Search results for "Organic chemistry"
showing 10 items of 17180 documents
Low-temperature single crystal X-ray diffraction and high-pressure Raman studies on [(CH3)2NH2]2[SbCl5]
2007
The structure of bis(dimethylammonium) pentachloroantimonate(III), [(CH{sub 3}){sub 2}NH{sub 2}]{sub 2}[SbCl{sub 5}], BDP, was studied at 15 K and ambient pressure by single-crystal X-ray diffraction as well as at ambient temperature and high pressures up to 4.87(5) GPa by Raman spectroscopy. BDP crystallizes in the orthorhombic Pnma space group with a=8.4069(4), b=11.7973(7), c=14.8496(7) A, and Z=4; R{sub 1}=0.0381, wR{sub 2}=0.0764. The structure consists of distorted [SbCl{sub 6}]{sup 3-} octahedra forming zig-zag [{l_brace}SbCl{sub 5}{r_brace}{sub n}]{sup 2n-} chains that are cross-linked by dimethylammonium [(CH{sub 3}){sub 2}NH{sub 2}]{sup +} cations. The organic and inorganic substr…
The use of in-line quantitative analysis to follow polymer processing
2009
In this work it is presented three applications of real time analysis during extrusion process using an optical device developed by our research group, which applies the concepts of light extinction. Monitoring of polymer blends morphology takes place to infer data concerned to dispersed phase size and concentration. The detector also enables information about melting temperature of polymer during extrusion and the level of viscous heating, and the exfoliation step during processing of a polymer-clay nanocomposite.
Hyaluronan-coated polybenzofulvene brushes as biomimetic materials
2016
Hyaluronic acid (HA) forms pericellular coats in many cell types that are involved in the early stages of cell adhesion by interacting with the CD44 receptor. Based on the largely recognized overexpression of the CD44 receptor in tumor tissues, a polybenzofulvene molecular brush has been enveloped into hyaluronan shells to obtain a tri-component polymer brush (TCPB) composed of intrinsically fluorescent backbones bearing nona(ethylene glycol) arms terminated with low molecular weight HA macromolecules. The nanoaggregates obtained in TCPB water dispersions were characterized on the basis of dimensions, zeta potential, and in vitro cell toxicity. This biomimetic multifunctional material beari…
Functional Bionanocomposite Fibers of Chitosan Filled with Cellulose Nanofibers Obtained by Gel Spinning
2021
Extremely high mechanical performance spun bionanocomposite fibers of chitosan (CHI), and cellulose nanofibers (CNFs) were successfully achieved by gel spinning of CHI aqueous viscous formulations filled with CNFs. The microstructural characterization of the fibers by X-ray diffraction revealed the crystallization of the CHI polymer chains into anhydrous chitosan allomorph. The spinning process combining acidic–basic–neutralization–stretching–drying steps allowed obtaining CHI/CNF composite fibers of high crystallinity, with enhanced effect at incorporating the CNFs. Chitosan crystallization seems to be promoted by the presence of cellulose nanofibers, serving as nucleation sites for the gr…
Block copolymers from ionic liquids for the preparation of thin carbonaceous shells
2017
This paper describes the controlled radical polymerization of an ionic-liquid monomer by RAFT polymerization. This allows the control over the molecular weight of ionic liquid blocks in the range of 8000 and 22000 and of the block-copolymer synthesis. In this work we focus on block copolymers with an anchor block. They can be used to control the formation of TiO2 nanoparticles, which are functionalized thereafter with a block of ionic-liquid polymer. Pyrolysis of these polymer functionalized inorganic nanoparticles leads to TiO2 nanoparticles coated with a thin carbonaceous shell. Such materials may, e.g., be interesting as battery materials.
Cyclo- and Polyphosphazenes for Biomedical Applications
2022
Cyclic and polyphosphazenes are extremely interesting and versatile substrates characterized by the presence of -P=N- repeating units. The chlorine atoms on the P atoms in the starting materials can be easily substituted with a variety of organic substituents, thus giving rise to a huge number of new materials for industrial applications. Their properties can be designed considering the number of repetitive units and the nature of the substituent groups, opening up to a number of peculiar properties, including the ability to give rise to supramolecular arrangements. We focused our attention on the extensive scientific literature concerning their biomedical applications: as antimicrobial age…
Polysarcosine-Based Lipids: From Lipopolypeptoid Micelles to Stealth-Like Lipids in Langmuir Blodgett Monolayers.
2016
Amphiphiles and, in particular, PEGylated lipids or alkyl ethers represent an important class of non-ionic surfactants and have become key ingredients for long-circulating (“stealth”) liposomes. While poly-(ethylene glycol) (PEG) can be considered the gold standard for stealth-like materials, it is known to be neither a bio-based nor biodegradable material. In contrast to PEG, polysarcosine (PSar) is based on the endogenous amino acid sarcosine (N-methylated glycine), but has also demonstrated stealth-like properties in vitro, as well as in vivo. In this respect, we report on the synthesis and characterization of polysarcosine based lipids with C14 and C18 hydrocarbon chains and their end g…
Comparison of the Properties of Activated Carbons Produced in One-Stage and Two-Stage Processes
2018
Activated carbons (ACs) can be produced from biomass in a thermal process either in a direct carbonization-activation process or by first carbonizing the biomass and later activating the bio-chars into activated carbons. The properties of the ACs are dependent on the type of process used for production. In this study, the properties of activated carbons produced in one-stage and two-stage processes are considered. Activated carbons were produced by physical activation of two types of starting materials: bio chars produced from spruce and birch chips in a commercial carbonization plant and from the corresponding raw chips. The activated carbons produced were characterized regarding specific …
Selective Laser Sintering of Metal-Organic Frameworks: Production of Highly Porous Filters by 3D Printing onto a Polymeric Matrix.
2019
Metal‐organic frameworks (MOFs) have raised a lot of interest, especially as adsorbing materials, because of their unique and well‐defined pore structures. One of the main challenges in the utilization of MOFs is their crystalline and powdery nature, which makes their use inconvenient in practice. Three‐dimensional printing has been suggested as a potential solution to overcome this problem. We used selective laser sintering (SLS) to print highly porous flow‐through filters containing the MOF copper(II) benzene‐1,3,5‐tricarboxylate (HKUST‐1). These filters were printed simply by mixing HKUST‐1 with an easily printable nylon‐12 polymer matrix. By using the SLS, powdery particles were fused t…
Inside Cover: Hydrogen-Bonded Open-Framework with Pyridyl-Decorated Channels: Straightforward Preparation and Insight into Its Affinity for Acidic Mo…
2017
International audience; A hydrogen-bonded open framework with pores decorated by pyridyl groups was constructed by off-charge-stoichiometry assembly of protonated tetrakis(4-pyridyloxymethyl)methane and [Al(oxalate)(3)](3-), which are the H-bond donor and acceptor of ionic H-bond interactions, respectively. This supramolecular porous architecture (SPA-2) has 1nm-large pores interconnected in 3D with large solvent-accessible void (53%). It demonstrated remarkable affinity for acidic organic molecules in solution, which was investigated by means of various carboxylic acids including larger drug molecules. Competing sorption between acetic acid and its halogenated homologues evidenced good sel…