Synthesis of Block Copolymers of Styrene with <Emphasis Type="Italic">D</Emphasis>,<Emphasis Type="Italic">L</Emphasis>-Lactide by the Sequential Controlled Cationic Polymerization and Ring-Opening Anionic Polymerization

The cationic polymerization of styrene initiated by the system 2-chloro-2-phenylpropane–TiCl₄–pyridine is studied in a mixture CH₂Cl₂–n-hexane at a temperature of –80°С. It is shown that under these conditions polymerization occurs via the living mechanism at [monomer]: [initiator] ≤ 100. The method of preparing polystyrenes with terminal primary hydroxyl groups (M_n = 4000–10000 g/mol) by the sequential controlled cationic polymerization of styrene and the in situ alkylation of 4-phenoxy-1-butanol by polystyrene macrocations is proposed. The resulting functionalized polystyrenes are used as macroinitiators of anionic-coordination ring-opening polymerization of D,L-lactide in the presence of tin bis(2-ethyl hexanoate) [Sn(Oct)₂] in toluene at 80°С. Copolymers polystyrene-block-poly(D,L-lactide) with the controlled length of the poly(D,L-lactide) block (M_n = 10000–17000 g/mol) and a relatively low molecular-weight distribution (M_w/M_n = 1.6–1.8) are synthesized. Formation of the block copolymers is confirmed by ¹Н NMR spectroscopy, gel-permeation chromatography, and atomic force microscopy.     

Synthesis of water soluble metalloporphyrin-cored amphiphilic star block copolymer photocatalysts for an environmental application

Two series of water-soluble metalloporphyrin-cored amphiphilic star block copolymers were synthesized by controlled radical polymerizations such as atom transfer radical polymerization (ATRP) and reversible addition fragmentation chain transfer (RAFT), which gave eight amphiphilic block copolymer arm chains consisting of poly(n-butyl acrylate-b-poly(ethylene glycol) methyl ether methacylate) (PnBA-b-PEGMEMA, M_n,GPC = 78,000, M_w/M_n = 1.2, 70 wt% of PPEGMEMA) and poly(styrene-b-2-dimethylamino ethyl acrylate) (PS-b-PDMAEA, M_n,GPC = 83,000, M_w/M_n = 1.2, 67 wt% of PDMAEA), yielding porphyrin(Pd)-(PnBA-b-PPEGMEMA)₈ and porphyrin(Pd)-(PS-b-PDMAEA)₈, respectively. Obtained metalloporphyrin polymer photocatalysts were homogeneously solubilized in water to apply to the removal of chlorophenols in water, and was distinguished from conventional water-insoluble small molecular metalloporphyrin photocatalysts. Notably, we found that the water-soluble star block copolymers with hydrophobic–hydrophilic core–shell structures more effectively decomposed the chlorophenol, 2,4,6-trichlorophenol (2,4,6-TCP), in water under visible light irradiation (k = 1.39 h^?1, t_1/2 = 0.5 h) in comparison to the corresponding water-soluble star homopolymer, because the hydrophobic core near the metalloporphyrin effectively captured and decomposed the hydrophobic chlorophenols in water.     

Semicontinuous microemulsion copolymerization of vinyl acetate and butyl acrylate: high solid content and effect of monomer addition rate

Vinyl acetate and butyl acrylate were copolymerized in microemulsion under monomer-starved conditions by a semicontinuous process using different monomer addition rates (R _a). A mixture of sodium dodecyl sulfate and polyethylene glycol dodecyl ether (Brij®35) were used as surfactants. Potassium persulfate was the initiator. High copolymer content latexes (around 40 wt.%), average particle diameters (D _p)?M _w) between 180,000 and 760,000. D _p and M _w of the copolymers decrease as R _a is decreased. As R _a increases, a shoulder in the molar mass distribution was observed at high values of M _w, which was ascribed to chain transfer to polymer. Homogeneous copolymer compositions were observed throughout the reaction, which cannot be obtained by the usual batch process.     

Metathesis polymer based on 5-trimethylsilylbicyclo[2.2.2]oct-2-ene: Synthesis and gas-transport properties

A new silicon-containing bicyclic monomer 5-trimethylsilylbicyclo[2.2.2]oct-2-ene has been synthesized, and its metathesis polymerization and gas transport properties of the polymer based on it have been studied. The monomer is synthesized by the two-step scheme using the Diels–Alder reaction from 1,3-cyclohexadiene and vinyltrichlorosilane followed by methylation with a Grignard reagent. The resulting 5-trimethylsilylbicyclo[ 2.2.2]oct-2-ene is inactive in metathesis homopolymerization in the presence of first- and second- generation Grubbs catalysts and a Hoveyda–Grubbs catalyst, but it slowly polymerizes when norbornene is present in the reaction mixture. The high-molecular-mass copolymer (M _w = 3.0 × 10⁵, M _w/M _n = 2.8) of 5-trimethylsilylbicyclo[2.2.2]oct-2-ene and norbornene possesses good film-forming properties, and its glass transition temperature is 126°C. The gas-transport properties of the copolymer have been studied.     

Paramagnetic centers related to Al,Sc, In,and Nb impurities in KTiOAsO<Subscript>4</Subscript>crystals

Electron paramagnetic resonance (EPR) is applied to study Al-, Sc-, In-, and Nb-doped KTiOAsO₄ (KTA) crystals. Paramagnetic hole centers O^? are observed after ionizing irradiation of KTA crystals. These centers are, as a rule, unstable at room temperature and are slowly annealed for about two weeks. Oxygen ions are bridging two cations in KTA. Near the impurity, two p-orbitals of oxygen atoms participate in covalent bonding with cations, whereas the third p-orbital remains free and under the radiation effect captures the hole thus forming the paramagnetic center of M ⁿ⁺-O^?-M^(n?1)+ (here M ⁿ⁺ is the lattice cation and M^(n?1)+ is the impurity cation of Al, In, Sc, or Nb). In the centers investigated the specific principal direction of the g-factor g ～ 2 is normal to the M ⁿ⁺-O^?-M^(n?1)+ plane, and the main value of g _max falls in this plane. The direction of the O^?-M^(n?1)+ bond is close to the selected direction of the hyperfine interaction with the impurity ion. The models of six hole centers and the found parameters of EPR spectra are discussed.     

Electron affinity and substituent effects in radical anions

The first vertical electron affinities EA of 13 series of molecules and free radicals D(X _i ) _n are related to the inductive (σ _I ), resonance (σ _R ^? ), and polarization (σ_α) parameters of substituents X _i by the dependences EA = EA _H + aΣσ _I + bΣσ _R/? + cΣσ_α: In radical anions D^+·(X _i ) _n , compared to radical cations D^+·(X _i ) _n , the polarization interaction is weaker or similar in magnitude but has an opposite sign. The previously unknown resonance parameters σ _R ^? of substituents SiMe₃ and CH₂SiMe₃ bound to the radical anion center H₂C=CH^?· were calculated.     

Supramolecular architecture of catechol and its 2:1 complex with dimethylsulfoxide

The crystal structures of catechol (o-dihydroxybenzene) and its 2:1 complex with dimethylsulfoxide are determined at T = 150 K. Crystal data: C₁₄H₁₈O₅S, M = 298.37, triclinic, space group P \(\bar 1\), unit cell parameters: a = 7.7285(13) Å, b = 9.9924(17) Å, c = 10.3188(18) Å, α = 89.963(4)°, β = 89.968(4)°, γ = 69.076(5)°, V = 744.3(2)ų, Z = 2, D _x = 1.331 g/cm³, R1 = 0.048; C₆H₆O₂, M = 110.11, monoclinic, space group P2₁/n, a = 9.8206(6)Å, b = 5.5903(3)Å, c = 10.4439(6)Å, β = 114.952(2)°; V = 519.85(5) ų, Z = 4, D _x = 1.407 g/cm³, R1 = 0.0289. In the 2:1 complex the molecules are joined in a supramolecular ensemble by D-H...A hydrogen bonds (D = O, C; A = O, π); in catechol they are bonded only by O-H...O. The state diagram of the catechol-dimethylsulfoxide system is examined by DTA.     

Transport and physicochemical parameters of polypentenamer

Physicochemical properties of a cis-polypentenamer—a hydrocarbon polymer with a low glass transition temperature (T _g = 168.8 K)—have been studied. Measurements of permeability coefficients P in rubbery material for a wide range of gases (He, H₂, O₂, N₂, CO₂, CH₄, C₂H₆, C₃H₈, and n-C₄H₁₀) indicate a high permeability of this polymer for which the values of P are only slightly lower than those of the most permeable rubber—poly(dimethylsiloxane). The method of inverse gas chromatography has been employed to estimate solubility coefficients S for n alkanes C₃–C₁₀ and cycloalkanes in cis-polypentenamer in the range from 25 to 150°C. It has been shown that the solubility coefficients linearly increase in lnS-T _cr ² coordinates, where T _cr is the critical temperature of a solute. In terms of the above correlation, the solubility coefficients of light gases have been estimated and the diffusion coefficients D of gases in the same polymer have been calculated via the formula P=DS. The free volume in cis-polypentenamer has been studied by positron annihilation lifetime spectroscopy. The temperature dependence of the positronium lifetime τ ₃ that characterizes the size of the free volume element in a polymer demonstrates saturation at temperatures above 250 K. This effect is probably related to a rapid migration of fluctuation holes in the rubbery polymer at temperatures remote enough from its glass transition temperature.     

Neutron diffraction study of Rb<Subscript>2</Subscript>UO<Subscript>2</Subscript>(SeO<Subscript>4</Subscript>)<Subscript>2</Subscript> · 2D<Subscript>2</Subscript>O

A powder of deuterated rubidium diselenatouranylate dihydrate Rb₂UO₂(SeO₄)₂ · 2D₂O has been studied by neutron diffraction. The compound is orthorhombic, space group Pna2₁, with the following unit cell parameters: a = 13.654(2) Å, b = 11.863(2) Å, c = 7.625(1) Å, Z = 4, R _F = 3.77, R _I = 6.12, and χ² = 2.21. Basic structure units are [UO₂(SeO₄)₂ · D₂O]^2? layers belonging to the AB ₂ ² M¹ crystal-chemical group (A = UO ₂ ²⁺ , B² = SeO ₄ ^2? , M¹ = D₂O) of uranyl complexes. The hydrogen atoms if the water molecules involved in the layer form intralayer hydrogen bonds with the terminal oxygen atoms of selenate ions. The outer-sphere water molecules are coordinated to the rubidium ions and are involved in hydrogen bonding with oxygen atoms of neighboring [UO₂(SeO₄)₂ · D₂O]^2? layers.     

A novel 3D energetic coordination polymer containing Co(II) atoms in a pentanuclear cluster

A novel coordination polymer [Co₅(OH)₂(dnbpdc)₄(H₂O)₆]·16H₂O (1) (dnbpdc = 6,6′-dinitro-4,4′-biphenyldicarboxylic acid) is obtained from a hydrothermal reaction. The structure of complex 1 is characterized by elemental analysis, IR spectroscopy, and single crystal X-ray diffraction analysis. The title compound (C₅₆H₇₀Co₅N₈O₅₆, M _r = 2045.85) crystallizes in the triclinic space group P-1 with a = 11.9349(2) Å, b = 12.1895(2) Å, c = 15.420(2) Å, α = 109.390(7)°, β = 94.786(1)°, γ = 108.027(9)°, V = 1968.4(4) ų, Z = 1, D _c = 1.726 g/cm³, F(000) = 1045, μ(MoK _α) = 1.154 mm^–1, T = 133(2) K, the final R = 0.0316 and wR = 0.0692 for 7032 observed reflections with I > 2σ(I). The coordination polymer is built of a pentanuclear Co(II) cluster, four dnbpdc ligands, two hydroxyl groups, six coordination water and sixteen crystal water molecules. Ligand oxygen atoms exhibit three types of coordination modes (monodentate, syn-syn bridging bidentate and bridging tridentate). Moreover, the infinite three-dimensional supramolecular network is generated by coordination and hydrogen bonds. The thermal stability of complex 1 is evaluated by differential scanning calorimetry and thermogravimetric analysis.     

Mononuclear cobalt (III) complexes with <Emphasis Type="Italic">N</Emphasis>-salicylidene-2-hydroxy-5-bromobenzylamine and <Emphasis Type="Italic">N</Emphasis>-salicylidene-2-hydroxy-5-chlorobenzylamine

Cobalt (III) complexes with N-salicylidene-2-hydroxy-5-bromobenzylamine (H₂sbba) and N-salicylidene-2-hydroxy-5-chlorobenzylamine (H₂scba), [n-(C₄H₉)₄N][Co(sbba)₂] (I) and [n-(C₄H₉)₄N][Co(scba)₂] (II), were synthesized. The crystal structure of II was determined by the single-crystal X-ray diffraction method at 90 K confirming its crystallization in the monoclinic space group P2₁/n with a = 11.729(2) Å, b = 16.901(3) Å, c = 21.483(4) Å, β = 98.840(4)°, V = 4208.2(14) ų, D_x = 1.295 g cm^?3, and Z = 4. The R1 [I > 2σ(I)] and wR2 (all data) values of 0.0664 and 0.1920, respectively, for all 9521 independent reflections. The compound is composed of a tetra(n-butyl)ammonium cation and an octahedral cobalt(III) complex anion with two scba^2? ligands in a meridional fashion. The electronic spectral features of I and II are consistent with the octahedral cobalt(III) ion with an N₂O₄ donor set.     

New conjugated poly(aryleneethynylenes) with main-chain photochromic units

New photochromic poly(aryleneethynylenes) have been synthesized on the basis of dibromodithienylmaleimide and bisacetylenes under the conditions of the Sonogashira reaction. Molecular masses and polydispersities of the poly(arylene ethynylenes) vary over the following ranges: M _w = 19 150–32 650, M _n = 12 000–19 200, and M _w/M _n = 1.47–1.70; the glass-transition temperatures are in the range 208–230°C; and the 10% weight-loss temperatures in air and argon are in the ranges 330–370 and 550–660°C, respectively. All poly(aryleneethynylenes) exhibit photochromic properties in both solutions and films. It has been shown that, when photochromes are incorporated into a polymer matrix, the efficiency of their photoinduced coloration diminishes, irrespective of whether they are fragments of macromolecular chains or components of polymer solutions.     

Aqueous RAFT polymerization of acrylamide: A convenient method for polyacrylamide with narrow molecular weight distribution

Controlled and homogeneous free-radical polymerization of acrylamide(AM) in aqueous phase was realized by using S,S'-bis(α,α'-dimethyl-α'-acetic acid)-trithiocarbonate as a reversible addition-fragmentation transfer(RAFT) agent. Linear increases in molecular weight with conversion and narrow molecular weight distribution were observed for polyacrylamide(PAM) throughout the polymerization. By this method, PAMs with controlled molecular weight(up to 1.0 × 10~6) and narrow molecular weight distribution(M_w/M_n 1.2) were prepared. This study provides an effective method for synthesis of PAMs with narrow molecular weight distribution under environmentally friendly conditions.     

Crystal structure and fluorescence of a 2D cadmium(II) coordination polymer based on flexible bis(2-methylbenzimidazole) and benzenedicarboxylate co-ligands

A new coordination polymer, {[Cd(bbmb)(bdc)]} _n (bbmb = 1,1′-(1,4-butanediyl)bis-(2-methylbenzimidazole), H₂bdc = 1,3-benzenedicarboxylic acid) was synthesized under hydrothermal conditions. The complex was structurally characterized by single crystal X-ray diffraction analyses, infrared spectroscopy (IR), elemental analyses. The compound crystallizes in the monoclinic system, space group P2₁/c with a = 10.860(6) Å, b = 13.115(7) Å, c = 21.009(9) Å, β = 120.94(2)°, V = 2567(2) ų, Z = 4, C₂₈H₂₆CdN₄O₄, M _r = 594.93, D _c = 1.540 g/cm³, μ = 0.893 mm^–1. Each cadmium center is six coordinated with four O atoms from two bdc^2– anions, and two N atoms of two bbmb ligands. The complex features a 4-connected 2D (4, 4) sheet with a point symbol {4².6^2}. Fluorescence properties of the title complex were investigated.     

Synthesis and study of ammonium decamolybdodimetallates

Ammonium decamolybdodimetallates (NH₄)_n[M₂Mo₁₀O₃₄(OH)₄] · 7H₂O, where M = Cr³⁺ (n = 6), Cu²⁺ (n = 8), or Ni²⁺ (n = 8), were synthesized for the first time and studied by X-ray diffraction, thermogravimetry, and IR spectroscopy. The compounds crystallize in the triclinic system with the following unit cell parameters: a = 10.68(2) Å, b = 9.46(2) Å, c = 7.97(2) Å, α = 75.12(3)°, β = 96.82(3)°, γ = 102.21(3)°, V = 754.4(3) ų, ρ_calcd = 4.05 g/cm³, Z = 1 for the chromium compound; and a = 10.57(2) Å, b = 9.29(2) Å, c = 8.47(2) Å, α = 73.91(3)°, β = 96.05(3)°, γ = 104.71(3)°, V = 854.3(3) ų, ρ_calcd = 3.68 g/cm³, Z = 1 (for the copper compound); and a = 10.96(2) Å, b = 8.95(2) Å, c = 7.40(2) Å, α = 71.76(3)°, β = 97.04(3)°, γ = 102.91(3)°, V = 875.3(3)ų, ρ_calcd = 3.65 g/cm₃, Z = 1 for the nickel compound.     

Quantum-chemical investigation of structure and stability of [<Emphasis Type="Italic">n</Emphasis>]-prismanes and [<Emphasis Type="Italic">n</Emphasis>]-asteranes

The study by DFT [B3LYP/6-311G(2df,p)] method of structural and energy characteristics peculiar to [n]-prismanes and [n]-asteranes demonstrated that prismanes of n = 3–10 and asteranes of n = 3–7 possessed a stable structure of D_nh-symmetry; the D_nh-geometry was distorted in the subsequent terms of the series.     

Crystal structure and spectroscopic characterization of a coordination polymer of Copper(II) chloride with ethylenediamine and the 2-hydroxybenzoate ion

A new mixed-ligand one-dimensional copper(II) coordination polymer [Cu(en)(sal)Cl] _n where en = ethylenediamine(C₂H₈N₂) and Hsal = 2-hydroxybenzoic acid (salicylic acid; C₇H₆O₃) is synthesized and characterized by FTIR spectroscopy and single crystal X-ray diffraction. The structure contains Cu²⁺ ions in two different distorted octahedral coordination environments: an axially extended CuN₄Cl₂ moiety arising from a pair of bidentate en ligands and a CuO₄Cl₂ moiety arising from a pair of asymmetrically coordinated sal^– anions. The chloride ions bridge the copper ions into a zigzag chain propagating in [001]. The structure is consolidated by N–H???O and N–H???Cl hydrogen bonds which generate a layered network. Crystal data: C₉H₁₃ClCuN₂O₃, M _r = 296.20, monoclinic, P2₁/c, a = 13.9179(10) Å, b = 10.4900(8) Å, c = 8.5181(6) Å, β = 105.518(4)°, V = 1198.30(15) ų, Z = 4, R(F) = 0.026, w R(F ²) = 0.068.     

Syntheses,Structures, and Magnetic Properties of Two Mn(II) Coordination Polymers Based on 4-Fluorocinnamic Acid and 1,10-Phenanthroline

Two Mn(II) coordination polymers, {[Mn₃ (Pfca)₆(Phen)₂] · 2DMF} _n (I) and [Mn(Pfca)₂(Phen)(H₂O)] _n (II) (HPfca = 4-fluorocinnamic acid, Phen = 1,10-phenanthroline), were synthesized and characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis, and singlecrystal X-ray diffraction (CIF files CCDC nos. 967513 (I), 1542972 (II)). Complex I crystallizes in the triclinic crystal system, space group Pī with a = 11.0821(11), b = 12.2632(12), c = 15.0288(15) Å, α = 87.3760(10)°, β = 88.4610(10)°, γ = 81.2220(10)°, V = 2016.0(3) Å3, ρ_c = 1.369 g/cm³, M _r = 1662.25, Z = 1, F(000) = 853, μ = 0.543 mm^–1, the final R = 0.0592 and wR = 0.1681 for 15498 observed reflections with I > 2σ(I). Complex II is of monoclinic system, space group P2₁/c with a = 18.0539(19), b = 8.5806(9), c = 18.758(2) Å, β = 116.5700(10)°, V = 2599.0(5) ų, ρ_c = 1.491 g/cm³, M _r = 583.44, Z = 4, F(000) = 1196, μ = 0.567 mm^–1, the final R = 0.0337 and wR = 0.0853 for 18139 observed reflections with I > 2σ(I). Complex I features linear Mn(II)-trinuclear units, which form 1D chain structure through F···F weak interactions, and complex II is 1D polymeric Mn(II)-chains. Antiferromagnetic coupling interactions exist within Mn(II)- carboxylate trinuclear in I (J =–0.40 cm^–1) and Mn(II)-carboxylate chain in II (J =–0.45 cm^–1).     

Crystal structure of magnesio-ferri-hornblendite □Ca<Subscript>2</Subscript>(Mg<Subscript>4</Subscript>Fe<Superscript>3+</Superscript>)[(Si<Subscript>7</Subscript>Al)O<Subscript>22</Subscript>](OH)<Subscript>2</Subscript> as a potentially new mineral of the amphibole supergroup

A sample of magnesio-ferri-hornblendite, a potential new mineral of the amphibole supergroup, was studied by X-ray diffraction and IR spectroscopy. The crystal chemical formula is (Z = 2): ^AK_0.04^M(4) (Ca_1.92Na_0.08) ^C[^M(1)(Mg_1.78Fe_0.22⁴⁺) ^M(2)(Mg_1.62Fe_0.26³⁺Al_0.12) ^M(3)(Mg_0.64Fe_0.32²⁺Mn_0.04)] [^T(Si_7.44Al_0.56)O₂₂] ^W(OH)₂. The monoclinic unit cell parameters are a = 9.855(1) Å, b = 18.084(1) Å, c = 5.289(1) Å, β = 104.853(2)°; V = 911.1(2) ų; space group C2/m; Z = 2. The crystal structure was refined to R = 2.82% in the anisotropic approximation for atomic displacement parameters using 1166 reflections with I > 2σ(I). The magnesio-ferri-hornblendite structure is generally similar to the structures of other monoclinic calcium amphiboles, and its key distinctive features are the predominance of Мg among C²⁺ cations and Fe³⁺ among C³⁺ cations.     

1,2- and 3,4-rich polyisoprene synthesized by Mo(VI)-based catalyst with phosphorus ligand

Polyisoprene with relatively high content of 1,2/3,4 structure was synthesized using a novel catalyst system composed of MoO₂Cl₂ supported by phosphorus ligand and Al(OPhCH₃)(i-Bu)₂ as co-catalyst. The effects of phosphites, phosphates and phosphoric acid as ligands were investigated in the coordination polymerization of isoprene in the chosen catalyst system. The studied ligands significantly affected the catalytic activity of the Mo–Al catalytic active center without significant effect on the stereoselectivity. Mo(VI)-based catalyst system was proved to be highly effective in the polymerization of isoprene even at low [Al]/[Mo] ratio (10), affording polyisoprene with 1,2- and 3,4-% structural units in the range of 44.6–52.5%, high molecular weights M_n ~ 10⁵, and relatively broad molecular weight distributions (M_w/M_n = 3.0–4.4). The effect of molar ratio of phosphorous ligand to Mo-catalyst on catalyst activity of isoprene polymerization was discussed, and the structures of Mo–phosphite complexes were preliminarily studied by IR.