Several new random copolyethers of styrene oxide (SO) and other monosubstituted oxirane as comonomer, i.e., propylene oxide (PO), isopropyl glycidyl ether (IPGE) or allyl glycidyl ether (AGE), were synthesized in THF solution at room temperature. As initiator monopotassium salt of dipropylene glycol activated by 18-crown-6 complexing agent was used. Synthesized copolyether-diols were characterized by SEC, C-13 NMR and MALDI-TOF techniques. They were unimodal and had M-n = 3500-4600 and relatively low dispersity (M-w/M-n = 1.16-1.18). Low unsaturation of the products resulted from chain transfer reaction to styrene oxide. Composition of SO/PO-diol, SO/IPGE-diol and SO/AGE-diol copolymers was determined by MALDI-TOF mass spectrometry. Homopolymers were not formed during the processes. [GRAPHICS] .