Conductivities of polysilanes

Measurements of the electrical conductivities of three types of polysilanes were carried out over a range of dc fields and temperatures. These polymers are varied in substituents and structures with formulas of [C₆H₅SiCH₃]_n, [(C₆H₅SiCH₃)₇₀(CH₃SiH)₃₀]_n, and [(C₆H₅SiCH₃)₅₀(C₆H₅SiH)₃₀(CH₃Si)₂₀]_n. Undoped polysilanes behaved as insulators since their conductivities were observed in the range of 10⁻¹⁰ to 10⁻¹³ S cm⁻¹, while SbF₅-doped polysilanes of all kinds behaved as semiconductors with conductivities in the range of 10⁻² to 10⁻⁴ S cm⁻¹. No significant difference in conductivities was observed among three SbF₅-doped polysilanes although these polymers are very different in chemical properties. These experimental results suggest that electrical conductivities of polysilanes are associated with the Si Si main-chain backbone rather than with the side groups. It is evident that the dopant is able to diffuse throughout the bulk of the polymer and the conductivity of the doped polymer is a function of the dopant concentration from the result of in situ monitoring of the resistance of the silane homopolymer during SbF₅ doping at room temperature. The conductivities of polysilanes appeared to be temperature-dependent. The activation energy for the conduction of SbF₅-doped silane copolymer was found to change at its glass transition temperature. © 1996 John Wiley & Sons, Inc.     

Synthesis of terminal Si-H irregular tetra-branched star polysiloxanes. Pt-catalyzed hydrosilylation with unsaturated epoxides. Polysiloxane films by photo-acid catalyzed crosslinking

Acid catalyzed insertion of octamethylcyclotetrasiloxane (D₄) into the Si-O bonds of tetrakis(dimethylsiloxy)silane leads to irregular tetra-branched star polymers—tetrakis(ω-dimethylsiloxy)poly(dimethylsiloxy)silane (I). The terminal Si-H bonds of I have been modified by Pt-catalyzed hydrosilylation with 4-vinylcyclohexane-1,2-epoxide to yield a tetra-branched star polydimethylsiloxanes (PDMS) with terminal 2′-ethyl-4-cyclohexanyl-1,2-epoxide groups (II). Solutions of this material and a catalytic amounts of diaryl iodonium hexafluoroantimonate, a photo-acid catalyst, were cast onto glass slides and subsequently irradiated. This results in formation of crosslinked PDMS films (V). The soluble tetra-branched PDMS stars have been characterized by ¹H, ¹³C, and ²⁹Si NMR as well as by IR spectroscopy. Their molecular weight distributions have been determined by gel permeation chromatography (GPC), multi-angle laser light scattering (MALLS), and end groups analysis. Their viscosities were measured with a Brookfield viscometer. The thermal stability of the polymers and the crosslinked films were determined by TGA. The glass transition temperatures (T_g)s of the polymers were determined by DSC. The loss (G″) and storage (G′) shear moduli of the films were determined by DMTA. Surface properties of the films were determined by measurement of static contact angles.Similar star polymers, tetrakis(dimethylsiloxy)poly[3′,3′,3′-trifluoropropylmethylsiloxyl]silanes (III) were prepared by acid catalyzed equilibration of tetrakis(dimethylsiloxy)silane with 1,3,5-trimethyl-1,3,5-tris(3′,3′,3′-trifluoropropyl)cyclotrisiloxanes (D₃^F). These were, likewise, modified by Pt-catalyzed hydrosilylation with 4-vinylcyclohexane-1,2-epoxide. Films (VI) of this material were similarly prepared by photo-acid catalyzed crosslinking.     

Substituent effect on the optoelectronic properties of poly(p‐phenylenevinylene) based conjugated‐nonconjugated copolymers

Two classes of light emitting Poly(p‐phenylenevinylene) (PPV) based conjugated‐nonconjugated copolymers (CNCPs) have been synthesized. The conjugated chromophores containing 2‐methoxy‐5‐(2′‐ethylhexyloxy)‐1,4‐phenylenevinylene (MEHPV) and 2,5‐dimethyl‐1,4‐phenylenevinylene (DMPV) moieties are rigid segments and nonconjugated portion containing hexyl units are flexible in nature. All copolymers were synthesized by well‐known Wittig reaction between the appropriate bisphosphonium salts and the dialdehyde monomers. The resulting polymers were found to be readily soluble in common organic solvents like chloroform, THF and chlorobenzene. The effect of chromophore substituents on the optical and redox properties of the copolymers has been investigated. Color tuning was carried out by varying the molar percentage of the comonomers. The UV‐Vis absorption and PL emission of the copolymers were in the range 314–395 nm and 494–536 nm respectively. All the polymers show good thermal stability. Polymer light‐emitting diodes (PLEDs) were fabricated in ITO/PEDOT:PSS/emitting polymer/cathode configurations of selected polymers using double‐layer, LiF/Al cathode structure. The emission maxima of the polymers were around 499–536 nm, which is a blue‐green part of the color spectrum. The threshold voltages of the EL polymers were in the range of 5.4–6.2 V. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Syntheses of polysilanes having cyclodisilazane units in the backbone

Summary Polysilanes containing cyclodisilazane units in the backbone were synthesized by the modified Wurtz-type coupling of available dichlorosilanes with N,N-bis (chlorodimethylsilyl)tetramethylcyclodisilazane in the mixture of solvents. The effect of solvent additives on the polymerization process was examined. These polymers are soluble in common solvents and very easily handled by molding or casting.     

TPA‐PPEs – New alternating donor copolymers for potential application in photovoltaic devices

A series of phenyleneethynylene copolymers with triphenylamine units as hole‐transporting moieties (TPA‐PPEs) were synthesized by the palladium‐catalyzed cross‐coupling polycondensation of diethynyltriphenylamines and selected dihalogen comonomers, for instance substituted benzene, thiophene, benzothiadiazole, or anthracene. Incorporation of the electron‐rich amino group into the PPE backbone does not interrupt the main chain conjugation. Furthermore, it has a decreasing effect on the oxidation potential, thus makes these polymers interesting as hole‐injection/hole‐transporting materials. The chemical structure of the new alternating copolymers was confirmed by ¹H and ¹³C NMR spectroscopy and elemental analysis and gel‐permeation chromatography (GPC; THF, M_n ≈ 15,000–30,000 g/mol) was conducted. Furthermore, their optical properties were investigated by UV/vis spectroscopy. The TPA‐PPEs exhibit absorption maxima at around 400 nm (π‐π*), except anthracene containing copolymer 3f (λ_max = 514 nm in THF) and benzothiadiazole containing one 3g (λ_max = 503 nm in THF). The TPA copolymers have oxidation potentials about 1.1 V (Ag/AgCl). They are good photoconducting materials ( 3a : I_Photo = 4 × 10^?10 A at 425 nm (400 V), 3g : I_Photo = 1.3 × 10^?11 A at λ_max = 500 nm (20 V)) and show emission after excitation at around 450 nm (560 nm 3f ). Their application in nonoptimized polymer solar cells (bulk heterojunction) led to power conversion efficiencies of around 1–1.8% after illumination with 100 mW/cm² of AM1.5. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

支化型有机硅/丙烯酸酯共聚乳液的合成及其性能

采用种子半连续乳液聚合,以γ-甲基丙烯酰氧基丙基三甲氧基硅烷(MPS)为交联单体,以具有支化型大体积疏水基团的有机硅单体γ-甲基丙烯酰氧基丙基三(三甲基硅氧基)硅烷(MATS)为功能单体,与丙烯酸丁酯和甲基丙烯酸甲酯进行乳液共聚,合成了稳定的交联型高硅含量硅丙乳液。对乳液聚合过程及聚合物膜性能的测试结果表明,随聚合体系中MATS用量由0增加到占单体总质量的10%,乳胶粒子的z-均粒径(Dz)由133.5 nm减小到123.7 nm,粒径多分散指数由1.150减小为1.131;聚合物膜的水表面接触角由61°增大到78,°48 h吸水率由5.9%降低为2.5%。     

Synthesis and Photochromic Behavior of Azo-Polydiphenylsilanes

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.     

Thermal degradation of polymers. XIV. Thermal analysis studies in air on homopolymers of m-N,N-dimethylaminostyrene and p-N,N-diethylaminostyrene and their copolymers with styrene

Homopolymers of m-N,N-diethylaminostyrene and p-N,N-diethylaminostyrene and their copolymers with styrene have been subjected to thermal analysis studies in air. Molecular weight and copolymer composition have been shown to influence the stability of the polymers and the shape of the TG and DSC curves in the case of polymers containing m-N,N-dimethylaminostyrene. Polymers containing p-N,N-diethylaminostyrene show TG and DSC curves essentially independent of molecular weight and copolymer composition. The behavior of the two systems is discussed in terms of the antioxidant effect of the chain-bound N,N-dialkylamino substituents and their secondary reactions.     

Amphiphilic block copolymers with pendant thiol groups in side chains by RAFT polymerization

A new synthetic approach to thiol functional, well-defined amphiphilic block copolymers, which can be used to prepare multifunctional polymers and polymeric nanoparticles, is presented. Starting with a hydrophilic macroRAFT transfer agent and hydrophobic (meth)acrylate monomers that possess protected thiol groups, amphiphilic block copolymers are prepared in high yield. It is proven that the protected thiol groups in the monomer do not interfere with the RAFT polymerization process. Polymers with defined molecular weight, narrow polydispersities (PDI < 1.30) and varying length of the hydrophobic block are presented. Polymers with thiol groups in side chains and chain ends are obtained by aminolysis. With pyrene fluorescence spectroscopy and NMR measurements, it is shown that all synthesized polymers self-assemble into micelles. Furthermore, the possible application of these new polymers is exemplified by the preparation of polymer nanoparticles.     

Water‐soluble aldehyde‐bearing polymers of 2‐deoxy‐2‐methacrylamido‐D‐glucose for bone tissue engineering

In this study the methods of synthesis of hydrophilic aldehyde‐bearing polymers and copolymers based on 2‐deoxy‐2‐methacrylamido‐D ‐glucose have been developed. Polymers with controllable aldehyde group content were synthesized via free‐radical polymerization and subsequent polymeranalogous modification. The water‐soluble polymers obtained were investigated in view of their capacity to be adsorbed on two commercial mineral supports used in bone tissue engineering. Besides, cytotoxicity of synthesized polymers was tested. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

含咔唑基聚合物的合成、发光性能及应用

采用封管聚合法合成了3种含咔唑基聚合物——聚乙烯基咔唑(PVK)、聚2-(9-咔唑基)乙基甲基丙烯酸酯(PCEM)和聚N-〔3-(9-乙基咔唑基)〕甲基丙烯酰胺(PECMA),考察了其紫外光谱和荧光光谱,探讨了取代基对咔唑基团发光性能的影响。结果表明,单体CEM和ECMA表现出明显的结构自猝灭效应(SSQE),而相应的聚合物未见SSQE。单体乙烯基咔唑(NVK)、CEM的荧光最大发射波长分别为440、435 nm,相对于咔唑(418nm)有明显的红移,ECMA则蓝移(410 nm),而相应的聚合物红移或蓝移都不明显。将聚合物作为空穴传输材料,通过共聚引入8-羟基喹啉铝高分子后,8-羟基喹啉铝高分子发光材料的电致发光起亮电压由14 V下降至9V,发光效率提高了3~4倍。     

Heterocyclic polyimides containing siloxane groups in the main chain

BACKGROUND: Among the polymers widely studied for applications in advanced techniques, aromatic polyimides have received considerable attention due to their outstanding thermal stability associated with good electrical and mechanical properties. However, these polymers are usually difficult to process, being insoluble and without a glass transition. To improve the processing characteristics of polyimides, modification of their structure is often achieved by the introduction of flexible linkages in the macromolecular chain or various substituents on the aromatic rings. RESULTS: A series of polyimides and intermediate polyamidic acids were synthesized from aromatic oxadiazole‐diamines and a dianhydride containing a siloxane bridge (? R₂Si? O? SiR₂? ). These polymers exhibit good solubility in certain organic solvents and can be cast into thin and very thin films from their solutions. They exhibit high thermal stability with decomposition being above 440 °C and relatively low glass transition temperatures in the range 160–190 °C. These polymers show strong photoluminescence in the blue spectral region. CONCLUSION: The introduction of oxadiazole rings together with siloxane groups into the chains of aromatic polyimides gives highly thermostable polymers with remarkable solubility and film‐forming ability and that emit blue light, being attractive for applications in micro‐ and nanoelectronics and other related advanced fields. Copyright © 2009 Society of Chemical Industry     

The influence of monomer ratios on the properties of copolymers of 3,3′-spirobiphthalide and bisphenol A diglycidyl ether

Summary A spirobislactone, 3,3-spirobiphthalide (SBP), has been copolymerized with the diglycidyl ether of bisphenol A (DGEBA), and the properties of the products have been evaluated and related to the proportion (1–15%) of SBP monomer used. Polymers were characterized by infrared spectral analysis,¹³C NMR, thermal analysis, and mechanical testing. Polymers containing SBP have lower glass transition temperatures and higher decomposition temperatures than DGEBA polymers cured with phthalic anhydride (PA). Materials with higher SBP content have higher T_alpha values. Mechanical properties of the SBP copolymers are similar to those of DGEBA-PA polymers.     

π-Conjugated soluble palladium poly-ynes: Synthesis and fluorescence properties

Insertion of thiophene-2,5-diyl, or 1,4-phenylene into palladium poly-ynes by the polycondensation of dihalide complexes PdCl₂(PR₃)₂ (R = Ph o γ n-butyl) with a di-yne monomer (obtained from the reaction of equimolar quantities of p-diethynyl-benzene with 2,5-diiodothiophene or 1,4-diiodobenzene) affords a series of palladium poly-ynes 1–6. The polymers/oligomers, soluble in common organic solvents, exhibit strong fluorescence at the excitation of UV-visible light at room temperature. The emission intensity of the polymers/oligomers with thiophene-2,5-diyl is 3–17 times stronger than that of the analogous polymers without thiophene-2,5-diyl. Polymers with phenyl substituted phosphine ligands emit stronger emission than those only with n-butyl phosphine ligands. The effects of molecular weight, ligands, solvents, and concentration on the fluorescence properties are also investigated. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 1657–1665, 1997     

Synthesis and monomer reactivity ratio of cobalt‐containing hybrid polysilanes

Dichloromethylsilylcobaltcarbonyl (DCMSC) was synthesized by the reaction of dichloromethylsilane (DCMS) with dicobaltoctacarbonyl (DCOC) and used to prepare metal‐containing polysilanes. Copolymers of DCMSC with dichlorodimethyl‐ (DCDMS), dichlorodiethyl‐ (DCDES), dichloromethylphenyl‐ (DCMPS) silane were obtained using reductive coupling polymerization. The molecular weight of the copolymers increased regularly in the initial stage of the reaction but approached equilibrium values as the reaction proceeded. Depending on the monomer reactivity ratios, copolymers 2, 3 and 4 could have either alternating or block‐like copolymer structures. Increasing amounts of carbons in the side‐chain of the copolymers leads to block‐like composition. Copyright © 2005 Society of Chemical Industry     

Depolymerization protocol for linear,branched, and crosslinked end‐of‐life silicones with boron trifluoride diethyl etherate as the depolymerization reagent

An important issue for current society is the accumulation of large amounts of end‐of‐life polymers, which are mainly deposited in landfills, converted by thermal recycling or down cycling to low‐quality materials. In contrast to that, the feedstock recycling of end‐of‐life polymers to produce new high‐quality polymers is only applied to a small portion of waste. In more detail, low‐molecular weight chemicals are generated by this methodology; they can be polymerized in a second step to produce new high‐quality polymers. Notably, with these depolymerization‐polymerization processes, contributions to a more sustainable, resource‐conserving, and environmentally benign society can be made. In this regard, we have set up a capable protocol for the depolymerization of polysiloxanes, which are applied extensively in numerous technological applications. Boron trifluoride diethyl etherate was used as a depolymerization reagent to transform Si? O bonds in linear, branched, and crosslinked silicones to Si? F bonds. As depolymerization products, difluorodimethyl silane for linear polysiloxanes and methyl trifluorosilane for branched polysiloxanes were obtained; these were suitable synthons for new polymers and will allow an overall recycling of polysiloxanes. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42814.     

A new type of precursor for fibers in the system Si–C

Ceramic fibers with compositions in the system Si–C have a great potential for high-temperature applications. In recent years, our efforts have been dedicated to the development of polymers consisting of polysilanes suitable to spin fibers and build up matrices for CMC as well. The polysilanes are synthesized via disproportionation of the so-called disilane fraction [Richter, R., Roewer, G., Böhme, U., Busch, K., Babonneau, F., Martin, H.-P. et al., Appl. Organomet. Chem., 1997, 11, 71 (and references cited therein)]. A further thermal treatment yields materials which are soluble in organic solvents, and these solutions can be dry-spun to give fibers which are subsequently pyrolyzed. Solubility and high ceramic yield make this precursor a promising candidate for matrix infiltrations, too. The chemistry and the adjustment of viscosity and solubility to the requirements of the fiber processing as well as the conversion of the dried fibers to pure SiC fibers by thermal treatment will be reported.     

Homopolymerization and copolymerization of phenyltrichlorosilane by sonochemical reductive coupling in the presence of sodium

Summary Soluble polymers have been prepared by the sonochemical reductive coupling of phenyltrichlorosilane in toluene in the presence of sodium. Copolymers of phenyltrichlorosilane with phenylmethyldi-chlorosilane were synthesized. The obtained products are of relatively low molecular weight (ˉM_n<10,000). Investigations by ²⁹ Si NMR, UV and by the kinetic studies of the iodine addition indicate that polymers consist of fused cyclopolysilanes with 40% content of strained rings (probably four-membered). Homopolymerization and copolymerization of n-hexyl-trichlorosilane and methyltrichlorosilane is compared with that of phenyltrichlorosilane. The former monomer yields soluble homopolymer and copolymers of relatively higher molecular weights than phenyltrichlorosilane. Methyltrichlorosilane yields usually insoluble products and only at a concentration below 20%, were soluble copolymers formed.     

Chemically Cross-linked Polysilanes as Stable Polymer Precursors for Conversion to Silicon Carbide

Cross-linked polysilanes were prepared by the co-polymerization of Me₂SiCl₂ or PhMeSiCl₂ with varying amounts of divinylbenzene (2–15% by weight) using molten sodium as the dehalogenating agent. All the cross-linked polysilanes were stable to air and could be processed thermally for conversion to silicon carbide. Polymers containing from 5–15% of the cross-linking agent underwent a uniform shrinkage during thermal treatment (1500 °C) to afford β-SiC in good yields. The ceramic was characterized by a variety of techniques including Raman and infrared spectroscopy, powder XRD, as well as Scanning Electron Microscopy (SEM). Dedicated to Prof. C. W. Allen in recognition of his outstanding contributions to inorganic polymers. Deceased in a tragic car accident in July 2004.     

Synthesis and characterization of the novel inimer-containing fluorene units and preparation of blue light-emitting polymers

The novel inimer-containing fluorene units was successfully synthesized and characterized. Hyperbranched homopolymer and copolymers with methyl methacrylate (MMA) were prepared by the novel inimer via atom transfer radical polymerization where CuBr/1,1,4,7,10,10-hexamethyltriethylenetetramine (HMTETA) were used as catalyst. The copolymerization of inimer and MMA was performed under different ratio of the initial inimer/MMA and the inimer acted as not only the branched point (BP) but also the functional groups which emit blue light. The number-average molecular weight (M _n) and polydispersity index (PDI) of polymers are in the ranges (3.6–18.4) × 10³ and (1.3–2.8), respectively. Thermal gravimetric analysis (TGA) results showed all polymers had good thermal stabilities. The number of the inimers acted as branched point in the copolymer backbone is estimated by ¹H NMR spectra and UV–Vis absorption spectra.