Viscosity of Polymers: Degree of Polymerisation & Molecular Weight

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SUMMARY

The viscosity of polymers, such as microcrystalline cellulose, is directly related to their degree of polymerization, meaning that larger polymers exhibit higher viscosity. This relationship is quantified through the Mark–Houwink equation, which establishes a correlation between molecular weight and viscosity for specific polymer-solvent pairs. While the discussion raises questions about the viscosity of non-polymers, such as isopropanol compared to ethanol, it is important to note that viscosity is influenced by multiple factors beyond molecular weight, and experimental determination is essential for accurate comparisons.

PREREQUISITES
  • Understanding of polymer chemistry and viscosity concepts
  • Familiarity with the Mark–Houwink equation
  • Knowledge of molecular weight and its implications on physical properties
  • Basic experimental techniques for measuring viscosity
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  • Research the Mark–Houwink equation and its applications in polymer science
  • Explore experimental methods for measuring viscosity in various solvents
  • Investigate the relationship between molecular weight and viscosity in non-polymeric substances
  • Study the effects of temperature and concentration on polymer viscosity
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Chemists, polymer scientists, and students studying material properties who are interested in the relationship between molecular structure and viscosity.

CrimpJiggler
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In college we measured the viscosity of microcrystalline cellulose and used the result to determine its degree of polymerisation. Is the viscosity of a polymer directly proportional to its degree of polymerisation or something? In other words the bigger the polymer, the more viscous it is? Does this apply to non polymers too? For example is isopropanol more viscous than ethanol simply because it has a greater molecular weight?
 
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