The amount of ethylene oxide oligomerization for functionalization of poly(styryl)lithium in benzene at 25 degreesC has been determined using MALDI-TOF MS and H-1 and C-13 NMR. Chemically insignificant amounts of oligomer were found using 4 equiv of ethylene oxide ([EO]/[PLi]) after 12 h. For reactions times ranging from 12 h to 4 weeks using 10 equiv of ethylene oxide, the corresponding amounts of dimeric oligomerization varied from 4% to 34%. Trimeric oligomerization of ethylene oxide was detected after 1 week (1%) and 4 weeks (4%) by MALDI-TOF MS. The quantitative results from MALDI-TOF MS were in good agreement with results from both H-1 and C-13 NMR analyses. The quantitative aspects of MALDI-TOF MS compared to H-1 and C-13 NMR for the determination of the amount of EO oligomerization have been established through the synthesis and characterization of the model dimeric oligomer product, omega-(2-(2-hydroxyethoxy)ethyl)polystyrene.