Radical polymerizationIn polymer chemistry, free-radical polymerization (FRP) is a method of polymerization by which a polymer forms by the successive addition of free-radical building blocks (repeat units). Free radicals can be formed by a number of different mechanisms, usually involving separate initiator molecules. Following its generation, the initiating free radical adds (nonradical) monomer units, thereby growing the polymer chain. Free-radical polymerization is a key synthesis route for obtaining a wide variety of different polymers and materials composites.
PolymerA polymer (ˈpɒlᵻmər; 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.
Photo-oxidation of polymersIn polymer chemistry photo-oxidation (sometimes: oxidative photodegradation) is the degradation of a polymer surface due to the combined action of light and oxygen. It is the most significant factor in the weathering of plastics. Photo-oxidation causes the polymer chains to break (chain scission), resulting in the material becoming increasingly brittle. This leads to mechanical failure and, at an advanced stage, the formation of microplastics. In textiles the process is called phototendering.
Anionic addition polymerizationIn polymer chemistry, anionic addition polymerization is a form of chain-growth polymerization or addition polymerization that involves the polymerization of monomers initiated with anions. The type of reaction has many manifestations, but traditionally vinyl monomers are used. Often anionic polymerization involves living polymerizations, which allows control of structure and composition. As early as 1936, Karl Ziegler proposed that anionic polymerization of styrene and butadiene by consecutive addition of monomer to an alkyl lithium initiator occurred without chain transfer or termination.
Emulsion polymerizationEmulsion polymerization is a type of radical polymerization that usually starts with an emulsion incorporating water, monomer, and surfactant. The most common type of emulsion polymerization is an oil-in-water emulsion, in which droplets of monomer (the oil) are emulsified (with surfactants) in a continuous phase of water. Water-soluble polymers, such as certain polyvinyl alcohols or hydroxyethyl celluloses, can also be used to act as emulsifiers/stabilizers. The name "emulsion polymerization" is a misnomer that arises from a historical misconception.
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.
CopolymerIn polymer chemistry, a copolymer is a polymer derived from more than one species of monomer. The polymerization of monomers into copolymers is called copolymerization. Copolymers obtained from the copolymerization of two monomer species are sometimes called bipolymers. Those obtained from three and four monomers are called terpolymers and quaterpolymers, respectively. Copolymers can be characterized by a variety of techniques such as NMR spectroscopy and size-exclusion chromatography to determine the molecular size, weight, properties, and composition of the material.
End groupEnd groups are an important aspect of polymer synthesis and characterization. In polymer chemistry, they are functional groups that are at the very ends of a macromolecule or oligomer (IUPAC). In polymer synthesis, like condensation polymerization and free-radical types of polymerization, end-groups are commonly used and can be analyzed by nuclear magnetic resonance (NMR) to determine the average length of the polymer. Other methods for characterization of polymers where end-groups are used are mass spectrometry and vibrational spectrometry, like infrared and raman spectroscopy.
Ethylene glycolEthylene glycol (IUPAC name: ethane-1,2-diol) is an organic compound (a vicinal diol) with the formula . It is mainly used for two purposes, as a raw material in the manufacture of polyester fibers and for antifreeze formulations. It is an odorless, colorless, flammable, viscous liquid. Ethylene glycol has a sweet taste, but it is toxic in high concentrations. This molecule has been observed in outer space. Ethylene glycol is produced from ethylene (ethene), via the intermediate ethylene oxide.
Diethylene glycolDiethylene glycol (DEG) is an organic compound with the formula (HOCH2CH2)2O. It is a colorless, practically odorless, and hygroscopic liquid with a sweetish taste. It is a four carbon dimer of ethylene glycol. It is miscible in water, alcohol, ether, acetone, and ethylene glycol. DEG is a widely used solvent. It can be a contaminant in consumer products; this has resulted in numerous epidemics of poisoning since the early 20th century. DEG is produced by the partial hydrolysis of ethylene oxide.
