Intrinsic Viscosity
Intrinsic Viscosity - Related Videos
08:04
Viscosity of Propylene Glycol Solutions
0 Views •
2023
Source: Michael G. Benton and Kerry M. Dooley, Department of Chemical Engineering, Louisiana State University, Baton Rouge, LA Viscosity is a measure of a fluid's resistance to flow, and it is a useful parameter in the design of efficient product processing and quality control in a wide range of industries. A variety of viscometers are used to obtain the most accurate readings of experimental materials. The standard method of measuring viscosity is through a glass tube viscometer, which...
01:17
Viscosity
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2023
When water is poured into a glass, it falls freely and quickly, whereas if honey or maple syrup is poured over a pancake, it flows slowly and sticks to the surface of the container. This difference in the flow of different kinds of liquids arises due to the fluid friction between the liquid layers and the liquid and the surrounding material. This property of fluids is called fluid viscosity. In this example, water has a lower viscosity than honey and maple syrup. The SI unit of viscosity is...
01:27
Viscosity
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2026
Viscosity is a property of fluids that measures their resistance to flow. It is influenced by factors such as the surface area of contact, the gradient of flow speed, and the fluid's viscosity constant, called the coefficient of viscosity. The coefficient of viscosity, also known as dynamic viscosity, is denoted by the symbol η. It determines the proportionality between the viscous force and the gradient of flow speed.Newton's law of viscosity states that the viscous force on a faster-moving...
02:57
Surface Tension, Capillary Action, and Viscosity
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2020
Surface Tension The various IMFs between identical molecules of a substance are examples of cohesive forces. The molecules within a liquid are surrounded by other molecules and are attracted equally in all directions by the cohesive forces within the liquid. However, the molecules on the surface of a liquid are attracted only by about one-half as many molecules. Because of the unbalanced molecular attractions on the surface molecules, liquids contract to form a shape that minimizes the number...
02:18
Intrinsically Disordered Proteins
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2020
Intrinsically disordered proteins are a group of proteins that do not fold into specific three-dimensional structures. Their structural flexibility allows them to complement ordered proteins to perform functions that are inaccessible to rigid structures. They are more common in eukaryotes than prokaryotes and may either be exclusively intrinsically disordered or hybrid proteins, consisting of a mix of ordered and disordered regions. The absence of a rigid structure in these proteins can be...
FAQs
Solvent quality influences how extended or compact a polymer chain becomes in solution. A solvent that promotes a more expanded conformation gives the molecule a larger hydrodynamic volume and generally increases the measured intrinsic viscosity. Because chain conformation changes the polymer’s flow contribution, comparisons between samples are meaningful only when solvent and temperature conditions are controlled.
Larger polymer molecules usually displace and move through the solvent as larger hydrodynamic entities, producing a stronger effect on solution flow. Chain conformation also changes the volume presented to the surrounding liquid, so molecules with different structures can show different intrinsic viscosities even when their chemical composition is similar. This makes the value useful for comparing polymer samples.
At finite concentration, polymer molecules can interact with one another, so the observed viscosity reflects both individual molecular behavior and concentration-dependent effects. Measuring several dilute solutions and extrapolating the concentration dependence to zero removes the contribution associated with those intermolecular interactions. The resulting value more closely represents the hydrodynamic behavior of isolated solute molecules.
Researchers prepare several dilute polymer solutions, measure their viscosities, and examine how the viscosity changes with concentration. They then extrapolate the measured concentration-dependent behavior to zero concentration. Consistent solvent and temperature conditions are important because both solvent quality and temperature can alter chain conformation and the flow response used in the extrapolation.
The Mark–Houwink relationship connects intrinsic viscosity with viscosity-average molar mass. After researchers determine the intrinsic viscosity of a polymer sample, they can use that relationship to estimate this molar-mass measure, provided the relevant relationship applies to the selected polymer, solvent, and temperature conditions. The result supports comparisons among samples and studies of molecular changes.
Changes in intrinsic viscosity can indicate that the polymer’s molecular size or chain structure has changed during synthesis, processing, or degradation. Comparing values obtained under consistent measurement conditions helps researchers assess whether samples differ in their hydrodynamic behavior. The technique therefore provides a solution-based way to track structural changes without relying only on processing history or visual observations.