Synthesis of SH‐ and NCO‐terminated thiocarbamate prepolymers

The addition reaction of 3,6‐dioxaoctane‐1,8‐dithiol with various diisocyanates, proceeding by addition of 1,4‐diazabicyclo[2.2.2.]octane as basic catalyst, was investigated. That way, NCO‐and SH‐terminated linear thiocarbamate telechelics (containing NHCOS‐groups) were synthesized. The structures were evaluated by IR and 13C NMR spectroscopy. Results show that side reactions of the NH protons with isocyanate (forming allophanates) can be excluded. The NCO‐terminated prepolymers are suitable to be used as participants in common isocyanate reactions. Thus, by treating with allyl alcohol, 2‐hydroxyethyl methacrylate or diallylamine, they can be transformed into telechelics with olefinic end‐groups (5, 6, 7). The products were characterized by their number‐average mol. wts. (VPO) and elemental analysis, and the expected chemical structures were confirmed by characteristic absorption bands.