Study of mechanical behavior on single use bags welding under gamma irradiation

Since a long time, biopharmaceutical industry utilizes more and more single use plastic bags due to its very easy use (long shelf-lives, mechanical properties), preparation, and storage properties (oxygen and water barriers). These plastic bags are composed of two welded multilayer polymer films. To ensure the function of the closure and the non-contamination from the external environment, welding must answer to several parameters according to norm (“ISO 15747,” 2018) and standard (F02 Committee, n.d.). In this present study, the behavior of weldings on Ethylene Vinyl Acetate (EVA) single use bags under gamma irradiation have been studied. Mechanical tests have been performed at several gamma irradiation doses (from 0 kGy to 270 kGy) and at different location of the bag (Figure 1). The first objective is to study the impact of gamma irradiation dose on the welding mechanical tensile behavior. The second objective is to evaluate the impact of the welding location on the welding tensile properties. Each tensile curve (Figure 2) has been decomposed in 6 characteristic points which were evaluated with Principal Component Analysis (PCA): Ultimate Tensile strength at break (UTS), Ultimate elongation or elongation at break, 1st Yield-Strength (Y1 Strength), 1st Yield-Strain (Y1 Strain), 2nd Yield-Strength (Y2 Strength), 2nd Yield-Strain (Y2 Strain). The study showed that weldings are never impacted during tensile testing: this evaluation reveals that in fine the film cracks before the welding modification. Its function of closure and bag content preservation from external environment is fully achieved whatever the gamma irradiation dose and the welding location. Only the multilayer film on both sides of the welding is altered after 100% elongation strain. The EVA bag showed no degradation up to 115 kGy whereas they become to be altered at 270 kGy. The welding location on EVA bag showed different film mechanical behavior correlated to the polymer film extrusion process orientation. Please click Additional Files below to see the full abstract

How intramolecular hydrogen bonding (IHB) controls the C-ON bond homolysis in alkoxyamines

International audienceRecent amazing results (Nkolo et al., Org. Biomol. Chem., 2017, 6167) on the effect of solvents and polarity on the C-ON bond homolysis rate constants kd of alkoxyamine R1R2NOR3 led us to re-investigate the antagonistic effect of intramolecular hydrogen-bonding (IHB) on kd. Here, IHB is investigated both in the nitroxyl fragment R1R2NO and in the alkyl fragment R-3, as well as between fragments, that is, the donating group on the alkyl fragment and the accepting group on the nitroxyl fragment, and conversely. It appears that IHB between fragments (inter IHB) strikingly decreases the homolysis rate constant kd, whereas IHB within the fragment (intra IHB) moderately increases kd. For one alkoxyamine, the simultaneous occurrence of IHB within the nitroxyl fragment and between fragments is reported. The protonation effect is weaker in the presence than in the absence of IHB. A moderate solvent effect is also observed

First proton triggered C-ON bond homolysis in alkoxyamines

International audienceRate constants k(d) of the C-ON bond homolysis in a new type of alkoxyamines (initiator/controller for Nitroxide Mediated Polymerization) carrying alkyl fragments capable of protonation were measured. A 20-fold increase was reported for the protonated alkoxyamine compared to the non-protonated homologue as predicted (Chem. Soc. Rev., 2011)

Theoretical investigations on the conversions of cyclic polysulfides to acyclic polysulfide diradicals and subsequent reactions of biological interest

International audienceSulfur is one of the most necessary biogenic elements in nature that must be assimilated by all organisms; it is an essential macronutrient for living organisms and has multiple roles in plant development. The oxidation of elemental sulfur is a complex process involving the contact of cells with sulfur particles, the oxidation of sulfur to sulfite, and the oxidation of sulfite to sulfate. To provide hypothesis concerning the most probable processes in the early states, we determined, by quantum-chemical calculations, the energies of some allotropic forms containing up to 32-40 sulfur atoms and energetics of their reactions with triplet dioxygen. The most probable reactions occurred with methylpolysulfane anions with an electron transfer to give the superoxide anion radical (and thiyls radicals) and especially the formation of peroxydic polysulfane anions. Calculations confirmed that the triplet diradical is more stable than the singlet one for acyclic polysulfide chains. (C) 2017 Elsevier Ltd. All rights reserved

Chemically Triggered C-ON Bond Homolysis in Alkoxyamines. 6. Effect of the Counteranion

International audienceWe showed (J. Org. Chem. 2012, 77, 9634) that the activation by methylation of pyridyl-based alkoxyamine 1 increased with the hydrogen bond donor properties of solvents. In this paper, activation of 1 by protonation with acids, CF3COOH and CSA, in tert-butylbenzene (t-BuPh) and in H2O/MeOH afforded, with CF3COOH, k(d) 28-fold larger in H2O/MeOH than in t-BuPh, whereas it was only 4-fold larger when CSA was used. This puzzling observation was ascribed to the dissociation of the intimate ion pair

Scavenging of Organic C‑Centered Radicals by Nitroxides

Scavenging of Organic C‑Centered Radicals by Nitroxide

Hyperfine coupling constants of beta-phosphorylated nitroxides: Subtle interplay between steric strain, hyperconjugation, and dipole-dipole interactions

International audienceSolvent effects in beta-phosphorylated nitroxides show that nitrogen and phosphorus hyperfine coupling constants a(N) and a(p), increase and decrease with increasing polarity, polarizity, and Hydrogen Bond Donor effects of solvents, respectively. In a series of articles, it was shown that the driving interaction controlling the change in a(p) is the maximization of the N+center dot O-center dot center dot center dot center dot center dot center dot P+-O- dipole - dipole interaction. In this work, we show that the steric strain in Spiro beta-phosphotylated nitroxides affords the opposite trend for a(p) that is, a(p) increases with increasing solvent properties features. (C) 2017 Elsevier Ltd. All rights reserved

Chemically Induced Dynamic Nuclear Polarization during the Thermolysis of Alkoxyamines: A New Approach to Detect the Occurrence of H-Transfer Reactions

International audienceThermal decomposition of alkoxyamines in the presence of scavengers was found to proceed with the formation of chemically induced nuclear polarization detected by 1H NMR. The distinctive Chemically Induced Dynamic Nuclear Polarization (CIDNP) features were studied using the example of three alkoxyamines: 4-nitrophenyl 2-(2,2,6,6-tetramethylpiperidin-1-yloxy)-2-methylpropanoate (1a), 4-nitrophenyl 2-(2,2-diphenyl-3-phenylimino-2,3-dihydroindol-1-yloxy)-2-methylpropanoa te (2a) and 4-nitrophenyl 2-(2,2,5,5-tetramethyl-4-phenyl-2H-imidazol-1-oxy)-2-methylpropanoate (3a) in the presence of PhSH. The analysis of CIDNP signs of methacrylate protons allows us to conclude on the occurrence of hydrogen atom transfer reaction in geminate radical pair formed in alkoxyamine thermolysis. Thus, CIDNP is a fast and sensitive method to detect the occurrence of intra/intermolecular hydrogen transfer in alkoxyamine thermolysis

Mass spectrometry of nitroxide-terminated poly(4-vinylpyridine): A case of unwanted reactive MALDI

International audienceReactive MALDI was evidenced to occur when using acidic matrices to assist ionization of poly(4-vinylpyridine) (P4VP) prepared by nitroxide mediated polymerization (NMP). The high accessibility of nitrogen atoms in each 4VP units would allow strong hydrogen bonding with acidic matrix molecules, which was shown to further weaken the fragile C-ON linkage between the last monomeric unit and the nitroxide end-group. As a result, release of the nitroxide upon laser irradiation of the MALDI sample would lead to radical chains capable of reacting with the matrix molecule in interaction with the last 4VP unit, yielding a new polymeric by-product where one matrix molecule is incorporated in the chain termination. The mechanism proposed for this reaction was supported by accurate mass measurements, MS/MS data as well as electron paramagnetic resonance (EPR) experiments. Interestingly, such matrix/polymer covalent adducts were no longer observed when using MALDI source operated at high vacuum. (C) 2016 Elsevier B.V. All rights reserved

Chemically Triggered C-ON Bond Homolysis of Alkoxyamines. 8. Quaternization and Steric Effects

WOS:000326320100037International audienceThe C-ON bond homolysis in alkoxyamine 2a was chemically triggered by quaternization of the 1-(pyridin-2-yl)ethyl fragment using protonation, acylation, and oxidation into the N-oxide. The solvent effect was also investigated, and DFT calculations were performed to explore this chemical activation. Alkoxyamines 2a-d were also compared to the 1-(pyridin-4-yl)ethyl analogues 3a-d