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The ring-opening polymerization of dimethylene urethane (3) (systematic name: 2-oxo-1,3-oxazolidine) with methyl trifluoromethane sulfonate as the initiator is inefficient. It was shown that equimolar amounts of dimethylene urethane and trifluoromethane sulfonate result in the expected active species - 2-methoxy-4,5-dihydro-1,3-oxazolium trifluoromethane sulfonate (5a) -: propagation, however, does not occur. Poly(dimethylene urethane) (4), was obtained by means of polycondensation of a linear monomer, i.e., 2-(2-phenoxycarbonylimino-1-ethoxycarbonylimino)-ethanol (9). This [3]-polyurethane is a semicrystalline material with a melting point of 200.7 °C. Heating above its melting point leads to dimethylene urethane by ring-closing depolymerization. The thermodynamical data support the experimental results with respect to the polymerization / depolymerization equilibrium.

The cationic ring-opening polymerization of tetramethylene urethane (TeU; systematic name, hexahydro-1,3-oxazepin-2-one, (1)) in the melt at 67 °C with methyl trifluoromethanesulfonate (TfOMe) as the initiator yields poly(tetramethylene urethane) (poly(TeU), (6)) with a regular microstructure. This [5]-polyurethane is a semicrystalline material with a Tg of 47 °C and a Tm of 209.5 °C. The reaction proceeds via an active chain end mechanism with a protonated cyclic endo iminocarbonate as the active species. The propagation step involves nucleophilic attack of the carbonyl oxygen of the monomer at the endocyclic methylene group adjacent to the oxygen atom of the active species. The propagation rate constant was 4.2 × 10-4 L·mol-1·s-1. The polymerization of tetramethylene urethane is accompanied by termination reactions; however, transfer reactions and backbiting reactions were not observed. Thermodynamic data support the ring-opening mechanism and the thermal stability (lack of ring-closing depolymerization...

Aliphatic [n]-polyurethanes were obtained by catalytic polycondensation of suitable α-hydroxy-ω-O-phenyl urethanes (III). 1H and 13C NMR analyses of the resulting [n]-polyurethanes (3 a–g) show a uniform microstructure consisting of urethane groups only, and with carbonate and urea groups being absent. The [n]-polyurethanes with linear alkylidene moieties (3 a–e) are highly crystalline materials, their melting points show the same odd-even effect as was observed for [n]-polyamides. The [n]-polyurethanes with branched alkylidene groups (3 f, g) show lower crystallinity (3 g) or are amorphous (3 f) materials. Upon heating, the [3]- and all the [4]-polyurethanes (3 a and 3 b, f, g) result in the corresponding cyclic urethanes by ring-closing depolymerization.

In an adiabatic vacuum calorimeter, the temperature dependence of the heat capacity C O p of dimethylene urethane (DMU) and poly(dimethylene urethane) (PDMU) was studied between 6 and 335 K with an uncertainty of about 0.2%. In a calorimeter with a static bomb and an isothermal shield, the energies of ΔU comb of the monomer and of the polymer were measured. From the experimental data, the thermodynamic functions C o p (T), H 0 (T) - H 0 (0), S 0 (T), G 0 (T) - H 0 (0) were calculated in the range from to 335 K, and enthalpies of combustion ΔH 0 comb and thermochemical parameters of formation ΔH 0 f , ΔS 0 f , ΔG 0 f of the substances studied were estimated at T = 298.15 K and standard pressure. The results were used to calculate the thermodynamic characteristics of the ring-opening polymerization of DMU in bulk (ΔH 0 pol , ΔS o pol , ΔG 0 pol ) with formation of linear poly(dimethylene urethane) in the range from 0 to 330 K. In addition, the ceiling temperature T 0 ceil was determined.

In an adiabatic vacuum calorimeter the temperature dependence of the heat capacity C 0 p of tetramethylene urethane (TMU) (2-oxo-hexahydro-1,3-oxazepine) and poly(tetramethylene urethane) (PTMU) was studied between 4.3 and 300 K with an uncertainty of about 0.2%. In a calorimeter with a static bomb and an isothermal shield the energies of combustion ΔU comb of the monomer and the polymer were measured. From the experimental data the thermodynamic functions C 0 p , H 0 (T)-H 0 (0), S 0 (T), G 0 (T)-H 0 (0) were calculated in the range of 0 to 300 K, and enthalpies of combustion ΔH 0 comb and thermochemical parameters of formation ΔH 0 f , ΔS 0 f , ΔG 0 f of TMU and PTMU were estimated at T= 298.15 K and standard pressure. The results obtained were used to calculate the thermodynamic characteristics of TMU polymerization in bulk (ΔH 0 pol , ΔS 0 pol , ΔG 0 pol with opening of the seven-membered ring and formation of the linear polymer PTMU, in the range of 0 to 300 K. It was found that the values of the standard Gibbs function of the process (ΔG 0 pol = (-41)-(-42) kJ.mol -1 ) are always negative and do not substantially depend upon temperature in the whole temperature interval studied. This implies that the equilibrium TMU ⇄ PTMU is far on the side of the polymer. The upper (ceiling) limiting temperature of TMU polymerization is T 0 ceil > 1 000 K.

A-B Di- and B-A-B triblock copolymers with poly(tetramethyleneoxy) (poly(THF)) and poly(tetramethyleneoxycarbonylimino) (poly(TeU)) blocks were prepared by sequential polymerization of tetrahydrofuran (THF) and tetramethyleneurethane (TeU) with the monofunctional initiator methyl trifluormethylsulfonate and the bifunctional initiator trifluoromethanesulfonic acid anhydride, respectively. The block copolymers obtained after purification exhibit a monomodal narrow molecular weight distribution and a uniform microstructure of the two blocks as was deduced from gel permeation chromatography and NMR analysis. The block copolymers are semicrystalline materials with distinct melting points of the poly(THF) and the poly(TeU) domains.