MALDI-ToF MS Method for the Characterization of Synthetic Polymers with Varying Dispersity and End Groups

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-ToF MS) is an effective analytical tool for characterizing synthetic polymers, offering precise molecular weight determination and structural insights such as repeat unit masses and end-group identification. This protocol details the steps for polymer analysis, including sample preparation with appropriate matrix and cation selection, data acquisition, and a calibration method to ensure accurate mass measurements. It highlights the versatility of MALDI-ToF MS in analyzing polymers, from monodisperse to highly disperse materials, while observing limitations in resolving highly disperse samples. By comparing theoretical and observed masses, including isotopic patterns, the method enables confident confirmation of repeat units and end groups. The protocol supports new users by presenting representative data on matrix selection, spectral interpretation across dispersity ranges, and characterization of polymers with unique isotopic features or metastable ion formations. Troubleshooting strategies include addressing issues such as matrix interference and samples that ionize without an added cation during sample preparation. Overall, this guide serves as a foundation for using MALDI-ToF MS as a rapid and reliable technique for polymer analysis.