Electrospinning of polyesteramides based on ε-caprolactam and ε-caprolactone from solution

The paper is focused on the preparation of nanofiber layers of polyesteramides with various ratios of ε-caprolactam/ε-caprolactone structural units. We have studied the effect of the system parameters, i.e., the composition of the copolymer, its molar mass and the concentration of the solution on morphology of fiber layers being formed during the electrostatic wet spinning. The process parameters were constant during the processing. Morphology of the fiber layers is given by the composition of the copolymer, i.e., by its polarity, the content of the crystalline phase and thus its separation in the process of evaporating the solvent. Fibers with diameters ranging from 100 to 160 nm were obtained for polyesteramides containing 20 or 40 mol% lactone units during optimizing the system parameters, i.e., the concentration of the solution and molar mass of polyesteramide.     

Thermodynamical properties of ε-caprolactone

The values of the combustion and enthalpies of formation for ε-caprolactone were determined by means of combustion calorimetry. The vapor pressures of lactone were measured in the range of 283–353 K, and the value of its enthalpy of vaporization was estimated by the transpiration method. Conformational analysis and calculations of the equilibrium structures, inertia moments, and sets of fundamental vibrations was performed by the B3LYP/6-311++G(3 df, 3 pd) quantum-chemical method. The total energies of the most stable lactone conformers were found and Δ_fH(g) was estimated using the composite G3MP2 method. The set of fundamental vibrations for the most stable conformers of the compound was developed on the basis of the available experimental IR spectra and calculated vibration frequencies. The values of the thermodynamic properties of ε-caprolactone were determined in the ideal ga s state in the range of 0—1500 K. A set of reliable and interconsistent thermodynamic parameters for ε-caprolactone was created. Thermodynamic analysis for liquid-phase polymerization of s-caprolactone in the temperature range of 220—500 K was carried out.     

Zur Kinetik der Polykondensation von ε-Caprolactam

Zusammenfassung Es wird ein Verfahren gezeigt, um aus der Chromaufnahme von Polyamidfasern, vornehmlich solchen aus Poly-ε-Caprolactam, bei einem bestimmten p_H-Wert die S?ure- und Basendissoziationskonstanten des Polymerisates zu ermitteln.

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Summary A method is shown by which the acid and lye dissociation constants of the polymerisate of polyamid fibres, especially such of poly-ε-caprolactam, at a certain P_H-value may be ascertained according to the absorption of chromium of such fibres.

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Krefeld, K?nigstra?e 192.     

Site-specific incorporation of ε-N-crotonyllysine into histones

A novel post-translationally modified amino acid, crotonyllysine (Kcr), was genetically incorporated into proteins in bacterial and mammalian cells using an evolved pyrrolysyl-tRNA/synthetase-tRNA pair. The ability to produce histones with homogenous, site-specific Kcr modifications will be valuable in elucidating the biological role of this recently identified post-translational modification.     

Study of ε-caprolactone polymerization by NIR spectroscopy

Near-infrared (NIR) spectroscopy is proposed for the in-line quantitative and kinetic study of the polymerization of ε-caprolactone and eventually to facilitate real-time control of the manufacturing process. Spectra were acquired with a fibre-optic probe operating in transflectance mode immersed in the reactor. The NIR data acquired were processed using a multivariate curve resolution alternating least squares (MCR-ALS) algorithm. The proposed method allows calculation of the concentration and spectral profiles of the species involved in the reaction. The key point of this method is the lack of reference concentrations needed to perform the MCR-ALS method. The use of an extended spectral matrix using both process and pure analyte spectra solves the rank deficiency. The concentration profiles obtained were used to calculate a kinetic fitting of the reaction, but the method was improved by applying kinetic constraints (hard modelling). The rate constants of batches at different temperatures and the energy of activation for this reaction were calculated. Whenever possible, the hard modelling combined with the MCR-ALS method improves the fit of the experimental data: the results show good correlation between the NIR and reference data and allow the collection of high-quality kinetic information on the reaction (rate constants and energy of activation).     

Polymerization of lactams. 99 Preparation of polyesteramides by the anionic copolymerization of ε-caprolactam and ε-caprolactone

Polyesteramides derived from the cyclic monomers ε-caprolactam and ε-caprolactone have been synthesized by the anionic polymerization and characterized. ε-Caprolactam magnesium bromide was employed as unique initiator giving high yield of copolymer across the whole range of monomer concentrations at 150 °C. Owing to a variation of the content of ester and amide component in polyesteramide backbone a large variety of materials having diverse physico-chemical and mechanical properties have been prepared. Materials prepared were examined for mechanical characteristic. Thermal properties were characterized using DSC, temperature modulated DSC, Hi-Res^TM TGA and DMA. Viscosity measurements were employed for molecular characterization.     

Reactions of Polyfluorinated Telomeric Alcohols with ε-Caprolactam

The possibility of preparing fluorinated oligomeric derivatives of -aminocaproic acid by reaction of polyfluorinated telomeric alcohols H(CF₂CF₂) _n CH₂OH (n = 1-4) with -caprolactam under conditions of homogeneous catalysis (triethylamine, dimethylformamide) was examined. The thermal stability of the oligomers was studied in relation to the fluorine content.     

Anionic Copolymerization of ε-Caprolactam with ω-Laurolactam

Polyamide 6/12 copolymers were prepared by employing two different initiation systems containing activator N-benzoyl-ε-caprolactam (BzCL) and initiator either sodium salt of ε-caprolactam (CLNa) or ε-caprolactam magnesium bromide (CLMgBr). Materials prepared by initiation with CLNa show one melting endotherm and are random copolymers. Materials prepared by initiation with CLMgBr show two melting endotherms and are probably composed from random copolymer and block copolymer containing blocks of random copolymer and blocks of copolymer with ε-caprolactam rich segments. The character of copolymers and fractionalized materials was evaluated by means of DSC and NMR.     

New ε-caprolactone diyne monomers aiming for biodegradable polymers

A substitution reaction of cyclohexane-1,4-diol with propargyl bromide gave 4-(prop-2-yn-1-yloxy)cyclohexanol. This compound was oxidized to the corresponding ketone (2-C₂H) and then to acetylene γ-substituted ε-caprolactone (3-C₂H). The latter compound was chain-extended to two butadiynyl monomers: symmetrical 5,5′-[hexa-2,4-diyne-1,6-diylbis(oxy)]bis(oxepan-2-one) (3-C₄-3) and unsymmetrical 5-{[5-(trimethylsilyl)penta-2,4-diyn-1-yl]oxy}oxepan-2-one (3-C₄TMS) via Eglinton and Cadiot–Chodkiewicz couplings, respectively. Both compounds were obtained through an alternative Baeyer–Villiger oxidation of immediate ketone precursors 2-C₄-2 and 2-C₄TMS.     

Thermal stability of nanocrystalline ε-Fe2O3

Thermal behavior of highly crystalline ε-Fe₂O₃ nanoparticles of different apparent crystallite sizes was characterized using thermogravimetry, differential thermal analysis, and analysis of evolved gas by mass spectrometry. Phase composition of the samples was monitored ex situ by X-ray powder diffraction. The results show that the thermal stability of this metastable iron oxide polymorph decreases with increasing particle size. For the particle diameter of 19(2) nm, the transformation temperature was equal to 794(5) °C, while for 28(2) nm only 755(10) °C. Surface of the nanoparticles contained adsorbed water and carbon dioxide. Elimination of these species proceeds in two steps. Water is removed at temperatures below 200 °C and CO₂ in the temperature range between 200 and 450 °C.     

Copolymerization Kinetics of N-Carboxyanhydrides of ε-Benzyloxycarbonyl-L-Lysine and L-Valine

Random copolypeptides have been considered as model compounds to understand, for instance, the conformational preference of individual monomers and the effect of comonomers on the folding of polypeptide chains [1,2]. The kinetics of copolymerization of N-carboxyanhydrides (NCA) of a-amino acids were reviewed earlier [3]. Reactivity ratios have been used in a few cases to determine the sequence length distribution and interchain heterogeneity [4] to arrive at the most probable primary structure for the polypeptide backbone. In the present communication we report the kinetics of copolymerization of e-benzyloxycarbonyl-Llysine NCA and Lvaline NCA in two solvents, dioxane and benzene/methylene chloride.     

Lanthanum heterocyclic Schiff-base complex initiated ring-opening polymerization of ε-caprolactone

Lanthanum complex supported by the heterocyclic Schiff-base ligand of N-(2-pyridyl)-3,5-di-tert-butyl-salicylaldimine was prepared and employed for the ring-opening polymerization(ROP)ofε-caprolactone(ε-CL).The polymers obtained with this initiator showed a unimodal molecular weight distribution implied that only one active species was present.Mechanism study revealed that the polymerization proceeds via acyl-oxygen bond cleavage.     

Hydrogen bonding in ε-caprolactam dimer: a quantum-chemical study

The equilibrium geometries, vibrational frequencies, and IR band intensities were calculated for the monomer and hydrogen-bonded cyclic dimer of -caprolactam (1) by the density functional B3LYP/6-311++G(d,p) method and compared with the experimental data. The gas phase IR spectrum of monomer of 1 was first measured. The calculated hydrogen bonding enthalpy H/2 in the hydrogen-bonded dimer in the gas phase (–5.93 kcal/mol) is consistent with the published data. The computed scaled (scaling factor 0.97) vibrational frequencies of the monomer and dimer are in good agreement with the experimental data. The geometry of the -caprolactam monomer remains nearly unchanged in its dimer except for the N-H, C-O, and C-N bond lengths that respectively change from 1.012, 1.230, and 1.369 in the former to 1.029, 1.246, and 1.350 in the latter. The frequencies, eigenvectors, and IR intensities of the amide modes of the monomer and dimer differ dramatically. The calculated NH and CO frequency shifts due to hydrogen bonding are in good agreement with the experimental data, but theoretical intensification of the NH IR band is much greater than that observed experimentally (by nearly 69 times vs. 11 times, respectively). The calculated N...O intermolecular distance in the structure of -caprolactam dimer equals the experimental value (2.89 ). The influence of the basis set employed on the results of calculations is discussed.Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1818–1825, September, 2004.     

Structure and characteristics of copolyamides based on ε-caprolactam and diisocyanates

The main supramolecular characteristics and the processing and service characteristics of copolyamides based on -caprolactam and hexamethylene diisocyanate were studied. The relation between the comonomer composition and supramolecular structure of copolymers was established.Translated from Zhurnal Prikladnoi Khimii, Vol. 77, No. 11, 2004, pp. 1891–1894.Original Russian Text Copyright © 2004 by Galibeev, Barnyagina, Kochnev, Arkhireev, Galimov.     

Studies on the α-acetylation of δ-valerolactone and ε-caprolactone

The synthetic approach to α-acetylated δ-valero- (7a) and ε-caprolactone (7b) is reported. While 7a was isolated in 21% yield from the respective iodoester 5a by an alkylation sequence involving transesterification and Finkelstein reaction, 7b was not obtained from 5b but the dimer 8. Also transesterification and olefin ring closing metathesis (RCM) failed to prepare 7b. RCM resulted in the dimeric lactone 10, showing that the formation of 14-membered rings is favored over that of seven-membered rings. A Mukaiyama-type Claisen reaction finally gave α-acetyl lactones 7a and 7b in practically useful quantity of about 10 g (62% yield): starting lactones 13a,b were converted to silylenolethers 14a,b, which were acetylated with acetic anhydride in presence of the Lewis acid catalyst TiCl₄. However, acetylation depends on the addition sequence of starting materials: if the mixture of Ac₂O/TiCl₄ is added to 14b, lactone 7b can be further converted to give bis-oxepanonyl ethanols 15a,b. Both compounds 15 were characterized by X-ray crystallography and NMR.     

Effects of binders and graphite on the sensitivity of ε-HNIW

In order to optimize formulations of PBX based on Hexanitrohexaazaisowurtzitane (HNIW) and meet the application in mixed explosive, the mold powder of HNIW coated by varied binders was obtained by aqueous suspension technology. Several particle sizes of graphite were added as additive with a 0.5 % mass ratio. The experiment results showed that fluorine resin (FPM) was better than polyurethane and cis-butadiene rubber when the mass percentage of binders was fixed at 4 %. The characteristic height of HNIW/FPM (96/4) mold powder was at 28 cm (2.5 kg hammer), while that of the neat HNIW was at 15 cm merely, and the friction explosion probability fell from 100 to 70 %. The addition of flake graphite with proper grain size would reduce the mechanical sensitivity of HNIW and improved the fluxion property of HNIW-based mold powders. The thermal stability characteristic of HNIW FPM (96/4) and HNIW/FPM/G (96/4/0.5) were studied by thermogravimetric analysis (TG) at 10 °C min^?1, the peak decomposition temperatures were at 251 and 250 °C, which were closed to that of neat HNIW(249 °C) and also identified superior thermal stability of compound.     

Copolymerisation of ε-caprolactone and trimethylene carbonate catalysed by methanesulfonic acid

The copolymerisation of ε-caprolactone (ε-CL) and trimethylene carbonate (TMC) catalysed by methanesulfonic acid was investigated. Preliminary copolymerisation tests using a monofunctional initiator confirm that the side bidirectional propagation previously detected in the homopolymerisation of TMC is also present in the copolymerisation. The comonomers in the ε-CL/TMC system do not follow first order kinetics. The values of the reactivity ratios obtained by the Kellen–Tüdös method (r_ε-CL = 2.90; r_TMC = 0.62) suggest that random copolymerisation can be achieved, although the copolymer will be richer in ε-CL. Dihydroxyl-telechelic ε-CL/ TMC random copolymers were prepared using a bifunctional initiator. ¹H and ¹³C NMR, SEC and DSC measurements show that the poly(TMC-co-ε-CL) samples presented the expected microstructural characteristics, a unimodal molar-mass distribution and a very narrow polydispersity. Based on these features a novel route for the preparation of block copolyesters with tuned properties, and highly regarded in the development of materials for biomedicine, may be foreseen.     

Degradable epoxy coatings by photoinitiated cationic copolymerization of bisepoxide with ε-caprolactone

Thermal and hydrolytical degradable epoxy coatings based on bis-phenol-A-diglycidyl ether (DGEBA) and ε-caprolactone (CL) were prepared by photoinitiated cationic polymerization using triphenylsulfonium hexafluoroantimonate (Ph₃S⁺SbF₆⁻) as photoinitiator. The photopolymerization kinetics were followed by real-time FT-IR analysis. The effect CL concentration on the rate of polymerization was demonstrated. Mechanical properties of the resulting networks were studied by dynamic mechanical thermal analysis (DMTA). Thermal and hydrolytical degradation investigations were also performed. Higher degradability of the cured films with the increasing content of CL in the formulation suggests that UV cured coatings obtained this way can potentially be used as reworkable thermosets.