Ring-opening polymerization IUPAC definition for ring-opening polymerization A polymerization in which a cyclic monomer yields a monomeric unit which is acyclic or contains fewer cycles than the monomer. Note: If the monomer is polycyclic, the opening of a single ring is sufficient to classify the reaction as ring-opening polymerization. Modified from the earlier definition[1] .[2] General scheme ionic propagation. The driving force for the ring-opening of cyclic monomers is via the relief of bond-angle strain or steric repulsions between atoms at the center of a ring. Cyclic monomers that are polymerized using ROP encompass a variety of structures, such as: History[edit] Ring-opening polymerization (ROP) has been used since the beginning of 1900s in order to synthesize polymers. Nowadays, ROP plays an important role in industry such as production of nylon-6. Mechanisms of ROP[edit] Radical ring-opening polymerization[edit] Mechanism[edit] Radical ring-opening polymerization of vinyl cyclopropane Initiation[edit]
Dialysis (biochemistry) In biochemistry, dialysis is the process of separating molecules in solution by the difference in their rates of diffusion through a semipermeable membrane, such as dialysis tubing.[1] Dialysis is a common laboratory technique that operates on the same principle as medical dialysis. In the context of life science research, the most common application of dialysis is for the removal of unwanted small molecules such as salts, reducing agents, or dyes from larger macromolecules such as proteins, DNA, or polysaccharides.[2] Dialysis is also commonly used for buffer exchange and drug binding studies. Diffusion is the random, thermal movement of molecules in solution (Brownian motion) that leads to the net movement of molecules from an area of higher concentration to a lower concentration until equilibrium is reached. Due to the pore size of the membrane, large molecules in the sample cannot pass through the membrane, thereby restricting their diffusion from the sample chamber.
Adhesion Adhesion of a frog on a wet vertical glass surface. Process of attachment of a substance to the surface of another substance. Note 1: Adhesion requires energy that can come from chemical and/or physical linkages, the latter being reversible when enough energy is applied. Note 2: In biology, adhesion reflects the behavior of cells shortly after contact to the surface. Note 3: In surgery, adhesion is used when two tissues fuse unexpectedly.[1] Surface energy[edit] Diagram of various cases of cleavage, with each unique species labeled.A: γ = (1/2)W11B: W12 = γ1 + γ2 – γ12C: γ12 = (1/2)W121 = (1/2)W212D: W12 + W33 – W13 – W23 = W132. If the surfaces are unequal, the Young-Dupré equation applies: W12 = γ1 + γ2 – γ12, where γ1 and γ2 are the surface energies of the two new surfaces, and γ12 is the interfacial tension. This methodology can also be used to discuss cleavage[disambiguation needed] that happens in another medium: γ12 = (1/2)W121 = (1/2)W212. Mechanisms of adhesion[edit] Strength[edit]
Adsorption Brunauer, Emmett and Teller's model of multilayer adsorption is a random distribution of molecules on the material surface. Increase in the concentration of a substance at the interface of a condensed and a liquid or gaseous layer owing to the operation of surface forces. Note 1: Adsorption of proteins is of great importance when a material is in contact with blood or body fluids. Note 2: Adsorbed molecules are those that are resistant to washing with the same solvent medium in the case of adsorption from solutions. Similar to surface tension, adsorption is a consequence of surface energy. Adsorption is present in many natural, physical, biological, and chemical systems, and is widely used in industrial applications such as activated charcoal, capturing and using waste heat to provide cold water for air conditioning and other process requirements (adsorption chillers), synthetic resins, increase storage capacity of carbide-derived carbons, and water purification. Isotherms[edit] where and
Dynamic light scattering Hypothetical dynamic light scattering of two samples: Larger particles on the top and smaller particles on the bottom Description[edit] The dynamic information of the particles is derived from an autocorrelation of the intensity trace recorded during the experiment. The second order autocorrelation curve is generated from the intensity trace as follows: where is the autocorrelation function at a particular wave vector, , and delay time, , and is the intensity. At short time delays, the correlation is high because the particles do not have a chance to move to a great extent from the initial state that they were in. as follows: where the parameter β is a correction factor that depends on the geometry and alignment of the laser beam in the light scattering setup. The most important use of the autocorrelation function is its use for size determination. Multiple scattering[edit] Data analysis[edit] Introduction[edit] where Γ is the decay rate. with for each particle size. Cumulant method[edit]
Elution Chromatography column Elution is a term used in analytical and organic chemistry to describe the process of extracting one material from another by washing with a solvent (as in washing of loaded ion-exchange resins to remove captured ions). In a liquid chromatography experiment, for example, an analyte is generally adsorbed, or "bound to", an adsorbent in a liquid chromatography column. The adsorbent, a solid phase (stationary phase), is a powder which is coated onto a solid support. Based on an adsorbent's composition, it can have varying affinities to "hold" onto other molecules—forming a thin film on its outside surface (or on its internal surface if there are cavities within the compound). Predicting and controlling the order of elution is a key aspect of column chromatographic methods. Eluotropic series[edit] Eluent[edit] The eluent or eluant is the "carrier" portion of the mobile phase. Eluate[edit] The eluate is the analyte material that emerges from the chromatograph. See also[edit]
Size-exclusion chromatography Size-exclusion chromatography (SEC) is a chromatographic method in which molecules in solution are separated by their size, and in some cases molecular weight.[1] It is usually applied to large molecules or macromolecular complexes such as proteins and industrial polymers. Typically, when an aqueous solution is used to transport the sample through the column, the technique is known as gel-filtration chromatography, versus the name gel permeation chromatography, which is used when an organic solvent is used as a mobile phase. SEC is a widely used polymer characterization method because of its ability to provide good molar mass distribution (Mw) results for polymers. Applications[edit] The main application of gel-filtration chromatography is the fractionation of proteins and other water-soluble polymers, while gel permeation chromatography is used to analyze the molecular weight distribution of organic-soluble polymers. Advantages[edit] Discovery[edit] Theory and method[edit] Analysis[edit]
PEGylation PEGylation (also often styled pegylation) is the process of covalent attachment of polyethylene glycol (PEG) polymer chains to another molecule, normally a drug or therapeutic protein, which is then described as PEGylated (pegylated). PEGylation is routinely achieved by incubation of a reactive derivative of PEG with the target molecule. The covalent attachment of PEG to a drug or therapeutic protein can "mask" the agent from the host's immune system (reduced immunogenicity and antigenicity), and increase the hydrodynamic size (size in solution) of the agent which prolongs its circulatory time by reducing renal clearance. History[edit] Around 1970, Frank F. Overview[edit] PEGylation, by increasing the molecular weight of a molecule, can impart several significant pharmacological advantages over the unmodified form, such as: PEGylated drugs also have the following commercial advantages: PEG is a particularly attractive polymer for conjugation. PEGylated pharmaceuticals on the market[edit]
Biodegradation IUPAC definition Degradation caused by enzymatic process resulting from the action of cells. Note: Modified to exclude abiotic enzymatic processes.[1] Biodegradation is the chemical dissolution of materials by bacteria or other biological means. Biodegradable matter is generally organic material such as plant and animal matter and other substances originating from living organisms, or artificial materials that are similar enough to plant and animal matter to be put to use by microorganisms. Monona Rossol wrote that "biodegradable substances break down into more than one set of chemicals, which are usually called primary and secondary degradation products. Meteorology[edit] In nature, different materials biodegrade at different rates, and a number of factors are important in the rate of degradation of organic compounds.[2] To be able to work effectively, most microorganisms that assist the biodegradability need light, water and oxygen. Biodegradability can be measured in a number of ways.
Copolymer IUPAC definition for copolymer A polymer derived from more than one species of monomer. Note: Copolymers that are obtained by copolymerization of two monomer species are sometimes termed bipolymers, those obtained from three monomers terpolymers, those obtained from four monomers quaterpolymers, etc. [1] Alternating copolymers: A copolymer consisting of macromolecules comprising two species of monomeric units in alternating sequence. Note: An alternating copolymer may be considered as a homopolymer derived from an implicit or hypothetical monomer.[1] Block copolymers: A portion of a macromolecule, comprising many constitutional units, that has at least one feature which is not present in the adjacent portions.[1] Graft macromolecule: A macromolecule with one or more species of block connected to the main chain as side-chains, these side-chains having constitutional or configurational features that differ from those in the main chain.[2] Vinyl Copolymer Milk Types of copolymers[edit]
Caprolactone ε-Caprolactone or simply caprolactone is a cyclic ester, a member of the lactone family, with a seven-membered ring with the formula (CH2)5CO2. This colorless liquid is miscible with most organic solvents. It is produced on a very large scale as a precursor to caprolactam. Production and uses[edit] The great majority of caprolactone is consumed, often in situ, as a precursor to caprolactam.[3] It is also a monomer used in the manufacture of highly specialised polymers. Caprolactone is prepared industrially by Baeyer-Villiger oxidation of cyclohexanone with peracetic acid. [edit] The dominant reaction for caprolactone is its conversion to caprolactam, billions of kilograms of which are produced annually. Carbonylation of caprolactone gives, after hydrolysis, pimelic acid. Related compounds[edit] Several other caprolactones are known, although none approaches the technological importance of ε-caprolactone. Safety[edit] References[edit]
Lactone In chemistry, a lactone is a cyclic ester[1] which can be seen as the condensation product of an alcohol group -OH and a carboxylic acid group -COOH in the same molecule. It is characterized by a closed ring consisting of two or more carbon atoms and a single endocyclic oxygen atom, coupled with an adjacent ketone (typical ester type functional group). Nomenclature[edit] Lactone nomenclature: α-acetolactone, β-propiolactone, γ-butyrolactone, and δ-valerolactone Lactones are usually named according to the precursor acid molecule (aceto = 2 carbons, propio = 3, butyro = 4, valero = 5, capro = 6, etc.), with a -lactone suffix and a Greek letter prefix that specifies the number of carbons in the heterocyle — that is, the distance between the relevant -OH and the -COOH groups along said backbone. The other suffix used to denote a lactone is -olide, used in substance class names like butenolide, macrolide, cardenolide or bufadienolide. Etymology[edit] Natural sources[edit] Synthesis[edit] [edit]