Influence of a zwitterionic surfactant on the chromogenic behavior of a dye-containing aqueous PVA-polyether gel network

The effect of the addition of a zwitterionic sulfobetaine to a dye-containing polymer gel composed of two polymers - poly(vinyl alcohol) (PVA) and polyether - was investigated. With increasing sulfobetaine content a remarkable reduction of the UV-vis-absorption intensity of the longest wavelength absorption band of Phenol Red in the aqueous polymer network was observed, even for sulfobetaine concentrations below its critical micelle concentration (CMC). It can be assumed that this effect is based on the formation of ionic complexes between dye molecules and either single sulfobetaine molecules or aggregates of sulfobetaine. Furthermore, thermotropic behavior occurs in the investigated polymer gel system even at a polyether concentration as low as 0.8 wt%.