The molecular weight of the polymers was analyzed by gel permeation chromatography (GPC) in chloroform as well as by matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS) (Table ). For poly(PCT-T), GPC indicated a number-average molecular weight (Mn) of 1.4 kDa and a weight-average molecular weight (Mw) of 2.0 kDa relative to polystyrene standards. For poly(PCT-2T), a slightly lower Mn of 1.2 kDa but a higher Mw of 2.6 kDa was found. The MALDI-MS measurements (Figure ) were in good agreement with these results, with peaks observed at m/z values corresponding to up to eight repeat units for poly(PCT-T) and up to six repeat units for poly(PCT-2T). Interestingly, the main peaks observed in the MALDI-MS spectra correspond to multiples of the mass of the repeat unit, without any additional end groups present (Table ). When analyzing the much smaller side peaks (Table ), the difference in m/z to the main peaks corresponds to additional thiophene/bithiophene or PCT units, with only very weak peaks indicating some presence of bromo or stannyl groups.