Phase separation and self-assembly in vitrimers: hierarchical morphology of molten and semi-crystalline polyethylene/dioxaborolane maleimide systems

Vitrimers - a class of polymer networks which are covalently crosslinked and insoluble like thermosets, but flow when heated like thermoplastics - contain dynamic links and/or crosslinks that undergo an associative exchange reaction. These dynamic crosslinks enable vitrimers to have interesting mechanical/rheological behavior, self-healing, adhesive, and shape memory properties. We demonstrate that vitrimers can self-assemble into complex meso- and nanostructures when crosslinks and backbone monomers strongly interact. Vitrimers featuring polyethylene (PE) as the backbone and dioxaborolane maleimide as the crosslinkable moiety were studied in both the molten and semi-crystalline states. We observed that PE vitrimers macroscopically phase separated into dioxaborolane maleimide rich and poor regions, and characterized the extent of phase separation by optical transmission measurements. This phase separation can explain the relatively low insoluble fractions and overall crystallinities of PE vitrimers. Using synchrotron-sourced small-angle X-ray scattering (SAXS), we discovered that PE vitrimers and their linear precursors micro-phase separated into hierarchical nanostructures. Fitting of the SAXS patterns to a scattering model strongly suggests that the nanostructures - which persist in both the melt and amorphous fraction of the semi-crystalline state - may be described as dioxaborolane maleimide rich aggregates packed in a mass fractal arrangement. These findings of hierarchical meso- and nanostructures point out that incompatibility effects between network components and resulting self-assembly must be considered for understanding behavior and the rational design of vitrimer materials

Control of Gelation and Network Properties of Cationically Copolymerized Mono- and Diglycidyl Ethers

International audienceThe development of low temperature curing systems has become a major objective in thermoset technologies for both environmental and economic reasons. The use of protic and chelating additives have recently been underlined for the control of the cationic ring opening polymerization of epoxies, a curing mode that is very efficient at temperatures close from the ambient but that can easily runaway. In this paper, we propose to use this strategy to control the kinetics of the cationic copolymerization of a diepoxy monomer(diglycidyl ether of bisphenol A, DGEBA) with a monoepoxy monomer(phenyl glycidyl ether, PGE). The purpose of the study is to tune the crosslink density (ν e) in order to control the mechanical properties of the materials. The sol-gel transition was first investigated in details at several frequencies by using the Fourier transform mechanical spectroscopy method (FTMS). We found that the gel time (t gel) and the critical conversion (α gel) can be controlled to a great extent by promoting transfers and complexing cationic species involved in the polymerization mechanism. The FTMS method also gives some insight into the structure of the polymer clusters at the sol-gel transition. The results indicate that the various additives used to control the transition have mostly no influence on the clusters' structure. The properties of the fully-cured networks were then investigated via swelling and dynamic mechanical measurements. Both methods indicate that ν e is strongly influenced by the crosslinker content (DGEBA) bu

Control of reactions and network structures of epoxy thermosets

International audienc

L'acide polymethacrylique est thermosensible en solvant organique

International audienc

Activating mutations in genes related to TCR signaling in angioimmunoblastic and other follicular helper T-cell-derived lymphomas.

Angioimmunoblastic T-cell lymphoma (AITL) and other lymphomas derived from follicular T-helper cells (TFH) represent a large proportion of peripheral T-cell lymphomas (PTCLs) with poorly understood pathogenesis and unfavorable treatment results. We investigated a series of 85 patients with AITL (n = 72) or other TFH-derived PTCL (n = 13) by targeted deep sequencing of a gene panel enriched in T-cell receptor (TCR) signaling elements. RHOA mutations were identified in 51 of 85 cases (60%) consisting of the highly recurrent dominant negative G17V variant in most cases and a novel K18N in 3 cases, the latter showing activating properties in in vitro assays. Moreover, half of the patients carried virtually mutually exclusive mutations in other TCR-related genes, most frequently in PLCG1 (14.1%), CD28 (9.4%, exclusively in AITL), PI3K elements (7%), CTNNB1 (6%), and GTF2I (6%). Using in vitro assays in transfected cells, we demonstrated that 9 of 10 PLCG1 and 3 of 3 CARD11 variants induced MALT1 protease activity and increased transcription from NFAT or NF-κB response element reporters, respectively. Collectively, the vast majority of variants in TCR-related genes could be classified as gain-of-function. Accordingly, the samples with mutations in TCR-related genes other than RHOA had transcriptomic profiles enriched in signatures reflecting higher T-cell activation. Although no correlation with presenting clinical features nor significant impact on survival was observed, the presence of TCR-related mutations correlated with early disease progression. Thus, targeting of TCR-related events may hold promise for the treatment of TFH-derived lymphomas

Copolymères à blocs réactifs SBMX (synthèse, structuration et renforcement de matrices vitreuses)

PARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Use of reversible covalent and non-covalent bonds in new recyclable and reprocessable polymer materials

PARIS-BIUSJ-Biologie recherche (751052107) / SudocSudocFranceF

Modification de polymères par la chimie supramoléculaire

PARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Erosion sélective et greffage de copolymères à blocs

PARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Erosion sélective et greffage de copolymères à blocs

PARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF