Vinyl Ester Oligomer Crosslinked Porous Polymers Prepared via Surfactant-Free High Internal Phase Emulsions

Using vinyl ester resin (VER) containing styrene (or methyl methacrylate) and vinyl ester oligomer (VEO) as external phase, Pickering high internal phase emulsions (Pickering HIPEs) having internal phase volume fraction of up to 95 vol% were prepared with copolymer particles as sole stabilizer. Polymerizing the external phase of these Pickering HIPEs led to porous polymers (poly-Pickering-HIPEs). Compared to the polystyrene- (PS-) based poly-Pickering-HIPEs which were prepared with mixture of styrene and divinylbenzene (DVB) as crosslinker, the poly-Pickering-HIPEs herein showed much higher elastic modulus and toughness. The elastic modulus of these poly-Pickering-HIPEs increased with increasing the VEO concentration in the external phase, while it decreased with increasing internal phase volume fraction. Increasing VEO concentration in the external phase also resulted in a decrease in the average void diameter as well as a narrow void diameter distribution of the resulting poly-Pickering-HIPEs. In addition, there were many small pores in the voids surface caused by the volume contraction of VER during the polymerization, which suggests a new method to fabricate porous polymers having a well-defined hierarchical pore structure

Augmented Tikhonov Regularization Method for Dynamic Load Identification

We introduce the augmented Tikhonov regularization method motivated by Bayesian principle to improve the load identification accuracy in seriously ill-posed problems. Firstly, the Green kernel function of a structural dynamic response is established; then, the unknown external loads are identified. In order to reduce the identification error, the augmented Tikhonov regularization method is combined with the Green kernel function. It should be also noted that we propose a novel algorithm to determine the initial values of the regularization parameters. The initial value is selected by finding a local minimum value of the slope of the residual norm. To verify the effectiveness and the accuracy of the proposed method, three experiments are performed, and then the proposed algorithm is used to reproduce the experimental results numerically. Numerical comparisons with the standard Tikhonov regularization method show the advantages of the proposed method. Furthermore, the presented results show clear advantages when dealing with ill-posedness of the problem

Loss of endothelial hypoxia inducible factor-prolyl hydroxylase 2 induces cardiac hypertrophy and fibrosis

BACKGROUND: Cardiac hypertrophy and fibrosis are common adaptive responses to injury and stress, eventually leading to heart failure. Hypoxia signaling is important to the (patho)physiological process of cardiac remodeling. However, the role of endothelial PHD2 (prolyl-4 hydroxylase 2)/hypoxia inducible factor (HIF) signaling in the pathogenesis of cardiac hypertrophy and heart failure remains elusive. METHODS AND RESULTS: Mice with Egln1Tie2Cre (Tie2-Cre-mediated deletion of Egln1 [encoding PHD2]) exhibited left ventricular hypertrophy evident by increased thickness of anterior and posterior wall and left ventricular mass, as well as cardiac fibrosis. Tamoxifen-induced endothelial Egln1 deletion in adult mice also induced left ventricular hypertrophy and fibrosis. Additionally, we observed a marked decrease of PHD2 expression in heart tissues and cardiovascular endothelial cells from patients with cardiomyopathy. Moreover, genetic ablation of Hif2a but not Hif1a in Egln1Tie2Cre mice normalized cardiac size and function. RNA sequencing analysis also demonstrated HIF-2α as a critical mediator of signaling related to cardiac hypertrophy and fibrosis. Pharmacological inhibition of HIF-2α attenuated cardiac hypertrophy and fibrosis in Egln1Tie2Cre mice. CONCLUSIONS: The present study defines for the first time an unexpected role of endothelial PHD2 deficiency in inducing cardiac hypertrophy and fibrosis in an HIF-2α– dependent manner. PHD2 was markedly decreased in cardiovascular endothelial cells in patients with cardiomyopathy. Thus, targeting PHD2/HIF-2α signaling may represent a novel therapeutic approach for the treatment of pathological cardiac hypertrophy and failure

Integrating PtNi nanoparticles on NiFe layered double hydroxide nanosheets as a bifunctional catalyst for hybrid sodium-air batteries

Hybrid sodium-air batteries (HSABs) are emerging systems for next-generation energy storage owing to their high theoretical energy density, high specific capacity, low cost, and environmental friendliness. However, the ungratified energy efficiency, large overpotential, and poor cycling stability associated with the sluggish oxygen reduction reaction/oxygen evolution reaction (ORR/OER) at air electrodes hamper their further development. Herein, we report a facile electrodeposition method to construct three-dimensional nickel defect-rich nickel-iron layered double hydroxide nanosheets decorated with platinum-nickel alloyed nanoparticles grown on macroporous nickel foam substrates (PtNi/NixFe LDHs) as a binder-free electrocatalyst. The optimal catalyst (Pt3Ni1/NixFe LDHs) demonstrates a low overpotential (265 mV at the current density of 10 mA cm-2), a small Tafel slope (22.2 mV dec-1) towards the OER and a high half-wave potential (0.852 V) for ORR, as well as superior long-term stability in comparison to commercial catalysts. Theoretical calculations revealed that the Ni-top site of Pt3Ni1/NixFe LDHs works as an active site for enhanced OER/ORR activities. The fabricated HSAB with Pt3Ni1/NixFe LDHs as the air cathode displayed not only an initial low overpotential gap (0.50 V) but also superior rechargeability and structure stability with high round-trip efficiency (∼79.9%) of over 300 cycles. These results provide a novel design of bifunctional and binder-free catalyst as the cathode for metal-air batteries. This journal i

Synthèse de copolymères à base de poly -caprolactone en phase fondue par polymérisations vivantes

In this dissertation, we investigate the continuous synthesis of functional poly( -caprolactone) (PCL) and controlled copolymerization of -caprolactone (CL) with n-butyl acrylate (BA). In the first part, Ti[O(CH2)4OCH=CH2]4 was synthesized and used to obtain double-bond functionalized PCL. The kinetics of Ti[O(CH2)4OCH=CH2]4 initiated ring-opening polymerization (ROP) of -caprolactone was thoroughly investigated and the gelation process of CL/Ti[O(CH2)4OCH=CH2]4/BA/BPO system was monitored by rheological method. Then the cross-linked PCL/PBA networks were in situ synthesized in poly(methyl methacrylate) (PMMA) matrix via reactive extrusion. In the second part, Ti[OCH2CCl3]4 was synthesized and used as difunctional initiator for ROP of -caprolactone and atom transfer radical polymerization (ATRP) of n-butyl acrylate. The kinetics of Ti[OCH2CCl3]4 initiated ROP of -caprolactone and ATRP of n-butyl acrylate were evaluated. PCL-block-PBA copolymers were synthesized by sequential combination of ROP of -caprolactone and ATRP of n-butyl acrylate. Then PBA synthsized by Ti[OCH2CCl3]4 initiated ATRP was used as a macroinitiator, PCL-block-PBA copolymer was in situ polymerized in PMMA matrix in Haake internal mixer to investigate the possibility of producing well-defined in PCL-block-PBA copolymer in PMMA matrix through reactive extrusionDans cette thèse, nous étudions la synthèse de poly( -caprolactone) (PCL) fonctionnelle ainsi que la copolymérisation contrôlée de l' -caprolactone (CL) avec l'acrylate de butyle (BA) dans une matrice polymère thermoplastique via l'extrusion réactive. Dans la première partie, l'initiateur de formule Ti[O(CH2)4OCH=CH2]4 a été synthétisé dans le but d'élaborer de la PCL fonctionnelle. La cinétique de polymérisation par ouverture de cycle (ROP) initiée par Ti[O(CH2)4OCH=CH2]4 a été étudiée. Par ailleurs, un processus de gélification a été mis en évidence par rhéologie lors de la polymérisation simultanée de l' -caprolactone et de l'acrylate de butyle. Dans un second temps, ces réseaux ont été élaborés dans une matrice de poly (methyl methacrylate) (PMMA) par voie fondue. Dans la deuxième partie, un initiateur schématisé par Ti[OCH2CCl3]4 a été synthétisé dans le but de coupler 2 techniques de polymérisations contrôlées, à savoir la polymérisation par ROP de l' -caprolactone et la polymérisation radicalaire par transfert d'atomes (ATRP) de l'acrylate de butyle. Les cinétiques de polymérisation ont été évaluées et des copolymères PCL-bloc-PBA ont été élaborés. Parallèlement, un macro initiateur porteur de chaînes de polybutylacrylate a été synthétisé par ATRP à partir de Ti(OCH2CCl3)4. Ce dernier a permis d'élaborer un copolymère avec de l' -caprolactone dans une matrice PMMA en mélangeur interne. L'objectif de cette dernière partie étant de synthétiser, in situ et en voie fondue dans une matrice thermoplastique, un matériau de structure contrôlée afin d'améliorer les propriétés de la matriceST ETIENNE-BU Sciences (422182103) / SudocSudocFranceChinaFRC

Synthesis of Monodisperse Styrene/Methyl Methacrylate/Acrylic Acid Latex Using Surfactant-Free Emulsion Copolymerization in Air

International audienceMonodisperse styrene/methyl methacrylate/acrylic acid (St/MMA/AA) copolymer microspheres have been prepared with surfactant-free emulsion polymerization in air. The presence of oxygen in the system not only caused an induction period but also decreased the average particle size (D(p)). However increasing AA concentration ([AA]) gave a reduction in the induction period. The FTIR and NMR analysis of the latex copolymer confirmed that the correlation of the copolymer compositions with the feed compositions was much better at the lower [AA] than at the higher levels. The AA contents of the copolymers obtained in air were much lower than those of the copolymers obtained under N(2) protection. Decreasing [AA] led to decrease in the copolymer molecular weight and broadening of the molecular weight distribution, but the particle size distribution (delta/D(p)) was unaffected. In addition, the average particle diameter (D(p)) was proportional to [AA](-0-2.55), and increasing comonomers feed content caused linear increase of D(p), and a monodisperse sample with final solids contents up to 34.2 wt % was obtained

Synthesis of Emulsion-templated Porous Polycaprolactone

Emulsion-templated porous materials have gained extensively in applications due to their low density and high porosity. However, by far most this type porous polymers are synthesized using conventional radical polymerization and most of the reactions are thermally initiated. Expanding the polymerization mechanisms available for emulsion-templated polymers synthesis is still highly desired. In this work, Diel-Alder (DA) reaction was used to synthesize emulsion-templated macroporous polycaprolactone (PCL). These macroporous polymers were prepared by DA reaction of polycaprolactone pendant with multiple furan group (PCL-furan) and 1,6-bis(maleimide)hexane (BisM) via a high internal 1phase emulsion as template. The porous materials have a typical structure of emulsion-templated 2materials

Polyurea-Urethane Supramolecular Thermo-Reversible Networks

International audienceNovel polyurea-urethane (PUU) supramolecular polymer networks based on triuret and tetrauret blocks were synthesized. The network formation was controlled through the conformation of hydrogen bonding moieties and their concentration. FTIR spectroscopy and solubility tests showed the presence of significant hydrogen bonds only in triuret moieties and that these bonds conducted to cross-linked materials at room temperature. Hydrogen bonding association constant, K-assn = 95 M-1, was calculated using H-1 NMR for triuret blocks' self-associations. Dynamic mechanical analysis confirmed that triuret blocks conduct to a network at room temperature and that decross-linking occurs between 105 and 135 degrees C. The tetrauret blocks had a folded conformation at room and relatively low temperatures. The polymers containing these moieties did not cross-link at room temperature and below. Temperature increase favored unfolded conformation and conducted to intermolecular hydrogen bonds and, at high temperature, to cross-linked materials

Interconnected Porous Material Prepared Via High Internal Phase Emulsion Stabilized by Mixture of Fe3O4 and Tween85

PolyHIPE monoliths with open-cell structure were prepared using an oil-in-water Pickering high internal phase emulsion (HIPEs) template. Fe3O4 nanoparticles and Tween 85 were used to stabilize the HIPE. The effects of surfactant concentration, nanoparticle amount and internal phase fraction on the average void and interconnecting pore diameter and interconnectivity degree were investigated. Efficiency of these PolyHIPEs as catalyst for Fenton reaction to decompose methyl orange was tested. The results showed that the PolyHIPE was an excellent and reusable supporter for Fenton reaction

Interconnected Porous Material Prepared Via High Internal Phase Emulsion Stabilized by Mixture of Fe

PolyHIPE monoliths with open-cell structure were prepared using an oil-in-water Pickering high internal phase emulsion (HIPEs) template. Fe3O4 nanoparticles and Tween 85 were used to stabilize the HIPE. The effects of surfactant concentration, nanoparticle amount and internal phase fraction on the average void and interconnecting pore diameter and interconnectivity degree were investigated. Efficiency of these PolyHIPEs as catalyst for Fenton reaction to decompose methyl orange was tested. The results showed that the PolyHIPE was an excellent and reusable supporter for Fenton reaction