Foam, Emulsion and Wetting Films Stabilized by Polymeric Surfactants

Emulsion and Wetting Films Stabilized by Polymeric Surfactants 

Thin liquid films have proven their advantages in the study of interaction forces in foam, emulsion, and wetting films stabilized by various types of surfactants see, for example. Refs. l-3]. DLVO and non-DLVO surface forces that stabilize these films have been established in many cases the relation between surface forces and film stability has also been found. Recently, several authors have reported results of model experiments with thin liquid films (foam, emulsion and wetting films) stabilized by polymeric surfactants. In our laboratories all three types of films from aqueous solutions of A-B-A triblock copolymers [4—6] or AB hydrophobically modified inulin [8-10] have been studied. The corresponding disperse systems (foams, emulsions, suspensions) stabilized by AB polymeric surfactants have also been studied extensively see, for example. Refs. [11-14]. It was supposed that the stabilizing forces are steric surface forces but they have not been directly proven and quantitatively studied. 

In most other papers, polyelectrolytes have been used [15-21] see also the comprehensive review of Ref [22]. Amphiphilic diblock copolymers have also been used for foam film studies [23-25]. Emulsion films stabilized by natural polymeric surfactants from bitumen [26] and thin liquid films from protein (biopolymer) aqueous solutions [27] should also be noted. 

Here we review the results obtained [4—10] with two types of non-ionic polymeric surfactants (i) A-B-A triblock copolymers and (ii) novel graft polymeric surfactants based on inulin. 

Two PEO-PPO-PEO three-block copolymers of the Synperonic series - F108 and P104 [28, 29] - have been employed. PPO represents the middle hydrophobic block B and both hydrophilic PEO form the two terminal chains A. These commercial, non-ionic, water-soluble polymeric surfactants were used as obtained from BASF. They are pure though not monodisperse. The molecular masses and average EO/PO contents are known from the manufacturer and yield approximate 

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Foam, Emulsion and Wetting Films Stabilized by Polymeric Surfactants... 

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