Multifunctional materials based on polyazomethines derived from 2,5‐dihydroxy‐1,4‐benzoquinone and siloxane diamines

New polyazomethines have been synthesized by the reaction between 2,5‐dihydroxy‐1,4‐benzoquinone and siloxane diamines differing by the siloxane sequence length. A dimer has also been prepared as a model compound. The products were characterized by spectral (FTIR and ¹H‐NMR) and elemental analyses, GPC, viscosity measurements, solubility tests, and transmission electron microscopy (TEM). The different properties have been investigated by adequate techniques: thermal (DSC and TGA), spectral (UV–vis and fluorescence spectroscopy), redox (Differential Pulse Voltammetry). pH‐sensitivity and metal complexing ability were also evaluated. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1862–1872, 2008     

1,4-bis(3-aminopropyl)piperazine libraries: from the discovery of classical chloroquine-like antimalarials to the identification of new targets

The purpose of this review is to provide an update on our work based on the 1,4-bis(3-aminopropyl)piperazine skeleton and how it allowed our group to validate a new target. After a brief introduction where we will relate the way this substructure was introduced in our 4-aminoquinolinyl derivatives, we will present first the different libraries synthesized around this moiety: (1) libraries of sulfonamides, amides and amines derived from 4-aminoquinolines and, (2) libraries where the 4-aminoquinoline nucleus is replaced. High throughput evaluation of biological activity and physicochemical parameters will be presented. The evaluation of the anti-malarial activity of the compounds will be discussed in the light of a chloroquine-like mechanism (accumulation in the acidic food vacuole and inhibition of beta-hematin formation). In a second part we will present active 1,4-bis(3-aminopropyl)piperazine as tools for identification and/or validation of new antimalarial targets. Fluorescence assays on some derivatives show that they are surprisingly localized outside the food vacuole, suggesting the existence of other target(s). Secondly, we will present a library of 1,4-bis(3-aminopropyl)piperazine as inhibitors of the cytosolic aminopeptidase Pfa-M1, a new potential target for antimalarials.     

Bridged Polysilsesquioxane Xerogels Functionalizated by Amine- and Thiol- Groups: Synthesis, Structure, Adsorption Properties

Bridged polysilsesquioxane xerogels containing amine (–NH₂; –NH(CH₂)₂NH₂; —NH) and thiol (–SH) groups were synthesized by hydrolytic polycondensation of 1,2-bis(triethoxysilyl)ethane, 1,4-bis(triethoxysilyl)benzene and appropriate trifunctionalized silanes in the presence of a fluoride-ion catalyst in an ethanol solution. ²⁹Si CP/MAS NMR give indication of the molecular framework of these materials formed by structural T¹, T² and T³ units. 3-aminopropyl or 3-mercaptopropyl groups accessible to proton or metal ions are fixed to the xerogel surface by the siloxane bonds. IR and ¹³C CP/MAS NMR data clearly show that 3-aminopropyl groups form hydrogen bonds. The same data testify that all xerogels contain non-condensed silanol groups and some fraction of non-hydrolyzed ethoxygroups. Functionalized polysilsesquioxane xerogels obtained by means of organic spacers have a porous structure (500–1000 m²/g) and a high content of functional groups (1.0–2.7 mmol/g). AFM data indicate that xerogels are formed by aggregating primary particles—the size of such aggregates is in the range 30–65 nm. It was established that the main factors influencing the structure and adsorption properties considered hybrid materials are: the nature and geometrical size of the functional groups, spacer flexibility and, in some cases, the ratio of the reacting alkoxysilanes and the ageing time of the gel.     

Exactly alternating silarylene–siloxane polymers. II. The condensation polymerization of arylenedisilanols and bisureidosilanes

A new method for the preparation of exactly alternating silarylene–siloxane polymers by the low temperature step-growth condensation polymerization reaction of arylenedisilanols and bisurei-dosilanes in chlorobenzene was investigated. To obtain high molecular weight products ¹H NMR spectroscopy and gel permeation chromatography were used to monitor the polymerization reaction. By using these procedures 12 different polymers were prepared from 1,4-bis(dimethylhydroxysilyl)-benzene, 4,4′-bis(dimethylhydroxysilyl)phenyl ether, bis(1,1-tetramethylene-3-phenylureido)-dimethylsilane, and bis(1,1-tetramethylene-3-phenylureido)-methylvinylsilane monomers. The polymers were obtained in high yields, purities, and molecular weights.     

Synthesis of amphiphilic polysiloxanes and their properties for formation of nano-aggregates

In this study, we prepared amphiphilic polysiloxanes by introduction of hydrophobic and hydrophilic parts into a water-soluble poly(3-aminopropyl)siloxane. Fatty acid (lauroyl, myristoyl, palmitoyl, and stearoyl) chlorides and gluconolactone were employed as the reactants for the hydrophobic and hydrophilic parts, respectively. The reaction of the poly(3-aminopropyl)siloxane with fatty acid chlorides was performed in water/DMF, followed by the reaction with gluconolactone in DMSO, giving the corresponding amphiphilic polysiloxanes. The results of the NMR spectra, SEM observations, and DLS measurements indicated the formation of nano-aggregates from the amphiphilic polysiloxanes in water. These analytical data also suggested that the structures and functionalities of the hydrophobic parts affected the formation properties of the nano-aggregates.     

Synthesis and characterization of imide ring and siloxane-containing cycloaliphatic epoxy resins

A novel imide ring and siloxane-containing cycloaliphatic epoxy compound 1,3-bis[3-(4,5-epoxy-1,2,3,6-tetrahydrophthalimido)propyl]tetramethyldisiloxane (BISE) was synthesized from 1,3-bis(3-aminopropyl)tetramethyldisiloxane and tetrahydrophthalic anhydride by a two-step procedure, which was then thermally cured with alicyclic anhydrides hexahydro-4-methylphthalic anhydride (HMPA) and hexahydrophthalic anhydride (HHPA), respectively. As comparison, a commercial available cycloaliphatic epoxy 3,4-epoxycyclohexylmethyl-3′,4′-epoxycyclohexane carboxylate (ERL-4221) cured with the same curing agents was also investigated. The experimental results indicated that the BISE gave the exothermic starting temperature higher than ERL-4221 no mater what kind of curing agents applied, implying the reactivity of the former is lower than the latter. The fully cured BISE epoxy resins have good thermal stability with thermal decomposition temperature at 5% weight loss of 346-348 °C in nitrogen, although they gave the relatively low glass transition temperatures due to the presence of flexible propyl and siloxane segments in the epoxy backbone. The BISE epoxy resins exhibited good mechanical and dielectric properties as well as low water absorption. The improved dielectric properties and the reduced water absorption of BISE epoxy resins are attributed to the low polarity as well as the hydrophobic nature of siloxane segment in the epoxy backbone.     

Synthesis and characterization of water-soluble poly(p-phenylene vinylene) derivatives via the dithiocarbamate precursor route

Two hydrophilic branched oligo(ethylene glycol)-substituted PPV derivatives, poly(2,5-bis(1,3-bis(triethoxymethoxy)propan-2-yloxy)-1,4-phenylene vinylene) (BTEMP-PPV) and poly(2-methoxy-5-(1,3-bis(triethoxymethoxy)propan-2-yloxy)-1,4-phenylene vinylene) (MTEMP-PPV), are presented. Polymerizations have been performed via the dithiocarbamate precursor route, using lithium hexamethyldisilazide (LHMDS) as a base, to obtain high molecular weight precursor polymers. After thermal conversion of the precursor polymers into the fully conjugated systems, the solubility of the polymers has been examined. The polar nonionic side chains of MTEMP-PPV and BTEMP-PPV render the PPV backbone soluble in a variety of solvents, including alcohols and even water, making these polymers suitable candidates to be used in optoelectronic devices that can be processed from environmentally friendly solvent systems.     

Synthesis, structures and membrane properties of siloxane-imide co-polymers produced by aqueous polymerization

We report for the first time, the synthesis of siloxane-imide co-polymers by the reaction of mixtures of 1,4-bis(aminobutyl)tetramethyldisiloxane (ABTMDS) and 1,3-bis(4-aminophenoxy)benzene (TPE-R) with bisphenol A diphthalic anhydride (BPADA) using water as the polymerization solvent. A series of co-polymers were prepared incorporating 10, 20, 40 and 100 mol% of ABTMDS with the aromatic diamine TPE-R as the co-monomer. The synthesized co-polymers showed number average molecular weights in the range of 25,000–60,000. As expected the glass transition temperatures (T_gs) and moduli of the polymers were found to decrease with increasing amounts of the siloxane monomer and the homo-polymer containing only the siloxane diamine showing the lowest T_g (60 °C). The resulting polymers could be solution cast into strong and flexible membranes which showed significant decreases in water absorption and moisture permeability compared to the control polymer without siloxane groups. The polymers were characterized by FTIR, ¹³C and ¹H NMR, GPC, DSC and mechanical properties and structural comparisons were made with similar polymers made by standard solvent synthesis methods. Also cross-linked polymers were prepared by the reaction of ABTMDS with the aromatic homo-polymer control and their membrane properties were compared to those of the water synthesized siloxane co-polymers with a similar siloxane content.     

Synthesis of siloxane-based PAMAM dendrimers and luminescent properties of their lanthanide complexes

The 0.5-2 generations of siloxane-based PAMAM dendrimers with 1, 3-bis(3-aminopropyl) tetramethyldisiloxane (G0) as core unit were synthesized by two different methods. Their structures were characterized by FTIR, ¹H NMR, ¹³C NMR, LC/MS, TGA, and DSC. Results show that method two is more suitable as its synthetic procedure is simple and it provides higher yield than method one. DSC analysis indicates that the introduction of the siloxane linkage into the interior of the dendrimers has significant effect on the flexibility of the dendrimer structures. Lanthanide complexes of the newly designed siloxane-based PAMAM dendrimers were obtained by complexing with Eu(III) and Tb(III), respectively. The luminescent properties of the complexes in the solution were investigated. Narrow-width red and green emissions were observed from the complexes of G0.5, G1.5, and G2.0, indicating intramolecular energy transfer process takes place between ligands and lanthanide ions.     

High‐temperature elastomers from silarylene‐siloxane‐diacetylene linear polymers

The syntheses and characterization of linear silarylene‐siloxane‐diacetylene polymers 3a–c and their thermal conversion to crosslinked elastomeric materials 4a–c are discussed. Inclusion of the diacetylene unit required synthesis of an appropriate monomeric species. 1,4‐Bis(dimethylaminodimethylsilyl)butadiyne [(CH₃)₂N? Si(CH₃)₂? C?C? C?C? (CH₃)₂Si? N(CH₃)₂] 2 was prepared from 1,4‐dilithio‐1,3‐butadiyne and 2 equiv of dimethylaminodimethylchlorosilane. The linear polymers were prepared via polycondensation of 2 with a series of disilanol prepolymers. The low molecular weight silarylene‐siloxane prepolymers 1a–c (terminated by hydroxyl groups) were synthesized via solution condensation of an excess amount of 1,4‐bis(hydroxydimethylsilyl)benzene with bis(dimethylamino)dimethylsilane. The linear polymers were characterized by ¹H and ¹³C NMR, Fourier transform infrared spectroscopy, gel permeation chromatography, thermogravimetric analysis (TGA), and DSC. The elastomers exhibited long‐term oxidative stability up to 330 °C in air as determined by TGA. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 88–94, 2002     

Reactivity of Iminophosphoranes. Formation of the Piperazine Ring

Reaction of 3-azidopropyl methanesulfonate with triphenylphosphine produced the 1,4-bis(triphenyl-phosphino)piperazine 5 by intermolecular cyclization, instead of formation azidine derivatives by an intramolecular pathway. Structural formulation of 5 was achieved by both spectral and X-ray crystal analysis. Hydrolysis of 5 under basic condition gives piperazine, whereas reaction of lithium diphenylphosphide with 5 produced 1,2-bis(diphenyl-phosphino)ethane (dppe) exclusively.     

Synthesis of π-conjugated poly(arylene)s by polycondensation of 1,4-bis(3-methylpyridin-2-yl)benzene and aryl dibromides through regiospecific C-H functionalization process

On the basis of the Ru-catalyzed regiospecific direct double arylation of benzene rings possessing 3-methylpyridin-2-yl substituents to produce 1-aryl-2-(3-methylpyridin-2-yl)benzene derivatives, the synthesis of poly(p-phenylene) derivatives having 2,5-bis(3-methylpyridin-2-yl) substituents is described. The reaction of 1,4-bis(3-methylpyridin-2-yl)benzene with bromobenzene (2 equiv) was carried out in the presence of [RuCl₂(η⁶-C₆H₆)]₂ (5 mol %) in 1-methyl-2-pyrrolidone at 120°C for 24 h to produce 1,4-bis(3-methylpyridin-2-yl)-2,5-diphenylbenzene in 99% yield as a sole product. Neither 2,6-diphenylated nor further phenylated products was produced under the examined conditions. This regiospecific double arylation process was then applied to the synthesis of π-conjugated polymers by use of aryl dibromides such as 1,4-dibromobenzene, 2,7-dibromo-9,9-dihexylfluorene, and 2,5-dibromothiophene. For example, a polymer was obtained in 73% yield by using 1,4-dibromobenzene, whose M_n and M_w/M_n were estimated to be 3300 and 1.51, respectively. The bathochromic shift of the ultraviolet (UV)–visible absorption spectrum with respect to that of the model compound, 1,4-bis(3-methylpyridin-2-yl)-2,5-diphenylbenzene, indicated the extension of the π-conjugation. The blue fluorescence was also observed for the polymer upon the UV irradiation. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 2771–2777     

Polymers from siloxane-containing epoxides

The synthesis and polymerization of seven epoxy polymer precursors which contained the siloxane linkage in varying structural arrangements was carried out. The polymers prepared from such precursors have utility as embedding compounds for electrical circuits. Polymerization of these epoxy intermediates with siloxane-containing diamines resulted in solid, thermosetting materials for which dielectric data were obtained. Dielectric constants of 3.1 were measured at 1 keps for polymers prepared by polymerization of 1,9-bis[p-(2,3-epoxypropyl)phenyl]decamethylpentasiloxane with 1,3-bis(p-am-inophenoxy)tetramethyldisiloxane, whereas polymers derived from 1,4-bis{[p-(2,3-epoxypropyl)phenyldimethylsiloxy]dimethylsilyl}benzene and the same diamine were characterized by slightly higher dielectric constants and a high degree of toughness, being nonbrittle at ?50°C.     

Photocurrent generation in multilayer self-assembly films fabricated from water-soluble poly(phenylene vinylene)

A novel, water-soluble, cationic PPV derivative poly[(2,5-bis(3-bromotrimethylammoniopropoxy)-phenylene-1,4-divinylene)-alt-1,4-(2,5-bis(2-(2-hydroxyethoxy)ethoxy))phenylene vinylene] (BH-PPV) has been synthesized by a Heck coupling reaction. Multilayered assemblies of the BH-PPV and the sodium salt of hexa(sulfobutyl)fullerenes (C(60)-HS) were fabricated successfully by an alternate deposition technique. The multilayer structures were studied by UV/Vis spectroscopy, small angle X-ray diffraction, and atomic force microscopy. The photoinduced charge transfer property of the self-assembled multilayer film was also measured by a three-electrode cell technique. A steady and rapid cathodic 5.5 microA cm(-2) photocurrent response was measured as the irradiation of the multilayer film was switched on and off. Importantly, the response of on/off cycling is prompt and reproducible. A possible mechanism for the electron-transfer process is proposed.     

Organometallic polymers. XXIX. Synthesis and characterization of ferrocene-containing siloxane polymers from bis(dimethylamino)silane–disilanol condensation

A new monomer, 1,1′-bis(dimethylaminodimethylsilyl)ferrocene, was synthesized by two routes and polymerized with three aryl disilanols: dihydroxydiphenylsilane, 1,4-bis(hydroxydimethylsilyl)benzene, and 4,4′-bis(hydroxydimethylsilyl)biphenyl, yielding three different polysiloxanes. Melt polymerizations carried out at 1 torr pressure and 100°C resulted in the highest molecular weight polymers. Intramolecular cyclization competed with intermolecular chain extension in polymerization of the bis(aminosilane) with dihydroxydiphenylsilane, resulting in isolation of a bridged derivative, 1,3,5-trisila-2,4-dioxa-1,1,5,5-tetramethyl-3,3-diphenyl[5]ferrocenophane. Cyclization did not compete significantly during the formation of polymers from this bisaminosilane and the two remaining diols, as evidenced by higher yields and greater molecular weights. These polymers could be cast as tough flexible films, and fibers could be drawn from their melts. TGA and DSC data showed the polymer formed from 1,1′-bis(dimethylaminodimethylsilyl)ferrocene and 1,4-bis(hydroxydimethylsilyl)benzene to be at least as thermally stable as an arylene siloxane polymer which differed from the ferrocenylsiloxane structure only in the replacement of the ferrocene moiety with a p-substituted phenylene linkage. The ferrocene-containing polymers were generally hydrolytically stable under conditions of refluxing THF–H₂O(10 : 1) for 1 hr. The polymer-forming reaction was found to follow second-order kinetics, and the specific rate constants for formation of two of the polymers were measured.     

Synthesis of isomeric 1,3- and 1,4-bis[3(4)-nitrofuroxan-4(3)-yl]nitrobenzenes by nitration of the corresponding isomeric 1,3- and 1,4-bis[3(4)-nitrofuroxan-4(3)-yl]benzenes

Isomeric 1,3- and 1,4-bis[3(4)-nitrofuroxan-4(3)-yl]nitro(dinitro)benzenes were synthe-sized in high yields by nitration of the corresponding 1,3- and 1,4-bis[3(4)-nitrofuroxan-4(3)-yl]benzenes with a mixture of 100% nitric acid and concentrated sulfuric acid. The influence of 3- and 4-nitrofuroxanyl fragments on the regioselectivity of the nitration was revealed. The structure of 1,3-bis(4-nitrofuroxan-3-yl)-4-nitrobenzene was confirmed by X-ray diffraction analysis. 1,3- and 1,4-Bis(3-nitrofuroxan-4-yl)nitrobenzenes underwent thermal isomerization to more thermodynamically favorable 1,3- and 1,4-bis(4-nitrofuroxan-3-yl)nitrobenzenes.     

The electrochemical properties of a series of phenylene-thienyl polymers in tetramethylene sulfone based electrolytes

Electronically conducting polymers based on polythiophene and polyparaphenylene exhibit generally, both n-doping and p-doping. In most cases, however, the n-doping process is associated usually with poor reversibility and stability. One approach to improve the doping behavior is to modify the structure of the monomer repeat unit at the molecular level. In this paper we report on the electrochemical properties of the polymer series: pTHP, pTFP (1,4-bis(2-thienyl)-2-fluorobenzene), pTF₂P (1,4-bis(2-thienyl)-2,5-difluorobenzene), and pTF₄P (1,4-bis(2-thienyl)-2,3,5,6-tetrafluorobenzene) in tetramethylene sulfone (sulfolane) TBABF₄ based electrolytes.     

SYNTHETIC STUDIES ON BLOOD COMPATIBLE BIOMATERIALS Ⅲ. SYNTHESIS, CHARAC-TERIZATION AND ANTITHROMBOGENICITY OF DIMETHYLDIPHEN YLPOLYSILOXANE/POLY (OXYTETRAM ETHYLENE)-POLYUREA SEGMENTED COPOLYMERS

A novel class of segmented copolymers, dimethyldiphenylpolysiloxane/poly (oxytetramethylene)-polyurea (PSPEU), was synthesized from α, ω-bis (γ-aminopropyl) dimethyldiphenylpolysiloxane (APMPS), which was prepared by means of basic ring-opening copolymerization of octamethylcyclotetrasiloxane, hexaphenylcyclotrisiloxane and 1, 3-bis (γ-aminopropyl) tetramethyl disiloxane. The relationships between the diphenylsiloxy contents and the properties of APMPS, including refractive index, glass transition temperature, solubility parameter as well as thermal stability, were investigated; meanwhile, the thermal stability, dynamic mechanical properties, mechanical properiesas well as the antithrombogenicity in vitro of the PSPEU were also revealed.     

Synthesis of oligosiloxanes with 3-aminopropyl groups and their testing as surfactants in the preparation of polymer microspheres

Polydimethyl-co-methyl(3-aminopropyl)siloxanes differing in the content of amino groups and molecular weight were synthesized by two pathways, namely, by hydrosilylation of oligodimethyl-co-methylhydrоsiloxane with N-(trimethylsilyl)allylamine (TMSAA) and by copolymerization of octamethylcyclotetrasiloxane with methyl(3-aminopropyl)cyclosiloxanes. The colloid-chemical properties of the synthesized oligomers were studied. The oligosiloxanes possess high surface activity and can reduce the interfacial tension in the interface surfactant solution in toluene–water to 6.7–4.2 mJ m². Aggregatively stable polystyrene suspensions with particle of 0.5 and 0.8 μm in diameter were obtained in the presence of the synthesized oligomers.     

1,4-Dialkynylbutatrienes: synthesis, stability, and perspectives in the chemistry of carbo-benzenes

The π-electron-rich C(8)-conjugated sequence of 1,4-dialkynylbutatrienes is identified as a fragile and fascinating motif occurring in carbo-benzene derivatives, and in Diederich's 1,4-bis(arylethynyl)- or 1,4-bis(triisopropylsilylethynyl)butatriene "capped" representatives, in particular, in tetraalkynylbutatriene. The family of symmetrical 1,4-dialkynylbutatrienes (E-C≡C)RC=C=C=CR(C≡C-E) is extended to functional caps (E=H, CH(3), C≡CPh, CPh=CHBr, or CPh=CBr(2)) with non-alkynyl substituents at the sp(2) vertices (R=Ph or CF(3)). The targets were selected for their potential in appealing retrosynthetic routes to carbo-benzenes, in which the aromatic C(18) macrocycle would be directly generated by sequential metathesis or reductive coupling processes. The functional 1,4-dialkynylbutrienes were synthesized by either classical methods used for the preparation of generic butatrienes (R'Li/CuX-mediated reductive coupling of gem-dihaloenynes or SnCl(2)/HCl-mediated reduction of 3,6-dioxy-octa-1,4,7-triyne precursors). Their spectroscopic and electrochemical properties are compared and analyzed on the basis of the relative extent of total conjugation.