What do the different notations Mw, Mn, Mv etc. used for the molecular weights for polymers indicate?
Unlike small molecules polymers are commonly made up of a mixture of varying sized molecules, with a wide range of molecular weights. As a result with long chain polymers it is normally only possible to determine the average molecular weight. There are several different methods for determing the molecular weight of a polymer; 1. Mn – Number-average molecular weight; is determined by measuring the molecular weight of n polymer molecules, summing the weights, and dividing by n. 2. Mw – Weight-average molecular weight; Weighted average of polymers. Always larger than Mn. Mw is used as a squared function to calculate the value. 3. Mz – Average molecular weight; Is measured by sedimentation analysis 4. Mv – Viscosity-average molecular weight; Average determined by viscosity measurements. Closer to Mn than Mw 5. Mp – GPC(SEC)peak molecular weight; Gel Permeation Chromatography (Size Exclusion Chromatography) Values given relative to a standard. Average weight relative to the peaks on chromat
