The PDI is the ratio of weight to number-average molecular masses, M̅w/M̅n. In natural polymer, which are generally monodispersed, PDI is ____ and in synthetic polymer which are always polydisperse, PDI is ____ because M̅w is always ____ than M̅n. Fill in the blanks

• A. Greater than 1, 1, higher
• B. 1, greater than 1, higher
• C. Less than 1, 1, lower
• D. 1, less than 1, lower

The PDI, or Polydispersity Index, is an important measure in polymer science that indicates the distribution of molecular masses in a given polymer sample. Here’s how it works for natural and synthetic polymers:

Understanding PDI in Different Polymers

Natural polymers, which are typically monodispersed, have a PDI of:

• 1

This indicates that all the polymer chains have the same molecular weight.

On the other hand, synthetic polymers are usually polydisperse, leading to a PDI that is:

• Greater than 1

This occurs because the weight-average molecular mass (M̅w) is always:

• Higher

than the number-average molecular mass (M̅n).

Final Answer

The correct option is: A. Greater than 1, 1, higher.