Adducts and oligomers of imines and isocyanates are promising candidates as meta-stable isocyanate blockers and latent telomeric block-copolymer sources.

Polymeric networks are produced by step-growth polyaddition and co-polyaddition reactions of 1-ethylimidazoline in combination with various diisocyanates. Five aromatic, two aliphatic diisocyanates and a polyurethane prepolymer are used as particular reactant in N,N-dimethylformamide as solvent at room temperature. Obviously, 1-ethylimidazoline can serve as trifunctional monomer, which enables a crosslinking reaction with diisocyanates. Molecular structure elements of the polymeric networks were studied by solid state 13C-NMR spectroscopy revealing that detailed molecular structure formations are determined whether aromatic or aliphatic diisocyanates are used. Quantum chemical calculations were used as supporting method to elucidate the complex reaction cascades. Hence, it can be shown that beside 3:1 stoichiometric structures 2:1 based structures are formed as well. These structures are observed as kinetically controlled products only when aromatic diisocyanate monomers are used. V C 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 977-985

The reaction of isocyanates with substituted imidazolines and the thermally induced cleavage of the resulting adducts are presented. For this purpose, reactions of various isocyanates [ethyl isocyanate, p-methylphenyl isocyanate, phenyl isocyanate, p-(trifluoromethyl)phenyl isocyanate] with 1-alkylimidazoline derivatives have been studied as a function of the substituent at the 2-position of the imidazoline ring. Three equivalents of isocyanate react with one equivalent of 1-ethylimidazoline to give a stoichiometric well-defined adduct. However, 1-ethyl-2-isopropylimidazoline reacts with isocyanates at 0 °C in another way, with formation of 2:1 adducts which belong to the family of 1,3-diphenyltetrahydroimidazo[1,2-a][1,3,5]triazine-2,4(1H,3H)-diones. The reaction of 1-ethyl-2-methylimidazoline with aromatic isocyanates at 0 °C also leads to 2:1 adducts, in this case of a malonamide type, which can react at 60 °C with an additional isocyanate equivalent to give the known pyrimidinediones. Thermal analysis (TG-MS/DSC) and trapping reactions with nucleophilic reagents, such as diphenylamine, show the release of isocyanate during the thermally induced cleavage reaction. Thus, blocked isocyanates are available by the reaction of isocyanates with 1-ethylimidazoline or 1-ethyl-2-isopropylimidazoline.