H-bonding template-directed synthesis of a complete m-PDA-bridged ladder polyhydrosiloxane (OLPHS)

A highly ordered m-phenylenediimino-bridged ladder polyhydrosiloxane (abbr. OLPHS) with Mn = 1.24 × 104 was synthesized under assistance of H-bonding template constructed from imino H-bonding, N(Si)-H⋯N(Si)-H, via a modified process of stoichiometric hydrolysis and dehydrochlorination condensation reaction between Si-Cl and Si-OH bonds. The complete ladder structure of OLPHS has been confirmed by the following three data. Two characteristic Bragg's peaks representing the ladder width (w=0.94nm) and ladder thickness (t = 0.42 nm) were observed in XRD analysis, which are consistent with those calculated by molecular simulation. The very sharp absorption with a small half-peak width (w1/2=0.5ppm) for [(-HN)HSiO2/2]n moiety of OLPHS in 29Si NMR spectrum indicated presence of the complete ladder structure. As collateral evidence, a higher glass transition temperature (Tg = 105 °C) is also recorded in the DSC measurement, implying the high stiffness of ladder chain of OLPHS.