Study of the Supramolecular Architecture-Directed Synthesis of a Well-Defined Triple-Chain Ladder Polyphenylsiloxane

High molecular weight (M-w) triple-chain ladder polyphenylsiloxane (TCLP) was synthesized by a supramolecular architecture-directed approach. First, a bis(phenyldihydroxysiloxy)dimethoxysilane ladder monomer wits self-assembled via hydrogen bonding interactions in acetonitrile/toluene (1:1, v/v) solution to form a ladder superstructure (LS). Then (lie LS was used as a template to direct the whole polymerization process. Lyophilization and surface-enhanced synchronous growth polycondensation process of the LS gave a ladder dimethoxysiloxy-bridged polyphenylsiloxane(DCLP)with gaseous triethylamine as condensation catalyst. Then DCLP wits hydrolyzed to form it triple-chain ladder superstructure (TCLS), which was further converied into the target TCLP via subsequent in situ dehydration condensation. The three ladder entities formed during the polymerization, that is LS, DCLP, and TCLP, have been well characterized. X-ray diffraction shows two Bragg reflections representing the ladder width and ladder thickness, respectively. Si-29 NMR analysis illustrates narrow peaks with the peak width at half-height of 0.5-2.5 ppm for the repeat units of the entities, indicating fine ladder regularity. In addition, an investigation of the dependence of the intrinsic viscosity [eta] Oil molecular weight (M,) in Mark-Houwink-Sakurada equation gave the exponent factor alpha = 1. 19, suggesting the target TCLP had a semirigid ladder structure. Meanwhile, high-resolution transmission electron microscopy observations showed it regular morphological structure for TCLP with a molecular width of ca. 1.4 nm. This value is quite close to the X-ray diffraction data. Dynamic mechanical analysis experiments also indicated TCLP has high storage modulus and high thermal stability.