Showing papers on "Polymer published in 1993"
Book•
14 Dec 1993
TL;DR: In this article, the authors discuss various mechanical properties of fiber-filled composites, such as elastic moduli, creep and stress relaxation, and other mechanical properties such as stress-strain behavior and strength.
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.
3,166 citations
Book•
30 Sep 1993TL;DR: Theoretical methods for polymers at interfaces are described in this article, where the authors show that polymers in solution can be represented by homopolymer adsorption and polyelectrolyte adorption.
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.
1,484 citations
TL;DR: 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 as mentioned in this paper, where transparent organic-inorganic composites can be prepared by dissolving preformed polymers into solgel precursor solutions and then allowing the tetraalkyi orthosilicates to hydrolyze and condense to form glassy SiO, phases of different morphological structures.
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.
1,347 citations
TL;DR: Understanding the effects of hierarchical structure can guide the synthesis of new materials with physical properties that are tailored for specific applications, as well as determining the bulk material properties.
Abstract: The role of structural hierarchy in determining bulk material properties is examined. Dense hierarchical materials are discussed, including composites and polycrystals, polymers, and biological materials. Hierarchical cellular materials are considered, including cellular solids and the prediction of strength and stiffness in hierarchical cellular materials.
1,202 citations
01 Jan 1993
TL;DR: In this article, electrical and electrochemical properties of ion conducting polymers are discussed. But they do not consider the properties of polymers with polymer electrolytes, as they do in this paper.
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.
824 citations
AT&T1
TL;DR: In this article, a silica optical fiber was imaged using an atomic force microscope (AFM) in both contact and tapping mode, and it was shown that tapping mode AFM can reduce the contact force significantly, estimated to be as low as a tenth of a nanonewton.
796 citations
Patent•
29 Sep 1993
TL;DR: In this article, products made of degradable materials which include a hydrolytically degradant polymer are disclosed. But they are not suitable for recycling after use or which are discarded into the environment in large volumes.
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.
717 citations
TL;DR: The phase behavior of the triblock copolymers dissolved in water has been studied using SANS as discussed by the authors, and the structural properties have been studied as a function of polymer concentration and temperature.
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
669 citations
TL;DR: In this article, the crosslinking of adjacent cyclodextrins in apolyrotaxane to create a molecular tube has been reported, with diameters of 0.45 nm, 0.7 nm and 0.85 nm.
Abstract: MUCH attention has been focused recently on the design and fabrication of large-scale molecular structures1. Carbon nanotubes formed by an arc-discharge method2,3 have attracted particular attention. These tubes range from about 1 to 30 nanometres in diameter and a micrometre or so in length. To construct smaller tubes, direct chemical synthesis may be a more convenient approach. The cyclic oligomers of glucose known as cyclodextrins (CDs) would seem to be ideal candidates for the components of a molecular tube: they contain cylindrical cavities about 0.7 nm deep, with diameters of 0.45 nm, 0.7 nm and 0.85 nm for α-CD, β-CD and γ-CD respectively4. Lehn has recently reported the use of 'bouquet molecules' built from β-CD with long side chains as artificial ion channels5. We have previously prepared rotaxane super-molecules in which CDs are threaded on a polymer chain, and we6 and others7,8, have reported polyrotaxanes with many threaded CDs. Here we report the crosslinking of adjacent CD units in apolyrotaxane to create a molecular tube. By removing the bulky ends of the polymer thread, the tube can be unthreaded and can act as a host for reversible binding of small molecules.
518 citations
491 citations
Book•
01 Jan 1993
TL;DR: In this paper, the relationship between surface analysis and surface modification techniques is discussed, and various methods for modifying the surfaces of polymers for certain applications are described, including adhesives, biomaterials, protective coatings, and composites.
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.
TL;DR: A review of theoretical equations of state for polymer liquids is presented in this article, where parameters for six equations, as well as parameters for the empirical Tait equation, are given for 56 polymers where pressurevolume-temperature (PVT) data over a wide range of conditions could be found in the literature.
Abstract: A review of theoretical equations of state for polymer liquids is presented Characteristic parameters for six equations of state, as well as parameters for the empirical Tait equation, are given for 56 polymers where pressure–volume–temperature (PVT) data over a wide range of conditions could be found in the literature New PVT data are presented for four polymers: poly(epichlorohydrin), poly(ϵ-caprolactone), poly(vinyl chloride), and atactic polypropylene All six equations of state provide adequate fits of the experimental specific volume data for the 56 polymers in the low pressure range (up to 500 bar) The modified cell model of Dee and Walsh, the Simha–Somcynsky hole theory, the Prigogine cell model, and the semiempirical model of Hartmann and Haque, were all found to provide good fits of polymer liquid PVT data over the full range of experimental pressures The Flory–Orwoll–Vrij and the Sanchez–Lacombe lattice–fluid equations of state were both significantly less accurate over the wider pressure range © 1993 John Wiley & Sons, Inc
TL;DR: In this paper, the degree of separation of the d and l enantiomers of PheNHPh (α value) is used to establish the influence of polymer morphology on polymer performance.
Journal Article•
TL;DR: The concept of mesophase polymers was introduced by as mentioned in this paper, 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.
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.
TL;DR: In this article, the idea that conjugated polymers with alternate donor and acceptor moieties in the main chain are characterized by a small band gap is explained and explained.
TL;DR: In this article, the Wittig reaction was used to obtain the polymer [O(CH 2 ) 8 Ph(OMe) 2 CH=CHPhCH=CH Ph(O 2 ) 2 ] n, which was found to emit blue light with a maximum peak in the electroluminescent spectrum.
Abstract: The polymer [O(CH 2 ) 8 Ph(OMe) 2 CH=CHPhCH=CHPh(OMe) 2 ] n was prepared by a Wittig reaction. It forms homogeneous solutions in THF and CHCl 3 from which transparent films can be cast. The films have good mechanical properties and are slightly yellow in thick section. This polymer was found to emit blue light with a maximum peak in the electroluminescent spectrum
TL;DR: The calculated effective DNA diameter is a sensitive function of electrolyte concentration and is several times larger than the geometric diameter in solutions of low monovalent cation concentration.
Abstract: During the random cyclization of long polymer chains, knots of different types are formed. We investigated experimentally the distribution of knot types produced by random cyclization of phage P4 DNA via its long cohesive ends. The simplest knots (trefoils) predominated, but more complex knots were also detected. The fraction of knots greatly diminished with decreasing solution Na+ concentration. By comparing these experimental results with computer simulations of knotting probability, we calculated the effective diameter of the DNA double helix. This important excluded-volume parameter is a measure of the electrostatic repulsion between segments of DNA molecules. The calculated effective DNA diameter is a sensitive function of electrolyte concentration and is several times larger than the geometric diameter in solutions of low monovalent cation concentration.
TL;DR: Stereocomplexation of PDLA and PLLA from the melt state was studied using DSC and polarizing microscopy in this paper, showing that homocrystallization was most prevalent upon annealing the polymer mixtures when the molecular weight of both poly(D-lactic acid) (PDLA) was below 6×10 3 and the PDLA content (X D ) was between 0.4 and 0.6.
Abstract: Stereocomplexation (racemic crystallization) of poly(D-lactic acid) (PDLA) and poly(L-lactic acid) (PLLA) from the melt state was studied using DSC and polarizing microscopy. Complexation predominantly occurred upon annealing the polymer mixtures when the molecular weight of both PDLA and PLLA was below 6×10 3 and the PDLA content (X D ) was between 0.4 and 0.6. In contrast, homocrystallization of PDLA or PLLA prevailed when X D was around 0 or 1 or the molecular weight of PDLA and PLLA was higher than 1×10 6
Book•
30 Jun 1993
TL;DR: In this article, the properties of two-phase polymers are modelled and compared using a model based approach, and the authors present practical techniques for studying the microstructure of polymers.
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.
Patent•
01 Feb 1993
TL;DR: In this paper, a contour drawing of the shape of the structure, determining the dimensions of thin cross-sectional layers of a shape, forming porous polymer membranes corresponding to dimensions of the layers, and laminating the membranes together to form a three-dimensional matrix having the desired shape.
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.
TL;DR: Erosion kinetics, photomicroscopy, and infrared spectroscopy were used to understand the erosion mechanism of two families of degradable polymers, polyanhydrides and polyesters.
Abstract: Degradable polymers are beginning to play an increasing role as materials for environmental and medical applications. Understanding factors that control erosion, such as bond cleavage and the dissolution and diffusion of degradation products, will be critical to the future development of these materials. Erosion kinetics, photomicroscopy, and infrared spectroscopy were used to understand the erosion mechanism of two families of degradable polymers, polyanhydrides and polyesters. Polyanhydrides exhibit behavior more characteristic of surface erosion, whereas the polyesters exhibit bulk erosion patterns. Control of erosion times from a few days to several years can be achieved by a judicious choice of monomer units and bond selection.
TL;DR: In this article, a 1 wt. % polystyrene in toluene solution into CO2 through a 100-μm nozzle is formed with diameters from 0.1 to 20 μm.
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.
TL;DR: The crystal structure of polystyrene-toluene molecular compound was studied by X-ray diffraction as discussed by the authors, and the crystal data are as follows: monoclinic system, space group P21/a (no. 14), a = 17.58, b = 13.26, c(chain axis) = 7.71 A, γ = 121.2 °, eight monomer units (two chains) and two toluene molecules per unit cell, the molar ratio of monomer: tofluene being 4:1.
Patent•
30 Apr 1993TL;DR: In this paper, 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.
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.
TL;DR: It is shown that, similar to natural macromolecules of the extracellular matrix, the synthetic polymers are able to participate in the control of cell function.
TL;DR: In this article, the effect of a pH-dependent polymer coating, Eudragit S, on its ability to protect a model drug and control its release from rapidly disintegrating tablets has been examined in vitro.
TL;DR: In this paper, conducting poly(9-alkylfluorene)s and poly( 9,9-dialkylfluoresine)s have been synthesized by chemical polymerization utilizing FeCl 3 as an oxidizing agent.
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
TL;DR: In this article, the volume fraction profiles of spherical and cylindrical polymers are analyzed, with special attention being paid to spherical polymers in athermal solvents.
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