Polyhydrosilanes - New Materials with NLO Properties (original) (raw)
Related papers
Functional Polysilanes and their Optical, Chiroptical and Photoluminescence Properties
Current organocatalysis, 2019
'Polysilanes' is an important class of inorganic polymers having Si-Si σ-conjugation along the backbone. They exhibit extraordinary electronic and photophysical properties and find suitable optoelectronics applications. They are typically synthesized by Wurtz coupling reaction of dichlorodialkylsilane or dichlorodiphenylsilane or dichloroalkylphenylsilane and their combinations under drastic reaction conditions by using sodium dispersion in boiling toluene. In such a drastic condition, no functional groups sustain with polysilane polymer. In order to achieve such functional materials, researchers have been interested in synthesizing functional polysilane with a different functional group like a chiral group, azobenzene containing chromophore and other heteroatoms in their main chain or side chain. Therefore, it is a very challenging task to synthesize polysilanes having effective functionality integrated with their structures. However, the modern technological demand of materials leads to efforts to obtain polymers having functional and multifunctional activity in a single material. In this review article, we cover the synthesis of polysilane with functional activity via pre-polymerization and post-polymerization with a functional group.
Polysilanes. A New Route Toward High Performance EL Devices
Macromolecular Symposia, 2008
The discovery of a remarkable class of plastics that can conduct electricity has opened a new era of plastics science and technology that has just been recognized by the award of the 2000 Nobel prize for chemistry. They can be used to make a wide range of electronic devices such as transistors, light-emitting diodes, solar cells and even lasers, through much simpler manufacture than conventional inorganic materials, increasing flexibility, reducing cost, and opening up new markets. Polysilanes are subject of an intensive research work aiming to various optoelectronic applications. Through this work the chemical structure of polydiphenylsilane was modified to obtain both solubility in common solvents and to induce new properties by attaching of various organic segments.
Optical properties of polysilanes and related materials
Synthetic Metals, 1995
A review is given on our late experimental investigations on optical properties of polysilanes and related materials with various dimensions and networks. In particular, we argue the control of electronic structures by chemical moditication of Si/Ge polymer structure and compositions. We show some successful examples to achieve wavelength-tunable luminescence bands in polysilanes/polygermanes, network copolymers, and polymorphic octasilacubanes. 0379-6779/95/$09.50 0 1995 Elsevier Science S.A. All rights reserved SSDI 0379-6779(94)03139-W
Polysilanes - prototypical σ-conjugated polymers
Synthetic Metals - SYNTHET METAL, 1989
Polysilanes constitute the first examples of spa-bonded o-conjugated high polymers. Their spectroscopic and electronic properties are strongly reminiscent of those of the ~-conjugated polymers, but, unlike the ~-conjugated polymers, polysilanes are generally fully soluble and airstable. They exhibit molecular weight dependent mid-UV absorption which is polarized along the silicon backbone and strongly thermochromic. The fluorescent emission is narrowed relative to the absorption and vibrationally decoupled, indicative of a highly delocalized singlet state. Consistent with the o-electron delocalization, the materials are excellent non-dispersive photoconductors, dopable to 0.5 S/cm conductivities, and exhibit large 3rd order optical non-linearities. Their extreme photosensitivity endows some polysilanes with promise as photoresist materials.
Electronic structures of polysilanes and related compounds
Journal of Electron Spectroscopy and Related Phenomena, 1996
UPS and Si K-and LED-edge NEXAFS spectra of various polysilanes, poly(dimethylsiloxane), and octakis(fbutyl)octa-silacubane (OTBOSC) were measured for elucidating their occupied and vacant electronic structures, in comparison with the results for polysilazane. The results revealed that the electronic structures are sensitive for the main chain structure, pendant, and the dimensionality of the Si-containing backbone.
Synthesis and Photochromic Behavior of Azo-Polydiphenylsilanes
Journal of Inorganic and Organometallic Polymers and Materials, 2009
This work presents the influence of the trans–cis photoisomerization process of azobenzene-segments onto the optical properties of polysilanes. For this purpose 4-(phenyldiazenyl)phenol and 4-[(4′-nitrophenyl)diazenyl]phenol groups were attached to poly[diphenylsilane-co-methyl(bromopropyl)silane] using the Williamson etherification conditions. Photoisomerization of the pendant azo-groups by irradiation with 365 nm UV light induced distortion of the polysilane backbone conformation in a reversible manner. This process was studied by UV spectral analysis and the photochromic behavior of both polymers was established by taking into account the variation of the σ–σ* absorption intensity.
Polymer Journal, 2003
In the family of optically active synthetic polymers, optically active polysilanes, which comprise a helical main chain of silicon-silicon single bonds and chiral and/or achiral side groups, exhibit unique absorption, circular dichroism, and fluorescence spectra around 300-400 nm due to σ-conjugation. Since the first brief report of optically active polysilane synthesis in 1992, the field has now widened to include various homo-and copolymers of optically active poly(dialkylsilane)s, poly(dialkoxysilane)s, poly[alkyl(aryl)silane]s, and poly(diarylsilane)s. This review comprehensively covers work on (i) the relationship between side chain structure, (ii) local structure-global shape relationship, (iii) (chir)optical properties, (iv) (semi)quantitative population analysis of right-and left-handed helices based on Kuhn's dissymmetry ratio, (v) several helical cooperativity effects, (vi) molecular imaging, (vii) inversion of screw-sense, (viii) chiroptical switch and memory, (ix) transfer and amplification of molecular chirality to aggregates, (x) cholesteric liquid crystallinity, (xi) helical supramolecular structures, and (xii) latent helicity, as consequences of side group internal interactions and other external stimuli. Such knowledge and understanding may stimulate optically active polymer research in the realm of nanomaterial science and nanotechnology at the sub-nm level as well as traditional polymer science, and may advance these polymers to new functional nanomaterials and thence to the realization of nanodevices in the future.
Phosphorus, Sulfur, and Silicon and the Related Elements, 2019
This work deals with the effect of chemical structure and iodine doping on electro-optical characteristics of different polysilanes in the solid state. The properties of polymethylphenylsilane homopolymer were compared with those of polysilane copolymers containing diphenylsilylene structural units associated with either methylhydrogen-or methylphenylsilylene moieties. Their optical parameters, such as Urbach energy and optical band gap, were evaluated using the method proposed by Tauc. The forbidden gap values for the studied polysilanes are reduced after doping from 3.22-3.46 eV to 2.47-2.64 eV, while the electrical conductivities were found in the range of 6.2 10 À11-1.2 10 À8 S/cm for pristine samples, and increased by 2-3 orders of magnitude following their doping, depending on the nature/content of the organic substituents attached to the silicon main chain. A simple mathematical approach starting from Tauc classical theory was used to establish allowed direct optical transitions for both undoped and doped polysilane samples. The obtained data indicated that the polysilane films with a high content of phenyl side groups presented the best properties for their use in electro-optical applications.
Perylene polyphenylmethylsiloxanes for optoelectronic applications
Journal of Polymer Science Part B: Polymer Physics
The incorporation of fluorescent organic dyes in an encapsulating matrix represents a route to generate stable and processable materials for optoelectronic devices. Here, we present a method to embed perylene dyes into a high refractive index (HRI) polysiloxane matrix applying an allyl functionalized perylene dye and hydrosilylation chemistry. In a first approach, the dye molecules were covalently integrated into the backbone of linear polyphenylmethylsiloxane chains. The fluorescent and liquid polymers were synthesized with molecular weights from 5660 up to 8400 g mol −1. In a second approach, the dye itself was used as a cross-linking agent between linear polyphenylmethylsiloxane chains. These preformed fluorescent batch polymers are liquids with dye concentrations between 0.025 and 8 wt %. The applied synthetic methods incorporated the dye covalently into the polymer structure and avoided the crystallization of the dye molecules and thus the formation of excimers, which would reduce the optical emission. The resulting products can be easily incorporated into curable commercially available HRI polyphenylmethylsiloxane resins. The formed materials are ideal LED encapsulants with a solid and flexible consistency, a uniform dispersion of the dyes, and adjustable mechanical properties, realized by changing the amount of perylene polymers. Further properties of the obtained materials are thermal stabilities up to 478 C, quantum yields larger than 0.97, and high photostabilities. Thus, the covalent integration of dyes into polyphenylsiloxane structures represents a possible route for the stabilization of the organic dyes against the extreme irradiance and thermal conditions in LED applications.