Rheological effects with a hydrophobically modified polymer

In cosmetics, rheological behaviour is directly related to ease of product use, skin feel and physical stability as well as aesthetic perceptions. Hydrophobically modified (HM) polymers allow formulators to exploit various types of interaction with the hydrophobic side chains: polymer–polymer (intrachain and interchain association), polymer–surfactant (charged and un-charged) and polymer–oil interaction.The polymer used was ammonium acryloyldimethyltaurate/beheneth-25 methacrylate crosspolymer. It was compared in several formulation types:polymer + water (aqueous gel: traditional hair gel)polymer + water + nonionic surfactant (“spray gel”: sprayable hair gel)polymer + water + anionic surfactant (shower gel)polymer + water + oil (“cream gel”: surfactant-free O/W emulsion)polymer + water + surfactant + oil (traditional O/W emulsion)The rheological requirements for the different formulation types are discussed in terms of surfactant and electrolyte effects on polymer properties. Above a certain critical polymer concentration a yield stress is observed. By carefully adjusting the polymer concentration it is possible to obtain formulations which are pourable but can suspend solid particles.