Evaluation of the Effect of Chemical or Enzymatic Synthesis Methods on Biodegradability of Polyesters

International audienceThis work compares the biodegradability of polyesters produced by an esterification reaction between glycerol and oleic di-acid (D 18:1) issued from green chemical pathways, via either classical thermo-chemical methods, or an enzymatic method using the immobilized lipase of Candida antartica B (Novozym 435). An elastomeric polymer synthesized by enzymatic catalysis is more biodegradable than an elastomeric thermo-chemical polyester synthesized by a standard chemical procedure. This difference lies in percentage of the dendritic motifs, in values of the degree of substitution, and certainly in cross-links inducing an hyper-branched structure less accessible to the lipolytic enzymes in a waste treatment plant. However, when the elastomeric polymer synthesized by enzymatic catalysis is processed at high temperature as required for certain industrial applications, it presents an identical rate of biodegradation than the chemical polyester. The advantages of the thermo-chemical methods are greater speed and lower cost. Enzymatic synthesis appears be suited to producing polyesters, devoid of metallic catalysts, which must be used without processing at high temperature to keep a high biodegradability

Assemblages supramoléculaires : Nouvelle réaction radicalaire appliquée à la synthèse des polyrotaxanes

Ce travail a pour objectif de synthétiser des polyrotaxanes à base de poly(oxyde d'éthylène) et d'a-cyclodextrines avec des rendements supérieurs à ceux annoncés par la littérature par Harada et coll. ou Yui et coll. qui s'élèvent respectivement à 16 et 8%. Le choix d'une méthode de fonctionnalisation des extrémités de la chaîne de poly(oxyde d'éthylène) par des groupements volumineux, a conduit à mettre au point une nouvelle réaction radicalaire. L'originalité de la réaction a rendu nécessaire une étude détaillée de manière à proposer un mécanisme de réaction grâce à la caractérisation des produits par spectrométrie de masse MALDI-TOF. La coupure homolytique réversible de la liaison C-succinimidyle a permis la polymérisation radicalaire de méthacrylate de 2-(N,N-diméthyle) amino-éthyle afin de former des copolymères triséquencés de type (MDMAE)p-(OE)n-(MDMAE)p. La nouvelle réaction radicalaire a été utilisée pour la synthèse des polyrotaxanes permettant d'atteindre des rendements de l'ordre de 95% et faire varier leurs architectures par copolymérisation de méthacrylates de 2-(N,N-dyméthyle) amino-éthyle.Carrying out a chemical reaction on a supramolecular assembly is always a challenge due to the risk or dismantlement. It was decided to investigate the problem on pseudopolyrotaxanes, the synthesis of which is carried out for instance by threading a polyethylene oxyde chain in cyclic molecules such as cyclodextrins. Blocking the chain ends (coupling) by a bulky group giving polyrotaxanes is difficult because this type of chemical modification can be prevented by dissociation in solution. It was demonstrated that choosing a blocking reaction of pseudopolyrotaxane such of a much higher rate than that of dissociation can be a solution to the problem of coupling. Thus, for the first time, high yields of polyrotaxanes were obtained by carrying out the reaction in heterogeneous medium. The comparison of the same reaction carried out on a solution of pseudopolyrotaxane shows that the homogenous situation does not provide good yields of the chemically modified suupramolecular assembly. Proofs of the structures are brought about by a combination of SEC,[exposant 1]H NMR spectroscopy, fluorescence and neutron scattering. This new radicalair reaction has also been used to form the type of copolymer (MDMAE)p-(EO)n-(MDMAE)p or the same based of polyrotaxane.EVRY-BU (912282101) / SudocSudocFranceF

Analysis of a Polydisperse Polyrotaxane Based on Poly(ethylene oxide) and α-Cyclodextrins Using Nanoelectrospray and LTQ-Orbitrap

Polyrotaxanes (PR) are among the most studied interlocked molecules in the field of supramolecular chemistry. Cyclodextrin based polyrotaxanes (CD based PRs) are well-known to be difficult to analyze by mass spectrometry (MS). Nanoelectrospray (nanoESI) employed during mass spectrometry (MS) and tandem mass spectrometry (MS/MS) experiments turns out to be particularly useful to analyze these noncovalent assemblies. While ESI/nanoESI based spectra usually contain multicharged species which greatly complicate the interpretation, particularly for such complex mixtures analysis, the hyphenation with a high resolution analyzer such as Orbitrap could overcome this limitation. This Article reports efforts to achieve a detailed structural deciphering by nanoESI-MS and nanoESI-MS/MS of CD based PRs constituted of αCDs, unmodified or surrounded by 1 or 2 sulfation(s), which were threaded along polydisperse poly(ethylene oxide) α,ω-dipyrenyl chains. The described method is more sensitive and less sample consuming than a typical NMR experiment and in good agreement with size-exclusion chromatography (SEC) results. Moreover, as compared to MALDI-TOF MS analysis, all populations were presumably elucidated without discrimination effect. Therefore, this MS development allowed us to estimate the PR sample content with 16 to 35 ethylene oxide units, 1 to 5 αCDs threaded, and 0 to 10 sulfo groups grafted on the overall CDs. Finally, the method afforded the possibility to unambiguously attribute supramolecular architectures from 2276.0278 to 7767.8342 g·mol^–1 corresponding to poly[2]- to poly[6]rotaxanes

Fonctionalization of polymers prepared by living free radical polymerization

International audienc

Fonctionalization of polymers prepared by living free radical polymerization

International audienc

Comparative analysis of the photo-oxidation of polystyrene and poly(α-methylstyrene)

International audienceThe photo-oxidation of poly(α-methylstyrene) (PαMS) has been studied by FTIR and mass spectroscopy. The samples have been submitted to various conditions of irradiation under oxygen, with different irradiation sources and at several temperatures. SF4 and NH3 treatments and photolysis under vacuum have been carried out on the photo-oxidized samples. The results obtained were compared to those obtained in the same conditions of irradiation for polystyrene samples. An identification of the photoproducts is proposed with their main ways of formation

Further Insight into the Detailed Characterization of a Polydisperse Cyclodextrin-Based Polyrotaxane Sample by Electrospray Ionization Mass Spectrometry

An easy and fast approach based on electrospray mass spectrometry (ESI-MS) was developed to provide a detailed characterization of a mixture containing polydisperse cyclodextrin-based polyrotaxane (CD-based PR). Here, method gave access to usual data such the weight-average molecular weight, the number-average molecular weight and the polydispersity index, but also to more specific features as the average number of CDs threaded and the average threading degree. Moreover, the nature and the average number of groups grafted per CD, such as sulfate or silyl groups, can be accurately determinate. This ESI-MS approach advantageously complements the widely used NMR and SEC methods and, thereby, constituting a milestone in the actual MS bottleneck regarding the analysis of polydisperse supramolecular assemblies

A New Versatile Radical Addition on α , ω ‐Dimethacrylate Poly(ethylene oxide)

International audienceThe synthesis of α ,ω ‐di(2‐methyl‐6‐pyrenyl‐2‐succinimidylhexanoic ester)poly(ethylene oxide) (Py(S)‐EOn ‐(S)Py) was obtained by a new radical reaction between 4‐pyrenylbutanoate N ‐hydroxysuccinimidyl ester and α ,ω ‐dimethacrylate poly(ethylene oxide). The reason for the choice of such bulky groups is a possible application of this reaction to the synthesis of polyrotaxane from polypseudorotaxane. Two reaction media were examined, heterogeneous in water at room temperature using persulfate as initiator, or homogeneous in DMSO at 60 °C using AIBN as initiator. Structural characterization of the functionalization products was carried out by SEC, MALDI TOF, and NMR spectroscopies. It was shown that two types of α ,ω ‐dipyrenyl PEO could be obtained, one corresponding to the expected product (Py(S)‐EOn ‐(S)Py), the other corresponding to the same structure but without the succinimidyl substituent (Py(H)‐EOn ‐(H)Py). It was also shown that in the soluble system macrocycles could be formed and this last aspect has been assigned to intramolecular interactions existing between the pyrenyl groups. An interesting aspect of this synthesis is the possibility to find conditions giving high yields without crosslinking and fairly reduced amount of coupling

Harnessing Polyisobutylene by Rotaxanation with γ-Cyclodextrin: Opportunities for Making Smart Molecular Necklaces

International audienceA new type of polyrotaxane based on the threading of γ-cyclodextrins (γ-CDs) along a highly hydrophobic polymer, polyisobutylene (PIB), is successfully prepared and finely characterized. The used radical coupling associated with tuned reaction time and temperature leads to a fast and controlled necklace synthesis with low reagent consumption. Synthesis exhibits appealing conversion and threading rates with almost 100% and 62–73%, respectively. A combination of well-established SEC and NMR techniques, with a more forefront MALDI-TOF MS approach, provides details on the original PIB and the resulting polyrotaxanes (M w , M n , PDI, and average number of γ-CD threaded). Interestingly, tetramethylguanidinium-2-(4-hydroxyphenylazo)benzoate in DMF for MALDI analysis is revealed as a suitable matrix to overcome solubility troubles widely observed with PIB. Moreover, rotaxanation appears as an alternative to the grafting of polar groups to modify/handle hydrophobic polymers. Such an approach offers new opportunities to achieve the synthesis, with unambiguous evidence, of new supramolecular necklaces based on highly hydrophobic polymers