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Dendrimer
Dendrimers are highly ordered, branched polymeric molecules. Synonymous terms for dendrimer include arborols and cascade molecules. Typically, dendrimers are symmetric about the core, and often adopt a spherical three-dimensional morphology. The word dendron is also encountered frequently. A dendron usually contains a single chemically addressable group called the focal point or core. The difference between dendrons and dendrimers is illustrated in the top figure, but the terms are typically encountered interchangeably. The first dendrimers were made by divergent synthesis approaches by Fritz Vögtle in 1978, R.G. Denkewalter at Allied Corporation in 1981, Donald Tomalia at Dow Chemical in 1983 and in 1985, and by George R. Newkome in 1985. In 1990 a convergent synthetic approach was introduced by Craig Hawker and Jean Fréchet. Dendrimer popularity then greatly increased, resulting in more than 5,000 scientific papers and patents by the year 2005. Properties Dendriti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dendrimer ChemEurJ 2002 3858
Dendrimers are highly ordered, branched polymeric molecules. Synonymous terms for dendrimer include arborols and cascade molecules. Typically, dendrimers are symmetric about the core, and often adopt a spherical three-dimensional morphology. The word dendron is also encountered frequently. A dendron usually contains a single chemically addressable group called the focal point or core. The difference between dendrons and dendrimers is illustrated in the top figure, but the terms are typically encountered interchangeably. The first dendrimers were made by divergent synthesis approaches by Fritz Vögtle in 1978, R.G. Denkewalter at Allied Corporation in 1981, Donald Tomalia at Dow Chemical in 1983 and in 1985, and by George R. Newkome in 1985. In 1990 a convergent synthetic approach was introduced by Craig Hawker and Jean Fréchet. Dendrimer popularity then greatly increased, resulting in more than 5,000 scientific papers and patents by the year 2005. Properties Dendritic m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Jean Fréchet
Jean M.J. Fréchet (born August 1944) is a French-American chemist and Professor Emeritus at the University of California, Berkeley. He is best known for his work on polymers including polymer-supported chemistry, chemically amplified photoresists, dendrimers, macroporous separation media, and polymers for therapeutics. Ranked among the top 10 chemists in 2021, he has authored nearly 900 scientific paper and 200 patents including 96 US patents. His research areas include organic synthesis and polymer chemistry applied to nanoscience and nanotechnology with emphasis on the design, fundamental understanding, synthesis, and applications of functional macromolecules. Fréchet is an elected fellow of the American Association for the Advancement of Science, the American Chemical Society, and the American Academy of Arts and Sciences, and an elected member of the US National Academy of Sciences, the US National Academy of Engineering, and the Academy of Europe ( Academia Europa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Donald Tomalia
Donald A. Tomalia (born September 5, 1938) is an American chemist who is known as one of the early discoverers of dendrimers. Biography Tomalia earned an undergraduate degree from the University of Michigan, a master's degree from Bucknell University and a Ph.D. in physical organic chemistry from Michigan State University. He worked at Dow Chemical for many years as a research scientist. In 1979, Tomalia created synthetic particles known as dendrimers, which have been used in nanotechnology and pharmaceuticals. In 1992, Tomalia founded his own company, Dendritech. The company was purchased by Dow Chemical a few years later. Tomalia was the scientific director of the Center for Biologic Nanotechnology at the University of Michigan Medical School. In 2001, Tomalia started Dendritic NanoTechnologies at Central Michigan University; Starpharma of Australia provided seed money for the venture and Dow took an equity position a few years later. In 2010, Tomalia founded NanoSynthons, L ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Macromolecule
A macromolecule is a very large molecule important to biophysical processes, such as a protein or nucleic acid. It is composed of thousands of covalently bonded atoms. Many macromolecules are polymers of smaller molecules called monomers. The most common macromolecules in biochemistry are biopolymers (nucleic acids, proteins, and carbohydrates) and large non-polymeric molecules such as lipids, nanogels and macrocycles. Synthetic fibers and experimental materials such as carbon nanotubes are also examples of macromolecules. Definition The term ''macromolecule'' (''macro-'' + ''molecule'') was coined by Nobel laureate Hermann Staudinger in the 1920s, although his first relevant publication on this field only mentions ''high molecular compounds'' (in excess of 1,000 atoms). At that time the term ''polymer'', as introduced by Berzelius in 1832, had a different meaning from that of today: it simply was another form of isomerism for example with benzene and acetylene and ha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dendronized Polymers
Dendronized polymers (or dendronised polymers) are linear polymers to every repeat unit of which dendrons are attached. Dendrons are regularly branched, tree-like fragments and for larger ones the polymer backbone is wrapped to give sausage-like, cylindrical molecular objects. Figure 1 shows a cartoon representation with the backbone in red and the dendrons like cake slices in green. It also provides a concrete chemical structure showing a polymethylmethacrylate (PMMA) backbone, the methyl group of which is replaced by a dendron of the third generation (three consecutive branching points). Figure 1. Cartoon representation (left) and a concrete example of a third generation dendronized polymer (right). The peripheral amine groups are modified by a substituent X which often is a protection group. Upon deprotection and modification substantial property changes can be achieved. The subscript n denotes the number of repeat units. Structure and applications Dendronized polymers can con ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cyanostar STM
A cyanostar (pentacyanopentabenzo 5nnulene) is a shape-persistent macrocycle that binds anions. Synthesis The cyanostar structure is synthesized in a one-pot process among five equivalents of a benzaldehyde bearing a ''meta''-cyanomethyl substituent. A series of Knoevenagel condensation reactions catalyzed by various bases stitches them together to make the C5-symmetric structure. Anion binding Cyanostar binds anions through hydrogen bonding from the C–H hydrogen bonds, as the hydrogen has a slight positive charge. It is the first binder to make use of cyanostilbene's electropositive CH groups. The hydrogen bonds create an electropositive region in the center of the macrocycle, creating a binding pocket. Cyanostar strongly binds anions that usually can only be bound weakly. The increased binding arises from the formation of a 2:1 complex, with two cyanostars sandwiching the anion on each side. An extended version of this structural pattern is a 4:3 alternating stack of cy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polymers
A polymer (; Greek ''poly-'', "many" + '' -mer'', "part") is a substance or material consisting of very large molecules called macromolecules, composed of many repeating subunits. Due to their broad spectrum of properties, both synthetic and natural polymers play essential and ubiquitous roles in everyday life. Polymers range from familiar synthetic plastics such as polystyrene to natural biopolymers such as DNA and proteins that are fundamental to biological structure and function. Polymers, both natural and synthetic, are created via polymerization of many small molecules, known as monomers. Their consequently large molecular mass, relative to small molecule compounds, produces unique physical properties including toughness, high elasticity, viscoelasticity, and a tendency to form amorphous and semicrystalline structures rather than crystals. The term "polymer" derives from the Greek word πολύς (''polus'', meaning "many, much") and μέρος (''meros'', ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Molecules
A molecule is a group of two or more atoms held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions which satisfy this criterion. In quantum physics, organic chemistry, and biochemistry, the distinction from ions is dropped and ''molecule'' is often used when referring to polyatomic ions. A molecule may be homonuclear, that is, it consists of atoms of one chemical element, e.g. two atoms in the oxygen molecule (O2); or it may be heteronuclear, a chemical compound composed of more than one element, e.g. water (two hydrogen atoms and one oxygen atom; H2O). In the kinetic theory of gases, the term ''molecule'' is often used for any gaseous particle regardless of its composition. This relaxes the requirement that a molecule contains two or more atoms, since the noble gases are individual atoms. Atoms and complexes connected by non-covalent interactions, such as hydrogen bonds or ionic bonds, are typically not c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Branching (polymer Chemistry)
In polymer chemistry, branching is the regular or irregular attachment of side chains to a polymer's backbone chain. It occurs by the replacement of a substituent (e.g. a hydrogen atom) on a monomer subunit by another covalently-bonded chain of that polymer; or, in the case of a graft copolymer, by a chain of another type. Branched polymers have more compact and symmetrical molecular conformations, and exhibit intra-heterogeneous dynamical behavior with respect to the unbranched polymers. In crosslinking rubber by vulcanization, short sulfur branches link polyisoprene chains (or a synthetic variant) into a multiple-branched thermosetting elastomer. Rubber can also be so completely vulcanized that it becomes a rigid solid, so hard it can be used as the bit in a smoking pipe. Polycarbonate chains can be crosslinked to form the hardest, most impact-resistant thermosetting plastic, used in safety glasses. Branching may result from the formation of carbon-carbon or various ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Molecular Weight
A molecule is a group of two or more atoms held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions which satisfy this criterion. In quantum physics, organic chemistry, and biochemistry, the distinction from ions is dropped and ''molecule'' is often used when referring to polyatomic ions. A molecule may be homonuclear, that is, it consists of atoms of one chemical element, e.g. two atoms in the oxygen molecule (O2); or it may be heteronuclear, a chemical compound composed of more than one element, e.g. water (two hydrogen atoms and one oxygen atom; H2O). In the kinetic theory of gases, the term ''molecule'' is often used for any gaseous particle regardless of its composition. This relaxes the requirement that a molecule contains two or more atoms, since the noble gases are individual atoms. Atoms and complexes connected by non-covalent interactions, such as hydrogen bonds or ionic bonds, are typically not ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
538 Arborol
Year 538 ( DXXXVIII) was a common year starting on Friday (link will display the full calendar) of the Julian calendar. At the time, it was known as the Year of the Consulship of Iohannes without colleague (or, less frequently, year 1291 ''Ab urbe condita''). The denomination 538 for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe for naming years. Events By place Byzantine Empire * March 12 – Siege of Rome: King Vitiges of the Ostrogoths ends his siege (after 374 days) and abandons Rome. He retreats with his Gothic army northeast along the ''Via Flaminia''. * Belisarius attacks the Goths when they have crossed the Milvian Bridge. After fierce resistance, Vitiges routs in panic, and many are slain or drowned in the river. * Gothic War: Vitiges strengthens the garrisons of various towns and besieges Ariminum. Byzantine forces under the Armenian general Narses arrive at Pi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chirality (chemistry)
In chemistry, a molecule or ion is called chiral () if it cannot be superposed on its mirror image by any combination of rotations, translations, and some conformational changes. This geometric property is called chirality (). The terms are derived from Ancient Greek χείρ (''cheir'') 'hand'; which is the canonical example of an object with this property. A chiral molecule or ion exists in two stereoisomers that are mirror images of each other, called enantiomers; they are often distinguished as either "right-handed" or "left-handed" by their absolute configuration or some other criterion. The two enantiomers have the same chemical properties, except when reacting with other chiral compounds. They also have the same physical properties, except that they often have opposite optical activities. A homogeneous mixture of the two enantiomers in equal parts is said to be racemic, and it usually differs chemically and physically from the pure enantiomers. Chiral molecule ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
