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Atom-transfer Radical-polymerization
Atom transfer radical polymerization (ATRP) is an example of a reversible-deactivation radical polymerization. Like its counterpart, ATRA, or atom transfer radical addition, ATRP is a means of forming a carbon-carbon bond with a transition metal catalyst. Polymerization from this method is called atom transfer radical addition polymerization (ATRAP). As the name implies, the atom transfer step is crucial in the reaction responsible for uniform polymer chain growth. ATRP (or transition metal-mediated living radical polymerization) was independently discovered by Mitsuo Sawamoto and by Krzysztof Matyjaszewski and Jin-Shan Wang in 1995. :The following scheme presents a typical ATRP reaction: Overview of ATRP ATRP usually employs a transition metal complex as the catalyst with an alkyl halide as the initiator (R-X). Various transition metal complexes, namely those of Cu, Fe, Ru, Ni, and Os, have been employed as catalysts for ATRP. In an ATRP process, the dormant species is activ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reversible-deactivation Radical Polymerization
In polymer chemistry, reversible-deactivation radical polymerizations (RDRPs) are members of the class of reversible-deactivation polymerizations which exhibit much of the character of living polymerizations, but cannot be categorized as such as they are not without chain transfer or chain termination reactions. Several different names have been used in literature, which are: *Living radical polymerization *Living free radical polymerization *Controlled/"living" radical polymerization *Controlled radical polymerization *Reversible deactivation radical polymerization Though the term "living" radical polymerization was used in early days, it has been discouraged by IUPAC, because radical polymerization cannot be a truly living process due to unavoidable termination reactions between two radicals. The commonly-used term controlled radical polymerization is permitted, but reversible-deactivation radical polymerization or controlled reversible-deactivation radical polymerization (RDRP ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Number Average Molecular Weight
In polymer chemistry, the molar mass distribution (or molecular weight distribution) describes the relationship between the number of moles of each polymer species () and the molar mass () of that species. In linear polymers, the individual polymer chains rarely have exactly the same degree of polymerization and molar mass, and there is always a distribution around an average value. The molar mass distribution of a polymer may be modified by polymer fractionation. Definitions of molar mass average Different average values can be defined, depending on the statistical method applied. In practice, four averages are used, representing the weighted mean taken with the mole fraction, the weight fraction, and two other functions which can be related to measured quantities: *''Number average molar mass'' (), also loosely referred to as ''number average molecular weight'' (NAMW). *''Mass average molar mass'' (), where stands for weight; also commonly referred to as ''weight av ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Metalloenzymes
Metalloprotein is a generic term for a protein that contains a metal ion cofactor. A large proportion of all proteins are part of this category. For instance, at least 1000 human proteins (out of ~20,000) contain zinc-binding protein domains although there may be up to 3000 human zinc metalloproteins. Abundance It is estimated that approximately half of all proteins contain a metal. In another estimate, about one quarter to one third of all proteins are proposed to require metals to carry out their functions. Thus, metalloproteins have many different functions in cells, such as storage and transport of proteins, enzymes and signal transduction proteins, or infectious diseases. The abundance of metal binding proteins may be inherent to the amino acids that proteins use, as even artificial proteins without evolutionary history will readily bind metals. Most metals in the human body are bound to proteins. For instance, the relatively high concentration of iron in the human body ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Piezoelectricity
Piezoelectricity (, ) is the electric charge that accumulates in certain solid materials—such as crystals, certain ceramics, and biological matter such as bone, DNA, and various proteins—in response to applied mechanical stress. The piezoelectric effect results from the linear electromechanical interaction between the mechanical and electrical states in crystalline materials with no inversion symmetry. The piezoelectric effect is a reversible process: materials exhibiting the piezoelectric effect also exhibit the reverse piezoelectric effect, the internal generation of a mechanical strain resulting from an applied electric field. For example, lead zirconate titanate crystals will generate measurable piezoelectricity when their static structure is deformed by about 0.1% of the original dimension. Conversely, those same crystals will change about 0.1% of their static dimension when an external electric field is applied. The inverse piezoelectric effect is used in the pro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Craig Hawker
Craig Jon Hawker (born 11 January 1964) is an Australian-born chemist. His research has focused on the interface between organic and polymer chemistry, with emphasis on the design, synthesis, and application of well-defined macromolecular structures in biotechnology, microelectronics, and surface science. Hawker holds more than 45 U.S. patents, and he has co-authored over 300 papers in the areas of nanotechnology, materials science, and chemistry. He was listed as one of the top 100 most cited chemists worldwide over the decade 1992–2002, and again in 2000–2010. In 2021, Hawker was elected a member of the National Academy of Engineering for contributions to polymer chemistry through synthetic organic chemistry concepts and the advancement of molecular engineering principles. He is the director of the California Nanosystems Institute and holds a number of other laboratory directorships at the University of California, Santa Barbara. He was elected a member of the National A ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Journal Of Colloid And Interface Science
The ''Journal of Colloid and Interface Science'' is a peer-reviewed scientific journal published by Elsevier. It covers research related to colloid and interface science with a particular focus on colloidal materials and nanomaterials; surfactants and soft matter; adsorption, catalysis and electrochemistry; interfacial processes, capillarity and wetting; biomaterials and nanomedicine; and novel phenomena and techniques. The editor-in-chief is Martin Malmsten (Uppsala University). The journal was established in 1946 as ''Journal of Colloid Science''. It obtained its current name in 1966. Abstracting and indexing The journal is abstracted and indexed in: According to the ''Journal Citation Reports'', the journal has a 2021 Impact Factor The impact factor (IF) or journal impact factor (JIF) of an academic journal is a type of journal ranking. Journals with higher impact factor values are considered more prestigious or important within their field. The Impact Factor of a jour ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Triethylamine
Triethylamine is the chemical compound with the formula N(CH2CH3)3, commonly abbreviated Et3N. Like triethanolamine and the tetraethylammonium ion, it is often abbreviated TEA. It is a colourless volatile liquid with a strong fishy odor reminiscent of ammonia. Like diisopropylethylamine (Hünig's base), triethylamine is commonly employed in organic synthesis, usually as a base. Synthesis and properties Triethylamine is prepared by the alkylation of ammonia with ethanol: :NH3 + 3 C2H5OH → N(C2H5)3 + 3 H2O The pKa of protonated triethylamine is 10.75,David Evans Research Group and it can be used to prepare buffer solutions at that pH. The hydrochloride |
Ascorbic Acid
Ascorbic acid is an organic compound with formula , originally called hexuronic acid. It is a white solid, but impure samples can appear yellowish. It dissolves freely in water to give mildly acidic solutions. It is a mild reducing agent. Ascorbic acid exists as two enantiomers (mirror-image isomers), commonly denoted "" (for "levo") and "" (for "dextro"). The isomer is the one most often encountered: it occurs naturally in many foods, and is one form (" vitamer") of vitamin C, an essential nutrient for humans and many animals. Deficiency of vitamin C causes scurvy, formerly a major disease of sailors in long sea voyages. It is used as a food additive and a dietary supplement for its antioxidant properties. The "" form ( erythorbic acid) can be made by chemical synthesis, but has no significant biological role. Etymology The term ''ascorbic'' means antiscruvy and denotes the ability to fight off scurvy. It is related to combating Vitamin C deficiency. History The antiscor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Activator Regeneration Atom Transfer Radical Polymerization
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Activator may refer to: * Activator (genetics), a DNA-binding protein that regulates one or more genes by increasing the rate of transcription * Activator (phosphor), a type of dopant used in phosphors and scintillators * Enzyme activator, a type of effector that increases the rate of enzyme mediated reactions * Sega Activator, a motion-sensing controller for the Sega Mega Drive/Genesis * Activator technique, a method of spinal adjustment * Activator appliance, an orthodontic functional appliance See also * Activate (other) * Activation In chemistry and biology, activation is the process whereby something is prepared or excited for a subsequent reaction. Chemistry In chemistry, "activation" refers to the reversible transition of a molecule into a nearly identical chemical or ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Star-shaped Polymer
In polymer science, star-shaped polymers are the simplest class of branched polymers with a general structure consisting of several (at least three) linear chains connected to a central core. The core, or the center, of the polymer can be an atom, molecule, or macromolecule; the chains, or "arms", consist of variable-length organic chains. Star-shaped polymers in which the arms are all equivalent in length and structure are considered homogeneous, and ones with variable lengths and structures are considered heterogeneous. Star-shaped polymers' unique shape and associated properties, such as their compact structure, high arm density, efficient synthetic routes, and unique rheological properties make them promising tools for use in drug delivery, other biomedical applications, thermoplastics, and nanoelectronicsDrew C. Forman; Florian Wieberger; Andre Gröschel; Axel H. E. Müller; Hans-Werner Schmidt; Christopher K. Ober; Comparison of star and linear ArF resists. Proc. SPIE 7 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ionic Polymerization
In polymer chemistry, ionic polymerization is a chain-growth polymerization in which active centers are ions or ion pairs. It can be considered as an alternative to radical polymerization, and may refer to anionic polymerization or cationic polymerization. As with radical polymerization, reactions are initiated by a reactive compound. For cationic polymerization, titanium-, boron-, aluminum-, and tin-halide complexes with water, alcohols, or oxonium salts are useful as initiators, as well as strong acids and salts such as . Meanwhile, group 1 metals such as lithium, sodium, and potassium, and their organic compounds (e.g. sodium naphthalene) serve as effective anionic initiators. In both anionic and cationic polymerization, each charged chain end (negative and positive, respectively) is matched by a counterion of opposite charge that originates from the initiator. Because of the charge stability necessary in ionic polymerization, monomers which may be polymerized by this method ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
ACS Macro Lett
''ACS Macro Letters'' is a peer-reviewed scientific journal published by the American Chemical Society. , ''ACS Macro Letters'' has the highest impact factor of any journal in the field of polymer science (6.131). With the launch of ''ACS Macro Letters'', all Communications to the Editor that were formerly published in ''Macromolecules'' will be published as Letters in ''ACS Macro Letters''. Researchers are advised turn to ''ACS Macro Letters'' for reports of early, urgent results in polymer science and to ''Macromolecules'' for more detailed discussions of comprehensive research findings. Scope Examining both synthetic and naturally occurring polymers, ''ACS Macro Letters'' reports major advances in polymer synthesis, modification reactions, characteristics, theory, simulation, surface properties, and kinetics and mechanisms. The journal reports on all areas of soft matter science where macromolecules play a key role, including nanotechnology, self-assembly, supramolecular ch ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
