Synthesis,functionalization and crosslinking reactions of poly(silylenemethylene)s

Novel poly(silylenemethylene)s have been prepared by the ring‐opening polymerization of 1,3‐disilacyclobutanes followed by a protodesilylation reaction with triflic acid. The silicon–aryl bond cleavage could be controlled by using different leaving groups, for instance phenyl‐ and para‐anisyl substituents. The reactions of the triflate derivatives with organomagnesium compounds, LiAlH₄, amines or alcohols gave functional substituted poly(silylenemethylene)s. Hydrosilylation reactions or reductive coupling with potassium–graphite led to organosilicon network‐polymers, which may serve as suitable precursors for silicon carbide and Si/C/N‐based materials. The structures of the polymers were identified by nuclear magnetic resonance spectroscopy (²⁹Si, ¹³C, ¹H). Copyright © 1999 John Wiley & Sons, Ltd.     

Synthesis and functionalization of Poly[5,5′‐(silylene)‐2,2′‐dithienylene]s using silyl triflate intermediates†

Treatment of 5,5′‐dilithio‐2,2′‐dithiophene with (dimethylamino)methylsily bis(triflate)‐ or α, ω‐bis(triflate)‐substituted trisilanes gave poly[5,5′‐(silylene)‐2,2′‐dithienylene]s in high yields. The amino–silyl bond was cleaved selectively by triflic acid, leading to triflate‐substituted derivatives. Conversion of these compounds with nucleophiles gave other functionalized polymers. Platinum‐catalyzed hydrosilylation reactions between silicon–vinyl and silicon–hydrogen derivatives result in polymer networks which may serve as interesting preceramic materials. The structures of the polymers were proven by NMR spectroscopy (²⁹Si, ¹³C, ¹H). Results of thermal gravimetric analysis (TGA), UV spectrometry and conductivity measurements are given. Copyright © 1999 John Wiley & Sons, Ltd.     

Study on the cationic ring‐opening polymerization of 1,3‐dioxepane in the presence of organic acids

1,3‐Dioxepane was polymerized with triflic acid as an initiator in the presence of acetic acid (AA) and hexane diacid. The structure of the poly(1,3‐dioxepane) (polyDOP) obtained was characterized by ¹H NMR spectra and gel permeation chromatography. The molecular weights (MWs) were determined by vapor pressure osmometry. The results obtained in both systems were completely different from those in which low‐MW polyols were used as chain‐transfer agents. When the molar ratio of carboxylic acid to triflic acid was low, high‐MW polyDOP with a controlled MW and narrow MW distribution was obtained. The content of the ester group in the final product depended greatly on the molar ratio of AA to triflic acid. The polymerization mechanism is discussed. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1232–1240, 2000     

Synthesis of diblock copolymers containing poly(N‐vinylcarbazole) by reversible addition‐fragmentation chain transfer polymerization

The reversible addition‐fragmentation chain transfer (RAFT) polymerization of N‐vinylcarbazole (NVK) mediated by macromolecular xanthates was used to prepare three types of block copolymers containing poly(N‐vinylcarbazole) (PVK). Using a poly(ethylene glycol) monomethyl ether based xanthate ( PEG‐X ), the RAFT polymerization of NVK proceeded in a controlled way to afford a series of PEG‐b‐PVK with different PVK chain lengths. Successive RAFT polymerization of NVK and vinyl acetate (VAc) with a small molecule xanthate ( X1 ) as the chain transfer agent was tested to prepare PVK‐b‐PVAc. Though both monomers can be homopolymerized in a controlled manner with this xanthate, only by polymerizing NVK first could give well‐defined block copolymers. The xanthate groups in the end of PVK could be removed by radical‐induced reduction using tributylstannane, and PVK‐b‐PVA was obtained by further hydrolysis of PVK‐b‐PVAc under basic conditions. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Convenient approach to novel functional substituted and branched poly(silylenemethylenes)

Novel poly(silylenemethylenes) have been prepared by the ring-opening polymerization of 1,3-disilacyclobutanes followed by a protodesilylation reaction with triflic acid. The silicon–aryl bond cleavage could be controlled by using different leaving groups, for instance phenyl- and para-anisyl substituents. The reactions of the triflate derivatives with organomagnesium compounds, LiAlH₄, amines, or alcohols gave functional substituted poly(silylenemethylenes). Hydrosilylation reactions or reductive coupling with potassium–graphite led to organosilicon network–polymers, which may serve as suitable precursors for silicon carbide and Si/C/N-based materials. The structures of the polymers were identified by NMR spectroscopy (²⁹Si, ¹³C, ¹H). © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 725–735, 1998     

Organosilicon Polymers—Synthesis,Architecture, Reactivity and Applications

Tailoring of polysilanes with given architectures and reactivities is a great challenge in the field of SiC pre-ceramic polymers. This paper reviews recent polysilane and related copolymer synthesis reactions. It is shown that the Wurtz-type polymerization of dichloro-, trichloro- or tetrachloro-silanes, so far the most extensively studied, enables access to a large variety of architectures ranging from one- to three-dimensional (3D) topologies, and based on secondary >SiR₂, tertiary RSi(Si)₃ or quaternary Si(Si)₄ silicon units in the polymer backbone. These polysilanes usually present an intrinsic low reactivity, detrimental for fiber processing. Examples are given to illustrate how this reactivity can be increased by secondary substitution reactions, which create reactive entities that can favor further crosslinking reactions. Secondly a novel route involving heterogeneously catalyzed disproportionation of chloromethyldisilanes, developed in our laboratory, is reviewed which offers a direct access to polysilyne-type 3D architecture constituted by arrangements of fused rings. The Lewis-base catalyzed disproportionation mechanism is discussed and seems to involve donor-stabilized silylenes as key intermediates in the polymer formation process. The experimental results are supported by ab-initio quantum chemical calculations. Silylenes attack the Si sites of higher functionality causing a high regioselectivity for the exclusive formation of branched oligosilanes. The oligomers undergo thermally induced branching and crosslinking reactions leading to poly(chloromethylsilane)s. Obviously, there are analogies to the oligomer and polymer formation of the transition-metal complex catalyzed dehydropolymerzation of methyldisilanes. Poly(chloromethylsilane)s exhibit a high reactivity due to the presence of Si–Cl bonds. Disproportionation of chloromethyldisilanes in presence of olefins such as styrene provides promising polymer precursors for SiC fibers. Their rheological properties have been investigated for various styrene contents. The polymer fibers spun from melt are cured under ammonia, and then pyrolyzed to silicon carbide fibers, showing temperature resistance up to 1500 °C. © 1996 by John Wiley & Sons, Ltd.     

Synthesis of organic–inorganic chiral block poly(methylphenylsilane) functional polymers,and study of their optical and chiroptical properties

Polysilanes upon UV irradiation give rise to silyl macroradicals which are capable to initiate radical polymerization. Hence, chiral block functional polysilanes were synthesized by UV irradiation of poly(methylphenylsilane) (PMPS) with a vinyl chiral monomer, (R)‐N‐(1‐phenylethyl)methacrylamide (R‐NPEMAM). The synthesized copolymer samples were characterized by FTIR, NMR, and UV–vis spectroscopy. The number and weight average molecular weights of PMPS and synthesized chiral‐block‐PMPS were measured by GPC analysis. Two glass transition temperatures (T_g) of the synthesized materials clearly indicate the formation of chiral‐block‐PMPS copolymers. SEM analysis also indicated the synthesized organic–inorganic block copolymers. The optical and chiroptical properties of the synthesized materials were studied. The cotton effect is observed not only at 276 nm due to aromatic ring of the chiral monomer units but also at 325 nm which is associated with the Si–Si conjugation of PMPS block of synthesized functional polysilanes. Such tunable chirality may find potential application in optoelectronics. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3626–3634     

Ring-opening polymerization of strained cyclotetrasilanes as a new route towards well defined polysilylenes

Ring-opening polymerization of cyclic silanes is described as a new synthetic route to well defined high molecular weight polysilylenes (polysilanes). Strained cyclotetrasilanes with phenyl and methyl substituents at each Si atom in the four-membered ring are prepared by partial dephenylation of octaphenylcyclotetrasilane with triflic acid and the subsequent treatment with methylmagnesium bromide. Chemoselectivity, regioselectivity and stereoselectivity of monomer synthesis is discussed in detail. In addition to classic anionic initiators for the ring-opening process, new catalysts and initiators based on transition metals (Cu, Pd, Pt) are described. They provide much better control of the microstructure than systems with Li⁺ counterion.     

Synthesis and characterization of different poly(1‐vinylindole)s for photorefractive materials

The main goal of this research was to verify if some advantages could be obtained by the replacement of poly(1‐vinylcarbazole), a component commonly employed for organic photorefractive materials, with various polymers containing side‐chain heteroaromatic moieties. For this purpose, poly(1‐vinylpyrrole), poly(1‐vinylindole), and some methyl‐substituted compounds of poly(1‐vinylindole) were considered. The best conditions for both monomer synthesis and polymerization were found. A first possible advantage of the new polymeric substrates resided in the values of the glass‐transition temperature, which, as expected, was constantly lower than that of poly(1‐vinylcarbazole). This could lead to a material that requires the introduction of a lower quantity of plasticizer in the final photorefractive blend to display photorefractive behavior at room temperature. In addition, the verified higher electric dipole moments of the pyrrole and indole derivatives could improve the compatibility of the optically nonlinear component required in the system, typically an azo‐molecule, by increasing its solubility inside the blend. All the synthesized vinyl monomers and polymers gave clear spectroscopic evidence of the formation of charge‐transfer complexes with 2,4,7‐trinitrofluorenylidenmalonitrile, an efficient sensitizer for photoconductivity. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 253–262, 2001     

A highly photoconductive poly(vinylcarbazole)/2,4,7-trinitro-9-fluorenone Sol-Gel material that follows a classical charge-generation model

Highly photoconductive properties are reported for organic-inorganic hybrid sol-gel thin film materials composed of a classical poly(vinylcarbazole)/2,4,7-trinitro-9-fluorenone (PVK/TNF) polymeric mixture, entrapped in a SiO(2) matrix, whose pores have been chemically modified by organic functional groups. The highest photosensitivity obtained, 3.4 x 10(-10) cm Omega(-1) W(-1) at E 22 V microm(-)1, at the optimum molar ratio between the active components, TNF, PVK, and SiO(2), is in the range of the highest values ever reported for any PVK/TNF-based classical photoconductive material. It is demonstrated that the PVK/TNF-based sol-gel films follow Onsager's classical charge-generation model. The analysis of the photocurrent efficiency (Phi) of PVK/TNF-based sol-gel films by such a model provides the primary quantum yield of thermalized pair formation and the initial thermalized pair distance, phi(0) = 0.12 and r(0) = 66.1 Angstrom, respectively, for the optimized sample. As a result of Onsager's analysis, a notorious improvement of the photocurrent generation process was achieved for low TNF concentrations.     

Higher α‐olefin polymerizations catalyzed by rac‐Me2Si(1‐C5H2‐2‐CH3‐4‐tBu)2Zr(NMe2)2/Al(iBu)3/[Ph3C][B(C6F5)4]

Polymerizations of higher α‐olefins, 1‐pentene, 1‐hexene, 1‐octene, and 1‐decene were carried out at 30 °C in toluene by using highly isospecific rac‐Me₂Si(1‐C₅H₂‐2‐CH₃‐4‐^t Bu)₂Zr(NMe₂)₂ (rac‐1) compound in the presence of Al(iBu)₃/[CPh₃][B(C₆F₅)₄] as a cocatalyst formulation. Both the bulkiness of monomer and the lateral size of polymer influenced the activity of polymerization. The larger lateral of polymer chain opens the π‐ligand of active site wide and favors the insertion of monomer, while the large size of monomer inserts itself into polymer chain more difficultly due to the steric hindrance. Highly isotactic poly(α‐olefin)s of high molecular weight (MW) were produced. The MW decreased from polypropylene to poly(1‐hexene), and then increased from poly(1‐hexene) to poly(1‐decene). The isotacticity (as [mm] triad) of the polymer decreased with the increased lateral size in the order: poly(1‐pentene) > poly(1‐hexene) > poly(1‐octene) > poly(1‐decene). The similar dependence of the lateral size on the melting point of polymer was recorded by differential scanning calorimetry (DSC). ¹H NMR analysis showed that vinylidene group resulting from β‐H elimination and saturated methyl groups resulting from chain transfer to cocatalyst are the main end groups of polymer chain. The vinylidene and internal double bonds are also identified by Raman spectroscopy. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1687–1697, 2000     

Gas permeation properties of poly(silamine) membrane

The gas permeation characteristics of poly(silamine) membrane, which consists of alternating 3,3-dimethyl-3-silapentane and N,N′-diethylethylenediamine units in the main chain, were investigated. Though poly(silamine) shows high flexibility (glass transition temperature of −88°C), the gas permeabilities were much lower than those of other rubbery polymers such as poly(dimethylsiloxane) and natural rubber. The activation energies of diffusion in poly(silamine) were much higher than that of natural rubber. On the basis of these results, we propose a model such that the interaction between the Si atom and gas molecules (O₂ and N₂) prevents the free diffusion of the gas molecule in the poly(silamine) membrane. © 1997 John Wiley & Sons, Ltd.     

Electro‐induced oxidative polymerization of N‐vinylcarbazole

In this study, a novel procedure to increase the yield of the non‐crosslinked, photoconductive, white form of linear poly(N‐vinylcarbazole) (LPVCz) is reported. The yield of LPVCz is increased (up to 53%) by the addition of catalytic amounts of ceric ammonium nitrate as an oxidant during the electrochemical polymerization of N‐vinylcarbazole in a divided electrochemical cell. The concentration of Ce(IV) remained constant during the polymerization since Ce(III) is readily oxidized to Ce(IV) electrochemically. Since the electrochemical oxidation of Ce(III) to Ce(IV) took place simultaneously at the anode, the deposition of dark green crosslinked polyvinylcarbazole on the electrode surface, which hinders the formation of white LPVCz, can be prevented. The Fourier transform infrared, ultraviolet–visible and fluorescence spectra of white LPVCz showed that the structures of polymers are the same as those produced by conventional polymerization. Copyright © 1999 John Wiley & Sons, Ltd.     

Synthesis and characterization of four-armed poly(1,3-dioxepane) tetraol

A new four-armed poly(1,3-dioxepane) tetraol was prepared by cationic ring-opening polymerization of 1,3-dioxepane (DOP) in the presence of 6,6-bis(5-hydroxyl-2-oxapentyl)-4,8-dioxaundecanediol-1,11 (THA) with triflic acid(I) as initiator. The structure of the poly(DOP) tetraol obtained was characterized by ¹H and ¹³C NMR spectra. The molecular weights of the obtained tetraols were controlled by the mole ratio of DOP consumed to initial THA, and it was found that each macromolecule contains only one THA unit on the average. GPC studies showed that the cyclic oligomers in the products were negligible. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2347–2353, 1999     

Side-Chain Sulfonated Poly(arylene ether)s for Fuel Cell Applications

Summary: Poly(arylene ether sulfone)s of high molecular weight and narrow molecular weight distribution were obtained by melt polycondensation of 4,4′-difluorodiphenyl- sulfone and trimethylsilylethers of 4,4′-dihydroxydiphenylsulfone and phenylhydroquinone using CsF as catalyst. Although a block-like structure of the polymers could be expected from the course of reaction, only a single T_g ranging from 190 °C to 230 °C could be detected by DSC and which depended on the copolymer composition. Contrary to the sulfonation of similar poly(ether ether ketone)s the poly(arylene ether sulfone)s here reported were sulfonated both in the side chain and the main chain. Nonetheless the sulfonated poly(arylene ether sulfone)s showed high hydrolytic stability in water at 130 °C.     

Thermo‐responsive fluorescent micelles from amphiphilic A3B miktoarm star copolymers prepared via a combination of SET‐LRP and RAFT polymerization

A novel amphiphilic A₃B miktoarm star copolymer poly(N‐isopropylacrylamide)₃‐poly(N‐vinylcarbazole) ((PNIPAAM)₃(PVK)) was successfully synthesized by a combination of single‐electron transfer living radical polymerization (SET‐LRP) and reversible addition‐fragmentation chain transfer (RAFT) polymerization. First, the well‐defined three‐armed poly(N‐isopropylacrylamide) (PNIPAAM)₃ was prepared via SET‐LRP of N‐isopropylacrylamide in acetone at 25 °C using a tetrafunctional bromoxanthate iniferter (Xanthate‐Br₃) as the initiator and Cu(0)/PMDETA as a catalyst system. Secondly, the target amphiphilic A₃B miktoarm star copolymer ((PNIPAAM)₃(PVK)) was prepared via RAFT polymerization of N‐vinylcarbazole (NVC) employing (PNIPAAM)₃ as the macro‐RAFT agent. The architecture of the amphiphilic A₃B miktoarm star copolymers were characterized by GPC, ¹H‐NMR spectra. Furthermore, the fluorescence intensity of micelle increased with the temperature and had a good temperature reversibility, which was investigated by dynamic light scattering (DLS), fluorescent and UV‐vis spectra. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4268–4278, 2010     

Reactive blending of functional polysiloxanes with poly(butylene terephthalate): Clarification of reaction mechanisms and kinetics from a model compound study

We clarify the reaction mechanisms and kinetics in melt‐reacted blends consisting of functional polysiloxanes and poly(butylene terephthalate) (PBT) with a model compound study. As models for polysiloxanes, we have selected two monodisperse ω‐functionalized siloxane oligomers with Si? H and Si? vinyl moieties. To mimic PBT, we have chosen low molecular weight compounds representative for in‐chain and end‐functional groups of the polymer; ester, carboxylic acid, alcohol, and vinyl. Uncatalyzed and platinum‐catalyzed reactions have been performed in sealed vials. Reaction products have been characterized by gradient polymer elution chromatography, Fourier transform infrared spectroscopy, and size exclusion chromatography. PBT functional groups reactive toward functional siloxane oligomers at high temperatures in the presence and absence of a catalyst have been identified, and an estimate of relative reaction kinetics has been provided. We suggest reaction mechanisms compatible with our results and with literature data. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1952–1961, 2002     

Synthesis and properties of novel poly(arylene ether)s and poly(arylene thioether)s based on a pyridazine biphenol or a phthalazine biphenol

Novel sulfur‐containing biphenol monomers were prepared in high yields by the reaction of 4‐mercaptophenol with chloropyridazine or chlorophthalazine compounds. High‐molecular‐weight poly(arylene ether)s were synthesized by a nucleophilic substitution reaction between these sulfur‐containing monomers and activated difluoro aromatic compounds. The inherent viscosities of these polymers ranged from 0.34 to 0.93 dL/g. The poly(pyridazine)s exhibited glass‐transition temperatures greater than 165 °C. The poly(phthalazine)s showed higher glass‐transition temperatures than the poly(pyridazine)s. A polymer synthesized from a bisphthalazinebiphenol and bis(4‐fluorophenyl)sulfone had the highest glass‐transition temperature (240 °C). The thermal stabilities of the poly(pyridazine)s and poly(phthalazine)s showed similar patterns of decomposition, with no significant weight loss below 390 °C. The poly(phthalazine)s were soluble in chlorinated solvents such as chloroform, and the poly(pyridazine)s were soluble in dipolar aprotic solvents such as N,N′‐dimethylacetamide. The soluble poly(pyridazine)s and poly(phthalazine)s could be cast into flexible films from solution. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 262–268, 2007     

Thianthrene-containing polyimides with monomer formation via nucleophilic aromatic substitution

Thianthrene-2,3,7,8-tetracarboxylic dianhydride was synthesized via nucleophilic aromatic substitution of N-phenyle-4,5-dichlorophthalimide with thiobenzamide, thioacetamide, and sodium sulfide. This monomer was then polymerized with aromatic diamines by the con-ventional low temperature technique in N,N-dimethylacetamide (DMAc) to yield soluble poly(amic acid)s. Polyimides were obtained by thermal cyclization of the poly(amic acid) films. Polymers obtained formed creasable thin films and had excellent thermal stability in air and nitrogen. The bent thianthrene structure limited crystallization and chain packing, as indicated by x-ray analysis. The amorphous thianthrene-containing polyimides were only soluble in H₂SO₄. © 1995 John Wiley & Sons, Inc.     

Photoconductive Polysilanes Bearing Charge-photogenerating Groups Based on Carbazole. 1 Synthesis via the Reductive Coupling of Diorganodichlorosilanes with Sodium

In order to prepare photoconductive organic materials with high charge-photogenerating quantum yield and high charge-carrier mobility, it was attempted to synthesize (9-carbazolyl)methyldichlorosilane, 1a , methyl-3-(9-carbazolyl)propyldichlorosilane, 1b , and methyl-4-(9-carbazolyl)phenyldichlorosilane, 1c and to homo- and copolymerize them with classical diorganodichlorosilanes in a Wurtz-type polymerization with sodium in the presence of polar additives. 1b did not homo- or copolymerize in these conditions. Low molecular weight homopolymers and copolymers with dimethyldichlorosilane and methylphenyldichlorosilane were easily obtained with 1c . Side reactions involving the ring-opening of tetrahydrofuran (THF) and occurring in the reaction of the Grignard derivative of 9-(4-bromophenyl)carbazole and methyltrichlorosilane in THF did not allow the isolation of 1c in a pure form. © 1997 John Wiley & Sons, Ltd.