Synthesis of organosilanylene–pentathienylene alternating polymers and their application to the hole-transporting materials in double-layer electroluminescent devices

A novel carborane-containing ceramic precursor: Synthesis, characterization, and ceramic conversion mechanism

Linear carborane-carbosilane-phenylacetylene polymers have been synthesized as precursors for ceramic and characterized by Fourier transform infrared (FT-IR), proton nuclear magnetic resonance (1H-NMR), and carbon-nuclear magnetic resonance (13C-NMR). Novel linear polymers have the advantage of being extremely easy to process and convert into ceramics, since they are either viscous liquids or low melting solids at room temperature and are soluble in most organic solvents. Ceramic conversion reaction of the polymers was studied, and the conversion mechanism using thermogravimetric analyzer, FT-IR, and pyrolysis-gas chromatography-mass spectrometry was proposed. During the early heating period in the mechanism, the precursor polymer is cured and oligomer is formed. Then the degradation of oligomer takes place at higher temperatures with the weak bond cleaved and cross-linked simultaneously. Ceramic yield of the polymer after heating up to 1000°C in nitrogen (N2) was 77.6%. The derived ceramics exhibit excellent thermal and thermo-oxidative stability, whose 5% mass loss temperature was identified to be 650°C in N2 and 665°C in air, respectively. Boron appears to be the key element to achieve the outstanding thermo-oxidative stability. The relevant kinetic data were obtained by two kinds of model-free-kinetic algorithms, differential Friedman and integral Kissinger–Akahira–Sunose. These two methods were combined to give the energy profile, which has been identified to be a function of the transformation degree ( α), since the energy demand at each degradation stage is different depending on α.

Oligothienyl catenated germanes and silanes: synthesis, structure, and properties

The synthesis of two new groups of oligothienyl catenated silanes and germanes, Me5M2Thn (1a-b), Me5M2ThnM2Me5 (2a-c) (terminal), and ThnM2Me4Thn (3a-d) (internal) (M = Si, Ge; n = 2, 3; Th = 2- or 2,5-thienyl), is reported. The study of their structural parameters as well as of their spectral (NMR), electrochemical (CV) and optical (UV/vis absorbance, luminescence) properties has been performed in detail; in addition, the unexpected compound [Th2Si2Me4Th]2 (3a') is also studied. Theoretical investigations have been performed for model compounds in order to establish structure-property relationships. The molecular structures of 2a (Me5Si2Th2Si2Me5), 2b (Me5Ge2Th2Ge2Me5), 3a (Th2Si2Me4Th2) and 3b (Th2Ge2Me4Th2) have been investigated by X-ray diffraction analysis. An effective conjugation with flattening of both Th planes in terminal 2a and 2b was observed. The main trends in the dependence of the optical and electrochemical properties on the structural parameters have been established. All of the compounds studied exhibit a strong emission within the 378-563 nm range, and the maximal quantum yield (up to 77%) is observed for the Si derivative 3a'. For the majority of the compounds, the quantum yields (20-30%) are significantly larger than for 2,2'-bi- and 2,2':5',5''-terthiophenes. Due to their good emission properties, these compounds could be used to develop new materials with specific spectral properties.

Highly heat resistant and thermo-oxidatively stable borosilane alkynyl hybrid polymers

A type of boron–silicon containing hybrid polymer with CC units (HBS) was prepared, and the effects of three different substituents on the properties of the polymers were studied.

Singlet Energy Migration along an Alternating Block Copolymer of Oligothiophene and Oligosilylene in Solution

The singlet excited-state properties of the block copolymers of oligothiophene and oligosilylene in solution were investigated with several fast spectroscopic methods. Time-resolved fluorescence measurements at room temperature and in a glassy matrix revealed that the singlet excited states of the block copolymers are deactivated accompanying structural changes of the polymer. It became clear from the transient absorption spectroscopy that the absorption peak of the singlet excited state shifted to the longer wavelength side compared to that of the corresponding oligothiophenes because of the sigma-pi conjugation of the oligothiophene and oligosilylene. The intersystem crossing process generating the triplet excited state was also revealed by the transient absorption spectroscopy. Energy migration along the polymer chain was revealed by the fluorescence anisotropy measurements. The time constant for the energy migration became faster as the size of the oligothiophene in the polymer repeating unit became shorter. From comparison with the Förster theory, the energy migration process was attributed to an incoherent hopping mechanism.