In physical

Physical chemistry

Physical chemistry is the study of macroscopic, atomic, subatomic, and particulate phenomena in chemical systems in terms of physical laws and concepts...

 and organic chemistry

Organic chemistry

Organic chemistry is a subdiscipline within chemistry involving the scientific study of the structure, properties, composition, reactions, and preparation of carbon-based compounds, hydrocarbons, and their derivatives...

, the polydispersity index (PDI), is a measure of the distribution of molecular mass

Molecular mass

The molecular mass of a substance is the mass of one molecule of that substance, in unified atomic mass unit u...

 in a given polymer

Polymer

A polymer is a large molecule composed of repeating structural units. These subunits are typically connected by covalent chemical bonds...

 sample. The PDI calculated is the weight average molecular weight divided by the number average molecular weight. It indicates the distribution of individual molecular mass

Molecular mass

The molecular mass of a substance is the mass of one molecule of that substance, in unified atomic mass unit u...

es in a batch of polymer

Polymer

A polymer is a large molecule composed of repeating structural units. These subunits are typically connected by covalent chemical bonds...

s. The PDI has a value equal to or greater than 1, but as the polymer chains approach uniform chain length, the PDI approaches unity (1).