Individual amphiphiles, polymers, and colloidal dispersions influenced by temperature, pH, and environmental conditions or interactions between their oppositely charged pairs in solvent medium often produce solvent-rich and solvent-poor phases in the system. The solvent-poor denser phase found either on the top or the bottom of the system is called coacervate. Coacervates have immense applications in various technological fields. This review comprises a concise introduction, focusing on the types of coacervates, and the influence of different factors in their formation, structures, and stability. In addition, their physicochemical properties, thermodynamics of formation, and uses and multifarious applications are also concisely presented and discussed.

This work reports a detailed investigation of the micellization of the cationic surfactant cetyltrimethylammonium bromide (CTAB) over the temperature range of 290–313 K. Conductometry, tensiometry, fluorimetry, and isothermal titration calorimetry (ITC) were used to study the overall solution behavior of amphiphilic self-aggregation. The CMC values showed a trend of first declining and then rising with a minimum temperature of 298 K. The adsorption at the air–water interface and micellization processes of CTAB are both spontaneous. The enthalpy of CTAB micellization is negative at 290 K and increases negatively as the temperature rises. The interfacial parameters—maximum surface excess concentration (Γ_max), minimum area per molecule (A_min), standard free energy of adsorption (A_min), and surface pressure at CMC (Π_CMC)—were calculated using surface tension data. The aggregation numbers (N) of CTAB micelles and others (SDS and CHAPS) determined at different [surfactant]>CMC by the static fluorescence quenching method were used to find out the N values at CMC (or N^CMC). The results revealed that the N^CMC values were 48, 54, and 4 for CTAB, SDS, and CHAPS micelles, respectively. Temperature-dependent N^CMC by the ITC method was also examined for the studied surfactants. Additionally, the ITC-determined specific heat of micellization was used to find out the extent of water penetration into the micelle interior of up to 8, 7, and 3 hydrocarbons for CTAB, SDS, and CHAPS, respectively.

Stability of hydrophobic colloids is an important phenomenon in colloid science. The hydrophobic colloids are known to get destabilized by the counterions of electrolytes leading to coagulation guided by Schulze–Hardy (S-H) rule. There are exceptions to this rule; effective improvement has been attempted but not with good success. Recently, the role of coions in the coagulation process was considered: an inverse Schulze–Hardy (iS-H) rule has been proposed. We have discussed the basics of colloid solutions, and colloid stability: also have tested the S-H and iS-H rules in terms of a number of positively and negatively charged hydrophobic colloids. Critical coagulation concentrations, zeta-potential, charges of coions and counterions, and ionic strengths have been separately (as well as together) considered to correlate the coagulation phenomenon. Partial agreements with the rules are only found. The article summarizes the fundamentals of the field of colloid stability, and its current status. Analysis of experimental findings in a new perspective (in terms of a new analytical procedure) has been proposed with a view to its projection toward future studies.