Classic Ubbelohde\nIntrinsic Viscosity Laboratory\nExercise Made Simple and Fast

Intrinsic viscosity is a foundational concept in a student’s\nunderstanding of macromolecular structures and solution behavior.\nIts measurement through simple laboratory techniques can teach undergraduate\nstudents the importance of accuracy and precision while learning concepts\nin polymer science such as hydrodynamic volume and the dependence\nof viscosity on concentration, density, and mass as well as mathematical\nprinciples such as the Taylor series and l’Hopital’s\nrule. Only simple and inexpensive equipment is required, but the measurements\nconsume much time and can frustrate both students and instructors.\nWe propose a faster method for conducting intrinsic viscosity measurements\nfor polystyrene in toluene without forfeiting any of the valuable\nlessons provided in a traditional intrinsic viscosity experiment.\nSplitting students into teams where each use their own viscometer\nto measure flow times of a single solution concentration allows for\nthe measurement of multiple concentrations at once. This practice\nalso eliminates the need for long-term and precise temperature control\nand diluting (or cleaning and purging) of viscometers between different\nconcentrations. Results from each team can be combined, allowing students\nto analyze one another’s data and make decisions on exclusion\nof erroneous measurements, data fitting, and uncertainty analyses.\nChoosing a polymer in pellet form reduces congestion at the analytical\nbalance and provides valuable lessons in refractive index matching\nand the torpid diffusion/dissolution of entangled macromolecules.\nIn this method, students can learn the same fundamental concepts in\npolymer science and critical data analysis in a much faster and less\nfrustrating manner.