Terpyridine‐Functionalized TentaGel Microbeads: Synthesis,Metal Chelation and First Sequential Complexation

The functionalization of polystyrene/poly(ethylene glycol) TentaGel® microbeads (d = 20 μm) with 2,2′:6′,2″‐terpyridine units is described resulting in a material with easily accessible ligands which possess an excellent affinity for transition metal ions. The subsequent loading with different metal ions via metal‐to‐ligand complexation yielded the corresponding Co^II, Ni^II, Fe^II, and Cu^II modified beads. The isolated materials were investigated in detail utilizing UV/vis spectroscopy, optical microscopy, atomic absorption spectroscopy (AAS), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Moreover, grafting of free terpyridine moieties via ruthenium(II )/ruthenium(III )‐chemistry onto the beads is demonstrated. This opens‐up new pathways for the selective modification of such microbeads and the preparation of functional materials.

Scheme of the formation of bis‐terpyridine‐metal complexes bound to polystyrene/poly(ethylene glycol) TentaGel® microbeads.     

Synthesis and Characterization of Biodegradable Poly(ε‐caprolactone)‐Polyglycolide‐Poly(ethylene glycol) Monomethyl Ether Random Copolymer

Summary: Poly(ε‐caprolactone)‐polyglycolide‐poly(ethylene glycol) monomethyl ether random copolymers were synthesized from ε‐caprolactone (ε‐CL), glycolide (GA) and poly(ethylene glycol) monomethyl ether (MPEG) using stannous octoate as catalyst at 160 °C by bulk polymerization. The copolymers with different composition were synthesized by adjusting the weight ration of reaction mixture. The resultant copolymer with a weight ratio (10:15:75) of MPEG2000, GA, and CL was characterized by IR, ¹H NMR, GPC and DSC. The new biodegradable copolymer has potential for medical applications since it is combined with properties of PCL, PGA and MPEG.

     

The Effect of Mold Temperature on the Performance of Injection Molded Poly(lactic acid)‐Based Bioplastic

This research investigates the effects of processing parameters, namely molding temperature on the mechanical performance of impact‐modified poly(lactic acid) (PLA). Polymer crystallization dictates many of the final properties of the material. Increasing the mold temperature, crystallization may progress to a further stage, increasing crystallinity. Molding at a lower temperature, and producing a highly amorphous polymer can increase the mechanical properties, namely elongation and impact strength. Molding at 30 versus 90 °C improved the elongation from 22 to 243% and the impact strength from 67 to 133 J · m^?1. This improvement is not without its drawbacks. By molding at 30 °C, the polymer becomes very amorphous, and thus is more susceptible to unwanted processes such as physical aging.

     

Co(acac)2‐Mediated Radical Polymerization of Acrylonitrile: Control Over Molecular Weights and Copolymerization With Methyl Methacrylate

The cobalt‐mediated radical polymerization of acrylonitrile in DMSO using cobalt (II) acetylacetonate [Co(acac)₂] as mediator is studied. Both the evolution of molecular weight and conversion over time under various conditions are monitored. Molecular weights increase sharply at the beginning of the reaction and subsequently grow linearly with conversion. No branching of the polymer is observed by ¹³C NMR. By a careful design of the reaction parameters, number‐average molecular weights >1.2 · 10⁵ g · mol^?1 with a PDI around 2.4 together with conversions of up to 90% within 24 h are achieved. The copolymerization parameters of acrylonitrile with methyl methacrylate in DMSO at 30 °C are determined using the Kelen‐Tüdõs approach giving r_AN = 0.33, r_MMA = 0.71.

     

Hydroxyethylierte Oligomere des ε-Caprolactams

The modification of ε-caprolactam oligomers with ethylene oxide was studied. The reaction was carried out in a solution of oligoamides with gaseous ethylene oxide in the presence of sulfuric acid as a catalyst at 60°C and atmospheric pressure. The product, obtained in that way can be presented by the following formula: where R¹ and R² are alkyl groups.     

The Hydrated Electron,The Hydroxyl Radical,and Hydrogen Peroxide in Radiation Damage in Cells

Spores of Bacillus megaterium, in suspension, are used to study the biological effects of the three principal products of radiolysis of water, i.e., e^?_aq, OH and H₂ O₂. A model is proposed accounting for the action of OH and H₂ O₂. This model involves two reactions: in which RH₂ is a “target” molecule, and \documentclass{article}\pagestyle{empty}\begin{document}$ \[ \underline {\rm R} \] $\end{document} is a lethally damaged molecule. Experimental evidence is given supporting this model. These studies of the effects of radiolysis products of water are extended by studies using sensitizers such as biacetyl, NO^?₃, and Ag⁺ in varying concentrations. Evidence for a possible relationship between peak sensitivities in anoxic conditions and chemical properties of the sensitizers is discussed. These results are also discussed with regard to the oxygen effect, and the general chemical characteristics of an efficient tumor sensitizer are outlined.     

Electron spin resonance study of γ-irradiated nylon 6

The free radicals trapped in oriented nylon 6 filaments after γ-irradiation under vacuum at room temperature were studied by ESR spectroscopy. The ESR spectrum measured after irradiation gradually changed to a broad singlet spectrum with decrease in the intensity. The ESR spectrum consisted of radicals with different orientation effects with respect to the outer magnetic field, and saturation effects in reference to microwave power. The simulation of the ESR spectrum from a Gaussian function gave a better fit to the observed spectrum than the calculation from a Lorentzian function. From the resolution of the spectrum from a Gaussian function, the observed spectrum is generated from three kinds of radicals: The relative radical concentration for the first, second, and third radical is about 75%, 6%, and 19% of the total radical concentration, respectively. With regard to the stability of the radicals, the third radical shows a comparatively long lifetime. The first and second radicals show almost identical lifetime, and their concentrations reduce to about 40% of the initial value during the 2 days at room temperature.     

Polymerization initiation by N-p-tolylglycine: Free-radical reactions studied by pulse and steady-state radiolysis

The extensive use of N-p-tolylglycine (NTG) and analogous compounds in adhesive bonding technologies requires a better understanding of their role in initiating free-radical polymerization. The fast oxidation and reduction reactions of NTG proceed via the formation of various free radicals and radical cation and anion intermediates. These intermediates were identified and their reactivity with oxygen, to produce the corresponding peroxyl radicals, was measured. Hydroxyl radicals (?H) were used to initiate oxidation reactions of NTG, while the reduction reactions were initiated with hydrated electrons (e). OH radicals react with NTG predominately by addition to the aromatic ring followed by OHÞ elimination to produce NTG⁺· radical cations. In the presence of oxygen, the OH–NTG^? adduct also reacts with oxygen to produce peroxyl radicals. The reaction of NTG with e forms the radical anion, which subsequently protonates on the aromatic ring to produce cyclohexadienyl radicals, or undergoes an amine elimination to yield an acetic acid free radical and 4-methylaniline. Hydroperoxyl radicals (HO) abstract hydrogen from the α position of NTG to form the corresponding alkyl free radical. © 1994 John Wiley & Sons, Inc.

1 This article is a US Government work and, as such, is in the public domain in the United States of America.

     

Chemical Kinetics,Simulation, and Thermodynamics of Glycolytic Depolymerization of Poly(ethylene terephthalate) Waste with Catalyst Optimization for Recycling of Value Added Monomeric Products

Reaction of poly(ethylene terephthalate) (PET) waste powder with ethylene glycol (EG) was carried out in a batch reactor at 1 atm pressure and at various temperatures ranging from 100–220 °C at the intervals of 10 °C. Particle size from 50–512.5 μm, reaction time from 30–150 min, amount of catalyst from 0.001–0.009 mol, and type of catalysts required for glycolysis of PET were optimized. To increase the PET weight (%) loss, various external catalysts were introduced during the reaction at different reaction parameters. Depolymerization of PET was increased with reaction time and temperature. Depolymerization of PET was decreased with increase in the particle size of PET. Reaction rate was found to depend on concentrations of liquid ethylene glycol and ethylene diester groups in the polyester. Analyses of value added monomeric products (DMT and EG) as well as PET were undertaken. Yields of monomers were agreed with PET conversion. A kinetic model was proposed and simulated, and observed consistent with experimental data. Comparisons of effect of various amounts of catalysts and type of catalysts on glycolysis rate were undertaken. Dependence of the rate constant on reaction temperature was correlated by Arrhenius plot, which shows activation energy of 46.2 kJ/mol and Arrhenius constant of 99 783 min^?1.

Arrhenius plot of the rate constant of glycolysis at 1 atm pressure for 127.5 μm PET particle size (KZA = rate constant using zinc acetate as a catalyst, KMA = rate constant using manganese acetate as a catalyst).     

Kinetics of Fluorescence Quenching by Electron and H-Atom Transfer

Fluorescence quenching rate constants, k_q, ranging from 10⁶ to 2 × 10¹⁰ M^?1 sec^?1, of more than 60 typical electron donor-acceptor systems have been measured in de-oxygenated acetonitrile and are shown to be correlated with the free enthalpy change, ΔG₂₃, involved in the actual electron transfer process in the encounter complex and varying between + 5 and ?60 kcal/mole. The correlation which is based on the mechanism of adiabatic outer-sphere electron transfer requires ΔG^≠₂₃, the activation free enthalpy of this process to be a monotonous function of ΔG₂₃ and allows the calculation of rate constants of electron transfer quenching from spectroscopic and electrochemical data. A detailed study of some systems where the calculated quenching constants differ from the experimental ones by several orders of magnitude revealed that the quenching mechanism operative in these cases was hydrogen-atom rather than electron transfer. The conditions under which these different mechanisms apply and their consequences are discussed.     

Radiation Crosslinking of Poly(ethylene‐co‐octene) with Electron Beam Radiation

Films of ethylene‐co‐octene copolymer are irradiated in air after moulding between Mylar® films with electron beam at different doses. To correlate the change in structure with properties, the irradiated and unirradiated samples are characterised by FTIR spectroscopy, swelling and mechanical measurements. Obtained changes are dependant on the radiation dose of the incident electron beam. Irradiation induces trans‐vinylene double bonds detected by FTIR spectroscopy in transmission mode. No hydroxyl (OH) and carbonyl (C?O) groups were recorded by FTIR spectroscopy. More drastic changes are observed with swelling method and by mechanical properties showing the crosslinking effect. Based on the results obtained by analytical techniques used in this study, free radicals mechanism involving mainly the pendant chains of the PE‐co‐O is proposed.

Strain at break versus gel fraction.     

Hydrolysis of 1,4-cyclohexanedimethanol-based copolyester

The solid state hydrolysis of a copolyester based on a mixture of 1,4-cyclohexanedimethanol and ethylene glycol condensed with terephthalic acid was studied at 100°C and 57 to 96 kPa water vapor partial pressure (55% to 95% relative humidity). The equilibrium water sorption in weight percent (C_∞) was found to be where P is the water vapor partial pressure in kPa. For specimens 0.32-cm thick, it took about 24 h to reach 0.9C_∞. The intrinsic viscosity (IV) was measured and used to calculate the relative change in molecular weight (M?_w) from the relationship IV ∝? (M?_w)^0.7. The decrease in molecular weight was linear with time, and the rate of decrease was found to be proportional to C_∞; the empirical correlation is where the rate constant, k, is in day^?1. A decrease of 50% in M?_w was observed after 22 days at 95% relative humidity.     

Synthesis of alternating polyamide esters by melt and solution polycondensations of N,N′-Di(6-hydroxycaproyl) diamines and N-6-hydroxycaproyl aminoalcohol with terephthalic and adipic dimethyl esters and dichlorides

Alternating polyamide esters of structures A and B were obtained by melt polymerization of dimethyl adipate and terephthalate or by solution polymerization of adipoyl and terephthaloyl chlorides, with N,N′-di(6-hydroxycaproyl)diamines and an N-6-hydroxycaproyl aminoalcohol: where R₁ is selected from dimethylene, hexamethylene, and p-phenylene radicals, and R₂ is selected from tetramethylene or p-phenyl radical. Polyamide esters of structure A′ were also prepared: Average values of melting points of the resulting polyamide esters were dependent on the starting diacid derivatives, amide diols, and methods of polymerizations as follows: where CPZ, CHD, CED, and CPPD are N,N′-di(6-hydroxycaproy1)-, each in this order: piperazine, hexamethylenediamine, ethylenediamine, and p-phenylenediamine. ECA is N-(2-hydroxyethyl)6-hydroxycaproamide. For a given polyamide ester obtained from the same starting materials and by the same method of polymerization, the melting points increased with inherent viscosities. Polyamide esters of high molecular weight were obtained from CHD with both adipic and terepbthalic derivatives both by melt and solution polymerizations. Polymerizations of the other amide diols gave lower molecular weights. Solution polymerization gave colorless or light-colored polymers, while melt polymerization gave deeper-colored polymers.     

Preparation and copolymerization of polyvalent metal salts of ethyleneglycol–methacrylate–phthalate

Preparation of polyvalent metal salts of ethyleneglycol–methacrylate–phthalate (EMP) was investigated by the reaction of the Na salt of EMP and chlorides of polyvalent metals such as Al³⁺, Cr³⁺, Fe³⁺, Ni²⁺, Co²⁺, and Cu²⁺. It was found that, among the metal salts obtained the Cr salt could be obtained in the form of (EMP? )_2? Cr(OH) in high purity and good yield where EMP? means EMP residue: (EMP? )_2? Cr(OH) is soluble in chief organic solvents and vinyl monomers such as styrene (St) and MMA. (EMP? )₂Cr(OH) was then copolymerized with St and MMA. As for the physical properties of the copolymers obtained, heat distortion temperature, compressive strength, and Rockwell hardness were generally improved by introducing (EMP? ₂)Cr(OH) into the polymers. Tensile strength, flexural strength, and impact strength were also improved by selecting the most suitable concentration of (EMP? )₂Cr(OH) according to the species of vinyl monomers. Moreover, the physical properties of (EMP? )₂Cr(OH)–MMA copolymers are generally superior to those of (EMP? )₂Cr(OH)–St copolymers. TGA and boiling water resistance of the copolymers were also discussed.     

A Radical Pathway for Direct Substitution of Benzyl Alcohols with Water‐Soluble Copper Catalyst in Water

We have developed a novel strategy for the direct substitution of benzyl alcohols with anthranilic acids using water‐soluble copper catalysts through a radical pathway in water, which offers efficient and environmentally friendly N‐, S‐, and C‐benzylations under neutral conditions. Radical scavengers strongly inhibited the benzylation. Radical clock experiments using α‐cyclopropylbenzyl alcohol were conducted to observe the rapid isomerization of the cyclopropylmethyl radical to the allylmethyl radical. Hammett plots could be fitted to a two‐parameter Hammett relationship containing both radical and polar contributions [log (k_X/k_H)=−1.24 σ^.–0.38 σ, R²=0.99]. The relative parameter ρ^./ρ of 3.3 suggested that these reactions involved a strong radical character with minor polar influence at the transition state.

     

Photochemistry of the Ferrocyanide Ion in Aqueous Solution: Hydrated Electron Formation and Aquation

Light absorption by the Fe(CN^?)^4?₆ ion in aqueous solution at selected wavelengths between 214 and 313 nm results in the formation of excited states which yield the reaction sequence: with φ_e, the quantum yield, decreasing from 0.9 at the lowest to 0.1 at the highest wavelength. At and above 337.1 nm φ_e = 0. The role of charge transfer to solvent (CTTS) intermediates in this process is demonstrated. Photoaquation according to is found to have very low, possibly zero quantum yield in this region. The role of acid-base equilibria, e. g. and of the protonated species, in the photochemistry of cyanoferrate (II) species is discussed.     

The fracture of epoxy- and elastomer-modified epoxy polymers in bulk and as adhesives

The fracture behavior of a piperidine/bisphenol A diglycidyl ether (A) resin has been determined in bulk and as an adhesive using the linear elastic fracture methods developed by Mostovoy¹. The effect of adding carboxy-terminated butadiene–acrylonitrile (CTBN) elastomer to resin A was investigated. The opening-mode fracture energy () of resin A was 120 to 150 J/m², and largely attributable to plastic deformation. Fractographic evidence was obtained for plastic flow at the crack tip during crack initiation. Propagation was unstable due to the rate dependence of the plasticity. There were no significant differences in the bulk and adhesive fracture behavior. Addition of 5–15% CTBN to resin A produced minute elastomer particles which increased to ～4000J/m² (at 15%). Further CTBN addition resulted in an elastomer–epoxy blend and a decrease in fracture energy. Fractography again indicated that crack initiation involved plastic deformation but that the elastomer had greatly increased the volume in which the deformation occurred. The adhesive fracture of the elastomer–epoxy was found to be strongly dependent on the crack-tip deformation zone size (r_yc) in that was a maximum when bond thickness was equal to 2 r_yc. At bond thicknesses less than 2 r_yc, there was a restraint on the development of the plastic zone resulting in lower values.     

Synthesis,structure, and olefin polymerization catalysis of a novel vanadium(III) 1,1′‐bi‐2‐naphtholate complex

The reaction of VCl₃ with (S)‐(–)‐Na₂ (binol) (binol = 1,1′‐bi‐2‐naphtholate) gave a new vanadium(III) complex, [Na(OEt₂)]₃[V(binol)₃] (Fig. 1 ). The X‐ray crystallographic structure of this complex (Complex 1 ) in Figure 1 reveals its propeller‐like structure, which is similar to those of the reported rare earth analogues. The complex showed moderate catalytic activities for ethylene polymerization upon activation with modified methylaluminoxane (MMAO) and with diethylaluminum chloride (DEAC). The Complex 1 /DEAC system also catalyzed the polymerization of propylene to give atactic polypropylene with low activity. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1659–1662, 2003 1 Complex 1

1. Molecular structure of [Na(OEt₂)]₃[V(binol)₃] (Complex 1 ).     

Photo-induced graft copolymerization of methyl methacrylate on oxidized poly(vinyl alcohol) fiber

Photo-induced graft copolymerization of methyl methacrylate on oxidized poly(vinyl alcohol) fiber was investigated. Oxidation of the fiber sample with sodium hypochlorite or periodic acid led the radical formation by photo-irradiation to intensify markedly. ESR spectra of the irradiated oxidized sample proved that a considerable amount of triplet component radical was contained in it, whereas the unoxidized sample mostly indicated a singlet. The spectra found in the irradiated unoxidized sample was assigned to two radicals, I and II, and for the oxidized sample, to III and IV. The spectrum for I must be a singlet, and a triplet for II, III, and IV. Among the last three, II was less stable toward heat. As the oxidized sample has a high activity for photoinitiation, the radicals of III and IV are presumed to be the sites of graft copolymerization:      

Odorless,Regioselective Synthesis of Diaryl Sulfides and α‐Thioaryl Carbonyls from Sodium Arylsulfinates via a Metal‐ Free Radical Strategy in Water

Regioselective arylthiolations of aromatic amines, arenols and ketones via C–H bond functionalization have been achieved with I₂ and PPh₃ in an aqueous system, whereby arylsulfenyl radicals are in situ generated from odorless sodium arylsulfinates. The arylsulfenyl radicals can react with free anilines containing electron‐withdrawing groups and complex substrates (estrone and progesterone). Further experiments and quantum chemical calculations were also performed to deduce a mechanism for the formation of arylsulfenyl radicals.