Hydrophobically Modified Hydroxyethyl Cellulose With Surface-active Agent Interaction And Its Co-stable Emulsion

The use of polymeric surfactants as emulsifiers and stabilizers in emulsions has attracted much attention in recent years, especially hydrophobically modified polymers (hm-polymer). This kind of polymer is a water-soluble polymer with a few hydrophobic groups in the hydrophilic macromolecular chain. They can lower the surface and interfacial tension due to their intrinsic amphiphilic properties, though their abilities are much lower than those of the conventional low-molecular-weight surfactants. However, their solutions showed much better thickening ability than low-molecular-weight surfactants solutions due to their large molecular structures and the association of the hydrophobic groups on the backbone. In practical application of polymer, surfactant often exists. Polymer-surfactant system usually displays intriguing and fascinating features, which are different from polymer or surfactant. For hm-polymers in the presence of surfactant, the hydrophobes induce a specific aggregation of surfactant micelles around the hydrophobe clusters to form mixed micelles, which leads to an increase of viscosity, foamability and emulsifying ability. The presence of polymer can also affect the physical and chemical properties of surfactants, such as surface tension, cmc, aggregation number and interfacial properties. Hydrophobically modified hydroxyethyl cellulose (HMHEC) is choosed in this paper. Interactions of HMHEC/surfactants (SDS, CTAB and Gemini surfactant) and their effect on the stability of emulsions are systematically investigated. The variation discipline of emulsions stability and emulsion stabilization mechanism are concluded. All of the results are of theoretical and practical meanings to the study of the emulsions prepared by this kind of polymer. This paper could be divided into two parts as follows:1. Emulsions stabilized by HMHEC/conventional surfactant systemInteractions between HMHEC and SDS, CTAB were studied by several methods. Emulsions stabilized by HMHEC/SDS and HMHEC/CTAB mixture systems were prepared and the stability of emulsion was studied.HMHEC has strong interaction with the two surfactants in aqueous solutions. The viscosity of HMHEC/surfactants solutions first increased and then decreased with increasing surfactant concentrations, corresponding to the classic rule of interaction between hydrophobically associating polymer and surfactants.HMHEC/surfactants solutions have a stronger ability to lower the oil/water interfacial tension, which make the emulsification process easier. The droplet size of emulsions prepared by HMHEC/surfactant solutions decreased with increasing surfactant concentrations. The interaction between HMHEC/SDS is stronger than that of HMHEC/CTAB, emulsions prepared by HMHEC/SDS has better stability than the latter at low surfactant concentration.2. Emulsions stabilized by HMHEC/Gemini surfactant systemInteraction between HMHEC/12-2-12 was studied by surface/interfacial tension measurements, steady-state fluorescence as well as rheological experiments. Emulsions stabilized by HMHEC/12-2-12 were prepared and the stability of emulsion was studied.Gemini surfactant has two head groups and two hydrophobic chains, which leads to a lower surface or interfacial tensions than its monomeric surfactant DTAB. HMHEC can interact with 12-2-12 in solutions to form weaker polarity hydrophobic micro domains. The mixture system has much stronger ability to low the surface or interfacial tensions than single surfactant. The variations of viscosity for HMHEC/12-2-12 mixture solution as surfactant concentration can be divided to three areas, which is different with the conventional surfactant/HMHEC system. At high surfactant concentration, 12-2-12 can form giant entangled thread-like micelles.Creaming stability of emulsions prepared by HMHEC/12-2-12 increases with surfactant concentration. At low surfactant concentration, adding of HMHEC can obviously increases emulsion stability.The chief characteristics of this thesis are as follows:1. The interactions between HMHEC and SDS, CTAB were studied. Properties of emulsions prepared by the two mixture systems were investigated. Properties of the two systems were compared. The mechanism of emulsion stabilization is put forward. The use of HMHEC/surfactant to prepare emulsion can reduce surfactant usage, which is environmental friendly.2. The interaction between HMHEC and Gemini surfactant (12-2-12) was studied. Emulsions stabilized by HMHEC/12-2-12 were prepared. These results can enrich the contents on the interaction between macromolecules and Gemini surfactant and their application to emulsion.