Showing papers on "Polymer published in 1993"

Mechanical Properties of Polymers and Composites

Abstract: Mechanical Tests and Polymer Transitions * Elastic Moduli * Creep and Stress Relaxation * Dynamical Mechanical Properties * Stress-Strain Behaviour and Strength * Other mechanical Properties * Particulate-Filled Polymers * Fiber- Filled Composites and Other Composites.

Polymers at Interfaces

Abstract: Preface. Polymers in solution. General features of polymers at interfaces. Experimental methods. Theoretical methods. Homopolymer adsorption. Adsorption of copolymers. Electrostatic effects: charged surfaces and polyelectrolyte adsorption. Terminally-attached chains. Fluid interfaces. Depletion. Interactions in the presence of polymers. Appendices. Glossary of symbols. Key word index.

Hybrid nanocomposite materials―between inorganic glasses and organic polymers

Abstract: The sol-gel process, with its associated mild conditions, offers a new approach to the synthesis of composite materials with domain sizes approaching the molecular level. Transparent organic-inorganic composites can be prepared by dissolving preformed polymers into sol-gel precursor solutions, and then allowing the tetraalkyi orthosilicates to hydrolyze and condense to form glassy SiO, phases of different morphological structures. Alternatively, both the organic and inorganic phases can be simultaneously formed through the synchronous polymerization of the organic monomer and the sol-gel precursors. Depending upon such factors as the structures of the organic and inorganic components, the phase morphology, the degree of interpenetration, and the presence of covalent bonds between the phases, the properties of these composites can vary greatly and range from elastomeric rubbers to high-modulus materials.

Applications of electroactive polymers

Abstract: Preface. Electrical and electrochemical properties of ion conducting polymers. Electrical and electrochemical properties of electronically conducting polymers. Highly-conductive polymer electrolytes. Solvation mechanisms in low molecular weight polyethers. Lithium batteries with polymer electrodes. Lithium polymer batteries. Electrochromic devices. Laminated electrochromic displays and windows. Functionalized conductive polymer membranes/films. Electroactive polymers in chemical sensors.

End use applications of biodegradable polymers

Abstract: Disclosed are products made of degradable materials which include a hydrolytically degradable polymer. The degradable materials can be internally or externally modified. The internally modified polymer composition has polymers modified by the use of comonomers having a relatively high molecular weight. The externally modified polymer composition includes a modifier, wherein the modifier is compatible with the polymer and the modifier is nontoxic, nonvolatile and nonfugitive. The various degradable materials include films, fibers, extruded and molded products, laminates, foams, powders, nonwovens, adhesives and coatings. The disclosed materials are particularly useful for the production of a variety of products in high volumes which are suitable for recycling after use or which are discarded into the environment in large volumes.

Structural study on the micelle formation of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer in aqueous solution

Abstract: The phase behavior of the triblock copolymers dissolved in water has been studied using SANS. The structural properties have been studied as a function of polymer concentration and temperature. At low temperature (T ≤ 15°C) and low polymer concentrations the unimers are fully dissolved Gaussian chains with radius R g =17 A. Close to ambient temperature, the hydrophobic nature of PPO causes aggregation of the polymers into spherical micelles with core sizes of the order of 40-50 A, somewhat temperature dependent. The concentration of micelles increased roughly linearly with temperature, until either a saturation is reached,where all the polymers are part of a micelle, or the volume density of micelles is so high that they lock into a crystalline structure of hard spheres

Polymer surface modification and characterization

Abstract: Illustrates the relationship between surface analysis and surface modification techniques. Polymers for use in adhesives, biomaterials, protective coatings, and composites need specific chemical and physical properties. These properties include: composition, hydrophilicity, roughness, crystallinity, conductivity, and lubricity. Various methods for modifying the surfaces of polymers for certain applications are described.

Liquid crystalline polymers

Abstract: Not much more than a decade ago, the plastics industry viewed itself as a mature branch of the heavy chemical industry. Its raison d'etre was the mass production of four or five main-line polymers, and profits were equated to tonnage output, plant efficiency, and clever downstream processing such as film blowing. The chemistry was essentially simple and the monomer, of course, cheap. There was, however, a spark of new thinking. A trend was developing toward the design and manufacture of more complex, more expensive polymers, with special properties which could command a special price. Such products would sell advanced scientific know-how, not just engineering expertise which could all too easily be exported to the major oil producers in the form of a polymer plant. Designing particular molecules to achieve desired properties is now a major theme of polymer producers. There is a move toward increasing the aromatic content of polymer backbones to achieve greater levels of chemical and thermal stability, while the development of new cross-linking systems remains as chemically intensive as ever. It is, however, the introduction of liquid crystalline polymers which, above all, has exploited the principles of molecular design, while at the same time challenging our understanding in a new area of polymer science. A polymer is “liquid crystalline” where the chains are sufficiently rigid to remain mutually aligned in the liquid phase although the perfect positional periodicity of a crystal is no longer present. In other words there is a long-range orientational order without long-range positional order (Figure 1). Structurally, therefore, the phase is intermediate between a crystal and a liquid leading to the use of the term mesophase . Where the liquid crystalline phase forms on melting the polymer, it is known as thermotropic , but where it is achieved by solvent addition it is called Inotropic. Increasing temperature, or solvent concentration, will eventually lead to the reversion of the liquid crystal phase to the normal isotropic polymer melt.

Polymer Blends and Alloys

Abstract: Overview. Rheology of two-phase blends. Practical aspects of processing of blends. Compatibilization and reactive blending. Practical techniques for studying blend microstructure. Modelling the properties of polymer blends. Toughened polymers. Blends containing liquid crystal polymers. Fibre forming blends and in situ fibre composites. References. Index.

Biocompatible polymer membranes and methods of preparation of three dimensional membrane structures

Abstract: Biocompatible porous polymer membranes are prepared by dispersing salt particles in a biocompatible polymer solution. The solvent in which the polymer is dissolved is evaporated to produce a polymer/salt composite membrane. The polymer can then be heated and cooled at a predetermined constant rate to provide the desired amount of crystallinity. Salt particles are leached out of the membrane by immersing the membrane in water or another solvent for the salt but not the polymer. The membrane is dried, resulting in a porous, biocompatible membrane to which dissociated cells can attach and proliferate. A three-dimensional structure can be manufactured using the polymer membranes by preparing a contour drawing of the shape of the structure, determining the dimensions of thin cross-sectional layers of the shape, forming porous polymer membranes corresponding to the dimensions of the layers, and laminating the membranes together to form a three-dimensional matrix having the desired shape.

Polymeric materials formed by precipitation with a compressed fluid antisolvent

Abstract: Polymer microspheres and fibers are formed with a versatile new process, precipitation with a compressed fluid antisolvent. By spraying a 1 wt. % polystyrene in toluene solution into CO2 through a 100-μm nozzle, microspheres are formed with diameters from 0.1 to 20 μm as the CO2 density decreases from 0.86 to 0.13 g/cm3. The uniform submicron spheres produced at high CO2 density are due in part to the rapid atomization produced by the large intertial and low interfacial forces. Fibers, with and without microporosity, are obtained at higher polymer concentrations where viscous forces stabilize the jet. The effect of CO2 density and temperature on the size, morphology and porosity of the resulting polymeric materials is explained in terms of the phase behavior, spray characteristics, and the depression in the glass transition temperature.

Tissue formation by injecting a cell-polymeric solution that gels in vivo

Abstract: A cell-polymeric solution is injected into an animal where the polymer crosslinks to form a polymeric hydrogel containing dispersed cells and the cells form new tissue in the animal. The polymer is biodegradable and is a natural polymer such as alginate or a synthetic polymer. The cells are chondrocytes, osteoblasts, muscle cells, fibroblasts or cells acting primarily to synthesize, secret or metabolize materials. Crosslinking of the polymer results from using cations or anions, altering the pH or changing the temperature. A polyion such as polyethyleneimine or polylysine can be added before injection to stabilize the polymeric hydrogel. A kit for tissue formation is provided by combining the cell-polymeric solution with a means for injecting the solution into an animal.

Synthesis of fusible and soluble conducting polyfluorene derivatives and their characteristics

Abstract: Conducting poly(9-alkylfluorene)s and poly(9,9-dialkylfluorene)s have been synthesized by chemical polymerization utilizing FeCl 3 as an oxidizing agent. The polymers obtained are found to be soluble in conventional organic solvents such as chloroform and have been characterized by 1 H- and 13 C-NMR. The results indicate that the fluorene moeities are mainly linked in the 2,7'-fashion to yield the straight chain polymer. The degree of polymerization is estimated (by GPC) to be of the order of 10. The polymers are found to be fusible and the thermal properties of the polymers have been characterized by DSC

Polymer brushes at curved surfaces.

Abstract: The polymer adsorption theory of Scheutjens and Fleer is used to describe polymer brushes at spherical and cylindrical surfaces that are immersed in a low molecular weight solvent. The volume fraction profiles of such brushes is analyzed, special attention being paid to spherical brushes in athermal solvents. These are shown to generally consist of two parts: a power law-like part and a part that is consistent with a parabolic potential energy profile of the polymer segments

Structure of organic aerogels. 1. Morphology and scaling

Abstract: Small-angle X-ray scattering is used to determine the structure of nanoporous organic aerogels made by the base-catalyzed polymerization of resorcinol and formaldehyde. This study probes the effect of several variables on the morphology of the supercritically dried aerogels including catalyst concentration, monomer concentration, acid aging, and pyrolysis. In addition, the development of structure during polymerization and aging of the precursor aquagels is reported. The data are consistent with a smooth-surfaced morphology with no indication of fractal clusters or rough surfaces in the length-scale regime from 10 to 600 [angstrom]. These results, taken together, indicate that microphase separation is the dominant process underlying the morphology of these unique materials.

Melt-stable amorphous lactide polymer film and process for manufacture thereof

Abstract: An amorphous film comprised of a lactide polymer. The lactide polymer comprises a plurality of poly(lactide) polymer chains, residual lactide in concentration of less than about 2 percent and water in concentration of less than about 2000 parts-per-million. A process for manufacturing an amorphous film with the lactide polymer composition is also disclosed.

Polymers for electronic and photonic applications

Abstract: Overview of Polymers for Elecrtronic and Photonic Applications. The Chemistry of Polymers for Microlithographic Applications. Interconnect Dielectrics. Recent Advances in IC Passivation and Encapsulation: Process Technqieus and Materials. Polyimides for Electrronic Applications. Polyimidesiloxanes: Chemistries and Applications. Applications of Epoxy Resins in Electronics. Advances in Thermoplastics for Electronic Applications. Polymers for Increased Circuit Density in Interconnection Technology. Piezoelectric and Pyroelectric Polymers. Polymers for Non-linear Optics. Polymers as Third-Order Nonlinear Optical Materials. Polymers for Integrated Optical Waveguides. Langmuir-Blodgett Manipulation of Electrically Responsive Polymers. Basic Concepts of Polymer Mechanical Behavior. Chapter Refernces. Index.

Molecular recognition in continuous polymer rods prepared by a molecular imprinting technique

Abstract: As new separation media, continuous rods of molecularly imprinted polymers were prepared by an in situ method. The preparation procedure was simple and easy to perform: a template compound, a functional monomer which interacts with the template molecules, and a cross-linker were placed in a stainless steel column and heated for polymerization. In this study, diaminonaphthalene and phenylalanine anilide were used as model template molecules. The molecular recognition capabilities of the prepared molecular-imprinted polymer rods were evaluated by separating positional isomers of diaminonaphtalene and resolving enantiomers of phenylalanine anilide. The results showed that the original template compounds were more strongly retained than their isomers

Synthesis of high molecular weight poly(methyl methacrylate) with extremely low polydispersity by the unique function of organolanthanide(III) complexes

Abstract: Polymerizations of methyl methacrylates by bis(pentamethylcyclopentadienyl)samarium hydride, [Sm(C 5 Me 5 ) 2 H] 2 , in toluene were found to afford the polymers of M n > 100×10 3 with extremely low polydispersity, M w /M n = 1.02. The polymerization is estimated to proceed in a living fashion. Highly syndiotactic polymerization (95.3%) proceeded by lowering the reaction temperature to -95°C.

Chemical tuning of the electronic properties of poly(p-phenylenevinylene)-based copolymers

Abstract: Molecular engineering has allowed the control of the HOMO-LUMO gap energy in a family of conjugated polymers based on poly(p-phenylenevinylene) (PPV). Random copolymerization of 1 and 6 afforded precursor polymers 10 with two different leaving groups. Treatment under thermal conditions led to a partially conjugated polymer 11 with regions of high and low HOMO-LUMO gap energy, showing a 30-fold improvement in electroluminescence efficiency compared with PPV, while treatment under acidic and thermal conditions gave more substantially conjugated polymers 12 with lower HOMO-LUMO gap energies. This chemistry enabled the formation of lithographically patterned polymers exhibiting electroluminescence. The scope of these copolymerizations was also explored with other copolymers, 19 and 22b,c.

Polymers derived from ethylene and 1-butene for use in the preparation of lubricant dispersant additives

Abstract: The invention pertains to oil soluble copolymers derived from ethylene and 1-butene which have a number average molecular weight between about 1,500 and 7,500, at least about 30 percent of all polymer chains terminated with ethylvinylidene groups, and ethylene-derived content of not greater than about 50 weight percent, and which form solutions in mineral oil free of polymer aggregates, as determined by light scattering measurements. Lubricating oil additives, particularly dispersants, produced by the functionalization and derivatization of these copolymers have enhanced performance (e.g., improved dispersancy and pour point) in lubricating oil compositions, attributable in part to the combination of properties characterizing the copolymers.

Responsive gels : volume transitions

Abstract: Coexistence of phases and the nature of first-order phase transition in poly-N-isopropylacrylamide gels.- Friction between polymer networks of gels and solvent.- Stimuli-responsive poly(N-isopropylacrylamide). Photo- and chemical-induced phase transitions.- Hydrogels as separation agents.- Synthesis, equilibrium swelling, kinetics, permeability and applications of environmentally responsive gels.- Polymer gel phase transition in condensation-decondensation of secretory products.- Novel applications for stimulus-sensitive polymer gels in the preparation of functional immobilized biocatalysts.- Molecular design of temperature-responsive polymers as intelligent materials.- Phase transition in gels of sub-millimeter size induced by interaction with stimuli.- An approach to artificial muscle using polymer gels formed by micro-phase separation.

Adhesive agent containing polysiloxane-grafted polymer, and cosmetic compositions thereof

Abstract: Polymeric adhesive agents are disclosed which comprise polysiloxane grafted polymers wherein: (a) the polymers are made by polymerization of polysiloxane-containing monomers and non-polysiloxane-containing monomers, typically by free radical polymerization; (b) the adhesive agent has a weight average molecular weight of at least about 20,000 and contains from about 1 % to about 50 %, by weight, of polysiloxane-containing monomer; and (c) the weight percentage of silicon present as unreacted polysiloxane-containing monomer and silicone-grafted polymer having a viscosity at 25 °C of below about 10,000,000 centistokes based on the total silicon present as unreacted silicon monomer and polysiloxane-grafted polymer is about 15 % or less. Also, the adhesive agent contains no more than about 4 %, by weight, of unreacted polysiloxane-containing monomer and polysiloxane-grafted polymer having a viscosity at 25 °C of below about 10,000,000 centistokes. Cosmetic compositions containing such adhesive agents are also disclosed.