Supramolecular Template-Directed Synthesis of Soluble Quadruple-Chain Ladder Polyphenylsiloxane (Ph-QCLP) with High Molecular Weight

Quadruple-chain ladder polyphenylsiloxane (Ph-QCLP) was synthesized by a supramolecular template-directed stepwise coupling and polymerization method including three steps: (1) Multifunctional ladder monomer M-2 with four Si-Cl, four Si-OMe, and four Si-N groups was designed and synthesized by precoupling reaction. In solution M(2)s spontaneously self-assembled to be ladder superstructure (LS) by synergy of the hydrogen bonding and the pi-pi stacking interactions. Directed by LS template in a neutral condition that guaranteed the Si-OMe and Si-N groups were left undestroyed, M(2)s underwent controlled hydrolysis of Si-Cl groups and dehydrochlorination polymerization to be 1,3-di(3-aminophenylamino)-tetramethoxyl-disiloxane-bridged ladder polyphenylsiloxanes (DCLP). (2) A precursor, his-m-phenylenediamine-bridged quadruple-chain ladder polyphenylsiloxanes (QCLP), was synthesized via the controlled hydrolysis of Si-OMe groups of DCLP followed by confined dehydration polymerization in an alkaline condition which guaranteed the Si-N groups were still undestroyed. (3) The target Ph-QCLP was obtained through synchronous bridge-cleavage and in situ condensation of QCLP. The whole reaction process was well monitored by a concerted combination of FTIR, H-1 NMR, X-ray diffraction (XRD), and Si-29 NMR measurements. In particular, Si-29 NMR, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) results confirmed that Ph-QCLP possessed well-defined quadruple-chain ladder structure and extremely high thermo-stability.