PHYSICAL-PROPERTIES OF MODEL VISCOELASTIC MATERIALS

Previous observations on polysaccharides used as viscoelastic agents i n ophthalmic surgery suggest that the pseudoplasticity of solutions of hyaluronan (HA) and the low surface tension of hydroxypropylmethylcel lulose (HPMC) solutions are physical properties that make these soluti ons useful clinically. Our laboratories are interested in correlating the physical properties of macromolecular solutions with the ability o f these molecules to protect ocular structures during eye surgery. The purpose of this study is to compare the physical properties of model viscoelastics with the properties of HA and HPMC. The results of these studies suggest that polysaccharides that form extended structures in solution at low shear rates and that are characterized by large decre ases in the axial ratio at high shear rates, exhibit pseudoplastic beh avior. In this study pseudoplasticity is exhibited by polysaccharides with molecular weights in excess of 450 000, and is insensitive to the backbone chemistry for linear macromolecules. In addition, low surfac e tension is associated with charged macromolecules that have a high p ositive second virial coefficient. (C) 1994 John Wiley & Sons, Inc.