Search results for " stability."

1990

New monomers are described for the synthesis of rod-like poly(1,4-phenyleneethynylene)s with long flexible aliphatic side chains. By palladium catalyzed polycondensation soluble polymers with melting points around 100°C could be obtained. The molecular weight was estimated by GPC, VPO and elemental analysis: GPC showed a multimodale distribution with Pn = 9–15. NMR spectra were found to be in agreement with the assumed polymer structure, but signals of the acetylenic carbons could not be detected. A broad, structureless absorption with a maximum at λ = 410 nm is seen in the UV-VIS-spectra. The thermal decomposition of the substituted PPE's starts at about 400°C and is comparable to that of …

Effect of the Biopolymer Charge and the Nanoclay Morphology on Nanocomposite Materials

2016

This work represents a contribution to the design, preparation, and characterization of nanocomposite materials based on biocompatible components. The effects of composition, filler geometry, and polymer charge were highlighted, and their role on the final properties of the nanocomposites was revealed. We combined some biopolymers (methylcellulose, alginate, chitosan) with two nanoclays (kaolinite sheets and halloysite nanotubes) to prepare nanocomposites by means of the casting method from water. The thermal stability, the surface wettability, and the mechanical properties of the obtained films were studied. SEM micrographs highlighted the surface morphology of the biocomposite materials. …

Impact of non-functionalized and ionic liquid modified carbon nanotubes on mechanical and thermal properties of ethylene- octene copolymer nanocompos…

2016

In this article the development and characterization of composites made from metallocene based ethylene-octene copolymer (EOC) with 38% octene content, non-modified or modified multi walled carbon nanotubes (MWCNTs), covalently functionalised with long chain hexadecyl moiety imidazolium ionic liquid (IL-f-MWCNTs), is presented. The procedure of MWCNTs functionalization is discussed. In order to obtain a good dispersion of the filler, composites with MWCNTs and IL-f-MWCNTs in the concentration range of 0.5-12 wt.% were made by ultrasonication / thermoplastic mixing method. The results indicated improvement in mechanical properties with increase of the filler content. The methodology of the d…

Enhanced Sieving of C2‐Hydrocarbon from Methane by Fluoro‐Functionalization of In‐MOF with Robust Stability

2021

Developing efficient adsorbent materials is crucial for adsorption and separation to realize the purification of energy source and raw chemicals. Here, we report a novel and robust 3D In-based MOF built up with fluorine-functionalized ligands, QMOF-2F, with improved separation properties of C2-light hydrocarbons over methane at room temperature respect isoreticular non-fluorinated MOF. QMOF-2F shows a remarkable chemical stability in different solvents, including water, and pH (2-12). DFT calculations support the key role of fluorine-functionalization on the improved performance of QMOF-2F.

A new macrocyclic dipyrazolate salt of diazatetraester structure able to efficiently and selectively interact with psychotropic phenethylammonium sal…

2002

Abstract The equilibrium stability constants (Ks) of a series of ammonium pyrazolate complexes [L22−]2RN(R′)H2+ (7, R′=H and 8, R′=Me) formed from a new macrocyclic disodium dipyrazolate salt of diazatetraester structure 6[L22−] 2Na+ and ammonium salts [RNH3+X− or RN(Me)H2+X−] of psychotropic drugs and neurotransmitter catecholamines has been evaluated by electrochemical methods in DMSO solution. The resulting Ks values demonstrate that in general, the diazatetraester crown-derived dipyrazolate salt 6 exerts a stronger complexing effect over phenethylammonium ions than that of the dioxatetraester crown-derived disodium dipyrazolate salt 2 previously reported. Interestingly, complexes formed…

Selective photocatalytic oxidation of 3-pyridinemethanol on platinized acid/base modified TiO2

2021

TiO2 catalysts, modified with acidic or alkaline solutions and then platinized, were used for the partial photocatalytic oxidation of 3-pyridinemethanol to 3-pyridinemethanal and vitamin B-3 under environmentally friendly conditions. The reaction took place in water under UVA light and air oxygen. Catalysts were characterized by TEM, photoluminescence, DRIFT-IR, Raman, DRS, XPS, and photocurrent measurements. The photocatalytic activity results show that Pt loading of untreated samples leads to a significant activity improvement (hence product yield) as much as acid and alkaline treatments do. Moreover, the alkaline treated TiO2 samples exhibit a further increase in activity after loading w…

Towards storage-stable high-content recycled tyre rubber modified bitumen

2018

The addition of crumb rubber particles as bitumen modifier can be currently considered as a well-established alternative to conventional polymers for bitumen modification. However, Recycle Tyre Rubber (RTR) modified binders still present drawbacks such as poor mix workability and hot storage stability. Within this study the authors try unlocking the full potential of devulcanised tyre rubber-heavy oils blend, named Liquid Rubber (LR), by exploring the possibility of tailoring recycled polymer modified bitumen with unconventional high-content of RTR and designed to overcome the above mentioned technological problems of RTR modified bitumen while keeping its advantages. Results show that LR-b…

Synthesis and properties of aromatic ionenes

1993

Cationic polyelectrolytes with aromatic segments can be synthesized by a repetitive alkylation reaction. The structure of the products, their synthesis and their solubility are described. All ionenes are not, or only in small amounts, water soluble. The best solubility can be achieved by mixtures of polar protic and aprotic solvents. Variations of the counterion produces sufficient solubility in THF. All ionenes show a typical polyelectrolyte effect. The thermal stability of aromatic ionenes and the glass transition temperature is dominated by the nature of the counterion. The molecular weight of oligomers can be described by using a combination of a conductive titration method and an ion s…

PBI-based composite membranes for polymer fuel cells

2010

Abstract In the present study poly(2,2-(2,6-pyridin)-5,5-bibenzimidazole) was used for the preparation of novel MEAs for high-temperature polymer fuel cells (HT-PEMFCs). We prepared hybrid materials with two types of silica fillers in order to increase the MEA performances using this polymer. The membranes were characterized in terms of their microstructure and thermal stability. Cell operation tests and Electrochemical Impedance Spectroscopy were used for the characterization of the MEAs. A maximum power density of about 80 mW cm−2 was obtained at 300 mA cm−2 by using an imidazole-modified silica filler. The EIS technique showed that the fillers chiefly help to reduce the charge transfer r…

Biomolecular-solvent stereodynamic coupling probed by deuteration.

1983

Thermodynamic interpretation of experiments with isotopically perturbed solvent supports the view that solvent stereodynamics is directly relevant to thermodynamic stability of biomolecules. According with the current understanding of the structure of the aqueous solvent, in any stereodynamic configuration of the latter, connectivity pathways are identifiable for their topologic and order properties. Perturbing the solvent by isotopic substitution or, e.g., by addition of co-solvents, can therefore be viewed as reinforcing or otherwise perturbing these topologic structures. This microscopic model readily visualizes thermodynamic interpretation. In conclusion, the topologic stereodynamic str…