Surfactants balance system

Kunieda, H., Hanno, K., Yamaguchi, S., and Shinoda, K. (1985) The three-phase behaviour of a brine/ionic surfactant/ nonionic surfactant/oil system evaluation of the hydrophile-lipophile balance (HLB) of ionic surfactant. 

Kunieda, H., and Miyajima, A. (1989) The effect of the mixing of oils on the hydrophile-lipophile-balanced (H LB) temperature in a water/non-ionic surfactant/oil system. /. Colloid Interface Sci, 128, 605-607. 

It should not be surprising to find some quantitative relationship between the Griffin HLB number and the Hildebrand 8, given that both concepts are related to the balance of interactions between hydrophobic tails and oil phases, and head groups and aqueous phases. For example, a study of various surfactant-solvent systems by Little led to the following relationship between 5 and HLB ... 

Through a surfactant balance. Smith and Ewart determined that the rate of polymerisation is proportional to the surfactant concentration to the 0.6 power, and to the initiator concentration to the 0.4 power. Smith used styrene as monomer and sodium dodecyl sulfate as surfactant in his experiments demonstrating the concept. In practice, most monomer/surfactant systems deviate from the ideal Smith-Ewart kinetics. However, equation (1) is rigorous for all emulsion polymer systems ... 

The initial step in the fabrication of a multiple emulsion (W/OAV) is to prepare a primary emulsion (W/0). It is generally agreed that the surfactant for the primary emulsion should have an HLB value of 3-6 (in the hydrophilic-lipophilic balance system of surfactant classification). Surfactants that have successfully been utilized include Span 80 (sorbitan oleate Nianxi et al, 1992 Zheng et al, 1993 Omotosho et al, 1990), E644 (polyamine Nianxieia/., 1992),N205 (polyamine Nianxi eta/., 1992), TX-4 (polyoxyethylene aUcylphenol ether Nianxi et al, 1992), MO A3 (polyoxyethylene aliphatic alcohol ether Nianxi et al, 1992), Brij 93 (Nianxi et al, 1992), polyoxamers [poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) block copolymer Law et al, 19861, and egg lecithin. The surfactant or combination of surfactants is then dissolved in the oil... 

Kunieda [18] found a correlation between the formation of a lamellar liquid-crystalline phase and the HLB of surfactants. The HLB of nonionic surfactants changes from hydrophilic to lipophilic with an increase in temperature and is considered to be just balanced at the temperature at which a lamellar liquid-crystalline phase is observed in a surfactant-water system. 

An a priori method for choosing a surfactant was attempted by several researchers (50) using the hydroph i1 e—1 ip oph i1 e balance or HLB system (51). In the HLB system a surfactant soluble in oil has a value of 1 and a surfactant soluble in water has a value of 20. Optimum HLB values have been reported for latices made from styrene, vinyl acetate, methyl methacrylate, ethyl acrylate, acrylonitrile, and their copolymers and range from 11 to 18. The HLB system has been criticized as being imprecise (52). 

Within a series with a fixed hydrophilic head group, detergency increases with increasing carbon chain length, reaches a maximum, and then decreases. This behavior frequentiy reflects a balance between increased surface activity of the monomer and decreased monomer concentration with increased surface activity. Similar effects are seen in surfactants in biological systems. 

FIG. 13 Phase diagram of a vector lattice model for a balanced ternary amphiphilic system in the temperature vs surfactant concentration plane. W -I- O denotes a region of coexistence between oil- and water-rich phases, D a disordered phase, Lj an ordered phase which consists of alternating oil, amphiphile, water, and again amphi-phile sheets, and L/r an incommensurate lamellar phase (not present in mean field calculations). The data points are based on simulations at various system sizes on an fee lattice. (From Matsen and Sullivan [182]. Copyright 1994 APS.)... 

This paper presents the physical mechanism and the structure of a comprehensive dynamic Emulsion Polymerization Model (EPM). EPM combines the theory of coagulative nucleation of homogeneously nucleated precursors with detailed species material and energy balances to calculate the time evolution of the concentration, size, and colloidal characteristics of latex particles, the monomer conversions, the copolymer composition, and molecular weight in an emulsion system. The capabilities of EPM are demonstrated by comparisons of its predictions with experimental data from the literature covering styrene and styrene/methyl methacrylate polymerizations. EPM can successfully simulate continuous and batch reactors over a wide range of initiator and added surfactant concentrations. 

Surfactants employed for w/o-ME formation, listed in Table 1, are more lipophilic than those employed in aqueous systems, e.g., for micelles or oil-in-water emulsions, having a hydrophilic-lipophilic balance (HLB) value of around 8-11 [4-40]. The most commonly employed surfactant for w/o-ME formation is Aerosol-OT, or AOT [sodium bis(2-ethylhexyl) sulfosuccinate], containing an anionic sulfonate headgroup and two hydrocarbon tails. Common cationic surfactants, such as cetyl trimethyl ammonium bromide (CTAB) and trioctylmethyl ammonium bromide (TOMAC), have also fulfilled this purpose however, cosurfactants (e.g., fatty alcohols, such as 1-butanol or 1-octanol) must be added for a monophasic w/o-ME (Winsor IV) system to occur. Nonionic and mixed ionic-nonionic surfactant systems have received a great deal of attention recently because they are more biocompatible and they promote less inactivation of biomolecules compared to ionic surfactants. Surfactants with two or more hydrophobic tail groups of different lengths frequently form w/o-MEs more readily than one-tailed surfactants without the requirement of cosurfactant, perhaps because of their wedge-shaped molecular structure [17,41]. 

Particularly useful is the physical classification of surfactants based on the hydrophile-lipophile balance (HLB) system [67,68] established by Griffin [69,70]. More than 50 years ago he introduced an empirical scale of HLB values for a variety of nonionic surfactants. Griffin s original concept defined HLB as the percentage (by weight) of the hydrophile divided by 5 to yield more manageable values ... 

To resolve the problem of negative /3 values obtained with the Frumkin theory, the improved Szyszkowski-Langmuir models which consider surfactant orientational states and aggregation at the interface have been considered [17]. For one-surfactant system with two orientational states at the interface, we have two balances, i.e., Ft = Fi + F2 and Ftco = Ficoi + F2C02, which can be used in conjunction with Eq. 24 to derive two important equations for determining the total surface excess and averaged molecular area required in the calculation of surface tension, i.e.,... 

The property of interest to characterize a surfactant or a mixture of surfactants is its hydrophilic-lipophilic tendency, which has been expressed in many different ways through a variety of concepts such as the hydrophiUc-lipophilic balance (HLB), the phase inversion temperature (PIT), the cohesive energy ratio (CER), the surfactant affinity difference (SAD) or the hydrophilic-lipophilic deviation (HLD) [1], which were found to be more or less satisfactory depending on the case. In the next section, the quantification of the effects of the different compounds involved in the formulation of surfactant-oil-water systems will be discussed in details to extract the concept of characteristic parameter of the surfactant, as a way to quantify its hydrophilic-lipophilic property independently of the nature of the physicochemical environment. 

Bourrel M, Chambu C (1983) The Rules for Achieving High Solubilization of Brine and OU by AmphiphUic Molecules. Soc Petrol Eng J 23 327-338 Kunieda H, Shinoda K (1985) Evaluation of the hydrophile-lipophile balance (HLB) of nonionic surfactants I. Multisurfactant systems. J Colloid Interface Sci 107 107-121 Kahlweit M, Strey R, Eirman P (1986) Search for tricritical points in ternary systems Water-oil-nonionic amphiphile. J Phys Chem 90 671... 

---