The key difference between monodisperse and polydisperse polymers is that monodispersed polymers have a precise and discrete molecular weight. But, polydispersed polymers have a range of components with a range of molecular weights.
A dispersion is a system in which particles of one phase are dispersed throughout a medium that is in a different phase. Therefore, a dispersion is a two-phase system. It is composed of a dispersion medium and a dispersed phase. The dispersion medium is a continuous medium in which the dispersed phase is distributed throughout. Dispersed phase, on the other hand, is the phase that is composed of particles that are distributed through another phase.
CONTENTS
1. Overview and Key Difference
2. What are Monodisperse Polymers
3. What are Polydisperse Polymers
4. Side by Side Comparison – Monodisperse vs Polydisperse Polymers in Tabular Form
5. Summary
What are Monodisperse Polymers?
Monodisperse polymers are macromolecular materials having a precise and discrete molecular weight. That means; all the components in the monodispersed polymer material have the same molecular weight. Therefore, this type of polymer material is uniform. The shape, size and mass distribution of the components in a unit volume of the material is consistent.
Figure 01: The Distribution of Components in a Monodispersed Polymer Material
What are Polydisperse Polymers?
Polydisperse polymers are macromolecular materials having a range of components with a range of molecular weights. That means; there are different components having different molar masses in the same polymer material. Therefore, the polymer material is non-uniform. In addition to these, the shape, size and the mass distribution of the components in a unit volume of the material are inconsistent.
Figure 02: The Distribution of Components in a Polydispersed Polymer Material
For this type of polydispersed polymers, we can calculate the polydispersity index for the molar mass distribution. The equation we can use to calculate the polydispersity index or PDI is as follows:
PDI = Mw/Mn
Where Mw stands for weight average molecular weight, Mn stands for number average molecular weight. The number average molecular weight (or Mn) is very sensitive to molecules having a low molecular weight. The weight average molecular weight of Mw is more sensitive to molecules having a high molecular mass.
What is the Difference Between Monodisperse and Polydisperse Polymers?
Polymers are macromolecules formed from the polymerization of monomers. Dispersity of a polymer is discussed regarding the molecular weight of the polymer. The key difference between monodisperse and polydisperse polymers is that monodispersed polymers have a precise and discrete molecular weight, whereas polydispersed polymers have a range of components with a range of molecular weights.
Moreover, monodisperse polymers have a consistent shape, size and mass distribution, while polydisperse polymers have an inconsistent shape, size and mass distribution. Therefore, monodisperse polymers are uniform, while polydisperse polymers are non-uniform.
The following table summarizes the difference between monodisperse and polydisperse polymers.
Summary – Monodisperse vs Polydisperse Polymers
According to the dispersity, there are two types of polymers as monodisperse polymers and polydisperse polymers. Monodisperse polymers are macromolecular materials having a precise and discrete molecular weight while polydisperse polymers are macromolecular materials having a range of components with a range of molecular weights. Therefore, the key difference between monodisperse and polydisperse polymers is that monodispersed polymers have a precise and discrete molecular weight, whereas polydispersed polymers have a range of components with a range of molecular weights.
Reference:
1. “Dispersity.” Wikipedia, Wikimedia Foundation, 15 Sept. 2019, Available here.
2. Konno, Mikio, and Daisuke Nagao. “Monodisperse Polymer Particles.” Encyclopedia of Polymer Science and Technology, 2014, pp. 1–26., doi:10.1002/0471440264.pst617.
Image Courtesy:
1. “Monodisperse Collection” By ScienceGuy5555 – Own work (Public Domain) via Commons Wikimedia
2. “Polydisperse Collection” By ScienceGuy5555 – Own work (Public Domain) via Commons Wikimedia