Structure Formation in Polymer-Modified Liquid Crystals

The objective is the investigation of the influence of two different polymers in a lamellar liquid crystalline sodium dodecyl sulfate (SDS)/decanol/water system. The polymers are, on the one hand, uncharged poly(ethylene glycol) (PEG), whose molecular weight is varied, and, on the other hand, a polycation with differing charge densities made of diallyldimethylammonium chloride (DADMAC) and N-methyl-N-vinylacetamide (NMVA). Applied methods were mainly small-angle X-ray diffraction (SAXS), rheology, and electron microscopy. Our major results are the observation of two coexisting lamellar structures of which one is a "nonswelling" and the other a "swelling" structure, which form multilamellar spherical structures on a supramolecular level. However, the variation of the molecular weight of PEG can be neglected, whereas the alteration of the charge density has a pronounced influence on the structure. Generally, one can conclude that the phenomena observed here can be understood on the basis of polymer-polymer interactions in contrast to polymer-surfactant interactions of preliminary electrostatic nature. Copyright 1999 Academic Press.