Reactive oligomers (ROs) constitute a starting material for the production of numerous polymeric materials with a pre-assigned set of physico-mechanical and physico-chemical properties. This book is the first to treat systematically various methods for determining the FTD and MWD of functional oligomers. Special attention is given to the application of liquid chromatography in different separation modes: exclusion (gel-permeation chromatography, GPC) and adsorption, as well as to the separation of functional oligomers in the critical region (SCR) at the boundary between the specified modes.