We just talked about the fact that polymers can have different molecular weights. Oftentimes in reactions that make polymers a range of molecular weights are produced. The molecules may be composed of the same repeating unit (monomer), but for a number of reasons the chains are different in length. It turns out that this distribution of lengths is important to a number of polymer properties. The details of how this number is calculated are not worth going into; it’s sufficient to know that a higher molecular weight distribution means that there is a larger spread of polymer chain lengths. A distribution of 1.0 would mean that every single polymer chain has the exact same molecular weight.