Polyelectrolyte-surfactant hydrogels – preparation, properties.

abstract

English

Oppositely charged polyelectrolytes and surfactants can form hydrogel-like materials at suitable conditions. Surfactant concentration should be sufficiently high, well above its critical micelle concentration. Micelles are supposed to form crosslinking points by electrostatic interactions with the oppositely charged groups on the polyelectrolyte chain. These materials are attractive as carriers of hydrophobic species within a hydrophilic matrix. This contribution illustrates variety of different components which can form such materials and some of their properties. Negatively charged hyaluronan was used as a representative of biopolymeric polyelectrolyte and positively charged Septonex surfactant as its reaction partner. Chitosan and aminated dextrane were used as positively charged polyelectrolytes and combined with several anionic surfactants – SDS, linear and branched STS. The formation of gels was tested in a broad concentration region and visualized using a hydrophobic dye Oil red O, which in the same time confirmed solubilization abilities of gels to hydrophobic molecules. Hydrogels can be prepared by two ways – wet method (mixing of precursor solutions) or dry method (mixing powdered precursors with liquid dispersion medium) giving products of similar properties. Example of prepared materials containing the dye are shown in Figure 1. Rheological measurements confirmed viscoelastic character of prepared materials which can be modified either by polyelectrolyte molecular weight or by the composition. This contribution also reports on the development of analytical technique for the determination of surfactant contents in hydrogels. The technique was based on colorimetric determination of surfactant remaining in the supernatant and surfactant in gels after their destruction in acidic media. It was also revealed that repetitive washing of hydrogels with the solvent used to prepare them decreased surfactant content. This investigation points to the presence of the surfactant also in the form of free micelles, that is micelles not anchored in the gel network.

hydrogels, interactions, surfactants, polyelectrolytes

PEKAŘ, M.; JARÁBKOVÁ, S.; VELCER, T.; SMILEK, J.; VENEROVÁ, T.; MRAVEC, F.

3. 9. 2017

Madrid

1