Chain Units Research Articles

Lipase-catalyzed synthesis of aliphatic polyesters via copolymerization of lactide with diesters and diols

Aliphatic lactate-bearing copolyesters were successfully synthesized via copolymerization of L-lactide (LLA) with diesters and diols using Candida antarctica lipase B (CALB) as the catalyst. The resultant copolymers had a Mw up to 38,000 Da with Mw/Mn between 1.5 and 2.0, and contained L-lactate units (up to 53 mol%), C6–C12 diester units, and C4–C6 alkylene units in the polymer chains. The lactate repeat units were present primarily as lactate–lactate diads in the polymers. The LLA-diester-diol copolymers were purified in good yield (70–85%) and all purified copolymers were optically active. Hydrolytic degradation study shows that LLA-diethyl adipate-1,6-hexanediol (LLA-DEA-HD) copolymers are degradable polymers as the molecular weight (Mw) of the copolymer with 53% lactate units decreased by ∼70% upon incubation in PBS solution under physiological conditions (37 °C, pH of 7.4) for 80 days. The LLA-diester-diol copolymers are thermally stable up to at least 300 °C with the temperature of maximum degradation rate ranging from 380 to 410 °C. The copolymers exhibit a wide range of physical properties (e.g., from white solid to wax and liquid) depending on their structure and composition. In particular, the LLA-DEA-HD and LLA-DEA-1,4-butanediol copolymers with ∼50 mol% lactate units are colorless, viscous liquids at ambient temperature. Biodegradable liquid polymers are potentially useful biomaterials for drug delivery to treat ocular ailments because of their good compatibility with sensitive soft tissues.

Demand Forecasting for Blood Components Distribution of a Blood Supply Chain

Abstract The blood center is the focus unit of a blood supply chain; and it has among its main assignments, the following activities: blood collection from donors, blood processing and blood components distribution to hospitals and healthcare institutions. It is surely the nervous center of the chain where planning, monitoring and controlling of these activities must be efficiently performed in order to prevent the stockout or outdate of blood components. All efficiency performance provided by a blood center will depend on the quality of its planning process, which starts with a good accuracy of forecasting required for blood supply and blood components. In this paper, a computational environment, which is oriented for forecasting of blood components, is presented. The idea is to improve the planning of the inventory balance process of the blood supply chain.

Manufacture and Analysis of Gas-Sensitive Elements Based on Polypyrrole and its Compounds with Nickel Ions

Various polymers have found application in ecological monitoring (as sensors of foreign matter in air). One of the most appreciated features of a great many of compounds of this class is an ability to change physical properties when being affected by a number of factors (e.g. resistance variation depending on application of certain substances). Properties of a polymeric material are determined not only by its composition, but by methods of polymerization, mutual arrangement of chain units and volume structure, as well, i.e. by its structure at the supramolecular level. We applied methods of quantum chemical calculation to determine the types of interaction between an ammonia molecule and a pyrrole pentamer.

Synthesis and thermal properties of novel room temperature vulcanized (RTV) silicone rubber containing POSS units in polysioxane main chains

Ethyoxyl-phenyl polyhedral oligomeric silsesquioxane (DOPO) was synthesized at first and then copolymerized with polydimethylsiloxane (PDMS) and finally cured to prepare room temperature vulcanized (RTV) silicone rubber (b-POS-SiR). Their structures and properties are characterized and evaluated by fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR), wide angle X-Ray diffraction (WAXD), and dynamic mechanical analysis (DMA). The thermal degradation mechanisms are investigated via thermal gravimetric analysis (TGA) coupled with FTIR analyses. The results show, that the thermal degradation temperatures (5 mass % loss) of the b-POS-SiR are significantly improved with addition of DOPO, e.g., 60 °C and 20 °C higher in nitrogen and in air, respectively, for the b-POS-SiR with 5 wt% DOPO compared that of PDMS rubber (PSiR). The variety of degradation mechanisms in the different atmospheres are also studied by using TGA coupled with FTIR.

Various Polar Tripeptides as Asymmetric Organocatalyst in Direct Aldol Reactions in Aqueous Media

A series of tripeptide organocatalysts containing a secondary amine group and two amino acids with polar side chain units were developed and evaluated in the direct asymmetric intermolecular aldol reaction of 4-nitrobenzaldehyde and cyclohexanone. The effectiveness of short polar peptides as asymmetric catalysts in aldol reactions to attain high yields of enantio- and diastereoselective isomers were investigated. In a comparison, glutamic acid and histidine produced higher % ee and yields when they were applied as the second amino acid in short trimeric peptides. These short polar peptides were found to be efficient organocatalysts for the asymmetric aldol addition reaction in aqueous media.

Poly[di-μ-aqua-di-aqua-bis-(μ7-oxalato-κ(9) O (1):O (1):O (1),O (2):O (2):O (2'):O (2'),O (1'):O (1'))calciumdicaesium

In the title compound, [CaCs2(C2O4)2(H2O)4]n, the Ca2+ ion, lying on a twofold rotation axis, is coordinated by four O atoms from two oxalate ligands and two bridging water mol­ecules in an octa­hedral geometry. The Cs+ ion is coordinated by seven O atoms from six oxalate ligands, one bridging water and one terminal water mol­ecule. The oxalate ligand displays a scarce high denticity. The structure contains parallel chain units runnig along [10-1], formed by two edge-sharing Cs polyhedra connected by CsO9 polyhedra connected by a face-sharing CaO6 octahedron. These chains are further linked by the oxalate ligands to build up a three-dimensional framework. O—H⋯O hydrogen bonds involving the water mol­ecules and the carboxyl­ate O atoms enhance the extended structure.

Molecular and biochemical characterization of three GH62 α-l-arabinofuranosidases from the soil deuteromycete Penicillium funiculosum

Penicillium funiculosum is an industrial fungus exploited for its capacity to secrete a wide array of glycosyl hydrolases (GHs) and glycosyl transferases (GTs). These enzymes are part of an enzymatic cocktail that is commercialized under the name RovabioExcel®, which is used as feed additive in animal nutrition. The genome sequence of this filamentous fungus has revealed a remarkable richness in several accessory enzymes, and notably in α-l-arabinofuranosidases (α-l-AFases) that participate in the hydrolysis of arabinoxylans (AX) in corn/wheat fibers used in poultry feed. Here, we report on the molecular and biochemical characterization of three GH62 family α-l-AFases encoding genes in this filamentous fungus. Amino acids sequences showed strong similarities (>65%) between them, as well with GH62 enzymes from other filamentous fungi. Interestingly, one of the three PfABF62, namely PfABF62c is unique in bearing at its N-terminus a canonical family 1 carbohydrate-binding module (CBM1) of 37 amino acids length, which was shown to help the protein to bind to microcrystalline cellulose. Also, this PfABF62c showed optimal pH and temperature of 2.8 and 50°C, respectively, whereas optimal activity for PfABF62a and PfABF62b were measured at 40°C and at pH ranging between 2.6 and 4.5. Arabinan and arabinoxylan, but no other sugars or polymers were found to augment the thermal transition of the three enzymes by 3–5°C as measured by differential scanning fluorimetry. Finally, enzymatic hydrolysis fingerprints of heteroxylans allowed concluding that the mode of action of the GH62 enzymes from this fungal species was to remove arabinofuranosyl residues linked in position O-2 and O-3 of substituted xylose units in arabinoxylan chains.

Synthesis and in vitro/in vivo antibacterial activity of oxazolidinones having thiocarbamate at C-5 on the A-ring and an amide- or urea-substituted [1,2,5]triazepane or [1,2,5]oxadiazepane as the C-ring

Oxazolidinones bearing a seven-membered [1,2,5]triazepane or [1,2,5]oxadiazepane heterocycle substituted with an amide or urea functionality as the C-ring and having a [1,2,3]triazole, a thiocarbamate, an isoxazole-3-ylamino, or a thioacetamide C-5 side chain unit on the A-ring instead of the typical acetamide were synthesized and their in vitro antibacterial activities towards various pathogens were evaluated. Several derivatives exhibited potent in vitro antibacterial activity toward not only Gram-positive, but also Gram-negative and linezolid-resistant pathogens. The in vivo therapeutic effects of amide 11a and ureas 16e, 17a were 2- to 3-fold greater than that of linezolid in a systemic mouse infection model treated by intravenous administration. Furthermore, compounds 11a and 17a showed lower monoamine oxidase (MAO)-inhibitory activity than our previously reported potent oxazolidinone antibacterials 3a and 3b.

Does franchising pay? Evidence from the restaurant industry

Franchising has taken a prominent position in service industries for several decades, but little is known about how franchising affects financial performance. Thus, we addressed the question of whether chains that franchise to some extent outperform those that are wholly owned. Then, among chains that franchise, we also addressed the question of whether more franchising is better – that is, whether the proportion of a chain's units that are franchised is associated with superior financial performance. To answer these questions, our study first compares the risk-adjusted performance of franchising vs. non-franchising restaurant firms. Second, it investigates the relationship between franchising propensity and firm financial performance. We considered five different measures of firm financial performance: the Sharpe ratio, the Treynor ratio, the Jensen index, the Sortino ratio, and the upside potential ratio. On comparison of franchising and wholly owned firms, all five measures indicated that franchising firms outperformed their non-franchising counterparts. When we focussed on just the franchising firms, however, the results were less clear. Among firms that franchise, the franchising–performance relationship was positive and significant only with respect to the Jensen index. Thus, we provide very robust evidence that franchising pays – that is, that some franchising is good – but among firms that franchise, it is unclear whether more franchising is better.

Crystal Structures and Raman Spectra of Imidazolium Poly[perfluorotitanate(IV)] Salts Containing the [TiF6]2–, ([Ti2F9]−)∞, and [Ti2F11]3– and the New [Ti4F20]4– and [Ti5F23]3– Anions

Reactions between imidazole (Im, C3H4N2) and TiF4 in anhydrous hydrogen fluoride (aHF) in different molar ratios have yielded [ImH]2[TiF6]·2HF, [ImH]3[Ti2F11], [ImH]4[Ti4F20], [ImH]3[Ti5F23], and [ImH][Ti2F9] upon crystallization. All five structures were characterized by low-temperature single-crystal X-ray diffraction. The single-crystal Raman spectra of [ImH]4[Ti4F20], [ImH]3[Ti5F23], and [ImH][Ti2F9] were also recorded and assigned. In the crystal structure of [ImH]2[TiF6]·2HF, two HF molecules are coordinated to each [TiF6](2-) anion by means of strong F-H···F hydrogen bonds. The [Ti2F11](3-) anion of [ImH]3[Ti2F11] results from association of two TiF6 octahedra through a common fluorine vertex. Three crystallographically independent [Ti2F11](3-) anions, which have distinct geometries and orientations, are hydrogen-bonded to the [ImH](+) cations. The [ImH]4[Ti4F20] salt crystallized in two crystal modifications at low (α-phase, 200 K) and ambient (β-phase, 298 K) temperatures. The tetrameric [Ti4F20](4-) anion of [ImH]4[Ti4F20] consists of rings of four TiF6 octahedra, which each share two cis-fluorine vertices, whereas the pentameric [Ti5F23](3-) anion of [ImH]3[Ti5F23] results from association of five TiF6 units, where four of the TiF6 octahedra share two cis-vertices, forming a tetrameric ring as in [Ti4F20](4-), and the fifth TiF6 unit shares three fluorine vertices with three TiF6 units of the tetrameric ring. The [ImH][Ti2F9] salt also crystallizes in two crystal modifications at low (α-phase, 200 K) and high (β-phase, 298 K) temperatures and contains polymeric ([Ti2F9](-))∞ anions, which appear as two parallel infinite zigzag chains comprised of TiF6 units, where each TiF6 unit of one chain is connected to a TiF6 unit of the second chain through a shared fluorine vertex. Quantum-chemical calculations at the B3LYP/SDDALL level of theory were used to arrive at the gas-phase geometries and vibrational frequencies of the [Ti4F20](4-) and [Ti5F23](3-) anions, which aided in the assignment of the experimental vibrational frequencies of the anion series.

One‐Component Intrinsic Self‐Healing Coatings Based on Reversible Crosslinking by Diels–Alder Cycloadditions

AbstractTerpolymers containing functional moieties for reversible crosslinking by DA reaction are synthesized for application as self‐healing coatings. The polymers are based on a methacrylate backbone containing furan as well as maleimide units in the side chains. No additional crosslinker is required to obtain a self‐healing polymeric material. After damage, the material can be heated to a temperature at which the retro‐DA reaction takes place. Subsequent cooling to room temperature leads to a healing of the scratch due to the coupling of the two reactive functional groups. This healing process can be repeated multiple times. The polymers are characterized by means of 1H NMR spectroscopy, size‐exclusion chromatography, matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry, thermogravimentric analysis, and differential scanning calorimetry. The self‐healing properties are studied using atomic force microscopy, scanning electron microscopy, and nanoindentation.magnified image

Dipole-Controlled Self-Assembly of 2,7-Bis(n-alkoxy)-9-fluorenone: Odd–Even and Chain-Length Effects

Fluorenone derivatives (F–OCn) with various lengths of peripheral alkyl chains (with carbon numbers of n = 12–18) were synthesized, and their self-assembled adlayers were investigated in solvents with different polarities and functionalities by scanning tunneling microscopy (STM) on a highly oriented pyrolytic graphite (HOPG) surface. The chain-length effect on the self-assembly of F–OCeven was observed in 1-phenyloctane. With the shortening of the side chain, the self-assembled pattern changed from a dense- and loose-packed structure to a pliers-like structure. Self-assembly of F–OCodd showed a uniform lamellar pattern. An even–odd effect was observed resulting from the direction of the end methyl group in the alkyl chain unit. Furthermore, when the samples using dichloromethane as solvent were observed within 3 h, a less ordered lamellar structure appeared in most cases. The pliers-like pattern was observed for self-assembly of F–OC16 and F–OC14. However, F–OC17 formed a zigzag structure. Observation of the odd–even and chain-length effects on the self-assembled adlayers might provide an analytical method for examining the structural and chemical homogeneities.

Synthesis, Crystal Structures, and Magnetic Properties of Ternary M(II)-Dicyanamide-hydroxypyridine Complexes

Three two-dimensional (2D) and 3D supramolecular coordination architectures based on ternary M(II)-dicyanamide-2-hydroxypyridine systems, [Co(hmpH)2(dca)2] (1), [Cu(hmpH)2(dca)2] (2), and [Mn(hepH)2(dca)2] (3) (dca = dicyanamide, hmpH = 2-(hydroxymethyl)pyridine, hepH = 2-(hydroxyethyl)pyridine), have been synthesized. 1 is a mononuclear Co(II) complex. The mononuclear units are interlinked into a 2D (4,4) hydrogen-bonded layer via O–H⋯N hydrogen bonds between the hydroxyl groups and the noncoordinating nitrile ends. These 2D layers are further extended into a 3D supramolecular architecture via the interlayer pyridyl-pyridyl stacking interaction. 2 has a 1D coordination chain structure formed by the double 1,5-dca bridged dinuclear [Cu2(1,5-dca)2(hmpH)2] unit and the 1,3-dca bridges via weak Cu–N coordination, and these 1D coordination chains are further extended into 2D hydrogen-bonded layers via strong O–H⋯N hydrogen-bonding interaction between the hydroxyl groups and the noncoordinating nitrile ends. 3 is a 2D (4,4) coordination network made of 1D [Mn(hepH)(1,5-dca)] helical chain units and interchain double (1,5-dca) bridges. Pairs of [Mn(hepH)(1,5-dca)] helical chains are interlinked by the double (1,5-dca) bridges into a racemic coordination layer structure, which is further extended into a 3D hydrogen-bonded network. Magnetic studies reveal that weak antiferromagnetic exchange occurs in 3.

Magnetic properties of the frustrated magnet Cu5(PO4)3(OH)4 on a peculiar spin network composed of pentagons and triangles

Orthorombic Cu5(PO4)3(OH)4 (pseudomalachite) is a layered compound. Each Cu-O layer in this compound is separated by PO4 tetrahedra. The spin network in the bc-plane of a pseudomlachite is composed of triangles and pentagons, which will induce the spin frustration effect. This network may be a new type of geometrically frustrated spin lattice. Magnetic susceptibility, specific heat, high field magnetization measurements are used to study the magnetic properties of Cu5(PO4)3(OH)4 in natural mineral samples. Magnetic ordering is observed at around 4.2 K. The spin entropy change at the transition temperature is about one-fifth times smaller than that expected for a usual long-range order. A 1/5 magnetization plateau is observed in the high-field magnetization curve. The plateau is explained based on a simple model in which the spin network is assumed to be composed of chain, dimer and monomer units.

Thermal fractionation of vinyl acetate-vinyl alcohol copolymers

Thermal fractionation via the method of successive self-nucleation and annealing was used for the first time to study the crystallinity of vinyl acetate-vinyl alcohol copolymers with different random distributions of chain units. The lamella-thickness distribution was calculated through the Gibbs-Thomson equation. It was shown that, for all samples, the minimum lamella thickness is the same and corresponds to a block of no less than 15 vinyl alcohol units. On the basis of these data and with the use of the computer simulation of the polymer-analogous reaction via the Monte Carlo method, the block-length distribution in the crystalline phase was found. It was shown through a comparison of the lamella-thickness and block-length distributions that the maximum lamella thickness increases with the block length and vinyl alcohol content in the copolymer. In crystallites, blocks with lengths exceeding the maximum lamella thickness comprise a significant fraction. Thus, it is probable that these blocks form folds. The dependences of melting temperatures of crystalline lamellas on their thicknesses, as well as the dependences of the melting temperatures of copolymers not subjected to thermal fractionation on the chain-structure parameters, are adequately described by the Flory crystallization theory.

Preparation and Characterization of Poly (Acrylonitrile-co-1-Acryloylpyrrolidine- 2-Carboxylic Acid) with High Molecular Weight

1-acryloylpyrrolidine-2-carboxylic acid (APCA) monomer was copolymerized with acrylonitrile (AN) by aqueous suspension polymerization. High molecular weight (HMW) copolymers of AN and APCA [poly(AN-co-APCA)] with different copolymer composition were successfully prepared by employing azobisisobutyronitrile (AIBN) as initiator and polyvinyl alcohol (PVA) as dispersant in a H2O/N,N-dimethylformamide (DMF) mixture at 60°C. The PAN homopolymer and copolymers were characterized by elemental analysis (EA), nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and X-ray diffraction (XRD). The EA results indicated that the content of oxygen increased significantly in PAN copolymers with increasing APCA content. The APCA copolymer composition calculated from the EA was higher than that from 1H NMR spectra. The FTIR spectra of PAN and poly(AN-co-APCA) with different monomer ratios confirmed that the contents of APCA units in the copolymer chains increased with increasing APCA content in the feed. The DSC exotherms revealed that copolymerization with APCA could slow the rate of the exothermic reactions during the heat-treatment processes. The XRD results indicated that the PAN homopolymer and copolymers poorly crystallized and the crystallinity decreased with increasing APCA contents.

PL.19 Cost Comparison of Routine Carbetocin Use at Caesarean Section

Objectives(1) To establish a cost consequence evaluation following introduction of routine use of carbetocin for all Caesarean Sections (CS) at Southmead Hospital.MethodsFollowing routine introduction of carbetocin for all CS (elective...

Control of Intrachain Charge Transfer in Model Systems for Block Copolymer Photovoltaic Materials

We report the electronic properties of the conjugated coupling between a donor polymer and an acceptor segment serving as a model for the coupling in conjugated donor-acceptor block copolymers. These structures allow the study of possible intrachain photoinduced charge separation, in contrast to the interchain separation achieved in conventional donor-acceptor blends. Depending on the nature of the conjugated linkage, we observe varying degrees of modification of the excited states, including the formation of intrachain charge transfer excitons. The polymers comprise a block (typically 18 repeat units) of P3HT, poly(3-hexyl thiophene), coupled to a single unit of F8-TBT (where F8 is dioctylfluorene, and TBT is thiophene-benzothiadiazole-thiophene). When the P3HT chain is linked to the TBT unit, we observe formation of a localized charge transfer state, with red-shifted absorption and emission. Independent of the excitation energy, this state is formed very rapidly (<40 fs) and efficiently. Because there is only a single TBT unit present, there is little scope for long-range charge separation and it is relatively short-lived, <1 ns. In contrast, when the P3HT chain and TBT unit are separated by the wider bandgap F8 unit, there is little indication for modification of either ground or excited electronic states, and longer-lived charge separated states are observed.

Polynitroxides from Alkoxyamine Monomers: Structural and Kinetic Investigations by Solid State NMR

A novel synthetic route toward poly(4-methacryloyloxy-2,2,6,6-tetramethylpiperidine-N-oxyl) (PTMA) is described. The polymerization of alkoxyamine-based monomers by atom transfer radical polymerization (ATRP) was investigated, as the polyalkoxyamine serves as the precursor for PTMA. The polydispersity indices (PDIs) and the kinetic data of the polymerization indicate a controlled reaction. The oxidative C–O bond cleavages of the polyalkoxyamine lead to PTMA. This transformation occurs with excellent yields, and it is possible to transfer the narrow PDIs of the prepolymer to PTMA. The material is characterized in detail using cyclic voltammetry in solution and magnetic susceptibility measurements as well as multinuclear solid state NMR and EPR spectroscopies. The conversion of the precursor polymer to the polynitroxide can be conveniently monitored by 1H and 19F magic-angle spinning (MAS) as well as 13C{1H} cross-polarization (CP)-MAS NMR. In addition, the intermolecular interaction of the nitroxide side chain units in the polymer at high conversion can be detected and monitored by the observation of pronounced low-frequency shifts.

Synthesis and characterization of a new series of rigid polytriazole resins

A novel series of polytriazole resins were synthesized by using aromatic diazides and N,N,N′,N′-tetrapropargyl-p,p′-diaminodiphenylmethane (TPDDM) as raw materials. The chemical structures of the resins were characterized by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance. Rheological behavior indicates that the resins can be processed in a low-temperature region, and some of them have good solubilities in common organic solvents. Differential scanning calorimetry and FTIR results demonstrated that the polytriazole resins can be cured at 70 °C. The glass transition temperature (T g) of cured resins increased with the increase in rigidity of diazide units in polymer chains and reaches up to 328 °C.