A series of 10 poly(urethanes) were synthesized by solution polymerization from bis(chloroformates) and aromatic diamines, containing both silicon or germanium as central atom. So, the polymers prepared contain two silicon atoms or two germanium atoms exclusively or combinations of both. Me, Et, and Ph groups were bonded to the central atoms according to the nature of the monomers employed. Poly(urethanes) were characterized by FTIR, 1 H, 13 C, and 29 Si NMR spectroscopy and the results agreed with the proposed structures. Additionally, intrinsic viscosity values were established in DMSO solutions and thermal analyses were developed. In all cases, thermostable oligomers were obtained, which showed a degradation process beginning at $240-2608C. Polymers showed a thermal dependence with the nature of the heteroatom employed. Thus, in general, when germanium was used as central atom, the thermal stability was higher than the polymers containing silicon which agrees with the lower polarity and higher energy of the CÀ ÀGe bond in comparison with the CÀ ÀSi one.

Abstract-Following the reaction route between a diphenol and phosgene/toluene solution in basic medium, six new bis(chloroformates) containing germarylene or silarylene units were synthesized with good yield. The variation on the structure is due to the nature of the groups bonded to the heteroatom. Therefore, combinations of Me, Et and Ph groups were used. 4,4 -(Diethylsilylene)bis(phenyl chloroformate), 4,4 -(ethylmethylsilylene)bis(phenyl chloroformate) and 4,4 -(diethylgermylene)bis(phenyl chloroformate) were obtained as a slightly yellow oil, while 4,4 -(diphenylsilylene)bis(phenyl chloroformate), 4,4 -(methylphenylsilylene)bis(phenyl chloroformate) and 4,4 -(diphenylgermylene)bis(phenyl chloroformate) were obtained as a white solid. The new bi-functional monomers were characterized by FT-IR, 29 Si-, 13 C-and 1 H-NMR spectroscopy and elemental analysis. The T m of the products in general was higher in samples containing germanium as the central atom, compared to those containing silicon.

(Rev Méd Chile 2004; 132: 493-9).

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