Hello!
When we purchase a biodegradable polyester (PLA, PCL, PHB and others), the manufacturer usually reports the viscosity of a chloroform solution of this polymer. For example, "viscosity ~1.5 dL/g for 0.1% solution at 25C".
I want to use the Mark-Kuhn-Houwink equation to calculate the molecular weight based on this data, and I face several problems.
1. The viscosity provided by the manufacturer seems to be the inherent viscosity rather than the intrinsic viscosity. Is there a reasonable way to estimate the intrinsic viscosity based on a single concentraion point?
2. The solutions of polyesters in chloroform, HFIP and the other commonly used solvents are widely used and extensively studied. I am almost sure that the relations between the molecular weights, concentrations and viscosities are long known and perfectly described. Is there a simple and straightforward source where I can find this information?
A single low-concentration data point may serve as an approximation for intrinsic viscosity if the solution is sufficiently dilute, but it inherently carries uncertainty. For more accurate molecular weight calculations, obtaining viscosity data at several concentrations and extrapolating is highly preferable.
Standard polymer science handbooks and textbooks are your first stop. They not only compile the Mark–Houwink parameters for various polymer–solvent systems but also explain the procedure for obtaining intrinsic viscosity values. Additionally, relevant review articles and technical reports offer detailed and current perspectives on these measurements.
To estimate molecular weight, use the Mark-Houwink equation after extrapolating intrinsic viscosity from inherent viscosity data. Find specific constants (K and a) for your polymer-solvent system in literature or databases to apply the equation effectively.
Look at references is "Article Intrinsic Viscosity of Polymers in Good Solvents
"
The molecular weight of polymers such as PLA can be measured and calculated using the following methods.
(1) Viscometry to measure relative molecular weight (viscosity-average molecular weight Mη)
(2) Low-angle laser light scattering to measure weight-average molecular weight (Mw)
(3) Size exclusion chromatography (SES) (also known as gel permeation chromatography (GPC))
(4) Mass spectrometry
- Badges
- Science topic
- Similar topics
- Physical Sciences
- Waves