Showing papers on "Polymer published in 1969"

The Chemistry of Hypervalent Molecules

Abstract: Molecules formed from atoms of Groups V–VIII of the periodic table in their higher valences are studied and a general theory for their electronic and geometric structure is presented These molecules, which we call hypervalent molecules, are unique in that a donor atom can possess two identical monovalent ligands which are bonded by different types of chemical bonds The present study provides a simple theoretical description of such molecules using doubly-occupied lone-pair orbitals to form hypervalent bonds, and these bonds are divided into two classes as to whether they involve p electrons alone or utilize s electrons as well While the theoretical classification is of some interest in itself, there are even more interesting problems concerning the physico-chemical properties of these molecules and the syntheses of new molecules and polymers We thus present a brief description of the energetics, possibilities for intermolecular inversion and site-exchange, and synthetic paths for the preparation of hypervalent molecules, as well as indicate a number of new molecules which can probably be synthesized using these ideas For corrigendum see DOI:101002/anie196901311

Biological Membranes behave as Non-porous Polymeric Sheets with Respect to the Diffusion of Non-electrolytes

Abstract: A model is put forward to describe the non-mediated transfer of non-electrolytes in terms of diffusion in homogeneous networks.

Attachment of amino groups to polymer surfaces by radiofrequency plasmas

Abstract: Low temperature gaseous plasmas of ammonia or nitrogen–hydrogen mixtures contain NH2 groups, or precursors thereof, formed in the plasma, which experimental evidence strongly suggests, can add to various polymer surfaces. The plasmas were established in the 0.3–1.5 torr range by radiofrequency (13.56 MHz) electrodeless excitation at powers ranging from 50 to 500 W. Samples of polypropylene, poly(vinyl chloride), polytetrafluorethylene, polycarbonate, polyurethane, and poly(methl methacrylate) were investigated. All these polymers added amino groups to varying degrees of amino site densities depending on the choice of plasma parameters and the reactivity of the polymer itself. In every instance the polymer was rendered more wettable, although no quantitative wettability measurements were made. Following the plasma treatment, degrees of amino attachment to the polymer were followed radiometrically and reported in terms of “heparin thicknesses” resulting from ionic heparin 35S attachment to quaternary sites produced from the amino groups. Two implications of such a surface modification are to adhesion and blood compatible materials preparation.

The glass transition temperature of filled polymers and its effect on their physical properties

Abstract: The glass transition temperature, dynamic shear moduli, and bulk viscosities of Phenoxy PKHH (a thermoplastic polymer made from bisphenol-A and epichlorohydrin) filled with glass beads and Attapulgite clay were investigated. The glass temperature of the polymer increased with increasing filler concentration and with increasing specific surface area of the filler. The data were interpreted by assuming that interactions between filler particles and the polymer matrix reduce molecular mobility and flexibility of the polymer chains in the vicinity of the interfaces. From the measured moduli and the viscosities of the filled and unfilled materials, the modulus reinforcement ratio in the glassy state and the relative viscosity in the viscous state were obtained as functions of the filler type and concentration. The relative modulus for the glass bead composite system follows the Kerner equation, while the clay-filled systems exhibit slightly greater reinforcement. The relative viscosities are strongly temperature dependent and do not follow conventional viscosity predictions for suspensions. It is suggested that the filler has a twofold effect on the viscosity of the composite materials; one is due to its mechanical presence and the other is due to modifications of part of the polymer matrix caused by interaction. Using the WLF equation to express all modifications of the matrix, one can isolate a purely mechanical contribution to the viscosity reinforcement. This mechanical part is approximately bounded by the theoretical predictions of Kerner,32 Mooney, 36 and Brodnyan,41 for suspension viscosities.

Shaped articles of blends of polyesters and polyvinyls

Abstract: BLENDS OF 1,4-BUTANEDIOL POLYESTERS SUCH AS DERIVED FROM 1,4-BUTANEDIOL AND TEREPHTHALIC OR NAPTHALENEDICARBOXYLIC ACID, WITH VINYL AROMATIC POLYMERS SUCH AS POLYSTYRENE GIVE SHAPED ARTICLES HAVING AN EXCELLENT BALANCE OF PHYSICAL PROPERITIES.

Activated gas plasma surface treatment of polymers for adhesive bonding

Abstract: Polyethylene, polypropylene, poly(vinyl fluoride) (Tedlar), polystyrene, nylon 6, poly(ethylene terephthalate) (Mylar), polycarbonate, cellulose acetate butyrate, and a poly(oxymethylene) copolymer were treated with activated helium and with activated oxygen. Mechanical strengths of adhesive-bonded specimens prepared from treated and from untreated coupons were compared. Polyethylene (PE) and polypropylene (PP) showed the greatest increases in bond strength. Oxygen and helium were both effective with polyethylene, but polypropylene showed no improvement when treated with activated helium. The results with excited helium parallel the effects of ionizing radiation on these two polymers, as does the appearance of unsaturation bands in the infrared (965 cm−1 in PE, and 887 and 910 cm−1 in PP). Active nitrogen produced excellent bond strength with polyethylene but not with polypropylene. Of the remaining polymers examined, Tedlar, polystyrene, and nylon 6 showed the greatest improvement in bondability after treatment, and Mylar showed moderate improvement. Polycarbonate, cellulose acetate butyrate, and the poly(oxymethylene) copolymer gave approximately two-fold increases in lap-shear bond strength. In several cases, significant differences in response to time of treatment and type of excited gas were found.

Diffusion in glassy polymers. III

Abstract: It is well known that the diffusion of organic vapors or liquids in glassy polymer often fails to obey Fick’s Law. Both experimental results and theoretical explanations of the “anomaly” were summarized by Park in 1968.1 By and large, the interpretations proposed at that time still appear to offer a sound basis, at least qualitatively, for the understanding of the complex phenomena. In the meantime, interest in this subject was further stimulated by the work of Alfrey, Gurnee and Lloyd.2 In their elegant paper, a limiting case of non-Fickian behavior of liquid diffusion in glassy polymers was characterized by the following features. (1) As the solvent molecules penetrate the polymer, a sharp advancing boundary separates the inner glassy core from the outer swollen shell. The existence of a sharp boundary, however, is not a sufficient criterion for non-Fickian diffusion.3 (2) At temperatures well below the glass temperature of the unswollen polymer, the distance of penetration, or the weight gain, increases linearly with time, i.e., the boundary between the glassy core and the swollen shell advances at a constant velocity, v. This limiting case was designated by Alfrey, et al., as case II diffusion.2

A topologically interpenetrating elastomeric network

Abstract: While chemically different monomers can be mixed, the mixing of the corresponding polymers in the solid state usually results in (multiphase) polyblends. Even the mixing of two different polymer solutions generally produces two liquid phases. This difficulty can be overcome, without resorting to grafting, by producing interpenetrating polymer networks (IPN). By crosslinking an initially linear polymer in the presence of a crosslinked network we can produce a polymeric catenane or an IPN held together predominantly by “permanent” entanglements, assuming chain transfer reactions can be suppressed. Several workers have made IPN's from either chemically identical or chemically similar polymers and have studied their properties. In this work, two different elastomers, a crosslinked polyether-based poly(urethane-urea) and a linear poly(butadiene-acrylonitrile), as aqueous emulsions, are mixed, together with crosslinking agents and stabilizers, films cast, and subsequently cured to form the IPN. A parti...

Process for the polymerization and/or copolymerization of olefins with the use of ziegler-type catalysts supported on carrier

Abstract: A PROCESS FOR POLYMERIZING AND/OR COPOLYMERIZING OLEFINS BY USING AN IMPROVED CATALYST CONSISTING OF A TRANSITION METAL COMPOUND SUPPORTED ON ELECTRONDONOR-PRETREATED INORGANIC SOLID PARTICLES TE TRANSITION METAL COMPOUND BEING A COMPONENT OF A ZIEGLER-TYPE CATALYST, AND AN ORGANOMETALLIC COMPOUND, WHEREBY THE POLYMERIZATION ACTIVITY OF THE CATALYST PER UNIT WEIGHT BOTH OF THE TRANSITION METAL AND ORGANOMETALLIC COMPONENT REMARKABLY INCREASES, THUS MAKING IT POSSIBLE TO REDUCE AN AMOUNT OF A CARRIER WHCH REMAINS IN THE RESULTANT POLYMER CAUSING INCREASED ASH CONTENT, AND ALSO POSSIBLE TO EASILY CONTROL THE MELT-INDEX OF THE RESULTANT POLYMER.

Fine structures and fracture processes in plastic/rubber two -phase polymer systems. I. Observation of fine structures under the electron microscope

Abstract: Detailed crazing behavior in several plastic/rubber twophase polymer systems was studied by means of direct observation of ultrathin sections under the electron microscope by employing osmium tetroxide staining and hardening procedure. Samples used are ABS polymer, high -impact polystyrene and several PVC/rubber blends. All of the systems investigated showed evidence of stress -crazing when under flexural stress. Relationships between the dispersed rubber particles and the crazing behaviors were studied, and the role of rubber particles in the toughening mechanism of plastics was discussed based on these observations.

Effect of immobilizing adsorption on the diffusion time lag

Abstract: A “dual sorption” model has been proposed by Michaels, Vieth, et al. to explain extensive equilibrium sorption data for several gases in some glassy polymers. To explain data on sorption kinetics, it was further postulated that one of the sorption modes immobilizes the gas molecules. Stated mathematically, this model leads to a modified form of Fick's second law. Both normal and desorption time lags for diffusion have been computed here for this model of diffusion in glassy polymers. The computed time lags are shown to be dependent on the boundary concentrations used in permeation. Experimental measurement of these time lags would be a sensitive and critical test to ascertain the validity of this theory.

Some chemical and biological characteristics of a new collagen–polymer compound material

Abstract: A new compound material is described, consisting of collagen sponge and glycol methacrylate, with a density varying from a compact to a highly porous spongelike material. Mechanical properties, swelling capacity, trypsin digestion rate, structural stability, and dynamics of tissue reactivity after subcutaneous and subperiostal implantation of this material were compared with collagen sponge, and the glycol methacrylate polymer alone. It has been shown that combined polymer collagen sponge with high porosity is quickly penetrated by connective tissue which maintains the character of highly vascularized loose connective tissue. The porosity of the material is a decisive factor for tissue permeation and the size of the pores should exceed 100 μ. The combination of the glycol methacrylate polymer gel with a collagen sponge increases the mechanical strength of this hydrophilic material. Optimal conditions for construction of the gel–collagen sponge were found.

Some physical properties of multilayered films

Abstract: Some properties of multilayered films are summarized in relation to the properties of the component materials. Polymers may be selected for co-extrusion into layered films to obtain various combinations of properties, such as barrier, stiffness, heat sealability, optics, and toughness. Properly chosen combinations of high and low modulus materials exhibit mutual interlayer reinforcement. Permeabilities of multilayer films can be calculated from layer geometry and individual component properties.

The effect of antiplasticization on secondary loss transitions and permeability of polymers

Abstract: Antiplasticizers are considered to be diluents which when added to polymers result in mechanical property behavior opposite to that of plasticization. The addition of antiplasticizers to certain polymers such as Bisphenol A polycarbonate, polysulfone, and polyvinyl chloride results in the elimination of the secondary loss transitions of these polymers. As a drop in modulus accompanies these transitions, their elimination results in higher tensile strength and tensile modulus. As secondary transitions are commonly associated with ductility and impact strength, their elimination also results in the observed embrittlement characteristics. The addition of anti-plasticizers to polymers also restricts the diffusion of penetrants resulting from the decrease of molecular flexibility in the polymer matrix.

The entropy of a confined polymer. I

Abstract: A study is made of the entropy of a random-flight polymer confined in a box of volume V. When the natural radius of the polymer approaches the linear size of the box, the entropy ceases to have the normal form of a thermodynamic function and the pressure is not a function of the density but takes the form PV= pi 2/3(Ll/R2) kappa T where L is the polymer length, l the step length and R equals V, and the density of the system even though strictly in equilibrium is not uniform. The introduction of constraints due to forces, cross linkages and very long-lived quasi-invariants restores the equation of state to a thermodynamic form P=P( rho ) where rho =L/Vl.

Morphology and mechanical behavior of block polymers

Abstract: The morphology of solution cast films of butadiene and styrene block polymers in both stretched and unstretched state has been studied by electron microscopy, and has been related to the mechanical behavior of these materials. These micrographs confirm the indications from dynamic properties that this material consists of a two-phase system in which the relationship between the phases is sensitive to the solvent system used in casting. Although the basic morphological unit is a polystyrene sphere of 100 A diameter dispersed in a matrix of polybutadiene, the interaction between spheres is complex. These spheres are more deformable than would be predicted from their glass transition temperature. The dynamic mechanical properties, stress-strain properties, and stress relaxation properties of block polymers of styrene and dienes can be explained in terms of the morphology and changes of morphology on stretching in the electron microscope.

Aromatic polyimide-co-amides. I

Abstract: A series of aromatic polyimide-co-amides of high thermal stability were synthesized. Low-temperature solution condensation involving aromatic diamines of varying basicity and bifunctional carboxylic acid chlorides containing performed imide rings was empolyed. This approach offers several advantages over the conventional polyamic acid route. The final polymers obtained are linear, soluble, and of high molecular weight. Solution of the final polymers are stable in contrast to polyamic acid solutions, which depolymerize hydrolytically due to the neighboring-group effect. Tough, flexible films were cast from solution and required no heat cure. The properties of one polymer made by the preformed ring approach were compared to its structurally related amide and imide homologs.

Estimation of Glass Transition on Temperatures from Gas Chromatographic Studies on Polymers

Abstract: In a recent communication, Smidsrod and Guillet showed that thermodynamic data on the interactions between poly (isopropylacrylamide) and various gaseous solutes could be obtained by making the polymer the stationary phase in a gas Chromatograph It was also shown that if a solute was used which was a nonsolvent for the polymer, a plot of the logarithm of the specific retention volume as a function of reciprocal temperature showed a marked inflection at a temperature close to the glass transition temperature for the polymer We wish to report similar data on several additional polymers which lead us to believe that the phenomenon is a general one and may be used to obtain an estimate of transition temperatures for a variety of polymeric materials

Polymerization of adsorbed monolayers

Abstract: Insertion poly(methyl methacrylate) homopolymers and copolymers with methacrylic acid were prepared from the corresponding monomers adsorbed as monolayers on the surface of sodium montmorillonite. The polymerization was carried out with γ-rays or benzoyl peroxide with or without crosslinking agent. Both insertion homopolymers and copolymers are associated in “packets” containing several macromolecules. The architecture of these aggregates is reminiscent of the elementary crystallite of montmorillonite. The aggregates can be dissociated irreversibly into individual macromolecules which display unusual light scattering and viscosity behavior. Only insertion homopolymers or copolymers prepared with benzoyl peroxide and without crosslinking agent follow the usual viscosity molecular weight relationship for linear (poly(methyl methacrylate). Insertion polymers or copolymers prepared with γ-rays display unusual viscosity and light scattering properties irrespectively of the presence of crosslinking agent. A compact two-dimensionally crosslinked architecture is compatible with the properties observed. This hypothesis is confirmed by the hydrodynamic properties of sodium salts of crosslinked insertion copolymers in methanol and in water. The polyelectrolytes appear to be extensively crosslinked and to display an oblate macromolecular conformation upon expansion.

Effect of adsorption, ionic strength and pH on the potential of the diffuse electric layer

Abstract: The potential,ϕ0, of the diffuse electric layer was determined by the equilibrium liquid film method (1). The method is based on calculating theϕ0-potential by means of the DLVO theory of the electrostatic disjoining pressure at known concentration,Cel of the solution forming the microscopic liquid film and at known thickness,hr of the film. The thickness of the film was measured by the microinterferometric method (7, 8). The calculation of the potential was carrried out by means of the more general eqs. [2] and [3], valid for a wide range ofCel andϕ0. The dependence of the potential of the diffuse electric layer on the concentration of surface activ agent (surfactant) stabilizing the liquid film was found. It was established that ionogenic SAS show a higher potential than the non-ionogenic ones. The potential of SAS-free solutions was determined — ca. 30 mV.

Adsorption of emulsifier on polystyrene and poly(methyl methacrylate) latex particles

Abstract: Adsorption of sodium dodecylbenzene sulfonate emulsifier has been measured on polystyrene (PS) and poly(methyl methacrylate) (PMMA) latex particles. Surface tension titration curves permit calculation of adsorption at various concentrations of emulsifier. The data fit a Langmuir isotherm equation and indicate a limiting area A 0 of 35 A 2 for an emulsifier molecule. The A 0 does not depend on the nature of the polymer. But at the critical micelle concentration the area A m per adsorbed emulsifier molecule is 53 A 2 on PS and 131 A 2 on PMMA in .005 N salt. For salt-free PS latex A m is 62 A 2 . Thus A 0 appears to be a characteristic of the emulsifier. But A m depends markedly on the nature of the polymer surface. Hence measurements of A m may be used to characterize a latex particle surface. PMMA grown on a PS seed latex appears to cover the PS surface completely, from an adsorption standpoint, with a PMMA shell as thin as 25 A.