Phase separation anion effect

Tb clarify the effect of addition of a cationic HC surfactant on phase separation behavior in the mixed monolayers of anionic HC and FC surfactants polyion complexed with cationic polymers, the mixed monolayers containing three amphiphilic components complexed with PVA were transferred on various substrate plates and studied by AFM, FFM, SSPM, and SIMS. As a cationic surfactant, ODTMAC was examined. 

Another subtle case, where specific interactions may obscure the effects of Coulombic criticality, is ethylammonium nitrate (EtNH3N03) +l-octanol (Tcs315K) [85], In contrast to all other known examples, the critical point is located in the salt-rich regime at a critical mole fraction of Xc = 0.77. Electrical conductance data indicate strong ion pairing, presumably caused by a hydrogen bond between the cation and anion which stabilizes the pairs in excess to what is expected from the Coulombic interactions [85]. This warns that, beyond the Coulombic/solvophobic dichotomy widely discussed in the literature, additional mechanisms may affect the phase separation [5]. 

A later publication from the same group [153] reporting on 31P- and 2H-NMR and DSC studies on zwitterionic and anionic phospholipids in the absence and presence of doxombicin (adriamycin) described different results [152], Doxorubicin had a stronger disordering effect on the membrane of lipid mixtures enriched with anionic lipids. However, extensive segregation of DOPE and DOPA or DPS was not observed even under conditions of Hlrphase formation . According to the authors, the reason for this discrepancy was that in the earlier paper the phase separation was obtained with membranes subject to gel-liquid crystalline phase transition , which was, however, discounted in the first paper. 

R. LoBrutto and Y. V. Kazakevich, Effect of chaotropic anions on analyte retention, in Proceedings, 22nd International Symposium on High Performance Liquid Phase Separations and Related Techniques, St. Louis, May 2-8,1998. 

Deposition of polyelectrolytes Lajimi et al. [56] explored the surface modification of nanofiltration cellulose acetate (CA) membranes by alternating layer-by-layer deposition of acidic chitosan (CHI) and sodium alginate (AEG) as the cationic and anionic polyelectrolyte, respectively. The supporting CA membranes were obtained by a phase separation process from acetone/formamide. The permeation rate of salted solutions was found to be higher than that of pure water. The rejection of monovalent salt was decreased, while that of divalent salt remained constant so that the retention ratio increased. Increasing the concentration of feed solutions enhanced this selectivity effect. 

A number of so-called double ion-pair methods have been described for the analysis of hydrophobic amines in which the mobile phase contains both a quaternary ammonium ion and an alkyl sulfate or sulfonate. At first glance, this combination of mobile phase additives is counterintuitive because one would expect the effect of the anionic and cationic additives to cancel. However, the combination of cationic masking agents to reduce peak tailing and an anionic ion-pairing agent to enhance retention is sometimes necessary for the reversed-phase separation of hydro-phobic amines. 

The factors that affect phase separation discussed in this section include anion effect, divalent effect, alkaline effect, mixing effect of interstitial flow, and the synergy of mixed surfactants. 

In a later report, the effect of the presence of bulky tetraphenylborate counteranion on the phase behavior was studied by SAXS.81 The copolymer with tetraphenylborate anion exhibited a lamellar phase-separated structure compared to the copolymer with hexafluorophosphate counteranion, which showed spherical aggregates. Upon heating to 80°C, disordered melt was... 

In order to increase the conversion rate, anionic detergents (2.5 wt.% relative to the catalyst solution) were added. A variety of anionic detergents, such as the sodium salts of fatty acids, alkylsulfonic acids, a-olefm sulfonates, fatty alcohol sulfates, fatty alcohol polyglycol ethers, alkylphenol ether sulfates, alkylphosphonic acids, and salicyclic acid, however, do not show any activating effects. Additionally, anionic detergents tend to produce foams and emulsions and in many chases phase separation is made impossible. 

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