Hydrophile group numbers

The hydrophilic group numbers of the sodium sulfonate (SOj Na+) is +11.0, of methylene (CH2) groups (and also for the methyl group) -0.475, and of difluoromethylene (CF2) groups (also valid for the trifluoromethyl group)... 

HLB = y (hydrophilic group number) - > (hydrophobic group number) + 7 (4.52)... 

HLB = 7 + (hydrophilic group numbers) - (hydrophobic group numbers)... 

HLB = 7 + number of hydrophilic groups number of lipophilic groups... 

Hydrophilic Group number Hydrophobic Group number... 

An important step in tire progress of colloid science was tire development of monodisperse polymer latex suspensions in tire 1950s. These are prepared by emulsion polymerization, which is nowadays also carried out industrially on a large scale for many different polymers. Perhaps tire best-studied colloidal model system is tliat of polystyrene (PS) latex [9]. This is prepared with a hydrophilic group (such as sulphate) at tire end of each molecule. In water tliis produces well defined spheres witli a number of end groups at tire surface, which (partly) ionize to... 

The presence of a large number of chain-ends in the fully synthesized dendrimer molecules makes them highly soluble and also readily miscible, for example with other dendrimer solutions. The solubility is controlled by the nature of the end-groups, so that dendrimers with hydrophilic groups, such as hydroxyl or carboxylic acid, at the ends of the branches are soluble in polar solvents, whereas dendrimers with hydrophobic end-groups are soluble in non-polar solvents. The density of the end-groups at the surface of the dendrimer molecule means that they have proportionately more influence on the solubility than in linear polymers. Hence a dendritic polyester has been shown to be more soluble in tetrahydrofuran than an equivalent linear polyester. 

To understand micelle formation quantitatively, critical micelle concentrations (cmc) have to be determined for a large number of surf actants ( 5 ). When the cmc values of the surfactants with the same hydrophilic group (a homologous series) are examined, a nearly 3-fold decrease in cmc is observed for nonlonlc and zwitterionlc surfactants (1,2) upon the addition of a methylene group into the hydrocarbon chain, whereas, a 2-fold or only 1.8-fold reduction in cmc can be observed for univalent (1,2) and blvalent( ) ionic surfactants,respectively. 

Figure 2.1 illustrates a number of orientations by which two linear acids may form a dimer. The partial neutralization of the hydrophilic groups leads to increased solubility of the acid in the organic solvent, but is not observed in the aqueous phase. The dimerization can be written as ... 

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