The ambient temperature condensation, to yield low molecular weight poly(methyloxothiazene) (M-w = 1 x 10(4); PDI = 1.4), can be achieved by the reaction of MeS(O-2)NHSiMe3 and SOCl2-this latter reaction being performed in an attempt to isolate ClSMe(O)NSiMe3 (6a). The in situ addition of a Lewis acid initiator (e.g., PCl5) to freshly prepared samples of N-silylsulfonimidoyl chlorides (ClSR(O)NSiMe3, 6a-d, R = Me, Et, Ph, p-C6H4Me) yielded high molecular weight, narrowly dispersed polymers, 5a-d (M-w = 6.7 x 10(4)-3.3 x 10(6); PDI = 1.2-1.6) of general formula [RS(O)=N](n). These materials have been characterized by GPC, NMR (H-1, C-13) spectroscopy, and DSC. UV-vis spectroscopy of CH2Cl2 solutions of 5a-d reveal a high-energy pi-pi* transition (lambda(max) = 300-350 nin) that tails into the visible. Additionally, theoretical modeling of oligomeric (rnethyloxothiazenes) at either a semiempirical, Hartree-Fock, or DFT level of theory suggests that these polymers adopt an irregular helical architecture.