Oligomeric cationic polymethacrylates: a comparison of methods for determining molecular weight

This study compares three common laboratory methods, size-exclusion chromatography (SEC), 1H nuclear magnetic resonance (NMR), and matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF), to determine the molecular weight of oligomeric cationic copolymers. The potential bias for each method was examined across a series of polymers that varied in molecular weight and cationic character (both choice of cation (amine versus guanidine) and relative proportion present). SEC was found to be the least accurate, overestimating Mn by an average of 140 , owing to the lack of appropriate cationic standards available, and the complexity involved in estimating the hydrodynamic volume of copolymers. MALDI-TOF approximated M n well for the highly monodisperse (Crossed D sign <1.1), low molecular weight (degree of polymerization (DP)