Poly-oxyethylene lauryl ether

The best steric stabilizers are amphipathic block or graft copolymers such as poly(oxyethylene lauryl ether) (Mr 1200). Commercial nonionic surfactants are classified according to the hydrophilic-lipophilic balance (HLB), which scales the relative solubilities of the two components in aqueous and nonaqueous media. The need for the anchor part of the stabilizing molecule can be eliminated if the stabilizing moieties can be covalently bonded to the latex particles. 

The inverse micellar solution consisted of 8% water and 92% Laureth 4 (or Brij 30), poly(4)-oxyethylene lauryl ether. No oil phase was required for this synthesis. The mixtures were aged for 24h. The silver particles were stable in air, so special atmospheric precautions were unnecessary. The average hydrodynamic radii of the particles were 25, 17 and 23 nm for procedures (i), (ii) and (iii) respectively. 

Micelles and cyclodextrins are the most common reagents used for this technique. Micellar electrokinetic capillary chromatography (MECC or MEKC) is generally used for the separation of small molecules [6], Sodium dodecyl sulfate at concentrations from 20 to 150 mM in conjunction with 20 mM borate buffer (pH 9.3) or phosphate buffer (pH 7.0) represent the most common operating conditions. The mechanism of separation is related to reversed-phase liquid chromatography, at least for neutral solutes. Organic solvents such as 5-20% methanol or acetonitrile are useful to modify selectivity when there is too much retention in the system. Alternative surfactants such as bile salts (sodium cholate), cationic surfactants (cetyltrimethy-lammonium bromide), nonionic surfactants (poly-oxyethylene-23-lauryl ether), and alkyl glucosides can be used as well. 

Figure 9.1.6. Result for a Py-GC/MS analysis of poly(oxyethylene)(23) lauryl ether (Brif 35). Pyrolysis done on 0.4 mg material at 60(f C in He, with the separation on a Carbowax type column.

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