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Peptoids constitute an emergent class of synthetic biocompatible macromolecules that are best described as polymers of N-substituted glycines. Peptides and peptoids are regioisomers with the side chains appended in peptoids to the nitrogen atoms rather than to the α-carbon atoms as in peptides. Peptide sequencing now takes great advantage of collision-induced dissociation experiments, based on the elucidation of the decomposition pathways of protonated peptides. In contrast, data on peptoid ion decompositions are to date scarcely present in the literature. Upon CID, protonated peptoids were recently shown to mostly dissociate by cleavages at the backbone amide bonds yielding B- and Y-fragment ions. In addition, the loss of the side-chain group and/or the formation of the side-chain fragment ion are common reactions for peptoids containing protonated N-α-aromatic side chain. In the present paper, we submitted protonated tailor-made peptoids to (energy-resolved) collision-induced dissociation experiments to investigate the side-chain loss reaction mechanisms. We also used orthogonal methods, such as quantum chemistry, ion mobility spectrometry and infrared photodissociation spectroscopy to establish the structures of the fragment ions. We ended up with different mechanistic scenarios consistent with the nature of the fragment ions and the kinetic energy dependence of decomposition reactions. Our mechanistic proposals associate the proton mobile model, proton bound dimer intermediacy and concerted rearrangement reactions.

Recent studies point to an additional stability of metal-complexed functionalized hydrocarbon chains. This additional stabilization is suggested to arise from a bidentate complexation of the metal cation with both the functional group and aliphatic chain, leading to more folded structures. In the present work, this issue is verified for silver complexed alkylamines by tandem mass spectrometry and ion mobility experiments combined with quantum-chemical calculations. Upon increasing the length of the hydrocarbon chains, the alkylamine/silver complexes undergo a structural transition to reach a folded structure in which the silver cation interacts with both the amine group and hydrogen atoms located at the chain end. This folding is further examined by monitoring the loss of AgH upon collision-induced dissociation experiments performed on alkylamines with different chain lengths. Ion mobility experiments performed on the fragment ions indicate that the removal of the silver cation induces the unfolding of the chain.

The epimerization of polylactide is reported in the presence of 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) at 105°C in toluene. The extent of the reaction depends on the amount of TBD introduced and the reaction time. Up to ca. 46% D units can be formed starting from poly(L-lactide) in the presence of 5 mol% TBD. The epimerization rate is slightly higher for D-stereoisomers vs. L-stereoisomers. From the decrease of the number-average molecular weight observed, a concomitant chain scission reaction is observed. A possible mechanism based on a nucleophilic attack of TBD is proposed based on NMR analyses, notably DOSY, MALDI ToF mass spectrometry and IR spectroscopy. The implications of the work in the field of polymer synthesis and chemical recycling of polylactide are discussed. 181;109188

The present work deals with the building of novel, fully bio-based polyamide 11 (PA11)/polylactide (PLA) diblock copolymers (PA11 x PLA y ). The adopted two-step synthetic strategy involves first the preparation of an amino-terminated PA11 prepolymer ( i.e. , having the amino end-group available and the carboxylic one protected), to be employed subsequently as a macro-initiator in the ring-opening polymerization of d -lactide (or l -lactide). Upon tuning the lactide conversion, diblock copolymers with different PA11/PLA ratios are targeted and achieved, as demonstrated by 1 H NMR and TGA analysis. The thermal properties of these double-crystalline polymers are characterized by means of DSC. Finally, fast stereocomplexation is demonstrated upon mixing the enantiomeric PA11 x PLA y diblock pairs. Indeed, the idea behind these systems is to conjugate the properties of PLA with those of the high-performance PA11, in a cumulative rather than intermediate fashion, as for widely reported random poly(ester amide)s, but without phase separation occurring, which is the case for PLA/PA11 immiscible blends. In addition, the presence of the stereocomplex, well-known for its improved chemical/thermal resistance over PLA homopolymer, could impart even further quality to the final materials.

© 2017 Elsevier Ltd Conjugated tootbrush copolymers are prepared by connecting end-capped poly(9,9’-dioctylfluorene) (PF) side-chains (PF) to a poly(3-alkylthiophene) (P3AT) backbone via the CuAAC reaction. The ratio of grafted/nongrafted segment is varied. The influence of the covalent attachment of sidechains to the backbone on the self-assembly is studied by UV–vis spectroscopy. By excitation of the PF side-chains energy transfer to the P3HT backbone is studied. ispartof: Polymer vol:112 pages:144-151 status: published

Magnetron sputter deposition of metals onto low vapor pressure liquids is a clean and straightforward method of nanoparticle (NP) production. Herein, we discuss the production of silver nanoparticles (Ag NPs) via magnetron sputtering of a silver target onto castor oil, a biocompatible and highly available liquid. A state-of-the-Art (bipolar) high-power impulse magnetron sputtering (HiPIMS) was used for the first time for the sputtering onto liquid procedure. The effect of several parameters such as sputter time, applied power, working gas pressure, and type of sputtering plasma (direct current magnetron sputtering (DC-MS) vs. HiPIMS and bipolar HiPIMS) onto NP properties has been studied by UV–vis spectroscopy and transmission electron microscopy (TEM). The scenario of Ag NPs formation is inferred from these analyses, and further supported by mass-spectrometry and quantum-chemistry calculations. Initial Ag NPs formed in castor oil have a diameter ranging from 0.8 nm to 4 nm, its stability is discussed in terms of the plasma-liquid surface interaction and the quantum chemistry data.

In this article we investigate association of the Ni-catalyst during Kumada catalyst transfer condensative polymerization (KCTCP) and hypothesize that when adding a para-phenylene monomer to a living thiophene block to synthesize poly(thiophene)-b-poly(para-phenylene), an equilibrium exist between the incorporation of the para-phenylene monomer and the trapping of the Ni-catalyst by association with the thiophene block. We suggest that this equilibrium shifts toward the association with the thiophene block with increasing length of the thiophene block and that significant trapping only occurs when this block consist of several thiophene units.

Monoterpene compounds were loaded onto pure cellulose and two cellulose-based matrices by impregnation method. The effects of initial ratio, structures of volatile compounds and polymers, i.e. cellulose, acetate cellulose and rice husk, on the release profiles were investigated. Four monoterpenes, namely α -pinene, citronellal, carvone and terpinen-4-ol, were tested as volatile compound models. In the case of carvone loaded onto cellulose, we observed that the release of the volatile molecule increases with increasing initial ratio in the formulation. Using different cellulose-based matrix to study the volatility of monoterpene models, the lowest release rates was obtained with rice husk formulations, with highly retention capacity over 50% for carvone, terpinen-4-ol and citronellal after 20 days at 21 °C. It was also concluded that the impregnation of terpinen-4-ol and carvone into cellulose and cellulose acetate respectively, could effectively help in prolonging the retention of these volatiles. α -Pinene, a highly hydrophobic molecule showed no significant retention. These results indicate that cellulose-based matrices could be potentially used as good carriers of active compounds for ecological pesticides formulation for postharvest applications.

The title ion (HBRC- 1 ) has recently been shown to be a stable hydrogen-bridged radical cation that is easily accessible by the decarbonylation of ionized methyl oxamate, NH 2 COCOOCH 3 . In this study, we report on the intriguing reactivity of HBRC- 1 and its deuterium isotopologue [NH 2 C O D OCD 2 ] •+ towards dioxygen in the ion-molecule reaction chamber of the Mons Autospec 6F mass spectrometer. Theory and experiment agree that the encounter complex [NH 2 C(O 2 ) O H OCH 2 ] •+ is the key starting configuration for the three product ions observed. These are: NH 2 C(OOH)OH + , the hydrogen-bridged ion [CH 2 O H N(H) C O] + and NH 2 C(O 2 )OH •+ , generated by loss of HCO • , O 2 H • and CH 2 O respectively. The peroxide-type ion NH 2 C(O 2 )OH •+ generated in this experiment is not observed in the reaction of solitary ions NH 2 C OH •+ with O 2 , which is ascribed to the stabilizing effect of the CH 2 O dipole in the terbody encounter complex.

Several methods for polymerizing 4-methyl-2-oxetanone (β-butyrolactone, BL) were developed allowing the controlled synthesis of polymers with molar masses up to 100 kDa. Although new catalytic systems have been described for the living anionic polymerization of BL, no detailed studies have been published on the influence of the monomer purity on the polymerization reaction. In the present study, nuclear magnetic resonance spectroscopy (NMR) and mass spectrometry (MS) are used for assessing monomer purity. These techniques indicate that an additional reaction of BL with an oxidizing agent such as potassium permanganate produces a monomer of higher purity as demonstrated by the higher rate of BL polymerization and improved control over the polymerization process that is initiated with either tetrabutylammonium acetate or carboxylic acid/phosphazene base (P1-t-Bu, P2-t-Bu and P4-t-Bu) systems.

Tandem mass spectrometry is increasingly applied to polymer ions in the context of in-depth structural characterization. In particular, the well-known collision-induced dissociation (CID) methodology is nowadays advantageously used to characterize end-groups and to distinguish isomeric polymer ions. When applied to sodium-cationized polyesters, CID was demonstrated to mainly involve charge remote fragmentation processes and consecutive as well as competitive dissociation pathways. In the present report, an experimental and theoretical study of collision induced dissociation of isomeric sodium cationized polylactide was investigated. The investigated polymers were designed to obtain oligomers only differentiated on the basis of regioisomeric end-groups, using ortho-, meta-, and para-methylbenzyl alcohols as initiators. The CID spectra revealed the presence of competitive charge driven and charge remote fragmentations. In particular, the charge induced fragmentations allowed the minute distinction between the three isomeric end-groups. The intermediacy of an ion/neutral complex was proposed to account for the observed decomposition and some theoretical calculations were performed to support the proposal.

In this paper, we describe the design and characterization of regioregular poly(3-hexylthiophene)-poly(e-caprolactone) di- and tri-block copolymers (RRP3HT- b -PCL and PCL- b -RRP3HT- b -PCL). The well-controlled synthesis of (di)hydroxyl-terminated RRP3HT makes possible to design block copolymer structures with a narrow molecular weight distribution. The microscopic morphology is investigated by atomic force microscopy, which reveals self-assembled fibrillar structures with the RRP3HT nanoribbons separated by narrow domains of insulating PCL. The charge transport properties are characterized in thin films field-effect transistors, and comparison between the devices performances is carried out in view of the nanoscale morphology within the transistor channel.

Using MS/MS/MS experiments and quantum chemical calculations, it is demonstrated that oxygen (carbonyl) methylated phthalic anhydride cations are produced when metastable dimethyl phthalate molecular ions expel a methoxyl radical. At higher internal energies, isomeric acyl ions are competitively generated.

In a previous study on the pyridine ion (1) and the pyridine-2-ylid isomer (2), we reported that ions 2 readily react with H2O to produce 2-pyridone ions at m/z 95, by O-atom abstraction. The mechanism for this intriguing reaction, however, was not established. This prompted us to use model chemistry calculations (CBS-QB3) to probe various mechanistic scenarios and to perform complementary experiments with the new, more versatile, ion–molecule reaction chamber of the Mons Autospec 6F mass spectrometer. It appears that H2O is not reacting neutral that produces the 2-pyridone ion of the above reaction, but rather O2 from air co-introduced with the water vapour. Theory and experiment agree that the exothermic reaction of O2 with the pyridine-2-ylid ion leads to loss of 3O from a stable peroxide-type adduct ion at m/z 111. Similarly, pyridine-3-ylid ions (3) generate 3-pyridone ions, but the reaction in this case is thermoneutral. The m/z 111:95 peak intensity ratios in the spectra of the ion–molecule products from ions 2 and 3 may serve to differentiate the isomers.