Search results for "polymer"

Method for polyamide synthesis

2004

Proton Exchange Membrane Fuel Cells (PEMFCs): Advances and Challenges

2021

The study of the electrochemical catalyst conversion of renewable electricity and carbon oxides into chemical fuels attracts a great deal of attention by different researchers. The main role of this process is in mitigating the worldwide energy crisis through a closed technological carbon cycle, where chemical fuels, such as hydrogen, are stored and reconverted to electricity via electrochemical reaction processes in fuel cells. The scientific community focuses its efforts on the development of high-performance polymeric membranes together with nanomaterials with high catalytic activity and stability in order to reduce the platinum group metal applied as a cathode to build stacks of proton …

Direct P-functionalization of azobenzene by a cationic phosphidozirconocene complex.

2016

International audience; We report that the cationic phosphidozirconocene complex [(eta(5)-C5H5)(2)Zr(PCy2)][CH3B(C6F5)(3)] (II) reacts with azobenzene, resulting in the expedient formation of Zr complex (2) bound to a tridentate PNN ligand. This reaction proceeds by a mechanism of cooperative nucleophilic substitution of hydrogen. The intermediate sigma(H) adduct (1) has been characterized by NMR spectroscopy.

Controlling Oxidative Addition and Reductive Elimination at Tin(I) via Hemi-Lability.

2021

We report on the synthesis of a distannyne supported by a pincer ligand bearing pendant amine donors that is capable of reversibly activating E–H bonds at one or both of the tin centres through dissociation of the hemi-labile N–Sn donor/acceptor interactions. This chemistry can be exploited to sequentially (and reversibly) assemble mixed-valence chains of tin atoms of the type ArSn{Sn(Ar)H} n SnAr ( n = 1, 2). The experimentally observed (decreasing) propensity towards chain growth with increasing chain length can be rationalized both thermodynamically and kinetically by the electron-withdrawing properties of the –Sn(Ar)H– backbone units generated via oxidative addition. peerReviewed

Influence of aryl hydrocarbon- (Ah) receptor and genotoxins on DNA repair gene expression and cell survival of mouse hepatoma cells

2009

The aryl hydrocarbon receptor (AhR) mediates toxicity of a variety of environmental pollutants such as polycyclic aromatic hydrocarbons (PAHs) and dioxins. However, the underlying mechanisms and genetic programmes regulated by AhR to cause adverse effects but also to counteract poisoning are still poorly understood. Here we analysed the effects of two AhR ligands, benzo[a]pyrene (B[a]P), a DNA damaging tumour initiator and promotor and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), a pure tumour promoter, on cell survival and on nucleotide excision repair (NER) gene expression. NER deals with so called "bulky" DNA adducts including those generated by enzymatically activated B[a]P. Therefore, t…

SMOOTHLY SHIFTING FLUORESCENT WINDOW: TUNABLE “OFF-ON-OFF”MICELLAR BIOSENSORS FOR pH

2009

Ethyl hexanoate transfer in paper and plastic food packaging by sorption and permeation experiments

2008

The barrier properties of one treated paper packaging and one standard plastic film (bi-oriented polypropylene, biOPP) were assessed for ethyl hexanoate. Three methods based either on sorption (gravimetry and micro-atmosphere-derived method) or permeation kinetic determination were used in controlled conditions of aroma vapor concentration (107 Pa), temperature (25 degrees C) and relative humidity (about 0 %). Ethyl hexanoate solubility values were on the same range of magnitude for both packaging films in spite of their different nature and composition. Ethyl hexanoate affinity for both films was well predicted by their respective solubility parameters. Solubility values were different acc…

Bio-polymeric based sponges for oily waste recovery

2015

Over the last years, many efforts were dedicated to the development of sustainable sorbent materials. The interest concerns a wide range of applications. Oily products and utilization are increasing all over the world as far as the possibility of spill oily accidents. In this direction, production of sponges showing lipophilic properties allows for the proper disposal of oily waste and does not cause secondary pollution. In this work, it is proposed an eco-friendly technology to prepare a polycaprolactone (PCL) biodegradable sponge for the selective absorption of oil from water. PCL biopolymer matrix was melt mixed with water-soluble porogen agents and then leached in water to obtain a poro…

Melt Processed PCL/PEG Scaffold with Discrete Pore Size Gradient for Selective Cellular Infiltration

2016

In order to develop scaffold able to mimic the natural gradient properties of tissues, biphasic and triphasic approaches were adopted. In this work, polycaprolactone/polyethylene glycol (PCL/PEG) scaffolds were prepared by using a combination of melt mixing and selective leaching without harmful solvents. The method permitted to develop three-layer scaffolds with high control of porosity and pore size. The mechanical properties were evaluated under physiological condition in order to simulate the real conditions of work. Co-culture of osteoblastic and fibroblastic mice cells were carried out in order to study the differential cellular permeation through the different pore size layers.

Remarkable effect of organoaluminum activator on catalytic performance of bis(phenoxy-imine) titanium complexes in ethylene polymerization

2009

Zsyntezowano i sprawdzono w polimeryzacji etylenu, po uprzedniej aktywacji zarówno MAO, jak i prostymi związkami glinoorganicznymi (Et3Al, Et2AlCl, EtAlCl2), trzy kompleksy tytanu z ligandami fenoksy-iminowymi: dichlorek bis[N-(3,5-di-tert-butylosalicylideno)anilino]tytanu(IV) (kompleks I), dichlorek bis[N-(3,5-di-tert-butylosalicylideno)-1-naftyloamino]tytanu(IV) (kompleks II) i dichlorek bis[N-(salicylideno)-1-naftyloamino]tytanu(IV) (kompleks III). Stwierdzono, że zarówno struktura ligandów, jak i rodzaj glinoorganicznego aktywatora mają wpływ na aktywność badanych kompleksów. Kompleks I, zawierający podstawnik fenylowy przy iminowym atomie azotu okazał się najaktywniejszy w połączeniu z…