Hydrophilic-lipophilic balances polymeric surfactants

In inverse polymerization, water-soluble monomers are emulsified with low HLB (hydrophilic-lipophilic balance) surfactants in an organic medium and the reaction is initiated with water-soluble or oil-soluble initiators. A review of the subject can be found in a recent publication of Greenshields [46]. 

In addition to a proper choice of ligand hydrophobicity, the surfactant used is also critical. In general, non-ionic surfactants were found to be efficient for colloidal stabilization of the polymer particles [221]. This is to be expected, as, owing to the ionic nature of the catalyst, and the corresponding ionic strength, electrostatic stabilization is likely to be poor. Adequate hydrophilic/lipophilic balance (HLB) [222] is also a necessary criterion to ensure latex stability in ATR emulsion polymerization [223]. 

For the encapsulation of hydrophilic magnetic nanoparticles, the surfaces have to be converted into more hydrophobic by functionalization with a surfactant having a low hydrophilic/lipophilic balance (HLB) value, with coupling agents or surface modifiers. Apart from the enhancement of the surface hydrophobicity of the inorganic particles, in some cases different reactive groups are introduced for polymerization with the hydrophobic monomer... 

In this process, an aqueous solution of a water-soluble monomer is dispersed in an organic continuous phase using a nonionic surfactant of low hydrophilic-lipophilic balance (HLB=4-6). The polymerization is initiated using oil-soluble initiators and the mechanisms involved are similar to those occurring in emulsion polymerization [47,48]. 

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