Atomic force microscopy studies on hydroxypropylguar gels formed under shear

Abstract

Atomic force microscopy (AFM) is used to image hydroxypropylguar gel structures formed under quiescent conditions as well as gels formed under varying levels of steady shear. Hydroxypropylguar (HPG) in aqueous solution is representative of a high molecular weight, flexible polysaccharide. HPG readily cross-links with borate ions to form a gel network. The steady-state rheological properties of borate cross-linked HPG gels are shown to be dependent on the shear rate applied during the gelation reaction. The storage modulus is used as an indication of the gel strength. The gel strength is shown to be enhanced under moderate shear conditions and is seen to decrease under high shear during gelat..