4,4'-Sulfonyldianiline (SDA) is reacted with 4,4'-(R1R2-silylene)bis(phenyl chloroformates) or 4,4'-(R1R2-germylene)bis(phenyl chloroformates) (where R-1 and R-2 are Me, Et, Ph combinations) in solution yielding poly(urethanes) (PUs) of moderate molecular weight containing silarylene, germarylene and sulfone moieties. DSC and TGA analyses were carried out. The highest glass temperatures (Tg) were obtained when one or two Ph groups were bonded to a heteroatom. However, these values were always low due to the flexibility gained by the chain due to the incorporation of the sulfone function. No-significant differences in Tg were observed when silicon was replaced by germanium in the main chain. All polymers were stable up to 200-220 A degrees C and underwent a complex decomposition process with a higher rate for PUs with side aliphatic groups. The thermal decomposition temperature (TDT) (10 wt%) for PUs based on Ph-Si-Ph moiety were higher than those obtained from germarylene-containing polymers.