Molecular weights of seven poly(phenylene ethynylene)-based water-soluble conjugated polyelectrolytes (CPEs) obtained through Sonogashira coupling are determined by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). A standard sample preparation protocol is developed to characterize the seven CPEs using 2,5-dihydroxybenzoic acid as the matrix (M) and AgTFA as the cationization reagent (CR). High-quality MALDI mass spectra are obtained at volume mixing ratios (CPE/M/CR) of 5/5/1 for anionic polymers (P1-P4) and 5/50/1 for cationic polymers (P5-P7). Molecular weight, molecular weight distribution, and end-group information are analyzed. The effects of molecular weight of CPEs on optical and quenching properties are also studied. (c) 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 2537-2543