A number of groups have invested considerable time synthesizing double-decker silsesquioxane (DD SQ) copolymers; however, to our knowledge, no one has sought to explore through-chain electronic communication between DD SQs via “conjugated” co-monomers. We recently demonstrated that stilbene derivatives of simple DD cages exhibit properties commensurate with formation of cage centered lowest unoccupied molecular orbitals (LUMOs), equivalent to LUMOs found in complete/incomplete SQ cages, [RStilbeneSiO1.5]8,10,12, [RStilbeneSiO1.5]7[O1.5SiMe/nPr], [RStilbeneSiO1.5]7[O0.5SiMe3]3, [RStilbeneSiO1.5]8[O0.5‑SiMe3]4, and [RStilbeneSiO1.5]8[OSiMe2]2. Such LUMOs support the existence of 3D excited-state conjugation in these cages. We describe here Heck catalyzed copolymerization of vinyl­(Me)­SiO­(PhSiO1.5)8OSi­(Me)­vinyl (vinylDDvinyl) with X–Ar–X, where X = Br or I and X–Ar–X = 1,4-dihalobenzene, 4,4′-dibromo-1,1′-biphenyl, 4,4″-dibromo-p-terphenyl, 4,4′-dibromo-trans-stilbene, 2,5-dibromothiophene, 5,5′-dibromo-2,2′-bithiophene, 2,5-dibromothieno­[3,2-b]­thiophene, and 2,7-dibromo-9,9-dimethylfluorene. Coincidentally model analogs were synthesized from vinylMeSi­(OMe)2. All compounds were characterized in detail by gel permeation chromatography (GPC), matrix-assisted laser desorption/ionization-time-of-flight, thermogravimetric analysis, nuclear magnetic resonance, Fourier transfer infrared spectroscopy, ultraviolet–visible spectroscopy, photoluminescence spectrometry, and two-photon absorption (2PA) spectroscopy. Modeling of HOMO–LUMO energy levels of related compounds with R = Me rather than Ph was also explored. In the current systems, we again see apparent conjugation in excited states, as previously observed, as indicated by 50–120 nm red shifts in emission from the corresponding model silane compounds. These results suggest unexpected semiconducting behavior via vinylMeSi­(O−)2 (siloxane) bridges between DD cages in polymers. The thiophene, bithiophene, and thienothiophene copolymers display integer charge transfer behavior on doping with 10 mol % F4TCNQ supporting excited-state conjugation; suggesting potential as p-type, doped organic/inorganic semiconductors.

Multiple studies have explored using cage silsesquioxanes (SQs) as backbone elements in hybrid polymers motivated by their well-defined structures and physical and mechanical properties. As part of this general exploration, we report unexpected photophysical properties of copolymers derived from divinyl double decker (DD) SQs, [vinyl(Me)Si-(O 0.5 ) 2 ][PhSiO 1.5 ] 8 [(O 0.5 ) 2 Si(Me)vinyl] (vinylDDvinyl). These copolymers exhibit strong emission red-shifts relative to model compounds, implying unconventional conjugation, despite vinyl(Me)Si(O-) 2 siloxane bridges. In an effort to identify minimum SQ structures that do/do not offer extended conjugation, we explored Heck catalyzed co-polymerization of vinyl-ladder(LL)-vinyl compounds, vinyl(Me/Ph)Si(O 0.5 ) 2 -[PhSiO 1.5 ] 4 (O 0.5 ) 2 Si(Me/Ph)vinyl, with Br-Ar-Br. Most surprising, the resulting oligomers show 30-60 nm emission redshifts beyond those seen with vinylDDvinyl analogs despite lacking a true cage. Further evidence for unconventional conjugation includes apparent integer charge transfer (ICT) between LL-co-thiophene, bithiophene, and thienothiophene with 10 mol % F 4 TCNQ, suggesting potential as p-type doped organic/inorganic semiconductors.

Multiple studies have explored using cage silsesquioxanes (SQs) as backbone elements in hybrid polymers motivated by their well-defined structures and physical and mechanical properties. As part of this general exploration, we report unexpected photophysical properties of copolymers derived from divinyl double decker (DD) SQs, [vinyl(Me)Si-(O 0.5 ) 2 ][PhSiO 1.5 ] 8 [(O 0.5 ) 2 Si(Me)vinyl] (vinylDDvinyl). These copolymers exhibit strong emission red-shifts relative to model compounds, implying unconventional conjugation, despite vinyl(Me)Si(O-) 2 siloxane bridges. In an effort to identify minimum SQ structures that do/do not offer extended conjugation, we explored Heck catalyzed co-polymerization of vinyl-ladder(LL)-vinyl compounds, vinyl(Me/Ph)Si(O 0.5 ) 2 -[PhSiO 1.5 ] 4 (O 0.5 ) 2 Si(Me/Ph)vinyl, with Br-Ar-Br. Most surprising, the resulting oligomers show 30-60 nm emission redshifts beyond those seen with vinylDDvinyl analogs despite lacking a true cage. Further evidence for unconventional conjugation includes apparent integer charge transfer (ICT) between LL-co-thiophene, bithiophene, and thienothiophene with 10 mol % F 4 TCNQ, suggesting potential as p-type doped organic/inorganic semiconductors.

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Organic electronic materials have advantages over inorganics in terms of versatility, cost, and processability. Recent advancements in organic materials for light-emitting diodes (OLED), field effect transistors (OFET), and photovoltaics have engendered extensive innovation potential on this field. In this research, we focus on synthesizing SQ (silsesquioxane) based oligomers cross-linked by dibromo-aromatic linkers and explore how the cross-linker influences their photophysical properties. Bis-trialkoxy silyl (linker) model compounds were synthesized to compare noncage photophysical properties with the oligomers. Several techniques such as UV/vis, fluorescence, FTIR, and thermal gravimetric analysis (TGA) have been used to characterize the systems. Time-resolved fluorescence and femtosecond transient absorption spectroscopy were used to understand the excited state dynamics of these materials. Studies were carried out to understand the differences between monomers and oligomers and potential energy transfer and charge transfer between the cages and cross-linking chromophores. Transient absorption showed lower energy absorption from the excited states, suggesting short-range communication between moieties. Single photon counting studies have shown distinct lifetime differences between most linkers and cages display possible excitation energy transfer through these materials. Transient absorption anisotropy measurements have shown signatures for excitation energy transfer between linker chromophores for oligomeric compounds. The silsesquioxane (SQ) backbone of the oligomers gives substantial thermal stability as well as solution processability, giving better flexibility for achieving energy transfer between linking chromophores.