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Physical properties of model viscoelastic materials.
F H Silver1, J J LiBrizzi, D Benedetto
1Department of Pathology, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, Piscataway 08854.
Journal of Applied Biomaterials : an Official Journal of the Society for Biomaterials
|January 1, 1994
Summary
Pseudoplastic behavior in ophthalmic viscoelastic agents is linked to high molecular weight polysaccharides forming extended structures. Low surface tension in these agents is associated with charged macromolecules and a high positive second virial coefficient.
Area of Science:
- Ophthalmic surgery
- Polymer science
- Biomaterials
Background:
- Polysaccharides like hyaluronan (HA) and hydroxypropylmethylcellulose (HPMC) are used as viscoelastic agents in ophthalmic surgery.
- Their clinical utility is attributed to properties such as pseudoplasticity (HA) and low surface tension (HPMC).
- Understanding the physical properties of these macromolecules is crucial for protecting ocular structures during surgery.
Purpose of the Study:
- To compare the physical properties of model viscoelastic solutions with those of HA and HPMC.
- To correlate macromolecular physical properties with their protective capabilities in ocular surgery.
Main Methods:
- Investigated pseudoplasticity in polysaccharides.
- Examined the relationship between molecular weight, backbone chemistry, and pseudoplastic behavior.
- Assessed the association between charged macromolecules, second virial coefficient, and surface tension.
Main Results:
- Pseudoplastic behavior was observed in polysaccharides with molecular weights exceeding 450,000.
- Pseudoplasticity was independent of backbone chemistry for linear macromolecules.
- Low surface tension was linked to charged macromolecules exhibiting a high positive second virial coefficient.
Conclusions:
- Polysaccharides forming extended structures at low shear rates and showing significant axial ratio decrease at high shear rates exhibit pseudoplasticity.
- Molecular weight is a key factor for pseudoplasticity in linear macromolecules.
- Charged macromolecules with a high positive second virial coefficient contribute to low surface tension in viscoelastic solutions.