Chemical modification of polymers by acyloxyimide derivatives in reactive extrusion

La fonctionnalisation post-polymérisation ou post-fonctionnalisation est une technique qui permet d’apporter des propriétés spécifiques à des polymères dont les caractéristiques intrinsèques sont limitées pour une application donnée. Parmi les différentes stratégies de post-fonctionnalisation, une des plus courantes est le greffage radicalaire en milieu fondu par extrusion réactive (T > 160 °C). Dans ce type de procédé, un précurseur de radicaux appelé agent de greffage est utilisé afin de greffer des unités fonctionnelles sur les chaines de polymère. A ce jour, ce sont les radicaux à base de peroxydes qui sont employés. Cependant, ces derniers engendrent souvent des réactions de réticulation de chaines qui réduisent l’efficacité du processus. Afin de surmonter ces inconvénients, il est alors important de développer de nouvelles structures pertinentes. Dans ce contexte, les travaux de recherche que nous avons entrepris dans cette thèse concernent la conception et l’étude de nouveaux agents de greffage dérivés d’acétoxyphtalimide (NAPI) pour la post-fonctionnalisation de polymères. Afin d’atteindre ces objectifs, notre démarche a été basée sur une approche multidisciplinaire comportant une étude théorique par modélisation moléculaire et une approche expérimentale incluant la synthèse et l’étude de réactivité des nouvelles structures. Par la suite, des essais de post-fonctionnalisation de polyéthylène, de polyamide ainsi que de poly(acide lactique) par ces nouveaux agents de greffage ont été réalisés. Ces essais ont montré des résultats prometteurs à l’utilisation de ces nouveaux composés par rapport aux peroxydes dans les systèmes d’extrusion.Post-functionalization is a technique which allows to introduce specific properties to polymers whose intrinsic characteristics are limited for a defined application. It has become an appropriate tool to answer the strong demand for performance materials that is constantly growing. Among the post-functionalization methods, one of the most exploited is the radical grafting of the polymers in the molten state by reactive extrusion (T> 160 ° C). In this type of process, a radical precursor called grafting agent is used to graft functional units (monomers) onto the polymer backbone. In this context, the conventional grafting agents used in extrusion are peroxides. However, the radicals generated by peroxide compounds often lead to side reactions, particularly crosslinking reactions of the polymer chains which limit the efficiency of the process. Thus, finding a new family of grafting agents remains a challenge to optimize these extrusion systems. In this research work, the main objective is to use new grafting agents based on acetoxyphthalimide (NAPI) for extrusion. To reach this goal, our strategy is based on a multidisciplinary approach which presents a theoretical study by chemical modeling and an experimental approach by the synthesis and the reactivity study of the targeted structures. To validate the concept, polyethylene, polyamide and polylactic acid post-functionalization tests through these new grafting agents have been carried out. The results obtained have shown that these NAPI derivatives are efficient to graft monomers and to reduce the crosslinking reaction compared to peroxide agents

Chemical modification of poly(lactic acid) induced by thermal decomposition of N-acetoxy-phthalimide during extrusion

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Functionalization of Poly(lactide) with N-Phenyl Maleimide Using N-Acetoxy-Phthalimide During Reactive Extrusion

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Peptide ligation from alkoxyamine based radical addition

International audienceIntermolecular radical 1,2-addition (IRA) of N-tert-butyl-N-(1-diethylphosphono-2,2-dimethylpropyl)aminoxyl (SG1) based alkoxyamines onto activated olefins is used as a tool for peptide ligation. This strategy relies on simple peptide pre-derivatization to obtain (i) a SG1 nitroxide functionalized resin peptide at its N-terminus (SG1-peptide alkoxyamine), (ii) a vinyl functionalized peptide (either at its C-terminus or N-terminus), and does not require any coupling agents

Acyloxyimide derivatives as efficient promoters of polyolefin C–H functionalization: application in the melt grafting of maleic anhydride onto polyethylene

International audienceAcyloxyimides as a new H-abstracting agent have been developed for the radical grafting of maleic anhydride (MA) onto polyethylene in the melt state. Their model decomposition in DMSO-d6 as well as in tetradecane that mimics polyolefins was performed. These studies confirmed first the complete decomposition of N-acetoxyphthalimide (NAPI) in 1 hour at 180 °C by a N–O bond dissociation mechanism and also the patching of the produced macroradicals by the phthalimide group. The reaction was then performed in a mini-extruder at 190–250 °C and the hydrogen abstraction ability of N-acyloxyphthalimide (NAP)-, N-acyloxynaphthalimide (NANP)- and N-acyloxysuccinimide (NAS)-based derivatives was demonstrated. Optimal experimental conditions were determined by varying the initial MA content and the degree of grafting of MA was quantified by infrared spectroscopy. The MA grafting degree was as high as 2.98 wt% when using tBu-NAP as the H-abstracting agent at 230 °C with only a slight modification of the PE chain structures as proved by rheological experiments while the use of a peroxide (L101) led to a lower grafting degree (1.9 wt%) and a cross-linking of the polymer chains, confirmed by the three–five fold higher complex viscosit