A Well-Defined Ladder Polyphenylsilsesquioxane (Ph-LPSQ) Synthesized via a New Three-Step Approach: Monomer Self-Organization−Lyophilization—Surface-Confined Polycondensation

Abstract

A high-molecular-weight and well-defined ladder polyphenylsilsesquioxane (Ph-LPSQ) was synthesized via a new three-step approach: monomer self-organization in solution, lyophilization, and surface-confined polycondensation. A ladder superstructure, which served as a template to direct the polycondensation, was self-assembled from the 1,3-diphenyl-tetrahydroxy-disiloxane monomer (M) in acetonitrile solution. Following that, it was lyophilized to form a thin layer on the inner surface of a flask. Subsequently, polycondensation of the ordered monomeric thin layer was performed under a triethylamine (TEA) atmosphere. This strategy increased the ladder regularity of the Ph-LPSQ by preventing common complications faced in solution polycondensation of silanol-containing monomers, such as cyclization and gelation side reactions. 29Si NMR analysis showed a very narrow peak (peak width at half-height, w 1/2 = 2.5 ppm) at δ = –78.5 (corresponding to a Ph-SiO3/2unit), indicating a high degree of regularity of the polymer structure.

Synthesis of Ladder Silsesquioxanes by in situ Polycondensation of Cyclic Tetravinylsiloxanetetraols

“…Hydrolytic condensation of ViSi(OEt) 3 catalyzed with K 2 CO 3 gave insoluble, crosslinked condensed solids (Vi-PSQ). 29 Si NMR analysis can be an indicator of high degree of regularity of the polymer structure [7]. It is generally accepted that the narrower the peaks corresponding to RSiO 3/2 the less the structural defects in the architecture of the polymer backbone.…”

“…The molecular design of the precursor was found to be of special importance. Weak supramolecular interactions (H-bonding or π -π stacking) between silanol groups and/or template molecules help in the synthesis of well-defined LPSQs via stepwise coupling and condensation polymerization [7]. The procedure is based on the template-directed formation of a pseudo-ladder superstructure.…”

“…It made possible the synthesis of soluble ladder polyphenylsiloxanes having triple [8] and even quadruple [9] chains. High-molecular-weight ladder polyphenylsilsesquioxanes of regular structure were also synthesized by use of "monomer self-organization-lyophilizationsurface-confined polycondensation" [7]. Well-defined ladder poly(methylphenylsilsesquioxanes) were obtained as well via nonhydrolytic condensation [10].…”

Ladder Polysiloxanes for Optoelectronic Applications

“…The typical example will be introduced in the following section. Zhang et al (Z. X. Zhang et al, 2008) synthesized a well-defined ladder polyphenylsilsesquioxane (Ph-LPSQ) via a three-step approach: pre-organizing in solution, freeze drying, surface confined polycondensation as shown in Scheme 6. In the first step, ladder superstructure was formed by self-assembly of 1, 3-diphenyl-tetrahydroxy-disiloxane monomer in an acetonitrile solution.…”

Alkali-Metal-Directed Hydrolytic Condensation of 3-Mercaptopropyltrimethoxysilane

“…Several synthetic methods were proposed for the preparation of ladder-like polysilsesquioxanes, including step wise coupling polymerization [3][4][5][6][7] or hydrolytic condensation of trifunctional organosilanes [2,[8][9][10]. However, the most promising method for the preparation of defect-free LPSQs is hydrolytic condensation of monomers containing cyclic siloxane units [11][12][13][14][15][16][17][18][19].…”