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

A highly ordered m-phenylenedfirnino-bridged ladder polyhydrosiloxane (abbr. OLPHS) with M-n = 1.24 x 10(4) 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 = 0.94 nm) 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 (w(1/2) = 0.5 ppm) for [(-HN)HSiO2/2](n) moiety of OLPHS in Si-29 NMR spectrum indicated presence of the complete ladder structure. As collateral evidence, a higher glass transition temperature (Tg = 105 degrees C) is also recorded in the DSC measurement, implying the high stiffness of ladder chain of OLPHS. (C) 2007 Rong Ben Zhang. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.