bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polymeric Drugs
Authors: Dhal Pradeep K. , Holmes‐Farley S. Randall , Mandeville W. Harry , Neenan Thomas X. 
Published: October 2003

AbstractThis article summarizes opportunities and challenges associated with discovery and development of polymeric drugs. Polymeric drugs possess unique pharmaceutical properties that are fundamentally different from low molecular weight drugs. The basic principles associated with polymeric drugs are examined and intrinsically active polymers as pharmaceutical agents are distinguished from polymers that act as carriers for drug delivery. In some applications, polymeric drugs involve selective recognition, binding, and removal of target disease‐causing substances. The design, discovery, and clinical development of polymeric drugs that act as sequestrants for low molecular weight cations and anions (eg, potassium, phosphate, and bile salts), which are responsible for different disease states, are surveyed. Examples of polymeric drugs that are on the market are provided. The use of the principle of “polyvalent interaction” to develop polymeric drugs is described. After a brief discussion of the theoretical framework for polyvalency, this section surveys the design of polymeric agents for the complexation of pathogens and pathogen‐derived substances (ie, toxins, viruses, and bacteria). Approaches for designing polymer structures to achieve highly active materials are described.
Polynucleotides
Authors: Kushon Stuart A. , Armitage Bruce A. 
Published: October 2003

AbstractThis article describes the structural and functional properties of polynucleotides, beginning with a description of the hierarchical levels of structure exhibited by the natural polynucleotides, DNA and RNA. This is followed by a description of modern methods for characterizing polynucleotides and their complexes, including electrophoresis, calorimetry, and spectroscopy. Enzymatic and chemical methods for synthesizing oligo‐ and polynucleotides are then reviewed. This leads to a description of synthetic polynucleotide analogues, which find widespread use in biotechnology and clinical diagnostics. Molecular mechanisms for sequence‐specific recognition of DNA and RNA are described, followed by a survey of methods for preparation and properties of functional polynucleotides, broadly defined as those sequences which fold into a well‐defined three‐dimensional structure that exhibits a function, such as selective binding to a ligand or catalysis of a chemical reaction. The article concludes with a summary of recent work in which polynucleotides are used as construction materials for the assembly of nanomaterials.
Polysilanes
Authors: Oka Kunio 
Published: October 2003

AbstractPolysilanes have σ‐conjugated backbones and organic side groups. The energy state of polysilane is influenced by molecular weight, conformation of the backbone, side groups, and branching points. Sigma‐conjugated polysilanes show strong absorption and efficient emission in the UV region. These properties are sensitive to external stimuli and show interesting thermochromism, piezochromism, electrochromism, and solvatochromism. Undoped polysilanes are insulators but they become conductive on doping. Polysilanes are also photoconductors showing high hole drift mobility. Polysilanes are thus studied as resist materials for photo or X‐ray lithography and as emissive or hole transport materials of LEDs. The siloxane part after photolysis is used for color filter production, recording material, printing material, and production of microlens. Polysilanes are synthesized by five methods: Wurtz coupling, dehydro‐coupling, ring‐opening polymerization, anionic polymerization of masked disilene, and redistribution polymerization of alkoxylated disilanes. Functional polysilanes are prepared from SiH, SiCl, and chloromethylphenyl groups. Block copolymers with carbon blocks are prepared by photolysis of polysilanes in carbon monomers, reaction of SiCl end with living carbon polymers, atom‐transfer polymerization with carbon monomers, and polymerization of carbon monomers with living polymer from masked disilene.
Polysulfides
Authors: Vietti David 
Published: October 2003

Abstract

Polysulfide elastomers were the first synthetic rubbers produced in the United States. They are made from simple, low cost starting materials. Polysulfides are available as viscous liquids which are commonly cured through oxidative coupling of the terminal thiol group (eg, with MnO
2
). But, this versatile end group allows these resins to be cured with other reagents such as diisocyanates, diacrylates, or epoxides. Polysulfide elastomers have unusually good resistance to solvents and to the environment. This and their good low temperature properties have made them particularly useful in the sealant applications. They are the standard sealant for virtually all aircraft integral fuel tanks and bodies. Polysulfides are the worldwide market leader in insulating glass sealants and have been used since the 1950s as construction sealants. Also, polysulfides are commonly used as flexibilizers and reactive diluents in epoxy formulations. Furthermore, the unique properties of polysulfides make them useful in a variety of specialty rubber applications.
Polysulfones
Authors: El‐Hibri M. Jamal , Weinberg Shari A. 
Published: October 2003

Abstract
Aromatic polysulfones are a family of polymers produced from the condensation polymerization of 4,4′‐dichlorodiphenylsulfone with one or more dihydric phenols. The three must commercially important polysulfones are bisphenol A based polysulfone (PSF), 4,4′‐dihydroxydiphenylsulfone‐based polyethersulfone (PES), and 4,4′‐dihydroxydiphenyl‐based polyphenylsulfone (PPSF). Polymers in this family are completely amorphous, exhibit high glass‐transition temperatures, and offer high strength and stiffness properties even at high temperatures, making them useful for demanding engineering applications. The polymers also possess good ductility and toughness and are transparent in their natural state by virtue of their fully amorphous nature. Additional key attributes include resistance to hydrolysis by hot water/steam and excellent resistance to acids and bases. The polysulfones are fully thermoplastic, allowing fabrication by most standard methods such as injection molding, extrusion, and thermoforming. They also enjoy a broad range of high temperature engineering uses. Some typical areas and industries where these polymers are used as materials of construction include hot food and beverage service, sterilizable medical components, hot water plumbing components, electrical/electronics, and a host of transportation uses in the automotive, rail, and aerospace industries.
Pressure‐Sensitive Adhesives
Authors: Cantor Adam S. , Menon Vinod P. 
Published: October 2003

AbstractA review of pressure‐sensitive adhesives (PSAs) and PSA tapes is presented. Typical constructions of PSA tapes are discussed along with a short section on the release surfaces used in conjunction with most PSAs. A discussion of the physical properties governing PSA performance is provided with emphasis on the effect of the viscoelastic nature of PSAs on adhesion. The most common types of tapes—industrial, consumer and office, medical, and labels—are described along with reference to other specialty constructions. Test methods, including peel, tack, shear, and rheology, are described for PSA tapes. Sections describing the most common materials used as PSAs—block copolymers, natural rubber, and acrylics—are included along with short descriptions of silicones, polyisobutylene, and polyolefins. A short section on general manufacturing methods of PSAs and PSA tapes is also included.
Protein Folding
Authors: Gazit Ehud 
Published: October 2003

Abstract
The process of protein folding is one of the most significant mechanisms in biology. In spite of its great importance, this process is not fully understood and a final folded structure of a protein cannot be predicted from its amino acid sequence. In this article the experimental and theoretical advances in the study of protein folding are discussed. A conceptual milestone in the understanding of protein folding is the “thermodynamic theory,” establisted by Christian A. Anfinsen in the 1950s and early 1960s. The thermodynamic hypothesis suggested that a particular three‐dimensional structure of a protein occurs because this certain molecular arrangement is the most stable thermodynamically. Another key insight regarding the mechanism of protein folding is the “Levinthal's paradox.” This paradox indicates that it is not possible for a folding protein to sample the entire conformational space during the process, and a certain folding pathway should exist. This was further developed into an energy landscape view of the folding process and into computational attempts to understand and predict the folding process. A major medical concern is related to cases of incorrect protein folding or “misfolding.” Recent studies pave new ways into true understanding of the process and ways of its control.
Radical Polymerization
Authors: Vana Philipp , Barner‐Kowollik Christopher , Davis Thomas P. , Matyjaszewski Krzysztof 
Published: October 2003

AbstractThe present article summarizes the fundamental principles and recent advances in free radical polymerization systems. Each individual reaction step in the polymerization process—initiation, propagation, transfer, and termination—is discussed in detail with regard to the underlying first principles and to the latest rate coefficient data. Novel methodologies, including living free radical polymerization, are also introduced within this context. In addition, the article gives an up‐to‐date overview of current state‐of‐the‐art experimental techniques for obtaining reliable kinetic and mechanistic information, embedded in an extensive coverage of the rates of radical polymerization, thermodynamics, and the chain‐length distribution. Such techniques range from now quasi‐classic experiments, such as pulsed laser polymerization, size exclusion chromatography, and the chain‐length distribution method for transfer constant determination, to cutting edge methodologies, such as the use of living free radical processes for chain‐length‐dependent rate coefficient determination. The fundamental differential equations governing free‐radical polymerization and the chemistry involved are both extensively covered along with ample tabular material, giving the practicing polymer chemist up‐to‐date and easily accessible data material backed up by over 500 references.
Recycling, Plastics
Authors: Khait K. 
Published: October 2003

AbstractWaste generation including plastics continues to increase, aided by the strong economic climate in the 1990s. In the United States, plastics contribute about 10 wt% of the total 230 million tons of waste generated. Most waste comes from municipal solid waste; other sources include autos, appliances, electrical and electronic components, and demolition and construction activities. Although millions of tons are landfilled annually, that is no longer considered a cheap or acceptable form of disposal.Plastic recycling issues are complex. Important aspects include the environmental impact of growing natural resource consumption, the need to revise collection and reprocessing infrastructures, the relatively new “eco‐design” approach to products, and life cycle analysis of “cradle‐to‐grave” use. This article reviews the state of worldwide plastics recycling, the challenges facing this industry in the new millennium, and emerging technologies for addressing these issues.
Reinforcement
Authors: Wagner H. D. 
Published: October 2003

Abstract
Most materials achieve their strongest forms when they are in a fibrous shape. They also often appear to be anisotropic. The present article provides some details for the inherent source of fiber strength and stiffness, and reviews the basic principles of fiber reinforcement. Key parameters, such as interfacial adhesion, are succinctly discussed. An overview of the morphology, physical properties, and preparation technology of various reinforcing fibers is presented. The potential of biological fibers, and nanoscale fibers such as carbon nanotubes, as reinforcement in future applications is briefly discussed.
Rigid‐Rod Polymers
Authors: Jiang Hao , Eby Ronald K. , Adams W. Wade 
Published: October 2003

AbstractThe synthesis, structure, properties, and applications of rigid‐rod polymers are described. PBZT and PBZO are selected as the models to be discussed in detail with respect to their fiber, film, and molecular‐composite processing, liquid‐crystal solution behavior, and computer simulations. Emphasis is placed on their ultimate tensile, thermal, chemical, electrical, and optical properties, and how to improve their compressive properties. The current and future usages of rigid‐rod polymers in various scientific, technical, and engineering areas also have been introduced. Many new rigid‐rod polymer materials, such as PPP, PPE, PPV, PTh, and other organometallic polymer systems are included.
Shape‐Memory Polymers
Authors: Lendlein Andreas , Kelch Steffen 
Published: October 2003

Abstract
Shape‐memory polymers are stimuli‐responsive materials. Upon exposure to an external stimulus, they have the capability of changing their shape. A change in shape initiated by a change in temperature is called thermally induced shape‐memory effect. The shape‐memory effect results from the polymer's structure, that is, its morphology in combination with a certain processing and programming technology.

The polymer is processed into its permanent shape by conventional methods. Afterwards, it is deformed and the desired temporary shape is fixed. The latter process is called programming. Heating the programmed polymer above a temperature higher than the transition temperature
T
trans
results in activating the shape‐memory effect. As a consequence, the recovery of the memorized, permanent shape can be observed. The described effect is called a “one‐way” shape‐memory effect.

The shape‐memory effect can be quantified by cyclic thermomechanical investigations. Important quantities describing the shape‐memory properties of the material for a certain strain ɛ
m
are the strain recovery rate
R
r
and the strain fixity rate
R
f
. The strain recovery rate
R
r
quantifies the ability of the material to memorize its permanent shape. The strain fixity rate
R
f
describes the ability of the material to fix the mechanical deformation ɛ
m
which has been applied during the programming process.
Silicones
Authors: Butts Matthew , Cella James , Wood Christina Darkangelo , Gillette Gregory , Kerboua Rachid , Leman John , Lewis Larry , Rajaraman Suresh , Rubinsztajn Slawomir , Schattenmann Florian , Stein Judith , Wengrovius Jeffrey , Wicht Denyce 
Published: October 2003

AbstractSilicones are a class of materials with unique properties that make them useful in a variety of applications of commercial interest and support a thriving global industry. This article updates a comprehensive survey of the chemistry and technology of silicones last published in Kirk‐Othmer Encyclopedia of Chemical Technology in 1997. The update contains more than 235 references not cited in the previous version and includes literature published through 2001. A new section dealing with fiber finishing applications has been included in the current version. The review provides an excellent primary reference for this interesting area of chemistry and technology.
Single‐Site Catalysts
Authors: Leino Reko 
Published: October 2003

AbstractThe recent rapid development of organometallic single‐site catalysts (SSCs) has revolutionized polymer synthesis and polyolefin production technologies. These well‐defined catalyst systems generally consist of a transition metal atom, such as titanium, zirconium, iron, nickel, or palladium, complexed with an organic ligand set and an initiating group(s). Activation with methylaluminoxane or other weakly coordinating anions generates the cationic active species responsible for olefin coordination and polymer chain growth. Representative examples of SSCs include the bis(cyclopentadienyl)‐type Group 4 metallocenes as well as the diimine complexes of nickel and palladium. By variation of the organic ligand and thus the steric and electronic environment of the metal center, these catalysts can be tailored to control the olefin polymerization reaction in an unprecedented fashion. Almost any vinyl monomer, irrespective of molecular weight or steric hindrance, can be polymerized by choosing the proper catalyst. Virtually all feasible poly(α‐)olefin microstructures ranging from atactic to isotactic, hemiisotactic, syndiotactic, and stereoblock polymers can be produced by rational modification of the catalyst structure. Functional monomers are readily copolymerized with the less oxophilic late transition metal catalysts. Entirely new materials, not accessible with traditional Ziegler–Natta catalysts, have emerged, including high melting syndiotactic polystyrene and cycloaliphatic polymers. This article provides a broad overview of SSCs and their application in olefin polymerization. Evolution and classification of SSCs, catalyst generation, polymerization of ethylene, propylene, cycloolefins, dienes, styrene, as well as as functional olefins, and the application of SSCs in enantioselective polymerization are covered. Finally, heterogenization of SSCs for use in industrial processes is briefly discussed.
Statistical Thermodynamics
Authors: Oono Yoshitsugu 
Published: October 2003

AbstractThe objective and mode of thinking of statistical thermodynamics are explained with key references. The problems of statistical thermodynamics fall into two categories: studies of universal structures and studies of materials constants. The modern statistical thermodynamics emphasizes the former category. Consequently, recognizing a universality class described by a well‐defined phenomenological framework and constructing a minimal model to elucidate it statistically are the key problems. From this modern point of view equilibrium and nonequilibrium statistical thermodynamics are outlined, with applications to polymer solutions.
Styrene Polymers
Authors: Priddy Duane 
Published: October 2003

AbstractThis article covers all aspects of styrene‐containing plastics and their copolymers, including properties, manufacturing processes, morphology, polymerization chemistry, environmental impact, rubber toughening, morphology, transparency, nanocomposites, and degradation. Special emphasis is given to new developments such as living free‐radical polymerization, transparent impact polystyrene, and polystyrene/inorganic nanocomposite materials.
Superabsorbent Polymers
Authors: Buchholz Fredric L. 
Published: October 2003

AbstractSuperabsorbent polymers are very high molecular mass, cross‐linked polyelectrolytes that can absorb more than 10 times their mass of water or aqueous solutions. The commercially available superabsorbent polymers are alkali matal salts of poly(acrylic acid) cross‐linked with multifunctional monomers. The polymers are usually made by means of free‐radical‐initiated polymerization of an aqueous solution of the monomers, followed by drying the resulting hydrogel, and grinding the dry polymers to a granular powder. The principal use of superabsorbent polymers is as a liquid absorbent in baby diapers, feminine hygiene products, and adult incontinence products. Smaller volumes are used in food packaging and in water‐blocking tapes for electrical and telecommunication cables. Total global usage of superabsorbent polymers in 2001 amounted to about 1093 kt.
Synchrotron Radiation
Authors: Bras Wim 
Published: October 2003

AbstractOver the last decades it has become possible to perform x‐ray scattering experiments at SR beamlines. The superior qualities of the x‐ray beams generated at these sources, combined with technological developments in position‐sensitive detector systems, has made time‐resolved x‐ray experiments possible. Polymer research has benefited in many ways from the possibilities created by these instruments. With the latest generation of SR sources, offering even higher fluxes, better collimation, and wavelength tuneability, the opportunities for innovative research have been greatly expanded. It has become possible to utilize sample environments and technique combinations hitherto unthinkable. In this article several examples of possible experiments are discussed. Also some of the latest experiments at the frontier of new developments will be treated to give an indication what the future might bring.
Syndiotactic Polystyrene
Authors: Malanga Michael , Newman Thomas H. 
Published: October 2003

AbstractSyndiotactic polystyrene is prepared from styrene monomer and organometallic catalysts. The material is a semicrystalline polymer with a crystallization rate high enough to make it practicable as an injection molding resin. The catalyst and polymerization chemistry is based on monocyclopentadienyl titanium complexes generally in combination with methylaluminoxane. The polymer has a melting point of 270°C with an excellent balance of processability, solvent resistance, and dimensional stability. The polymer can be filled with glass reinforcement, impact modified, and rendered ignition resistant, providing a new set of properties for the engineering plastics industry to use in electronic, automotive, electrical, and other market areas.
Test Methods
Authors: Furches Barbara J. 
Published: October 2003

AbstractPlastics testing covers analytical, thermal, physical, and environmental procedures for determining the composition, structure, as well as mechanical and other responses to a variety of environmental conditions of plastic materials. General uses of Fourier transform infrared, nuclear magnetic resonance, Raman, and X‐ray techniques are reviewed and illustrated with specific examples. Developments in neutron and X‐ray scattering techniques, as well as molecular weight determination techniques such as gel‐permeation chromatography and turbidimetric methods, are also covered. Thermal tests, thermogravimetric analysis, differential thermal analysis, differential scanning calorimetry, and dynamic mechanical analysis are all useful for understanding degradation and phase changes in polymers and their influence on material behavior. New techniques of atomic force microscopy and positron annihilation are allowing studies of the microstructure of polymers and free volume determinations. Several mechanical testing techniques are used in plastics for normal quality control testing and initial application screening of polymers. These tests and those used for more fundamental understanding of polymer response to stress, including fracture mechanics procedures, are referenced. Flammability tests commonly used for plastics include oxygen index, flammability ratings, and smoke generation. Work on the use of cone calorimeters to characterize behavior of plastics under fire conditions is also covered. Finally, environmental testing, chemical exposure, weathering, radiation, and biological agents are reviewed. Emphasis is given to test development or applications reported since 1990.