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The preparation and the X-ray structure of 2,5-dibromo-3-styryl and 3-2',3',4',5',6'-pentafluorostyryl-thiophenes have shown a supramolecular arrangement controlled by [pi]-[pi] interactions between the aromatic rings. An indirect evidence of well-defined nanostructured organization is provided by the partial photocyclization of pendant styryl moieties under UV irradiation.

Catalystsare commonly used in polymer synthesis. Traditionally,catalysts used to be metallic compounds but some studies have pointedout their toxicity for human health and environment, and the removalof metal impurities from synthetic polymer is quite expensive. Organocatalystshave been intensively synthesized and are now widely used in ring-openingpolymerization (ROP) reactions to address these issues. However, formost of them, there is not any evidence of their safety. The presentstudy attempts to assess whether well-established organo-based ROPcatalysts used for the preparation of FDA-approved polyesters maypresent a certain level of cytotoxicity. In vitro toxicity is evaluatedusing a methyl-thiazol-tetrazoliumcytotoxicity assay on two cell models (FHs74Int and HepaRG). Amongthe investigated organocatalysts, only functionalized thiourea showsan important cytotoxicity on both cell models. 4-Dimethylaminopyridine(DMAP), 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD), and meta-(trimethylammonio)phenolate betaine (m-BE) showcytotoxicity against HepaRG cell line only at a high concentration. [ABSTRACT FROM AUTHOR]

Wereport the use of an organic catalyst system capable of switchingbetween active and dormant propagating states during the ROP of cyclicmonomers. While the ROP of both ε-caprolactone and trimethylenecarbonate proceeds under nitrogen, the simple addition of CO2results in a dormant “off” state. Cycling betweenatmospheres provides the ability to regulate the molecular weightsof the resulting polymers without appreciable loss of catalytic activityfor several “on/off” cycles. [ABSTRACT FROM AUTHOR]

Synthetic polymers occupy a unique place in the field of ion mobility mass spectrometry (IMS–MS). Indeed, due to their intrinsic dispersity, they have the asset to offer a broad range of homologous ions with different lengths that can be detected in several charge states. In addition, the gas-phase structure of polymer ions mostly depends on their ability to screen the adducted charges. Several works dealing with linear, cyclic, and star-shaped polymers have already shown that the gas-phase structure of polymer ions heavily relies on the polymer architecture, i.e. the primary structure. In the present work, we move a step further by evaluating whether a relationship exists between the primary and secondary structures of synthetic homo and copolymers. The IMS–MS experiments will be further complemented by MD simulations. To highlight the effectiveness of IMS separation, we selected isomeric homo and copolymers made of lactide (LA) and propiolactone (PL) units. In this way, the mass analysis becomes useless since isomeric comonomer sequences can coexist for any given chain length. An UPLC method was implemented in the workflow to successfully separate all PL–LA comonomer sequences before infusion in the IMS–MS instrument. The analysis of doubly charged copolymers showed that the comonomer sequence has an impact on the IMS response. However, this only holds for copolymer ions with precise sizes and charge states, and this is therefore not a rule of thumb. [ABSTRACT FROM AUTHOR]

One of the main issues when using traveling wave ion mobility spectrometry (TWIMS) for the determination of collisional cross-section (CCS) concerns the need for a robust calibration procedure built from referent ions of known CCS. Here, we implement synthetic polymer ions as CCS calibrants in positive ion mode. Based on their intrinsic polydispersities, polymers offer in a single sample the opportunity to generate, upon electrospray ionization, numerous ions covering a broad mass range and a large CCS window for different charge states at a time. In addition, the key advantage of polymer ions as CCS calibrants lies in the robustness of their gas-phase structure with respect to the instrumental conditions, making them less prone to collisional-induced unfolding (CIU) than protein ions. In this paper, we present a CCS calibration procedure using sodium cationized polylactide and polyethylene glycol, PLA and PEG, as calibrants with reference CCS determined on a home-made drift tube. Our calibration procedure is further validated by testing the polymer calibration to determine CCS of numerous different ions for which CCS are reported in the literature. [ABSTRACT FROM AUTHOR]

The low-kinetic energy collision-induced dissociation (CID) behavior of different sodium-cationized polylactide (PLA) oligomers was thoroughly investigated to shed some light on the analytical potentialities of CID experiments in the context of polymer characterization. Indeed, investigation of several end-groups modified PLA reveals that, in addition to the expected end-group specific dissociations, collisionally-excited PLA.Na+ suffer from a backbone cleavage. The so-obtained sodium-bound dimer cations consecutively undergo the loss of a monomeric residue that corresponds to neutral acrylic acid. The experimental observations, performed on a hybrid Q-ToF instrument, were totally corroborated by a theoretical study involving DFT calculations, molecular mechanics, and molecular dynamics calculations. [Copyright &y& Elsevier]

Folding and unfolding processes are key aspects that should be mastered for the design of foldamer molecules for targeted applications. In contrast to the solution phase, in vacuo conditions represent a well-defined environment to analyze the intramolecular interactions that largely control the folding/unfolding dynamics. Ion mobility mass spectrometry coupled to theoretical modeling represents an efficient method to decipher the spatial structures of gaseous ions, including foldamers. However, charge solvation typically compacts the ion structure in the absence of strong stabilizing secondary interactions. This is the case in peptoids that are synthetic peptide regioisomers whose side chains are connected to the nitrogen atoms of the backbone instead of α-carbon as in peptides, thus implying the absence of H-bonds among the core units of the backbone. A recent work indeed reported that helical peptoids based on N spe units formed in solution do not retain their secondary structure when transferred to the gas phase upon electrospray ionization (ESI). In this context, we demonstrate here that the helical structure of peptoids bearing ( S )- N -(1-carboxy-2-phenylethyl) bulky side chains ( N scp) is largely preserved in the gas phase by the creation of a hydrogen bond network, induced by the presence of carboxylic moieties, that compensates for the charge solvation process.

Polylactide (PLA) has emerged as one of the most promising bio-based alternatives to petroleum-based plastics, mainly because it can be produced from the fermentation of naturally occurring sugars and because it can be industrially compostable. In spite of these benefits, the industrial ring-opening polymerization (ROP) of l-lactide (L-LA) still requires the use of highly active and thermally stable metal-based catalysts, which have raised some environmental concerns. While the excellent balance between activity and functional group compatibility of organic acid catalysts makes them some of the most suitable catalysts for the metal-free ROP of L-LA, the majority of these acids are highly volatile and subject to decomposition at high temperature, which limits their use under industrially relevant conditions. In this work we exploit the use of a nonstoichiometric acid-base organocatalyst to promote the solvent-free and metal-free ROP of L-LA at elevated temperatures in the absence of epimerization and transesterification. To do so, a stable acidic complex was prepared by mixing 4-(dimethylamino)pyridine (DMAP) with 2 equiv of methanesulfonic acid (MSA). Both experimental and computational results indicate that DMAP:MSA (1:2) not only is highly thermally stable but also promotes the retention of stereoregularity during the polymerization of L-LA, leading to PLLA with a molar mass of up to 40 kg mol -1 and a chiral purity in excess of 98%. This result provides a new feature to exploit in organocatalyzed polymerization and in the design of new catalysts to facilitate the path to market., Competing Interests: The authors declare no competing financial interest., (© 2021 American Chemical Society.)

Despite significant advances in organocatalysis, stereoselective polymerization reactions utilizing chiral organocatalysts have received very little attention, and much about the underlying mechanisms remains unknown. Here, we report that both commercially available ( R , R )- and ( S , S )-enantiomers of chiral thiourea-amine Takemoto's organocatalysts promote efficient control and high isoselectivity at room temperature of the ring-opening polymerization (ROP) of racemic lactide by kinetic resolution, yielding highly isotactic, semicrystalline and metal-free polylactide (PLA). Kinetic investigations and combined analyses of the resulting PLAs have allowed the stereocontrol mechanism, which eventually involves both enantiomorphic site control and chain-end control, to be determined. Moreover, epimerization of rac -LA to meso -LA is identified as being responsible for the introduction of some stereoerrors during the ROP process.

Novel well-defined amphiphilic poly(D-lactide)-b-poly(N,N-dimethylamino-2-ethyl methacrylate) (PDLA-b-PDMAEMA) and poly(L-lactide)-b-poly(N,N-dimethylamino-2-ethyl methacrylate) (PLLA-b-PDMAEMA) copolymers were obtained. The synthesis strategy consisted of a three-step procedure: (i) controlled ring-opening polymerization (ROP) of (D- or L-)lactide initiated by Al(O(i)Pr)(3), followed by (ii) quantitative conversion of the polylactide (PLA) hydroxyl end-groups with bromoisobutyryl bromide and (iii) atom transfer radical polymerization (ATRP) of DMAEMA. The PLA block molecular weight was kept below 5000 g/mol. The macromolecular parameters of the (co)polymers were determined by (1)H NMR spectroscopy and size exclusion chromatography (SEC). The stereocomplexes of PDLA-b-PDMAEMA/PLLA-b-PDMAEMA diblock copolymers were prepared via solvent casting. The stereocomplex formation was evidenced by differential scanning calorimetry (DSC) and X-ray diffraction (XRD) analyses. The obtained stereocomplexes had melting temperature of about 65 degrees C above that of the individual copolymers and exhibited diffraction patterns assigned to the stereocomplex crystallites. In addition, for the first time it was shown that the replacement of one of the PLA partners with high molecular weight PLLA or PDLA did not hamper the stereocomplex formation. The presence of PDMAEMA blocks proved to impart hydrophilicity of the synthesized copolymers and related stereocomplexes, as determined by static water contact angle measurements.