Strain energies cyclic amines

Cationic polymerization of cyclic amines proceeds usually with a high activation energy and often requires relatively high temperatures, even for the strained four-membered rings, e.g. for 1,3,3-trimethylazetidine AH = 73 kJ mol-1, kp = 1.4 xl0 4mor1 -1-s"1 at 78 °C 5). 

Polymerization of cyclic amines proceeds usually with high activation energies, due to the high strength of the C—N bond. To attain significant rates (k 10-3 mol-1 1 s 1) requires temperatures from 30 to 100 °C for azetidines and about 200 °C for the less strained bicyclic six-membered amines quinuclidine and triethylenediamine 9). Cyclic sulfides polymerize more rapidly than amines but much slower than ethers of a comparable structure (e.g. for 3,3-dimethylthietane k, = 2 10-2 mol-1 1 s at 35 °C, which is at least 104 times lower than for 3,3-dimethyloxetane (cf. Adv. Polymer Sci. 37 (1980)). 

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