Copolymerization of various isocyanates with ethylene oxide

Copolymerization of various monoisocyanates with ethylene oxide was attempted in relation to the alternate copolymerization of phenyl isocyanate with ethylene oxide by triethylaluminum catalyst. It was found that aliphatic and alicyclic isocyanates are not copolymerizable at all while many of aromatic isocyanates give the copolymer. The copolymer obtained was supposed to be alternate one. As to the substituted phenyl isocyanates, it was shown that ortho‐substituted isocyanates give the copolymer in high yield, with one exception: o‐anisyl isocyanate. There is no relation between the copolymer yields and HAMMETT'S substituent constants. These results suggest that triethylaluminum may preferentially coordinate with the oxygen atom rather with the nitrogen of the isocyanate group and that the coordination of the catalyst with the substituent may also occur. These expectations were confirmed by the infrared technique and the copolymer structure.