t / (1 - t) calculated from crossover theory and compared with the corresponding curve from mean-field theory (i.e. from figure A2.5.15). Reproduced from [30], Povodyrev A A, Anisimov M A and Sengers J V 1999 Crossover Flory model for phase separation in polymer solutions Physica A 264 358, figure 3, by pennission of Elsevier Science.

Another important characteristic of the late stages of phase separation kinetics, for asynnnetric mixtures, is the cluster size distribution fimction of the minority phase clusters n(R,z)dR is the number of clusters of minority phase per unit volume with radii between R and + cW. Its zeroth moment gives the mean number of clusters at time r and the first moment is proportional to die mean cluster size. 

In electron spin echo relaxation studies, the two-pulse echo amplitude, as a fiinction of tire pulse separation time T, gives a measure of the phase memory relaxation time from which can be extracted if Jj-effects are taken into consideration. Problems may arise from spectral diflfrision due to incomplete excitation of the EPR spectrum. In this case some of the transverse magnetization may leak into adjacent parts of the spectrum that have not been excited by the MW pulses. Spectral diflfrision effects can be suppressed by using the Carr-Purcell-Meiboom-Gill pulse sequence, which is also well known in NMR. The experiment involves using a sequence of n-pulses separated by 2r and can be denoted as [7i/2-(x-7i-T-echo) J. A series of echoes separated by lx is generated and the decay in their amplitudes is characterized by Ty. ... 

Straniok S J, Parikh A N, Tao Y-T, Allara D L and Weiss P S 1994 Phase separation of mixed-oomposition self-assembled monolayers into nanometer soale moleoular domains J. Phys. Chem. 98 7636... 

If the poorer solvent is added incrementally to a system which is poly-disperse with respect to molecular weight, the phase separation affects molecules of larger n, while shorter chains are more uniformly distributed. These ideas constitute the basis for one method of polymer fractionation. We shall develop this topic in more detail in the next section. 

Acryhc stmctural adhesives have been modified by elastomers in order to obtain a phase-separated, toughened system. A significant contribution in this technology has been made in which acryhc adhesives were modified by the addition of chlorosulfonated polyethylene to obtain a phase-separated stmctural adhesive (11). Such adhesives also contain methyl methacrylate, glacial methacrylic acid, and cross-linkers such as ethylene glycol dimethacrylate [97-90-5]. The polymerization initiation system, which includes cumene hydroperoxide, N,1S7-dimethyl- -toluidine, and saccharin, can be apphed to the adherend surface as a primer, or it can be formulated as the second part of a two-part adhesive. Modification of cyanoacrylates using elastomers has also been attempted copolymers of acrylonitrile, butadiene, and styrene ethylene copolymers with methylacrylate or copolymers of methacrylates with butadiene and styrene have been used. However, because of the extreme reactivity of the monomer, modification of cyanoacrylate adhesives is very difficult and material purity is essential in order to be able to modify the cyanoacrylate without causing premature reaction. 

Diethylene glycol monoethyl ether [111-90-0] M 134.2, b 201.9", d 0.999, n 1.4273, n 1.4254. Ethylene glycol can be removed by extracting 250g in 750mL of benzene with 5mL portions of water, allowing for phase separation, until successive aqueous portions show the same volume increase. Dried, and freed from peroxides, as described for diethylene glycol mono-n-butyl ether. 

The reflux accumulator is a separator used to separate the acid gases from the condensed water. The water is accumulated and pumped back (n the top of the stripper as reflux. With the vapor and liquid rates know n. the accumulator can be sized using the procedures in Volume 1 for iwo phase separator.s. 

Another example of phase transitions in two-dimensional systems with purely repulsive interaction is a system of hard discs (of diameter d) with particles of type A and particles of type B in volume V and interaction potential U U ri2) = oo for < 4,51 and zero otherwise, is the distance of two particles, j l, A, B] are their species and = d B = d, AB = d A- A/2). The total number of particles N = N A- Nb and the total volume V is fixed and thus the average density p = p d = Nd /V. Due to the additional repulsion between A and B type particles one can expect a phase separation into an -rich and a 5-rich fluid phase for large values of A > Ac. In a Gibbs ensemble Monte Carlo (GEMC) [192] simulation a system is simulated in two boxes with periodic boundary conditions, particles can be exchanged between the boxes and the volume of both boxes can... 

The phase separation process at late times t is usually governed by a law of the type R t) oc f, where R t) is the characteristic domain size at time t, and n an exponent which depends on the universality class of the model and on the conservation laws in the dynamics. At the presence of amphiphiles, however, the situation is somewhat complicated by the fact that the amphiphiles aggregate at the interfaces and reduce the interfacial tension during the coarsening process, i.e., the interfacial tension depends on the time. This leads to a pronounced slowing down at late times. In order to quantify this effect, Laradji et al. [217,222] have proposed the scaling ansatz... 

The pH is adjusted to 5.5 and the water phase separated and extracted with additional ether in order to remove the surplus dimethyl anilin. After addition of an excess of ammonia to the solution, the reaction product, N-methylpipecolic acid 2,6-dimethyl anilide, is recovered by extraction with isoamyl alcohol. The isoamyl alcohol solution is evaporated to dryness, the product dissolved in dilute hydrochloric acid, treated with charcoal and reprecipitated with NaOH. N-methylpipecolic acid 2,6-dimethyl anilide is obtained in crystalline form. 

The validity of mean field theory for N —y oo has striking consequences for the initial stages of phase separation. " In a metastable state slightly inside the coexistence curve, the nucleation free energy barrier is due to spherical droplets with a radius R The free energy excess of a droplet is written in terms of bulk and surface terms " "... 

A more accurate analysis of this problem incorporating renormalization results, is possible [86], but the essential result is the same, namely that stretched, tethered chains interact less strongly with one another than the same chains in bulk. The appropriate comparison is with a bulk-like system of chains in a brush confined by an impenetrable wall a distance RF (the Flory radius of gyration) from the tethering surface. These confined chains, which are incapable of stretching, assume configurations similar to those of free chains. However, the volume fraction here is q> = N(a/d)2 RF N2/5(a/d)5/3, as opposed to cp = N(a/d)2 L (a/d)4/3 in the unconfined, tethered layer. Consequently, the chain-chain interaction parameter becomes x ab N3/2(a/d)5/2 %ab- Thus, tethered chains tend to mix, or at least resist phase separation, more readily than their bulk counterparts because chain stretching lowers the effective concentration within the layer. The effective interaction parameters can be used in further analysis of phase separation processes... 

Synthesis and mechanical and morphological characterization of (AB)n, ABA and BAB type copolymers of m-phenylene-isophthalamide and polydimethylsiloxane have been reported241 242>. The effect of copolymer type, chemical composition and segment molecular weights on phase separation and the solution behavior of these systems have also been discussed. 

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