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Topochemical Polymerization
Topochemical polymerization is a polymerization method performed by monomers aligned in the crystal state. In this process, the monomers are crystallised and polymerised under external stimuli such as heat, light, or pressure. Compared to traditional polymerisation, the movement of monomers was confined by the crystal lattice in topochemical polymerisation, giving rise to polymers with high crystallinity, tacticity, and purity. Topochemical polymerisation can also be used to synthesise unique polymers such as Polydiacetylenes, polydiacetylene that are otherwise hard to prepare. Various reactions have been adopted in the field of topochemical polymerisation, such as [2+2], [4+2], [4+4], and [3+2] cycloaddition, linear addition between dienes, trienes, diacetylenes. Other than linear polymers, they can also be applied to the synthesis of two dimensional covalent networks. History The term "topochemistry" was first introduced by Kohlschütter in 1919, referring to the chemical react ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tacticity
Tacticity (from , "relating to arrangement or order") is the relative stereochemistry of adjacent chiral centers within a macromolecule. The practical significance of tacticity rests on the effects on the physical properties of the polymer. The regularity of the macromolecular structure influences the degree to which it has rigid, crystalline long range order or flexible, amorphous long range disorder. Precise knowledge of tacticity of a polymer also helps understanding at what temperature a polymer melts, how soluble it is in a solvent, as well as its mechanical properties. A tactic macromolecule in the IUPAC definition is a macromolecule in which essentially all the configurational (repeating) units are identical. In a hydrocarbon macromolecule with all carbon atoms making up the backbone in a tetrahedral molecular geometry, the zigzag backbone is in the paper plane with the substituents either sticking out of the paper or retreating into the paper;, this projection is called ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polydiacetylenes
Polydiacetylenes (PDAs) are a family of conducting polymers closely related to polyacetylene. They are created by the 1,4 topochemical polymerization of diacetylenes. They have multiple applications from the development of organic films to immobilization of other molecules. History The first polydiacetylene to be discovered was Poly(1,6-bishydroxy hexa-2,4-diacetylene) by Gerhard Wegner in 1969. This was achieved by exposing crystals of 1,6-bishydroxy hexa-2,4-diyne to UV light. Polymerization was assumed to occur because of the spatial arrangement of diynes in the crystal, but this was not confirmed until 1972 when Raymond H. Baughman coined the term "topochemical polymerization" to describe polymerization due to spatial arrangement and put forth the spatial requirements needed for a polymerization of this sort. Synthesis Synthesis of polydiacetylenes occurs through topochemical polymerization of 1,3-diynes. Typically, this must occur in the solid state, because many diynes under ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Early Examples Of Topochemical Polymerization
Early may refer to: Places in the United States * Early, Iowa, a city * Early, Texas, a city * Early Branch, a stream in Missouri * Early County, Georgia * Fort Early, Georgia, an early 19th century fort Music * Early B, stage name of Jamaican dancehall and reggae deejay Earlando Arrington Neil (1957–1994) * Early James, stage name of American singer-songwriter Fredrick Mullis Jr. (born 1993) * ''Early'' (Scritti Politti album), 2005 * ''Early'' (A Certain Ratio album), 2002 * Early Records, a record label Other uses * Early (name), a list of people and fictional characters with the given name or surname * Early effect, an effect in transistor physics * Early, a synonym for ''hotter'' in stellar classification See also * * The Earlies, a 21st century band * Earley (other) * Earlie Earlie is a masculine given name which may refer to: * Earlie Fires (born 1947), American jockey * Earlie Thomas (1945–2022), American National Football League player * Earlie End ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Single-crystal X-ray Diffraction
X-ray diffraction is a generic term for phenomena associated with changes in the direction of X-ray beams due to interactions with the electrons around atoms. It occurs due to elastic scattering, when there is no change in the energy of the waves. The resulting map of the directions of the X-rays far from the sample is called a diffraction pattern. It is different from X-ray crystallography which exploits X-ray diffraction to determine the arrangement of atoms in materials, and also has other components such as ways to map from experimental diffraction measurements to the positions of atoms. This article provides an overview of X-ray diffraction, starting with the early history of x-rays and the discovery that they have the right spacings to be diffracted by crystals. In many cases these diffraction patterns can be Interpreted using a single scattering or kinematical theory with conservation of energy (wave vector). Many different types of X-ray sources exist, ranging from ones u ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Criteria Of Topochemical Polymerization
Criterion (: criteria) may refer to: General * Criterion, Oregon, a historic unincorporated community in the United States * Criterion Place, a proposed skyscraper in West Yorkshire, England * Criterion Restaurant, in London, England * Criterion Stakes, a horse race in Newmarket, England * Criterion Summit, a mountain pass in Oregon, United States * Criterion Wind Project, a wind farm in Maryland, United States Science and mathematics * Criteria air contaminants, air pollutants that cause smog, acid rain, and other health hazards *Criterion validity, in psychometrics, a measure of how well one variable or set of variables predicts an outcome *Criterion-referenced test, translates a test score into a statement about the behavior to be expected of a person *Problem of the criterion, in epistemology, an issue regarding the starting point of knowledge Publishing * ''Criterion'' (journal), the first philosophy journal in Catalan, published from 1925 to 1969 * ''The Criterion'', ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stress Of Topochemical Polymerization
Stress may refer to: Science and medicine * Stress (biology), an organism's response to a stressor such as an environmental condition * Stress (linguistics), relative emphasis or prominence given to a syllable in a word, or to a word in a phrase or sentence * Stress (mechanics), the internal forces that neighboring particles of a continuous material exert on each other * Oxidative stress, an imbalance of free radicals * Psychological stress, a feeling of strain and pressure ** Occupational stress, stress related to one's job * Surgical stress, systemic response to surgical injury Arts, entertainment, and media Music Groups and musicians * Stress (Brazilian band), a Brazilian heavy metal band * Stress (British band), a British rock band * Stress (pop rock band), an early 1980s melodic rock band from San Diego * Stress (musician) (born 1977), hip hop singer from Switzerland * Stress (record producer) (born 1979), artistic name of Can Canatan, Swedish musician and record ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Control Of Tacticity
Control may refer to: Basic meanings Economics and business * Control (management), an element of management * Control, an element of management accounting * Comptroller (or controller), a senior financial officer in an organization * Controlling interest, a percentage of voting stock shares sufficient to prevent opposition * Foreign exchange controls, regulations on trade * Internal control, a process to help achieve specific goals typically related to managing risk Mathematics and science * Control (optimal control theory), a variable for steering a controllable system of state variables toward a desired goal * Controlling for a variable in statistics * Scientific control, an experiment in which "confounding variables" are minimised to reduce error * Control variables, variables which are kept constant during an experiment * Biological pest control, a natural method of controlling pests * Control network in geodesy and surveying, a set of reference points of known geospatial co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polymerization Reactions
In polymer chemistry, polymerization (American English), or polymerisation (British English), is a process of reacting monomer molecules together in a chemical reaction to form polymer chains or three-dimensional networks. There are many forms of polymerization and different systems exist to categorize them. In chemical compounds, polymerization can occur via a variety of reaction mechanisms that vary in complexity due to the functional groups present in the reactants and their inherent steric effects. In more straightforward polymerizations, alkenes form polymers through relatively simple radical reactions; in contrast, reactions involving substitution at a carbonyl group require more complex synthesis due to the way in which reactants polymerize. As alkenes can polymerize in somewhat straightforward radical reactions, they form useful compounds such as polyethylene and polyvinyl chloride (PVC), which are produced in high tonnages each year due to their usefulness in manu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
