A polymer is a substance or material that consists of very large molecules,or macromolecules,that are constituted by many repeating subunits derived from one or more species of monomers. 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.
In 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.
An elastomer is a polymer with viscoelasticity and with weak intermolecular forces,generally low Young's modulus (E) and high failure strain compared with other materials. The term,a portmanteau of elastic polymer,is often used interchangeably with rubber,although the latter is preferred when referring to vulcanisates. Each of the monomers which link to form the polymer is usually a compound of several elements among carbon,hydrogen,oxygen and silicon. Elastomers are amorphous polymers maintained above their glass transition temperature,so that considerable molecular reconformation is feasible without breaking of covalent bonds. At ambient temperatures,such rubbers are thus relatively compliant and deformable.
Colloidal gold is a sol or colloidal suspension of nanoparticles of gold in a fluid,usually water. The colloid is coloured usually either wine red or blue-purple . Due to their optical,electronic,and molecular-recognition properties,gold nanoparticles are the subject of substantial research,with many potential or promised applications in a wide variety of areas,including electron microscopy,electronics,nanotechnology,materials science,and biomedicine.
A polyolefin is a type of polymer with the general formula (CH2CHR)n where R is an alkyl group. They are usually derived from a small set of simple olefins (alkenes). Dominant in a commercial sense are polyethylene and polypropylene. More specialized polyolefins include polyisobutylene and polymethylpentene. They are all colorless or white oils or solids. Many copolymers are known,such as polybutene,which derives from a mixture of different butene isomers. The name of each polyolefin indicates the olefin from which it is prepared;for example,polyethylene is derived from ethylene,and polymethylpentene is derived from 4-methyl-1-pentene. Polyolefins are not olefins themselves because the double bond of each olefin monomer is opened in order to form the polymer. Monomers having more than one double bond such as butadiene and isoprene yield polymers that contain double bonds (polybutadiene and polyisoprene) and are usually not considered polyolefins. Polyolefins are the foundations of many chemical industries.
Thermoplastic elastomers (TPE),sometimes referred to as thermoplastic rubbers (TPR),are a class of copolymers or a physical mix of polymers that consist of materials with both thermoplastic and elastomeric properties.
Nanocomposite is a multiphase solid material where one of the phases has one,two or three dimensions of less than 100 nanometers (nm) or structures having nano-scale repeat distances between the different phases that make up the material.
Polyphosphazenes include a wide range of hybrid inorganic-organic polymers with a number of different skeletal architectures with the backbone P-N-P-N-P-N-. In nearly all of these materials two organic side groups are attached to each phosphorus center. Linear polymers have the formula (N=PR1R2)n,where R1 and R2 are organic (see graphic). Other architectures are cyclolinear and cyclomatrix polymers in which small phosphazene rings are connected together by organic chain units. Other architectures are available,such as block copolymer,star,dendritic,or comb-type structures. More than 700 different polyphosphazenes are known,with different side groups (R) and different molecular architectures. Many of these polymers were first synthesized and studied in the research group of Harry R. Allcock.
Shape-memory polymers (SMPs) are polymeric smart materials that have the ability to return from a deformed state to their original (permanent) shape when induced by an external stimulus (trigger),such as temperature change.
Photothermal therapy (PTT) refers to efforts to use electromagnetic radiation for the treatment of various medical conditions,including cancer. This approach is an extension of photodynamic therapy,in which a photosensitizer is excited with specific band light. This activation brings the sensitizer to an excited state where it then releases vibrational energy (heat),which is what kills the targeted cells.
Polymer engineering is generally an engineering field that designs,analyses,and modifies polymer materials. Polymer engineering covers aspects of the petrochemical industry,polymerization,structure and characterization of polymers,properties of polymers,compounding and processing of polymers and description of major polymers,structure property relations and applications.
Temperature-responsive polymers or thermoresponsive polymers are polymers that exhibit drastic and discontinuous changes in their physical properties with temperature. The term is commonly used when the property concerned is solubility in a given solvent,but it may also be used when other properties are affected. Thermoresponsive polymers belong to the class of stimuli-responsive materials,in contrast to temperature-sensitive materials,which change their properties continuously with environmental conditions. In a stricter sense,thermoresponsive polymers display a miscibility gap in their temperature-composition diagram. Depending on whether the miscibility gap is found at high or low temperatures,either an upper critical solution temperature (UCST) or a lower critical solution temperature (LCST) exists.
An emulsion dispersion is thermoplastics or elastomers suspended in a liquid state by means of emulsifiers.
In polymer chemistry,in situ polymerization is a preparation method that occurs "in the polymerization mixture" and is used to develop polymer nanocomposites from nanoparticles. There are numerous unstable oligomers (molecules) which must be synthesized in situ for use in various processes. The in situ polymerization process consists of an initiation step followed by a series of polymerization steps,which results in the formation of a hybrid between polymer molecules and nanoparticles. Nanoparticles are initially spread out in a liquid monomer or a precursor of relatively low molecular weight. Upon the formation of a homogeneous mixture,initiation of the polymerization reaction is carried out by addition of an adequate initiator,which is exposed to a source of heat,radiation,etc. After the polymerization mechanism is completed,a nanocomposite is produced,which consists of polymer molecules bound to nanoparticles.
A high-refractive-index polymer (HRIP) is a polymer that has a refractive index greater than 1.50.
The Charles Goodyear Medal is the highest honor conferred by the American Chemical Society,Rubber Division. Established in 1941,the award is named after Charles Goodyear,the discoverer of vulcanization,and consists of a gold medal,a framed certificate and prize money. The medal honors individuals for "outstanding invention,innovation,or development which has resulted in a significant change or contribution to the nature of the rubber industry". Awardees give a lecture at an ACS Rubber Division meeting,and publish a review of their work in the society's scientific journal Rubber Chemistry and Technology.
In polymer chemistry,graft polymers are segmented copolymers with a linear backbone of one composite and randomly distributed branches of another composite. The picture labeled "graft polymer" shows how grafted chains of species B are covalently bonded to polymer species A. Although the side chains are structurally distinct from the main chain,the individual grafted chains may be homopolymers or copolymers. Graft polymers have been synthesized for many decades and are especially used as impact resistant materials,thermoplastic elastomers,compatibilizers,or emulsifiers for the preparation of stable blends or alloys. One of the better-known examples of a graft polymer is a component used in high impact polystyrene,consisting of a polystyrene backbone with polybutadiene grafted chains.
Christopher Ward Macosko (1944) is an American chemical engineer and professor emeritus in the department of chemical engineering and materials science at the University of Minnesota. He is internationally known for his work in polymer science and engineering,especially in the areas of rheology and polymer processing. Macosko is an author of more than 500 academic papers,dozens of patents,and two books including the text:"Rheology:Principles,Measurements and Applications". He served as director of the Industrial Partnership for Research in Interfacial and Materials Engineering (IPRIME),a university-industry consortium at the University of Minnesota,from 1999 to 2018. Macosko and his wife Kathleen have been married since 1967 and are long-time residents of Minneapolis. They have four children and 12 grandchildren.
Nanoparticle drug delivery systems are engineered technologies that use nanoparticles for the targeted delivery and controlled release of therapeutic agents. The modern form of a drug delivery system should minimize side-effects and reduce both dosage and dosage frequency. Recently,nanoparticles have aroused attention due to their potential application for effective drug delivery.
Andy Haishung Tsou is a retired ExxonMobil materials scientist known for developing synchrotron X-ray scattering and atomic force microscopy techniques for polymer research,applying the techniques in service of development and commercialization of new polyolefin materials.
