Question

Which one of the following permits the direct determination of intrinsic viscosity of a polymer solution for known molecular weight of the polymer?

• A. Flory-Huggins equation
• B. Newton’s law of viscosity
• C. Williams-Landel-Ferry equation
• D. Mark-Houwink equation

Hint:

Remember: The Mark-Houwink equation is the fundamental bridge between polymer intrinsic viscosity and molecular weight — crucial in polymer characterization.

Answer 1

The Correct Option is D

Step 1: Recall key equations.
- Flory-Huggins equation: Deals with thermodynamics of polymer solutions, not intrinsic viscosity.
- Newton’s law of viscosity: Relates shear stress to shear rate in Newtonian fluids, not polymer molecular weight.
- Williams-Landel-Ferry (WLF) equation: Describes the temperature dependence of polymer viscosity near glass transition, not intrinsic viscosity.
- Mark-Houwink equation: Expresses relationship between intrinsic viscosity \([\eta]\) and molecular weight \(M\) as: \[ [\eta] = K M^a \] where \(K\) and \(a\) are constants depending on polymer-solvent system. This equation directly connects intrinsic viscosity and molecular weight.

Step 2: Conclusion.
Thus, the correct choice is the Mark-Houwink equation. \[ \boxed{[\eta] = K M^a} \]