(23a) Predicting Surfactant-Related Properties for Chemical-Based Product Design

The chemical industry is changing, going beyond commodity chemicals to higher value added products. These are structured products, constituted of numerous chemicals, but still mainly designed and analyzed through experimental techniques. A systematic approach for the design of these products could significantly reduce both time and cost connected to the product development by reducing the amount of experiments needed, provided reliable property prediction methods.

Recently, systematic methodologies for the design of chemical based liquid formulations have been developed, but many of the chemical-based products, especially household and personal care products, are emulsions where active ingredients, surfactants, solvents, additives, etc.are mixed together to determine a desired emulsified product. A major difference between the design of liquid formulation and that of emulsion based products is the presence of two immiscible phases, kept together in a stable form by proper emulsifiers, most often surfactants. The presence of these ingredients in the emulsified products is clearly crucial and then their selection is one of the key-steps of the product development. Selection criteria for surfactants consider their effectiveness, safety and toxicity issues, environment, cost or a combination of the aforementioned criteria. Therefore, it is necessary to have available as many properties as possible in order to perform a proper selection based on reliable data. Unfortunately, experimental data are scarce and for some of the key-properties one often finds different values related to different models that cannot be verified due to the absence of an experimental value.

Because of the scarce availability of experimental data, property prediction models for surfactants are needed: critical micelle concentration, cloud point, Krafft temperature and surface tension reduction are considered fundamental properties to have access to in order to perform a proper surfactant design for emulsions. Even though none of these are strictly pure component properties, it is possible to adopt group-contribution methods to describe the available experimental data and then to extrapolate the correlation results to perform predictions. Quantitative structure-property relationship (QSPR) models have already been developed in relation to several of these properties, but in this work it has been decided to use group-contribution methods, based on the Marrero and Gani model, for its easier use in the computer-aided molecular design, predictive power an reliability.

For nonionic surfactants, new third order groups based on the characteristic structures of the most common families of surfactants have been defined and they are included in the Marrero and Gani model. Results from the modeling of critical micelle concentration, cloud point and surface tension reduction are presented and discussed. Also preliminary results regarding the modeling of critical micelle concentration, Krafft temperature and surface tension reduction are presented and discussed for ionic surfactants.

The application of these property models in the systematic methodology for computer-aided product design for emulsion based products is then highlighted.