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The dynamic mechanical relaxation behavior of two series of amorphous polyolefins, was investigated from 4.2 K to the glass transition. Most of the polymers show a damping maximum or plateau in the 40 to 50 K region. Various mechanisms which have been suggested for cryogenic relaxations in amorphous polymers are considered as they might relate to the polyolefins. Two secondary relaxation processes above 80 K are distinguished. A relaxation at about 160 K (beta) in the second and third member of each series is associated with restricted blackbone motion. This process requires a certain degree of chain flexibility since it is not observed in the first member of each series. A lower temperature process (gamma) is observed in each member of the second series and is attributed to motion of the ethyl side group.

Development of an indirect method of estimating the solubility parameter of high molecular weight polymers. The proposed method of estimating the solubility parameter, like Small's method, is based on group additive constants, but is believed to be superior to Small's method for two reasons: (1) the contribution of a much larger number of functional groups have been evaluated, and (2) the method requires only a knowledge of structural formula of the compound.

High temperature pyrrones molding, discussing covalent organic bonds breakage and subsequent structural rearrangement of crosslinked polymer network

Thermal conductivity theory based on molecular structure model to study linear amorphous high polymers, specifically polyethylene

The configurations of flexible macromolecules are discussed with particular emphasis on some problems arising in the theory of the volume effect. The main points considered are: (1) the relationship between the Kuhn statistical chain element and the carbon bond length; (2) the assumption that a polymer chain is equivalent to a collection of independent beads normally distributed with respect to the center of gravity (“Gaussian gas” model); (3) the distribution of segments of a polymer chain with respect to the center of gravity; (4) the theory of the execluded volume for plane models of a polymer molecule; (5) the relationship between the excluded volume and the local density of polymer segments; (6) the influence of the solvent on the excluded volume; (7) polymer configurations and viscosity.

In this review a short outline of the results of the application of IR-spectroscopy to the study of polymer physics is summarized. Questions of rotational isomerism, mechanical deformation of polymers, crystallization, intramolecular order, and microtacticity determination are discussed. Details are given on the authors' data concerning polypropylene, 1,4-trans-polybutadiene, poly(methyl methacrylate), and cellulose triacetate, and also data on calculations of spectra for different conformations of poly(vinyl chloride), poly(vinyl bromide), and poly(ethylene terephthalate).

O~E of the main problems of modern polymer physics is the determination of relationships between the properties of individual macromolecules and the properties of macromolecules in a sohd body Although theories of structure and properties of macromolecules in dilute solutions are now being actively developed, their results cannot be applied to the properties of bulk polymers firstly because the effects of molecular interaction are not taken into account in dilute solutions. Molecular influences the behaviour of chains and their conformations in a solid polymer, which differ substantially from the conformations of individual chains. From this point of view considerable interest is at tached to the explanation of the problem of how the properties of individual macromolecules are transferred to the properties of a polymer body and how this occurs. Relatively little information of this kind is available in the literature. I t was reported in some studies [1-9] that, in addition to the main changes involved in glass transition, further temperature transitions in polymers were observed as anomalies in the temperature dependence of some properties. Similar transitions were observed both in pure polymers and in solutions [2, 3, 8, 9] Thus, an additional conformation transition, for example for bulk-polymerized polystyrene appears as: a diffuse maximum near 50 ° on the curve of differential thermal analysis (DTA) [7], clear drop in internal pressure (i e cohesive energy) [5], an increase in the Bragg distances between the phenyl groups [6], a discontinuity in dilatometric linearity [4]. In solutions similar transitions were shown in the form of anomalous dependence on temperature [3] of intrinsic viscosity and globule dimensions (~2)1/2 [3, 9], tangent of dielectric loss angle [1, 2], decrease in chain anisotropy, decrease in surface tension [8] and appearance of a discontinuity in the dilatometric linearity [4]. Daane and Barker [4] found transitiSn temperatures for cellulose esters and concluded that these temperatures arc subject to a variation in the molecular mechanism of macromolecular motion. Thus, a minimum number of possible conformations corresponds to the lower

In the field of polymer physics, X-ray diffraction line profile analysis methods have yet to acquire the significance which they possess in the analysis of the fine structure of metals and alloys. The present paper attempts to put these methods on a solid theoretical basis and to introduce new concepts in the analysis of polymeric X-ray diffraction profiles. The theory of paracrystals has been used to calculate the expressions for integral line breadth and variance–range function of 0k0 diffraction profiles. The methodology is illustrated by an application of the integral breadth and variance methods to a polynosic viscose fibre, Tufcel, whose axial structure has been shown to be `paracrystalline'. Special emphasis is laid on the elimination of diffuse background scatter, the correction of profiles for angular variation factors, the problem of overlapping reflexions etc. and the superiority of the variance method over the integral breadth method in the analysis of polymeric X-ray diffraction profiles is established.

Volume-temperature data at atmospheric pressure used to verify principle of corresponding states for oligomer and high polymer liquids

Network rupture hypothesis and molecular structure considerations used in obtaining constitutive equations for flow of polymer melts and solutions

The strength of technical joints formed with (soft) polymeric ad hesives is discussed from the detailed viewpoint of fracture mechanics. A new approach to the analysis of technical joints has been attempted by considering the variety of complex modes by which fracture can progress in such joints. Particular attention has been given to separat ing the geometric and loading factors of a joint from strength charac teristics attributable entirely to the properties of the materials in volved. By drawing on the creep or relaxation behavior of the polymer and on the fracture energy of the bond interface, or of the adhesive, the time-dependence of the process is discussed in the absence of a corrosive atmosphere. Finally, analytic reasons and a criterion are given for the possible rate dependence of the failure path location along different interfaces of adherends and the adhesive.

Heats of mixing of polymers with each other have been measured, the behavior of the mixtures of solutions of various polymers has been studied, and the dependence of mechanical properties of polymer mixtures on the ratio of components has been investigated. It has been shown that mixing of polymers with each other is usually an endothermic process and, therefore, leads to formation of macroscopically homogenous, but actually microheterogenous, systems with an extremely high degree of dispersion. These microheterogenous polymer mixtures are formed because of the enormous viscosity of polymer mixtures, which prevents macroscopic separation into phases but does not hinder the considerable mobility of the segments of flexible chain molecules. It has been shown that the dependence of mechanical properties of microheterogenous polymer mixtures on the ratio of polymers in the mixture have sharp maxima or minima which cannot be found in the case of true polymers in polymer solutions. It has been found that the behavior of some polymer pairs is anomalous, in that exothermal mixing is supplemented by separation of the solution mixture into phases and by the appearance of maxima or minima in the dependences of the properties of polymer mixtures on the ratio of polymers in the mixture. This anomaly has been attributed to the effect of loose packing of the molecules of the polymers which show anomalous behavior. It has been shown that, in these systems, there necessarily exists a lower critical temperature of mixing whose value can be decreased by adding low-molecular solvents to the loosely packed polymer. Attention has been drawn to the fact that, although mixing of amorphous polymers should be considered on a thermodynamic basis to be a mutual solution of two liquid phases, the large dimensions and the flexibility of polymer chain molecules require a critical revision of the possibility of formal application of the basis thermodynamic concepts and relations to a theoretical analysis of the behavior of polymer mixtures.

Studies of extended chain crystals carried out over the last 10 years have been reviewed. Crystallization in an extended chain conformation is possible either by chain folding followed by extension in the solid state, or by crystallization during polymerization. The equilibrium isometric crystal habit is only rarely exhibited. Crystals which derive from folded chain macroconformation by subsequent chain extension have lamellar habit, crystals which crystallize during polymerization often show fibrillar habit because of nucleation limitation. The morphology of extended chain crystals is analogous to folded chain crystals. Their properties have been shown to be close to the extrapolated equilibrium properties.

For the past few years our research has been concerned with the preparation of polymers which are compatible with and have usable mechanical properties in the presence of liquid oxygen. These are stringent requirements and the need for oxidative stability necessitated investigation of halogen-containing polymers, in particular, polymers containing fluorine. Since only a few fluorocarbon monomers are commercially available, this study required an extensive synthesis program. A comprehensive search of the literature and an attempt to systematically study the effect of polymer structure on low-temperature properties directed our initial work toward the synthesis of some novel, highly fluorinated vinyl monomers and polymers. In this article the effect of structure on polymer glass transition temperatures will be discussed and the synthesis and characterization of some fluorocarbon vinyl ethers and their polymers will be described.

Diffusion coefficient of ordinary low molecular weight solutes in polymer solutions, noting variation of diffusivity from value in pure solvent

Transitions in glasses at low temperatures, noting molecular relaxation dependence on copolymer composition

The parallel between fibers and metals is discussed in terms of their behavior upon heat treatment, crystallite size and orientation, and diffusion of atoms and molecules. It is pointed out that the degree of crystallinity employed to interpret the x-ray diffraction patterns of fibers is not an important physical parameter. The need for critical study of the mechanism of the growth of primary and secondary walls is stressed for a better understanding of the physical properties of fibers. Reference is made to Hosemann's theory of paracrystals which will help to resolve the “open” problems in polymer physics.

Polymer type, temperature, crystallinity and orientation effects on fracture mode, discussing macroload carrying capacity, nylon fiber tie chains and molecular behavior

It has recently been shown that the techniques of EPR spectroscopy can be used to monitor atomic bond rupture during fracture of polymeric materials and thus provide important new insights of the molecular mechanisms of fracture in these materials. In particular, this method can be used as a fundamental check of the several atomistically-derived theories of polymer fracture. In this paper such a check is made of two representative such theories, those of S. N. Zhurkov and W. G. Knauss. It is shown that these theories do not provide physically realistic models of the fracture mechanisms in oriented polymeric fibers and it is suggested that their lack of relevance is due to the unique morphological structure of highly oriented polymers.

Numerical distributions of end-to-end distances were generated by a Monte Carlo method for hard-sphere off-lattice polymers of length N = 20, 40, 60, 80, 98, and 298 atoms. Comparison by xz tests against five recently proposed theoretical distribution functions showed that for N = 80 and N = 98, the data could be described, with 95% confidence, by the equation f(r) = exp[ -(ar2 + br + c)], where a and b are fitted parameters and c is a normalization constant. For N = 298, limitations of sample size lead to lower confidence limits (about 80%), but good fit. The above equation, and not its gaussian counterpart exp( -cr^2), is probably the limiting distribution function. The function accurately predicts the 1st through 12th observed moments at all chain lengths.

The phenomenological theory previously prsented for describing the rheological properties of non-Newtonian materials was applied to two polymer solution systems. The basic shear diagram is needed over a wide range of shear rates and polymer concentrations, and such data are not readily available; however, what could be found supported the analysis. In order to confirm the theory further, ten solutions of polymethylmetacrylate in diethyphthalate with concentrations up to 55% were investigated at 40°C. The results indicated that the forward and reverse orders were 1 and 2 respectively and that the two parameters of the theory (a susceptibility to shear term and an equilibrium type of constant) were constant over the range of concentrations investigated. The flow data were reproduced to within a few percent for all solutions, although the errors were large for the very dilute concentration, where experimental difficulties precluded obtaining reliable data. The method allows correlation of polymer solution data over the range from lower to upper Newtonian viscosities and over a wide concentration range.

Bond rupture and fracture in semicrystalline polymers, noting agreement with random length molecular tie chain scission model

超音波が,コウモリやコウロギなど生物の手から人間の技術となってからすでに50年以上になる。この50年の間に,超音波の技術は,一つは物性測定技術として発達し,音波物性学という部門を生んだ。気体から始まって,液体,固体とこの部門は発展し,現在ではそれらの総合的知識が高分子の音波物性学の基礎となっている。この小文は,この分野の,なるべく新しく特徴的な部分を拾って展望する。超低周波域から超高周波域まで,10-3Hzから1011Hzまでの14ケタにわたる測定技術は,さらに延長されて下はクリープや応力緩和とつながり,上は格子振動,分子内振動とつながる。高分子の音波物性学の今後の発展は期してまつべきものがあろう。

Boundary tension is the best known property of liquid surfaces. This property is of outstanding importance in the phenomenon of adhesion which is an interdisciplinary subject involving surface chemistry, rheology, polymer physics, and fracture mechanics. Adhesion plays an important role in various industrial applications such as in packaging, construction and manufacturing. Also, the behavior of solder and printing inks in their respective practical applications is influenced by boundary tension.

Linear high polymer heat capacities by adding contributions from chain segments, deriving table of heat capacity contributions of polymer constituents

Polyalkyl methacrylates multiple transitions from torsion pendulum and linear expansion tests over temperature range, discussing free volume and expansion coefficients

High speed automatic osmometer applied to measurements of diffusible branched polyethylene samples, discussing apparent molecular weight observations

The cut growth and fatigue properties of a typical cellular polyurethane soling material are considered in terms of the tearing energy theory established for vulcanised solid rubbers. The minimum value of tearing energy (T0) below which no cut growth occurs in the absence of chemical effects is compared with practical results from shoe soles in wear. The existence of large holes in a soling material which can contribute to flex cracking failure is considered and a recent theory for their existence in solid rubbers is discussed. The scanning electron microscope has been used to illusstrate poor water absorption properties of low density polyurethane soling materials.

The effects of excluded volume interactions upon the dynamical behavior of random‐coil polymer chains are studied by obtaining autocorrelation functions for vector end‐to‐end length of lattice‐model chains of 9, 15, 33, and 63 beads by a Monte Carlo simulation technique. It is found that relaxation of the vector end‐to‐end length requires from 4 to 7 times as long as relaxation of its square, in contrast to the predictions of simple models without excluded volume effects.

Integral equations with an even displacement kernel (which depends only on the difference of the two variables multiplied by a parameter) appear frequently in several applications, e.g. neutron transport theory, electrodynamics and polymer physics. Because of the large range of parameter values of interest, each problem has often led to a separate technique of solution. In this paper, a technique is presented which covers all parameter values. It applies to arbitrary displacement kernels and uses an expansion in Legendre polynomials to give a rapidly converging numerical solution. For small and large parameter values the behaviour of the eigenvalues is theoretically investigated and numerically illustrated. The computational effort involved is relatively very small.

A simple restatement is given for the description of polymer optical properties in terms of the interaction matrix coupling monomers. Two‐ and three‐state solutions are given explicitly and in detail for the polypeptide alpha helix, beta sheets, and polyproline helices. The results are compared with perturbation‐theory results. Agreement with experimental data is good except for polyproline II. The role played by the amide band recently observed in the gas phase is discussed, as is the extension of the calculations to other regular polymers and amorphous polymers.

Electron microscopy and methods of polymer physics were used to investigate the texture of bacterial storage granules, namely, poly-β-hydroxybutyrate. The first level of native granule morphology is 100 to 150 A fibrils, involving extended polymeric chains. Fibrils are believed to represent a unique morphology which develops because of the simultaneous synthesis and crystallization which occurs during some stage of formation. It is assumed that fibrillar aggregates are important in the internal organization of the granule, based on differences both in response to temperature and in small-angle scattering of native poly-β-hydroxybutyrate granules compared to single-crystal poly-β-hydroxybutyrate. The fibrils can re-organize into 50 A thick ribbons when in aqueous acetone, and are further transformed into single-crystal lamellae with folded chains. Polymer synthesis and crystallization are discussed and a model is presented to explain how these events might occur on the surface of the polymerizing enzyme.

In recent years polymer physics has developed rapidly, and it now embraces the structure and the mechanical, optical, electrical and magnetic properties of solid polymers, melts and polymer solutions. In this review we will discuss only the structure and mechanical properties of solid polymers.

A high-temperature linear amorphous hydrocarbon polymer synthesized cationically from 2,5-norbornadiene was studied thermomechanically with respect to physical transitions and stability in nitrogen. The glass transition temperature was determined to be 320 C (at less than 1 cps), which is probably the highest known for a linear hydrocarbon addition polymer. The thermomechanical technique of torsional braid analysis, together with thermogravimetric analysis, differential thermal analysis, infrared analysis, and solubility studies, was used to investigate the sequential events of the glass transition and degradation. The polymer is of particular interest since it is a high-temperature plastic which in the bulk form would probably need to be processed at high speeds in the vicinity of the glass transition temperature in an inert atmosphere. The presence of tertiary hydrogen atoms should render it amenable to degradation by the earth's environment.

Aerospace technology has established the demand for thermally stable polymers which retain useful properties at high temperatures. The reliability of a re-entry shield is directly dependent on the performance of the polymers used as ablators. Polymeric ablation materials are sacrificial and are classified as subliming and charring ablators. Subliming polymeric ablators function by (a) depolymerization-vaporization, (b) pyrolysis-evaporation, and (c) melting-vaporization. Polymers which depolymerize quantitatively and reversibly are ideal subliming ablators. Under hyperthermal conditions, charring polymeric ablators must generate a large amount of char residue which will act as a binder at high temperatures for the reinforcements embedded in the char layer. Generally, the higher the thermal stability of the polymer, the higher the yield of char. The maximum thermal stability in polymers is usually obtained when: (a) thermally unreactive ring structures constitute a major portion of the polymer, (b...

Radiation, molecular orientation, crystallinity and molecular weight influences on thermoconductivity of high polymers

THE texture of crystalline polymers is typically one of thin (100 A thick) lamellae within which the long (103–105 A) molecules lie transversely in chain-folded configurations. In certain circumstances, however, much thicker lamellae, often as thick as the molecular length, have been observed in polyethylene1–3. An example is shown in .Fig. 1. Because a variety of evidence indicates little or no chain-folding in these layers (that is, the molecules, which lie across them, are essentially in extended configuration) they have become known as extended-chain lamellae (ECL) in contrast to the more familiar folded -chain lamellae (FCL). The circumstances in which ECL form are: (i) growth at low supercoolings for long times1 and (ii) by recrystallization under high pressure2,3. The layers themselves vary in thickness, being most regular in slowly crystallized samples1. In pressure crystallized material, thicknesses varying by a factor of two for the same lamella, and ten for different ones, have been observed3. ECL are also mechanically very different from FCL, because the toughening effect of molecules crystallizing through several lamellae must then be small. In fact ECL are no longer plastic but waxy as befits their paraffinoid structure. It is, however, the growth of ECL that has provided a long standing problem in polymer physics.

Extended chain polymer crystals temporary superheating before final melting, discussing hexagonal selenium crystals data

Refractory grains of graphite and silicates ejected from cool giant stars acquire mantles of organic polymers typified by polyoxymethyline in interstellar clouds. Infrared emission from the Trapezium nebula is consistent with the occurrence of such polymers.

Low modulus solid propellants family for low thrust-to-mass ratio fully case bonded end-burning motors, using polymer network theory for binder formulation

HOMOPOLYPEPTIDES have long been considered as model systems for the study of protein conformation1,2, and synthetic homopolypeptides are now available commercially. Solid state and polymer physics have advanced to where the simpler homopolypeptides can be treated theoretically by lattice dynamics and experimentally by the physical techniques of neutron, infrared and Raman spectroscopy, which are more suited to the examination of the optical vibrational modes of a molecule which are of energy higher than, say, 70 cm−1. Specific heat methods, on the other hand, have the advantage that by measuring at low temperatures (1–20 K) only the acoustic modes are appreciably excited thermally (a temperature of 1 K corresponds approximately to 0.7 cm−1). Moreover, the specimen need not be in single-crystal form, and at low temperature the vibrational spectrum is easier to interpret, and the useful picture of Debye3 holds well. The specific heat measurements reported here are believed to be, by a factor of 100, the lowest temperature specific heat measurements made on a biopolymer4. Such measurements can give information about the proportion of a protein which is in alpha-helical or beta-sheet structure, and also will be necessary in evaluating the basic thermodynamics of enzyme reactions5.

ASYMMETRIC adsorption of organic compounds on bio-polymers such as polysaccharides1–7, wool8,9 and casein9 has been reported, but the resulting optical activities of these were usually very low and the capacity for adsorption was very small. On the other hand, several studies of optical resolution by preferential crystallization have been reported (reviewed in ref. 10). Recently, DL-aspartic acid copper complex11, DL-aspartic acid, DL-glutamic acid, DL-asparagine and DL-glutamine12 have been resolved almost completely by the preferential crystallization method in our laboratory.