Polymerization of propylene with TiCl3–AlEt2Cl–polymeric electron donor catalyst

Polymeric donors having ether or carbonyl groups were added to the TiCI₃–AlEt₂CI catalyst system as the third component, and the effects on the polymerization of propylene were investigated in comparison with the effect of the electron donors with low molecular weight. The polymeric donors were effective in making the catalyst more active, but the donors of low molecular weight depressed the catalyst activity. In the case of poly(propylene glycol dimethyl ether) (PPG-DME), PPG–DME with a number of propylene oxide units (n) of more than 6.7 was effective in enhancing the catalyst activity. These effects were considered to be due to the different reactivities between TiCI₃ and AlEt₂CI-polymeric donor complexes having various chain lengths.     

Effect of composition on the width of the calorimetric glass transition in polymer–solvent and solvent–solvent mixtures

The calorimetric glass‐transition temperature (T_g) and transition width were measured over the full composition range for solvent–solvent mixtures of o‐terphenyl with tricresyl phosphate and with dibutyl phthalate and for polymer–solvent mixtures of polystyrene with three dialkyl phthalates. T_g shifted smoothly to higher temperatures with the addition of the component with the higher T_g for both sets of solvent–solvent mixtures. The superposition of the differential scanning calorimetry traces showed almost no composition dependence for the width of the transition region. In contrast, the composition dependence of T_g in polymer–solvent mixtures was different at high and low polymer concentrations, and two distinct T_g's were observed at intermediate compositions. These results were interpreted in terms of the local length scale and associated local composition variations affecting T_g. The possible implications of these results for the dynamics of miscible polymer blends were examined. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1155–1163, 2004     

Properties of ethylene–propylene–vinyl chloride graft copolymers. I. Viscoelasticity of ethylene–propylene copolymers

The viscoelastic behavior of two different ethylene–propylene copolymers was studied as a function of the molar ratios of the components and the distribution of the lengths of the ethylene and propylene sequences. The glass transition temperatures T_g agree with the values calculated from relations between T_g and component ratio established by other authors. The copolymer with longer ethylene and propylene sequences was found to exhibit a relaxation spectrum with a slope less steep than ?0.5. This broadening is explained by the broader distribution of friction factors of the statistical segments in this copolymer and by differences in crystallike nearest-neighbor packing.     

Perchloric Acid–Silica (HClO4⋅SiO2)‐Catalyzed Synthesis of 14‐Alkyl‐ or 14‐Aryl‐14H‐dibenzo[a,j]xanthenes and N‐[(2‐Hydroxynaphthalen‐1‐yl)methyl]amides

The synthesis of 14‐aryl‐ or 14‐alkyl‐14H‐dibenzo[a,j]xanthenes 3 involving the treatment of naphthalen‐2‐ol ( 1 ) with arenecarboxaldehydes or alkanals 2 in the presence of HClO₄?SiO₂ as a heterogeneous catalyst was achieved (Table 1), and this reaction was extended to the preparation of N‐[(2‐hydroxynaphthalen‐1‐yl)methyl]amides 5 by a three‐component reaction with urea ( 4a ) or an amide 4b – d as a third reactant (Table 2).     

Poly(silarylene–siloxane)polyimides from allyl‐terminated oligoimides and hydride‐functional silarylene–siloxanes via hydrosilylation polymerization

This research was focused on the design and execution of new synthetic routes to low‐temperature‐curable poly(silarylene–siloxane)polyimides. The synthesis of individual oligoimide and silarylene–siloxane blocks was followed by hydrosilylation polymerization to produce crosslinked copolymers. The silarylene–siloxane and polyimide blocks were structurally characterized by IR and ¹H NMR spectroscopy and size exclusion chromatography. The high‐temperature resistance of the copolymers was evaluated through the measurement of heat distortion temperatures (T_HD's) via thermomechanical analysis and by the determination of the weight loss at elevated temperatures via thermogravimetric analysis. Glass‐transition temperatures (T_g's) of the silarylene–siloxane segments were measured by differential scanning calorimetry. Hydrosilylation curing was conducted at 60 °C in the presence of chloroplatinic acid (H₂PtCl₆). The copolymers displayed both high‐temperature resistance and low‐temperature flexibility. We observed T_g of the silarylene–siloxane segment as low as ?77 °C and T_HD of the polyimide segment as high as 323 °C. The influence of various oligoimide molecular weights on the properties of copolymers containing the same silarylene–siloxane was examined. The effect of various silarylene–siloxane molecular weights on the properties of copolymers containing the same oligoimide was also examined. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4922–4932, 2005     

Formation of mixed-ligand complexes in the complexing polymer sorbent-Pb<Superscript>2+</Superscript>-dinitrophenol systems

The complexation of lead(II) with a group of synthesized sorbents based on aminopolystyrene and substituted phenols having structurally different substituents of various electronic natures in the para position with respect to phenolic hydroxyl was studied. As third components, α-dinitrophenol and γ-dinitrophenol were examined. The following most important parameters of sorption were determined: the optimum pH value of quantitative sorption (pH_opt), the recovery (R, %), the sorption capacity of the sorbent (SCS_Pb, mg/g), the half-sorption pH value (pH₅₀), and the temperature and time (τ) of sorption in the presence of a third component. The structure of the mixed-ligand complex was determined.     

cyclo(‐Cha–Oxz–d‐Val–Thz–Ile–Oxz–d‐Val–Thz‐) N,N‐di­methyl­acetamide dihydrate: a square form of cyclo­hexyl­alanine‐incorporated ascidiacycl­amide having the strongest cytotoxicity

The title compound, 1‐cyclo­hexyl­methyl‐1‐de(1‐methyl­propyl)­asci­dia­cycl­amide N,N‐di­methyl­acet­amide di­hy­drate, C₃₉H₅₆N₈O₆S₂·C₄H₉NO·2H₂O, a cyclo­hexyl­alanine‐incorporated ascidiacycl­amide analogue ([Cha]ASC), shows a square form similar to natural ASC. On the other hand, CD (circular dichroism) spectra showed [Cha]ASC to have a folded structure in solution, making it the second known analogue to show a discrepancy between its crystal and solution structures. Moreover, the cytotoxicity of [Cha]ASC (ED₅₀ = 5.6 µg ml⁻¹) was approximately two times stronger than that of natural ASC or a related phenyl­alanine‐incorporated analogue, viz. cyclo(‐Phe–Oxz–d ‐Val–Thz–Ile–Oxz–d ‐Val–Thz‐) ([Phe]ASC), and was confirmed to be associated with the square form. However, [Phe]ASC was previously shown to be folded in the crystal structure, which suggests that the difference between the aromatic and aliphatic rings affects the molecular folding of the ASC mol­ecule.     

Copper‐catalyzed Synthesis of N‐alkylated 2‐(4‐substituted‐1H‐1,2,3‐triazol‐1‐yl)‐1H‐indole‐3‐carbaldehyde by Step‐wise and One‐pot Three‐component Huisgen's 1,3‐dipolar Cycloaddition Reaction

An efficient method for the synthesis of N‐alkylated 2‐(4‐substituted‐1H‐1,2,3‐triazol‐1‐yl)‐1H‐indole‐3‐carbaldehyde has been developed starting from oxindole and indole using Huisgen's 1,3‐dipolar cycloaddition reaction of organic azides to alkynes. The effect of catalysts and solvent on these reactions has been investigated. Among all these conditions, while using CuSO₄·5H₂O, DMF was found to be the best system for this reaction. It could also be prepared in a one‐pot three‐component manner by treating equimolar quantities of halides, azides, and alkynes. The Huisgen's 1,3‐dipolar cycloaddition reaction was performed using CuSO₄·5H₂O in DMF with easy work‐up procedure.     

NMR spin–spin relaxation in solid and molten polyethylene structures

The NMR spin-spin relaxation (T₂) spectra of high-density polyethylene (PE) has been investigated over a wide range of temperatures, both in the solid and molten states. Previous work in these laboratories has shown that the T₂ relaxation spectrum of molten polyethylene differs from that of other polymers studied in that (a) it cannot be decomposed into two relaxation spectra (T_2S and T_2L) and (b) there is some evidence of a memory effect. This paper attempts to elucidate these observations, and compare them with the spin-spin relaxation of polyethylene at lower temperatures. In the solid state, the T₂ decay comprises both a Gaussian distribution for the crystalline region, and an exponential decay for the amorphous component. The effects of crystallization conditions and of temperature were determined. In the molten state the T₂ decay is more complex, but can be resolved into three exponentials. The longest (T_2L) component arises as expected from the most mobile, low molecular weight fraction. The T_2S component is due to an entangled but mobile network, as in other polymers. In addition, a short relaxation component T_2X is observed, which is influenced by previous crystallinity and the processing history of the material, and is ascribed to some vestigial degree of structure in the molten phase.     

Volumetric Properties of Ternary–Pseudobinary Mixtures [(Styrene + Ethyl Acetate or Benzene) + (<Emphasis Type="Italic">N</Emphasis>-Methyl-2-pyrrolidone + Ethyl Acetate or Benzene)]

The densities of the ternary-pseudobinary mixtures [(styrene + ethyl acetate or benzene) + (N-methyl-2-pyrrolidone + ethyl acetate or benzene)], formed by adding the third component (ethyl acetate or benzene) to the binary system (styrene + ethyl acetate), have been measured as a function of composition by means of a vibrating-tube densimeter at atmospheric pressure at 298.15 K. The excess molar volumes V _m ^E were calculated from the densities and correlated using the Redlich–Kister equation to estimate the coefficients and standard errors. The experimental and calculated quantities are used to discuss the mixing behavior of the components. The results show that the third component, ethyl acetate or benzene, have quite different influences on the interaction between styrene and N-methyl-2-pyrrolidone.     

Polymeric sodium 3,5‐di­carboxy­benzene­sulfonate–urea–water (1/1/1)

In the title compound, poly­[sodium‐μ₄‐3,5‐di­carboxy­benzene­sulfonato‐κ⁴O:O′:O′′:O′′′‐μ₂‐urea‐κ²O:N] monohydrate], {[Na(C₈H₅O₇S)(CH₄N₂O)]·H₂O}_n, the organic anions are arranged almost vertically within (001) monolayers, with the sulfonate and carboxylic acid groups pointing into the interlayer region. The inversion‐related aromatic rings of the anions inside the layers are arrayed via offset face‐to‐face interactions into molecular stacks along the crystallographic a axis. The `up' and `down' arrangement of the aromatic portions makes both faces of the layers ionic and hydro­philic, whereas the interiors of the layers are primarily hydro­phobic. The interleaving of the anions is such that the carboxylic acid groups are oriented more toward the interior than are the sulfonate groups. The aromatic rings in neighbouring layers are arranged in a herring‐bone fashion. The coordination sphere of the Na⁺ ions contains two sulfonate and two carboxylic acid O atoms, from a total of four different acid anions belonging to two neighbouring anionic monolayers. The urea mol­ecules are positioned between translation‐related anionic stacks inside the (001) layers, serving a triple function, viz. they fill in the large meshes (empty cavities) formed within the anionic–cationic network, and they provide additional Na⁺ coordination and hydrogen‐bond sites.     

Vier Natrium‐di(arensulfonyl)amide: Lamellare Schichten mit kurzen Zwischenschichtkontakten C–H…O(Nitro), C–H…F–C oder C–I…I–C

Structures of Ionic Di(arenesulfonyl)amides. 3. Four Sodium Di(arenesulfonyl)amides: Lamellar Layers Exhibiting Short C–H…O(nitro), C–H…F–C, or C–I…I–C Interlayer Contacts Low‐temperature X‐ray crystal structures are reported for NaN(SO₂C₆H₄‐4‐X)₂ · n H₂O, where X = NO₂ and n = 3 ( 1 , monoclinic, space group P2₁, Z = 2), X = F and n = 3 ( 2 , monoclinic, P2₁/c, Z = 4), X = F and n = 1 ( 3 , orthorhombic, Pccn, Z = 8), or X = I and n = 1 ( 4 , monoclinic, P2₁/c, Z = 4). The four compounds are examples of layered inorgano‐organic solids where the inorganic component is comprised of metal cations, N(SO₂)₂ groups and H₂O molecules and the outer regions are formed by the 4‐substituted phenyl rings of the folded anions. In the two‐dimensional coordination networks, the cations adopt either an octahedral [Na(O–S)₂(OH₂)₄] ( 1 , 2 ) or a distorted monocapped octahedral [NaN(O–S)₄(OH₂)₂] ( 3 , 4 ) environment. Taking into account the differing crystal symmetries within the two pairs of compounds, it is remarkable that the trihydrates 1 / 2 and the monohydrates 3 / 4 each display chemically identical and nearly isometric Na–O or Na–O/N networks. In the crystal packings, parallel layers are connected through weak hydrogen bonds C–H…O(nitro) ( 1 ) or C–H…F ( 2 , 3 ), or through short “type I” I…I contacts ( 4 ). There is good evidence that the strikingly distinct crystal symmetries in the halogenated homologues 3 / 4 are determined by the specific complementarity requirements of the interlayer binding centres.     

2H NMR spin relaxation study of the soft segment motion in alternating ethylene–propylene copolymers

We synthesized three partially deuterated polymer samples, namely a poly(ethylene‐alt‐propylene) (EP) alternating copolymer, a poly(styrene‐b‐EP) diblock copolymer (SEP) and a poly(styrene‐b‐EP‐b‐styrene) triblock copolymer (SEPS). The ²H spin–lattice relaxation time, T₁, of EP soft segments above their glass transition temperature was measured by solid‐state ²H NMR spectroscopy. It was found that the block copolymers had a fast and a slow T₁ component whereas EP copolymer had only a fast component. The fast T₁ components for SEP and SEPS are similar to the T₁ value of EP above ca 20°C. The slow T₁ component for SEP and SEPS exhibited a minimum at 60°C and approached the value of the fast component near the T_g of polystyrene. The motional behavior of the EP units for SEP is similar to that of SEPS over the entire range of temperature. Copyright © 2001 John Wiley & Sons, Ltd.     

Boc–Pro–Hyp–Gly–OBzl and Boc–Ala–Hyp–Gly–OBzl,two repeating triplets found in collagen

The protected tripeptides benzyl N‐{2‐[N‐(tert‐butoxy­carbon­yl)­prol­yl]‐4‐hydroxy­prol­yl}glycinate or Boc–Pro–Hyp–Gly–OBzl, C₂₄H₃₃N₃O₇, and benzyl N‐{2‐[N‐(tert‐butoxy­carbon­yl)­alan­yl]‐4‐hydroxy­prol­yl}glycinate or Boc–Ala–Hyp–Gly–OBzl, C₂₂H₃₁N₃O₇, are the minimum repeating triplets found in collagen. Within the crystal structure of each are two independent peptide mol­ecules with similar structures. The peptides are arranged anti­parallel to one another and inter­act through hydrogen bonds involving the main chains and the 4‐hydroxy­prolyl groups. The structures exhibit characteristics of a triple helix, but the peptides tend to assume a sheet‐like structure.     

Donor–Acceptor (D–A)‐Substituted Polyyne Chromophores: Modulation of Their Optoelectronic Properties by Varying the Length of the Acetylene Spacer

A series of donor–acceptor‐substituted alkynes, 2 a – f , was synthesized in which the length of the π‐conjugated polyyne spacer between the N,N‐diisopropylanilino donor and the 1,1,4,4‐tetracyanobuta‐1,3‐diene (TCBD) acceptor was systematically changed. The effect of this structural change on the optoelectronic properties of the molecules and, ultimately, their third‐order optical nonlinearity was comprehensively investigated. The branched N,N‐diisopropyl groups on the anilino donor moieties combined with the nonplanar geometry of 2 a – f imparted exceptionally high solubility to these chromophores. This important property allowed for performing INADEQUATE NMR measurements without ¹³C labeling, which, in turn, resulted in a complete assignment of the carbon skeleton in chromophores 2 a – f and the determination of the ¹³C–¹³C coupling constants. This body of data provided unprecedented insight into characteristic ¹³C chemical shift patterns in push–pull‐substituted polyynes. Electrochemical and UV/Vis spectroscopic studies showed that the HOMO–LUMO energy gap decreases with increasing length of the polyyne spacer, while this effect levels off for spacers with more than four acetylene units. The third‐order optical nonlinearity of this series of molecules was determined by measuring the rotational averages of the third‐order polarizabilities (γ_rot) by degenerate four‐wave mixing (DFWM). These latter studies revealed high third‐order optical nonlinearities for the new chromophores; most importantly, they provided fundamental insight into the effect of the conjugated spacer length in D–A polyynes, that can be exploited in the future design of suitable charge‐transfer chromophores for applications in optoelectronic devices.     

Kinetics and mechanism of grafting of undecylenic acid onto acrylonitrile–butadiene–styrene terpolymer

The graft copolymerization of undecylenic acid onto acrylonitrile–butadiene–styrene terpolymer (ABS) was initiated with benzoyl peroxide (BPO) in a 1,2‐dichloroethane solution. IR spectra confirmed that undecylenic acid was successfully grafted onto the ABS backbone. The influence of the concentrations of undecylenic acid, BPO, and ABS on the graft copolymerization was studied. A reaction mechanism was proposed: the grafting most likely took place through the addition of poly(undecylenic acid) radicals to the double bond of the butadiene region of ABS. A monomer cage effect on the graft reaction was observed to depend on the 1.5 power of the monomer concentration from the experimental results of the initial rate of graft copolymerization. The initial rate of graft copolymerization was written as R_p = 1.77 × 10⁻³[P][I₂][M]^2.5/([P]+2.75[M]^2.5)². © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 486–494, 2001     

Rock salt–urea–water (1/1/1) at 293 and 117 K

The crystal structure of NaCl·CH₄N₂O·H₂O has been determined at 117 K and redetermined at room temperature. It can be described as consisting of alternating `organic' and `inorganic' planar layers. While at room temperature the structure belongs to the space group I2, the low‐temperature structure belongs to the space group Pn2₁m. All water O atoms are located on positions with crystallographic symmetry 2 (m) in the room‐temperature (low‐temperature) structure, which means that the water molecules belong, in both cases, to point group mm2. During the phase transition, half of the urea molecules per unit cell perform a 90° rotation about their respective C—O axes. The other half and the inorganic parts of the structure remain unaltered. The relationship between the two phases is remarkable, inasmuch as no obvious reason for the transition to occur could be found; the internal structures of all components of the two phases remain unaltered and even the interactions between the different parts seem to be the same before and after the transition (at least when looked at from an energetic point of view).     

The chemical composition and bonding structure of B–C–N–H thin films deposited by reactive magnetron sputtering

The chemical composition and bonding structures of B–C–N–H films fabricated by medium frequency magnetron sputtering, with N₂+CH₄+Ar gas mixture sputtering the boron target, were investigated. XPS and FTIR spectrometric analyses show that the increase of CH₄ flow rate during deposition causes an increase of the C content in the films. The increase in the CH₄ flow rate promotes an increase in the B–C, C–N single and C?N double bonds which are the components of the hybridized B–C–N bonding structure. From the results of Raman spectroscopy analysis, it is seen that the intensity of the D band of the films' Raman spectrum decreases with increasing CH₄ flow rate, indicating a decrease of the sp²‐phase content or the sp² C cluster size. The decreases of I_D/I_G also reflect the formation of more boron‐ or nitrogen‐ bound sp³‐coordinated carbons in the films. Copyright © 2009 John Wiley & Sons, Ltd.     

An Oligothiophene–Fullerene Molecule with a Balanced Donor–Acceptor Backbone for High‐Performance Single‐Component Organic Solar Cells

A new balanced donor–acceptor molecule, namely, benzodithiophene (BDT)‐rhodanine‐[6,6]‐phenyl‐C₇₁ butyric acid methyl ester (Rh‐PC₇₁BM) comprising two covalently linked blocks, a p‐type oligothiophene‐containing BDT‐based moiety and an n‐type PC₇₁BM unit was designed and synthesized. The single‐component organic solar cell (SCOSC) fabricated from Rh‐PC₇₁BM molecules showed a power conversion efficiency (PCE) of 3.22 % with an open‐circuit voltage (V_oc) of 0.98 V. These results rank are among the highest values for SCOSCs based on a monomolecular material. In particular, the one‐molecule Rh‐PC₇₁BM device exhibits excellent thermal stability compared to reference Rh‐OH:PC₇₁BM device. The success of our monomolecular strategy can provide a new way to develop high‐performance SCOSCs.