ACID-BASE CHEMISTRY OF [PCl2N]3

An understanding of the chemistry of [¹⁵NPCl₂]₃ is very important because this trimer is the major precursor to phosphazene polymers. In order to understand its sensitivity toward reaction conditions, [¹⁵NPCl₂]₃ has been synthesized and characterized by modern spectral techniques. The goal of the study was to detect reactive impurities in the trimer, impurities that may account for the irreproducibility of the ring opening polymerization. Reactions of [¹⁵NPCl₂]₃ with various acids and bases were conducted and the products have been characterized by multinuclear and variable temperature NMR spectroscopy and mass spectrometry. Particular attention was given to understanding the reactivity at the ¹⁵N site toward acid and base reagents.     

New sulfonate-containing network polymers based on immobilized <Emphasis Type="Italic">cis</Emphasis>-metacyclophane-3,5,10,12,17,19,24,26-octols

Polymeric metacyclophaneoctol-based sulfonic acids have been synthesized, and their ion-exchange properties have been studied. New polymeric sulfonic acids have been obtained through the sulfonation of network polymers based on immobilized cis-metacyclophane-3,5,10,12,17,19,24,26-octols. The structure of the polymers has been investigated by means of IR spectroscopy, potentiometric titration, and elemental analysis. The polymers thus obtained possess a high ion-exchange capacity with respect to Na⁺, Cu²⁺, [Pd(NH₃)₄]²⁺, and In³⁺ cations in a wide pH range. Selectivity coefficients of Na⁺-H⁺, Cu²⁺-H⁺, and In³⁺-H⁺ ion exchange have been estimated.     

New hyperbranched carbosiloxane–carbosilane polymers with aromatic units in the backbone

New hyperbranched polymers based on a carbosiloxane–carbosilane skeleton with aromatic units in the backbone have been prepared via one-pot hydrosilylation reaction using HSi(Me)₂–O–CH₂–C₆H₄–OSiMe–(CH₂)₄(C₃H₅)₂ as a novel AB₂ monomer. These polymers are easy to prepare, have narrow polydispersity values and present allyl groups on the surface which can be used as synthetic platforms for the introduction of different terminal groups like amine groups through hydrosilylation reactions, opening the door to functionalized polymers. The polymerization process was monitored using real-time ¹H NMR spectroscopy and the resulting hyperbranched polymers were characterized using ¹H NMR, ¹³C NMR, ²⁹Si NMR and SEC/MALLS. The degree of branching in these polymers was determined by quantitative ²⁹Si NMR spectroscopy and found to be very close to the theoretical value of 0.50 for AB₂ systems. The hydrolytic degradation of these polymers in protic solvents has been studied by ²⁹Si NMR.     

Template Assembly of Polyiodide Networks at Complexed Metal Cations: Synthesis and Structures of [Pd2Cl2([18]aneN2S4)]1.5I5(I3)2 and [K([15]aneO5)2]I9

The cations [Pd ₂ Cl ₂ L] ²⁺ and [KL ₂ ^{′ +} (L = [18]aneN₂S₄, L′ =[15]aneO₅) have been used as templates for the synthesis of unique three-dimensional polyiodide networks. The metal cations in [Pd₂Cl₂L]_1.5I₅(I₃)₂ are linked into infinite chains by pairwise hydrogen bonding; the resulting cationic polymers run through channels formed by the extended polyiodide network. [KL₂^′]I₉ shows a three-dimensional network of puckered cubic cages of I₉⁻ ions whose cavities are occupied by the metal cations (section from the structure shown on the right).     

Synthesis and characterization of copolymers based on cyclopenta[c]thiophene and bithiazole and their transistor properties

Two new copolymers, P1 and P2 , containing 5,5‐bis(dodecyloxymethyl)?5,6‐dihydro‐4H‐cyclopenta[c]thiophene (DCPT) or DCPT‐based thiophene trimer (as donor) and 4,4′‐dibutyl‐2,2′‐bithiazole (BTz, as weak acceptor) have been synthesized. To reduce the steric hindrance and enhance the conjugation, the thiophene spacers have been incorporated between DCPT and BTz in P2 , which play an important role in maintaining the side chain ordering and π‐stacking interactions. Both the polymers showed π‐stacking with similar distances (～0.37 nm) but with larger extent in P2 . Combination of DCPT with BTz has resulted in low lying HOMO levels for the resulting polymers with significant improvement in oxidative stability. P1 and P2 showed p‐type mobility of 0.03 and 0.052 cm² V^?1 s^?1 with current on/off ratio (I_on/I_off) in the order of 10⁴ and 10³, respectively. These differences in characteristics may be attributed to the variation in donor (D)–acceptor (A) property, supramolecular ordering, extent of π‐stacking, and film microstructure. The polymers were further characterized by GPC, TGA, DSC, PXRD, cyclic voltammetry, and atomic force microscopy. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4481–4488     

Syntheses and structures of Cd(II) and Co(II) compounds of 4-[(3-pyridyl)methylamino]benzoate anion

Three coordination polymers containing Cd(II) and Co(II), connected via 4-[(3-pyridyl)methylamino]benzoate (L^?), have been synthesized in hydrothermal conditions. In [Cd(L)Cl] _n (1), adjacent Cd(II) cations are linked by carboxylates to give a dinuclear cluster. Pairs of L^? bridge the dinuclear cluster to form double helical chains, and these chains are further linked by Cl^? to produce a 4-connected net with (4²?·?6³?·?8) topology. [CdL₂] _n (2) contains 1-D ladder-like chains. The packing structure displays a 3-D supramolecular structure, with π?···?π interactions stabilizing the framework. [CoL₂] _n (3) has a 2-D extended supramolecular structure via π?···?π interactions of 1-D coordination polymers of 3. The crystal structures of 1–3 have been determined by single-crystal X-ray diffraction. Luminescent properties for 1 and 2 are discussed.     

Redox-initiated vinyl polymerization with thiourea as the reductant

A few redox systems containing thiourea as reductant have been found to be quite effective in initiating vinyl polymerization in aqueous media and polymers obtained in the process have all been found to contain amino endgroups to various extents by the application of dye techniques. Quite a few oxidants have so far been utilized for this purpose; among them are ferric chloride (Fe³⁺), ethylene dibiguanide complex salts of tripositive silver (Ag³⁺), hydrogen peroxide (H₂O₂), persulfate (S₂O₈^2?), bromate (BrO₃^?) + hydrochloric acid (HCl). In case of oxidants Fe³⁺ and Ag³⁺, amino endgroups are mainly incorporated in polymers; but in case of oxidants H₂O₂ and S₂O₈^2?, fragments of oxidants are also incorporated as hydroxyl and sulfate endgroups. BrO₃^?, however, forms a very efficient redox-initiating system with thiourea, as is evidenced by its capability of polymerizing even hydroquinone-stabilized water-soluble vinyl monomers at very low temperature (～0°C.) and at a quite rapid rate. Besides amino endgroups, sulfonate endgroups have also been detected in polymers in this case, and the relative extents of these two types of endgroups depend generally on the acid concentration of the system. Evidences so far collected indicate the generation of S? C(?NH)NH₂ radicals in the system by oxidation of isothiourea, HS? C(?NH)NH₂, and these are incorporated in polymers as endgroups. Sulfonate endgroups may be generated by oxidation of these amino-bearing endgroups. Suitable initiation mechanisms have been suggested in each case.     

Syntheses,structures and characterization of isomorphous CoII and NiII coordination polymers based on 2‐[(1H‐imidazol‐1‐yl)methyl]‐6‐methyl‐1H‐benzimidazole and benzene‐1,4‐dicarboxylate

Careful choice of the organic ligands is one of the most important parameters in the rational design and synthesis of coordination polymers. Aromatic polycarboxylates have been widely used in the preparation of metal–organic polymers since they can utilize various coordination modes to form diverse structures and can act as hydrogen‐bond acceptors and donors in the assembly of supramolecular structures. Nitrogen‐heterocyclic organic compounds have also been used extensively as ligands for the construction of polymers with interesting structures. In the polymers catena‐poly[[[diaquabis{2‐[(1H‐imidazol‐1‐yl)methyl]‐6‐methyl‐1H‐benzimidazole‐κN ³}cobalt(II)]‐μ₂‐benzene‐1,4‐dicarboxylato‐κ²O ¹:O ⁴] dihydrate], {[Co(C₈H₄O₄)(C₁₂H₁₁N₄)₂(H₂O)₂]·2H₂O}_n , (I), and catena‐poly[[[diaquabis{2‐[(1H‐imidazol‐1‐yl)methyl]‐6‐methyl‐1H‐benzimidazole‐κN ³}nickel(II)]‐μ₂‐benzene‐1,4‐dicarboxylato‐κ²O ¹:O ⁴] dihydrate], {[Ni(C₈H₄O₄)(C₁₂H₁₁N₄)₂(H₂O)₂]·2H₂O}_n , (II), the Co^II or Ni^II ion lies on an inversion centre and exhibits a slightly distorted octahedral coordination geometry, coordinated by two N atoms from two imidazole rings and four O atoms from two monodentate carboxylate groups and two water molecules. The dicarboxylate ligands bridge metal ions forming a polymeric chain. The 2‐[(1H‐imidazol‐1‐yl)methyl]‐6‐methyl‐1H‐benzimidazole ligands coordinate to the Co^II or Ni^II centres in monodentate modes through an imidazole N atom and are pendant on opposite sides of the main chain. The two structures are isomorphous. In the crystal, the one‐dimensional chains are further connected through O—H…O, O—H…N and N—H…O hydrogen bonds, leading to a three‐dimensional supramolecular architecture. In addition, the IR spectroscopic properties, PXRD patterns, thermogravimetric behaviours and fluorescence properties of both polymers have been investigated.     

Metallomacrocycle (MacM) complex with cyanide as bridged ligand: Electronic structures of [MacMCN]n

The electronic structures of complexes and one‐dimensional metallomacrocycles with cyanide as bridged ligand, such as [MacM(CN)₂]^? and [MacM(CN)]_n [Mac=phthalocyanine, tetrabenzoporphyrine; M=Co(III), Rh(III)] have been investigated using density functional theory. The results of this study show that the intrinsic semiconductivity properties depend on the frontier bands. The valence band is composed by the π‐macrocycle orbital. The conduction band for the cobalt polymers is a mixture of orbitals between this metal and the cyanide ligand along of the stacking direction. However, in the rhodium polymers such a band is exclusively composed of the π* system of the macrocycles. © 2002 John Wiley & Sons, Inc. Int J Quantum Chem, 2002     

An easy electrochemical procedure for tailoring thin films containing the [Fe(bpy)2(CH3CN)2] and/or [Fe(bpy)3]-like cores (bpy=2,2-bipyridine). Application to the design of a modified electrode with a supramolecular structure

A simple electrochemical procedure to tailor thin polymeric films containing the [Fe^II(bpy)₂(CH₃CN)₂]²⁺ and/or [Fe^II(bpy)₃]²⁺-like cores have been described (bpy=2,2^′-bipyridine). The procedure is based on the electroreductive precipitation of soluble polymers prepared in situ in CH₃CN by mixing Fe³⁺ ions and a bis bipyridyl ligand, (chiragen: chir). In the resulting [Fe^II(chir)(CH₃CN)₂]_n²⁺ films, the two labile S ligands can be easily replaced by a bidentate ligand. This method has been applied with success to design a modified electrode with a supramolecular structure.     

[Ni(H2O)6]2[Na(H2O)3]2[V10O28]·4H2O,bis(nickel hexahydrate) bis(sodium trihydrate) decavanadate tetrahydrate

Polyoxometallates are capable of including transition metals in their crystal structures as either discrete cations or heteroatoms. The title compound crystallizes with triclinic symmetry and consists of a centrosymmetric [V₁₀O₂₈]^6? anion, a trimeric {[Na(H₂O)₃][Ni(H₂O)₆][Na(H₂O)₃]}⁴⁺ cation, an [Ni(H₂O)₆]²⁺ cation and four water molecules of crystallization. The compound possesses two Ni atoms (each on independent inversion centres), one as a discrete cation and one in a disodium–nickel trimeric cation involved in the one‐dimensional polycation–polyanion hybrid polymer. The polymers are bound together via hydrogen bonds to the water mol­ecules and the nickel(II) hexahydrate cation. Several structures of decavanadate compounds having transition metal atoms, monovalent cations and [V₁₀O₂₈]^6? anions in the ratio 2:2:1 have been reported previously. However, the present compound differs from these in its arrangement of monovalent cations and transition metal atoms.     

New synthesis of liquid polysulfide polymers in the presence of hydrazine. II. The synthesis of linear polymers from 1,1′-[methylenebis(oxy)]-bis-[2-chloroethane] and Na2S3 or Na2S2.5

Liquid polysulfide polymers with the thiol groups on the end of the chains and of the average molecular weight of 7000–510 g mol⁻¹ have been obtained by the reaction of BClE and Na₂S₃, i.e., Na₂S_2.5 in the presence of hydrazine. The average molecular weight of the obtained polymers depends on the quantity of hydrazine used for the syntheses. With the aim to obtain polymers of the similar average molecular weight it is necessary to use on average 0.5 mol of hydrazine per polymer segment less if Na₂S_2.5 is used instead of Na₂S₃. The sulfur content in the obtained polymers is on average less than 2 sulfur atoms per polymer segment and amounts to 1.90 sulfur atoms when Na₂S₃ is used and is 1.76 sulfur atoms per polymer segment when Na₂S_2.5 is used for the synthesis. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1369–1373, 1997     

Co9S8@CN Composites Obtained from Thiacalix[4]arene-Based Coordination Polymers for Supercapacitor Applications

Metal sulfides have been recognized as promising electrodes for electrochemical energy storage owing to their remarkable electrochemical properties. Here, we demonstrate the preparation of Co₉S₈ nanoparticles anchored on a carbon matrix (denoted as Co₉S₈-X@CN (X=1, 2)) from precursor sources, two 1D infinite coordination polymers 1 and 2 . The two polymers were assembled by linking Co₄-TC4A secondary building blocks (SBUs) with ligands L₁ and L₂, respectively (H₄TC4A=p-tert-butylthiacalix[4]arene, L₁=1,4-bis(2H-tetrazol-5-yl)benzene, L₂=1,3-bis(2H-tetrazol-5-yl)benzene). The composites obtained from 1D polymers showed different morphologies, that is, the Co₉S₈ nanoparticles of Co₉S₈-1@CN are octahedral with a size of ca. 140 nm, while the lamellar Co₉S₈ nanoparticles in Co₉S₈-2@CN possess different sizes (50–150 nm). The Co₉S₈-2@CN immobilized on nickel foam (Co₉S₈-2@CN/NF) show better supercapacitive performance than that of Co₉S₈-1@CN. Co₉S₈-2@CN showed exceptionally high activities, combining higher specific capacitances (445.2 F g⁻¹ at 2 A g⁻¹ and 393.9 F g⁻¹ and 5 A g⁻¹), rate capacity (94.5% retention at 2 A g⁻¹), and long-term stability (79.2% retention at 5 A g⁻¹ over 1000 cycles). The smaller size and larger BET surface area of Co₉S₈-2@CN nanoparticles can improve the electrical conductivity and provide facile pathways for charge transport, thus leading to conspicuous electrochemical performance of Co₉S₈-2@CN compared with its Co₉S₈-1@CN counterpart.     

Synthesis and characterization of functionalized amphiphilic polymers for utilization as surfactants

Eight novel PEG-based amphiphilic block copolymers having self-assembling properties has been reported in the present study. The polymers have been synthesized by reacting Poly(ethylene glycols) (PEGs) of different molecular weights viz. 600, 1000, 1500 and 2000 and dimethyl-5-hydroxyisophthalate in presence of concentrated H₂SO₄ as catalyst in solventless condition at 80–90°C and further alkylating the resulting polymers by attaching octyl and hexadecanyl chains to phenolic hydroxyl group. The resulting functionalized amphiphilic polymers have been characterized by ¹H and ¹³C-NMR spectroscopy. These polymers, when dissolved in water, aggregate to form micelles, giving sizes ranging from 13.00 to 87.24 nm as determined by Dynamic Light Scattering (DLS) instrument. The molecular weights have been also calculated from the DLS and are in the range 3.5×10⁴ to 1.8×10⁶ KDa (Kilo Daltons). Critical Micelle Concentrations (CMC) of the synthesized polymers was determined using electrical conductivity meter with values in the range of 105 to 138 mg L^?1 (milligrams per litre).     

Polysilanes with various architectures

Copolymers and homopolymers containing silicon atoms connected to three and four other silicon atoms have been prepared and characterized. We report the first evidence of dendritic polymers with silicon backbones. Copolymers made from RSiCl₃ and R¹R²SiCl₂ resemble hybrid materials of polysilyne and polysilanes. Polymers, which contain tetrasilyl-substituted Si atoms, [(SiMe₂)₄Si]_n and (Si)_m(Me₂Si)_n, have also been synthesized. These molecules appear to be the first hyperbranched polymers, which have applications based on their electronic properties. The properties of these molecules fit into the hierarchy of 1-D to 3-D topologies known for Si materials.     

High performance semiconducting polymers containing bis(bithiophenyl dithienothiophene)‐based repeating groups for organic thin film transistors

New dithienothiophene‐containing conjugated polymers, such as poly(2,6‐bis(2‐thiophenyl‐3‐dodecylthiophene‐2‐yl)dithieno[3,2‐b;2′,3′‐d]thiophene, 4 and poly(2,6‐bis (2‐thiophenyl‐4‐dodecylthiophene‐2‐yl)dithieno[3,2‐b;2′,3′‐d]thiophene, 8 have been successfully synthesized via Stille coupling reactions using dodecyl‐substituted thiophene‐based monomers, bistributyltin dithienothiophene, and bistributyltin bithiophene; these polymers have been fully characterized. The main difference between the two polymers is the substitution position of the dodecyl side chains in the repeating group. Grazing‐incidence X‐ray diffraction (GI‐XRD) gave clear evidence of edge‐on orientation of polycrystallites to the substrate. The semiconducting properties of the two polymers have been evaluated in organic thin film transistors (OTFTs). The two conjugated polymers 4 and 8 exhibit fairly high hole carrier mobilities as high as μ_ave = 0.05 cm²/Vs (I_ON/OFF = 3.42 × 10⁴) and μ_ave = 0.01 cm²/Vs, (I_ON/OFF = 1.3 × 10⁵), respectively, after thermal annealing process. The solvent annealed films underwent reorganization of the molecules to induce higher crystallinity. Well‐defined atomic force microscopy (AFM) topography supported a significant improvement in TFT device performance. The hole carrier mobilities of the solvent annealed films are comparable to those obtained for a thermally annealed sample, and were one‐order higher than those obtained with a pristine sample. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Synthesis and ionic conductivity of polymer ionic liquids

Four vinyl monomers containing a covalently bonded cation ethylimidazolium and various anions—Br^?, (CF₃SO₂)₂N^?, (CN)₂N^?, and CF₃SO ₃ ^? —have been synthesized. High-molecular-mass polymers (M _w up to 1.84 × 10⁶) having the structure of ionic liquids have been prepared via the free-radical polymerization of 1-vinyl-3-ethylimidazolium in bulk and molecular and ionic solvents. The thermal stability and heat resistance of the resulting polymer salts have been estimated. It has been demonstrated that the thermal characteristics of these salts significantly depend on the nature of anions. The glass-transition temperatures of the polymers range from 19 to 235°C. The ionic conductivity of the polymer salts and their compositions with individual ionic liquids has been studied in the frequency range 50–10⁶ Hz. The highest conductivity (1.5 × 10^?5 S/cm) is exhibited by the polymer containing the (CN)₂N^? anion.     

Syntheses and Structures of two Cobalt Coordination Polymers with Iminodiacetate Ligands: [CoII2(ida)2(H2O)2]n and [Na2CoIII2(ida)4(H2O)4]n·2nH2O

Two cobalt coordination polymers [Co^II₂(ida)₂(H₂O)₂]_n ( 1 ) and [Na₂Co^III₂(ida)₄(H₂O)₄]_n·2nH₂O ( 2 ) (H₂ida = iminodiacetic acid) have been synthesized and characterized by single‐crystal X‐ray diffraction analysis. Compound 1 exhibits a two‐dimensional framework, in which two cobalt atoms exhibit different coordination environments: one is equatorially coordinated by two ida ligands, while another is coordinated by two water molecules and four ida ligands. It is most interesting that, in compound 2 , the ida ligands exhibit different coordination modes. The organic coordination anions [Co^III(ida)₂]^— are linked up by sodium ions to form a two‐dimensional layer.     

Synthesis of cyclolinear polymethylsiloxanes with two reactive groups and liquid-crystalline polymers on their basis

Cyclolinear polymethylsiloxanes with reactive vinyl groups at the silicon atoms in the fragment SiO_3/2 have been synthesized for the first time by heterofunctional polycondensation of [2,6(2,8)-dichloro-2,6(2,8)-divinyl]methylcyclotetra(hexa)siloxanes with the corresponding dihydroxy derivatives. Their hydrosilylation with chlorodimethylsilane gives rise to cyclolinear polymers with 2-chlorodimethylsilylethyl substituents, hydrolysis of which leads to the corresponding hydroxy derivatives. Liquid-crystalline polymers with mesogenic cyanobiphenyl groups have been synthesized by hydrosilylation with (4’-cyanobiphenyl-4-yl) 11-(1, 1, 3, 3-tetramethyldisiloxanyl)undecanoate. The structures of the polymers obtained have been studied by ¹H and ²⁹Si NMR and IR spectroscopy, GPC, viscometry, X-ray diffraction, and polarization optical microscopy.     

Synthesis and Characterization of Reversible Chemosensory Polymers: Modulation of Sensitivity through the Attachment of Novel Imidazole Pendants

Three novel electron donor–acceptor conjugated polymers ( P1 – P3 ) bearing various imidazole pendants have been synthesized. Their excellent photophysical and electrochemical properties make them suitable transduction materials for chemosensing applications. Indeed, polymers P1 – P3 have been found to show remarkable sensing capabilities towards H⁺ and Fe²⁺ in semi‐aqueous solutions. Upon titration with H⁺, polymers P1 and P2 showed hypsochromic shifts of their absorptions and photoluminescence (PL) maxima with enhanced fluorescence intensities. However, P3 showed diminished absorption and fluorescence intensities under similar conditions due to static quenching. The anomalous behavior of P3 compared with P1 and P2 has been clarified in terms of electronic distributions through computational analysis. Furthermore, P3 (K_SV=1.03×10⁷) showed a superior sensing ability towards Fe²⁺ compared with P1 (K_SV=2.01×10⁶) and P2 (K_SV=4.12×10⁶) due to its improved molecular wire effect. Correspondingly, the fluorescence lifetime of P3 was greatly decreased (almost 11‐fold) compared to those of polymers P1 (4.6‐fold) and P2 (6.2‐fold) in the presence of Fe²⁺. By means of a fluorescence on‐off‐on approach, chemosensing reversibilities in protonation–deprotonation and metallation–demetallation have been achieved by employing triethylamine (TEA) and the disodium salt of ethylenediaminetetraacetic acid (Na₂‐EDTA)/phenanthroline, respectively, as suitable counter ligands. ¹H NMR titrations have revealed the unique behavior of P3 compared with P1 and P2 . To the best of our knowledge, there have been no previous reports of Fe²⁺ sensors based on single imidazole receptors conjugated to a main‐chain polymer showing such a diverse sensitivity pattern depending on their attached substituents.