Homologous Polymers Research Articles

The effect of temperature, molecular weight and polydispersity on the relaxation time spectrum of rubbers

A method has been developed for investigation of stress relaxation in polymers with relaxation times ranging from 10 −2 to 10 5 sec. A study was made of stress relaxation in polyisobutylene at different temperatures and in polybutadiene rubbers (SKDL) differing in molecular weight and in their degree of polydispersity. The calculated relaxation time spectra (RTS) characterized by the presence of maxima in the high elastic region temperature-time superposition principle is insufficiently accurate. The effect of temperature, molecular weight and polydispersity on the RTS of polymer homologues was ascertained.

Thermodynamic interactions in polymer systems by gas–liquid chromatography. III. Polyethylene–hydrocarbons

AbstractThermodynamic interaction parameters have been calculated from gas–liquid chromatographic measurements for linear and branched polyethylene interacting with selected hydrocarbons. The values of the interaction parameter χ are substantial in spite of chemical similarities between the polymer and low molecular weight hydrocarbon species, a fact attributed to significant differences in the respective thermal expansion coefficients. A systematic increase of χ is observed in going from branched to linear polyethylene systems. The thermal expansion coefficients of these polymer homologs therefore may not be identical. The present χ values differ substantially from those reported in earlier literature. The comparison confirms suspicions that some older data, based on equilibrium sorption experiments, were erroneously low because of an underestimate in the reduced melting temperature of polymer in the presence of excess solvent.

Sulfur‐containing polymers. VI. Preparation of poly[alkylene bis(oxycarbonyl) disulfides] and related polymers

AbstractPoly[alkylene bis(oxycarbonyl) disulfides] have been prepared for the first time by the reductive coupling of alkylene bis(oxycarbonylsulfenyl chlorides). Potassium iodide and a variety of transition metals or their salts were employed as reducing agents. Of these potassium iodide and cuprous chloride gave the best results. Pyrolysis, desulfurization. and thiol‐induced fragmentation of the polymers have been studied. Homologous polymers, i.e., monosulfide polymer, trisulfide polymer, and tetrasulfide polymer, have been also synthesized. Monosulfide and disulfide polymers were highly crystalline solids. Trisulfide polymer was a white solid with a low degree of crystallinity. These polymers were soluble in chloroform and dichloromethane. Tetrasulfide polymer was a crystalline yellow solid and was soluble only in HMPA.

Sedimentation equilibrium in nonideal heterogeneous systems. I. Fundamental equations for heterogeneous solute systems and some preliminary results

AbstractThe sedimentation‐equilibrium method is extended to treat nonideal solutions of heterogeneous macromolecules. The solute is assumed to be heterogeneous not only in molecular weight but also in other quantities such as partial specific volume, second virial coefficient and specific refractive increment. General expressions for various observable molecular weights, especially for weight‐average, z‐average, and number‐average molecular weights, are derived. Their dependences on sedimentation parameter and solute concentration are discussed in detail. For the extrapolation of observable molecular weights, giving a type of weight‐average, and z‐average, to infinite dilution to estimate the molecular weight and the second virial coefficient, average concentration is superior as a concentration variable to original concentration. The plots of observable molecular weight versus average concentration are usually less influenced by the choice of the sedimentation parameter, especially of rotor speed. The general expressions are applied to a few special cases; monodisperse polymer, polydisperse homologous polymer, and polymer blend. The results are compared with experiments on a monodisperse, polystyrene, a polydisperse poly(methyl methacrylate), and a mixture of the two polymers, all in 2‐butanone at 25°C. The agreement between the theory and experiments is satisfactory.

Determination of molecular weight of acid mucopolysaccharides by gel electrophoresis

Electrophoresis in polyacrylamide gels can be utilized to estimate the molecular size of ultramicro samples of acid mucopolysaccharides. The distance of migration of hyaluronate, chondroitin sulfate A, and chondroitin sulfate C varied linearly with the logarithm of the molecular size for each set of homologous polymers.

Structural Studies of Polyesters. IV. Molecular and Crystal Structures of Poly(ethylene succinate) and Poly(ethylene oxalate)

In the course of structural studies of aliphatic polyesters of the type [–O–(CH2)x–O–CO–(CH2)y–CO–]n, the molecular and crystal structures of polyethylene succinate) (x=2, y=2) and poly(ethylene oxalate) (x=2, y=0) were determined by interpretation of X-ray diffraction patterns and complementary study of infrared spectra.The crystallographic data are:Poly(ethylene succinate); a=7.60 A, b=10.75 A, c (fiber axis)=8.33 A, orthorhombic space group Pbnb-D2h10, four molecular chains pass through the unit cell.Poly(ethylene oxalate); a=6.44 A, b=6.22 A, c (fiber axis)=11.93 A, orthorhombic space group Pbcn-D2h14, two molecular chains pass through the unit cell.The chain conformation of poly(ethylene succinate) is T3GT3G, in which the two C(H2)–C(H2) bonds in the chemical repeating unit are G or G, where T means trans form and G and G are used to discriminate right-handed and left-handed gauche forms, respectively. The chain conformation of poly(ethylene oxalate) is T5GT5G, in which the C(H2)–C(H2) bond is G or G. There are some close similarities between the molecular and crystal structures of poly(ethylene succinate) and poly(ethylene oxalate), and their structures are quite different from polyethylene-like structures for the higher members (x=2, y≥4) of the ethylene glycol series. The high melting points of poly(ethylene succinate) and poly(ethylene oxalate) among the homologous polymers may be related to these molecular and crystal structures.

Preparation of monodisperse polyethylene oxides by gel permeation chromatography of discontinuous polymer-homologous series

Starting from triethylene glycol, monodisperse polyethylene oxides of a molecular weight (MW) up to 2000 (degree of polymerisation (DP) < 45) were synthesised in a two-step process. During the first step the ditosylate of triethylene glycol is reacted with the sodium alkoxide of the same diol at room temperature. The condesation product (polymer homologues of triethylene glycol) was separated by molecular distillation and yielded the pure oligomers nonaethylene glycol (DP = 9, MW 414) and pentadecaethylene glycol (DP = 15, MW = 678), as proved by gel chromatography. During the next step the polymer homologues of nonaethylene glycol were synthesised in a similar way. The pure oligomers hepteicosa (DP = 27, MW = 1207) and pentatetracontaethylene glycol (DP = 45, MW = 2000) were isolated by preparative gel permeation chromatography on a polystyrene gel cross-linked with 2% divinylbenzene. Using a column, 200 × 5 cm, samples of up to 5 g could be separated. The separation of technical polyethylene oxides prepared by polymerisation indicated that up to a DP of approximately 27 adjacent oligomers are still resolved.

Electric strength of polymer homologs of styrene acted on by standard pulses

Electric strength of polymer homologs of styrene acted on by standard pulses

Polysaccharides of soy-beans. V. Acidic polysaccharides from the hulls.

Acidic polysaccharide fractions from soy-bean hulls have been examined by partial hydrolysis or partial acetolysis. Oligosaccharides, which have been characterised, include 2-O-α-L-fucopyranosyl-D-xylose, 2-O-β-D-galacto-pyranosyl-D-xylose, 4-O-β-D-galactopyranosyl-D-galactose and its polymer homologues, 4-O-(α-D-galactopyranosyluronic acid)-D-galacturonic acid and the polymer-homologous trisaccharide, 2-O-(α-D-galactopyrano-syluronic acid)-L-rhamnose, higher oligosaccharides containing galacturonic acid and rhamnose residues, and small amounts of glucuronic acid-containing aldobiouronic acids. The results of partial hydrolysis and of methylation of some of the fractions indicate that the acidic polysaccharides comprise a group of structurally related polysaccharides of the pectic acid type.

Rheological properties of polymer melts

AbstractA new method of treating experimental data on the viscous and viscoelastic properties of various polymer melts is suggested. The dependence of the apparent viscosity on the molecular weight, temperature and shear stress can be represented as the product of three independent functions, each of them having a single argument. All three functions are universal, at least in first approximation, and the dependence of the apparent viscosity on the variables indicated is determined by two parameters (glass transition temperature and critical molecular weight), characteristic of each homologous polymer series. The viscoelastic characteristics (dynamic, relaxation, creep, as well as relaxation and retardation spectra) of polymer melts are universal in shape in the linear region and contain only one individual polymer parameter, viz., maximum Newtonian viscosity. It is shown that upon normalization of certain nonlinear characteristics with respect to the maximum Newtonian viscosity, they can also be represented in the universal form.

ANTIGENICITY OF POLYPEPTIDES (POLY ALPHA AMINO ACIDS). XIV. STUDIES ON IMMUNOLOGICAL TOLERANCE WITH STRUCTURALLY RELATED SYNTHETIC POLYMERS.

SummaryIt. has been shown that neonatal injections of the polymers G60A40 and G42L28A30 can establish acquired immunological tolerance against these homologous polymers. Neonatal injections of polyglutamic acid are more effective than G42L28A30 in establishing cross tolerance against G60A40. Neither polyglutamic acid nor G60L40 when injected neonatally. were effective in reducing an adult, response against G42L28A30. However, G60A40 did reduce the response against a first course of immunization with G42L28A30. This tolerance was broken by a second immunization with polymer in complete adjuvants.

Analysis of intrinsic viscosity data

AbstractIn order to interpret quantitatively intrinsic viscosity data for polymer solutions, especially for chains of poor flexibility, the partially free draining effect discussed in the theories of Kirkwood and Riseman and Debye and Bueche must be also taken into account, as well as the excluded volume effect considered in the theory of Flory and Fox. Although the Flory‐Fox theory is widely used at present for analysis of intrinsic viscosity data, it appears that in most actual cases the draining effect may also play an important part and the two effects may overlap each other to some extent. A new method has been presented in this paper, through which the separation of these tow contributions becomes possible. The exponent a in the Mark‐Houwink equation, [η] = KmM̄va, is divided into two parts: a1, related to the volume effect, and Δ, related to the draining effect. Making use of the theoretical relationship between Km and a, which was derived in the preceding paper, we can calculate the value of Δ, if the Mark‐Houwink constants have been established for a given series of polymer homologues in two solvents. In this way, we can discuss the volume effect and the draining effect separately, and interpret completely intrinsic viscosity data in terms of the parameters appearing in the Flory‐Fox and Kirkwood‐Riseman theories. Furthermore, a new method has been proposed for estimating the Mark‐Houwink constants from the measurements of intrinsic viscosity and molecular weight for a single sample. Only one sample need be used, and thus recourse to the usual more laborious methods is unnecessary. General applicability of our methods has been shown by several examples cited from published data.

A note on intrinsic viscosity–molecular weight relationships

From an examination of experimental data on a number of series of well-fractionated polymer homologs in various solvents, interesting correlations were found between the constants Km and a in the Mark-Houwink equation often used in describing the relationship between intrinsic viscosity and molecular weight. For a given series of polymer homologs in different solvents, Km regularly decreases with increasing a; moreover, in the Km−a curves, plots for various polymeric substances all conform to one of two typical curves, the one being for flexible, noncrystallizable polymers and the other for semiflexible, crystalline polymers. In this paper an attempt has been made to put these experimental relationships on a theoretical basis. Combination of the theoretical expressions obtained by Flory and Fox with the Mark-Houwink equation yields the equation where β = a − 1/2, K is a constant characteristic of the polymer chain, and M0 is the arithmetical average of the upper and lower limits of the molecular weight range covered. The experimental relations between Km and a mentioned above can be quite adequately accounted for by this equation. Although eq. (1) was originally derived for molecularly homogeneous polymers, it has been shown to be valid also for molecularly heterogeneous polymers if K is replaced by K*, which reflects the molecular heterogeneity of a series of fractionated (or unfractionated) polymer homologs. Although this value gives only an average heterogeneity over a series of the polymer homologs used and depends upon the method of molecular weight determination, its use furnishes a convenient method either for the examination of newly obtained [η] vs. M data or for the choice of the most reliable relationship among those obtained by various authors for a given polymer-solvent combination. When the theory of Flory and Fox is applicable and K is known for a given polymer, the Houwink constants can be easily computed through use of eq. (1) from the measurements of [η] and M for only one (carefully fractionated) sample, without recourse to more laborious methods usually used. This is, so to speak, a “one-point method” of obtaining the intrinsic viscosity–molecular weight relationship.

Molecular weight relations and chain extensions of some vinyl alkyl ethers

AbstractRelationships between intrinsic viscosity and weight‐average molecular weight were obtained for fractions of polyvinyl methyl ether and, approximately, for samples of homologous polymers having ethyl, isopropyl, and n‐butyl alkyl groups in the side‐chain.Within the range of molecular weights between 1 · 104 and 5 · 105, the equation [η] = 1.37 · 10−3 M0.54 holds for fractions of polyvinyl methyl ether dissolved in butanone at 30°C. For molecular weights between about 5 · 104 and 5 · 105, the equation [η] = 9.2 · 10−4 M0.58 gives a better fit. For solutions in benzene, the overall equation [η] = 7.6 · 10−6 M0.60 is valid.At least for high molecular weights (1 · 105 &lt; M &lt; 1 · 106), the equation [η] = 1.37 · 10−3 M0.54 also represents the data well for solutions of unfractionated samples of polyvinyl ethyl ether and polyvinyl isopropyl ether. On the other hand, data for two samples of polyvinyl n‐butyl ether do not fit this equation.The degree of steric hindrance was found to depend on the size or bulkiness of the alkyl side chain, and decreased in the following order: equation image

An Investigation of the Molecular Weight Distribution of Polymers with the Aid of the Ultracentrifuge

Abstract In the present paper a method for studying the molecular weight distribution of linear polymers, involving the following stages, is developed: 1. Fractionation of the polymer into a series of sufficiently narrow fractions and investigation of these fractions with the aid of the ultracentrifuge and diffusion. 2. Plotting the distribution functions of sedimentation constants for each fraction and subsequent summation of curves in order to build up the distribution function of the sedimentation constants for the whole polymer. 3. Discovery of a general functional relation between the sedimentation constants and molecular weights for a given series of polymer homologs and construction of the distribution function of molecular weights of the polymer. The basis of the method developed by us (method of equivalent Gaussian distributions) was confirmed by direct experiment. Application of this method of investigation to a number of industrial polymers will be described in the next paper.

The Effect of Non-Homogeneity of Molecular Weight on the Scattering of Light by High Polymer Solutions

The general theory of the turbidity of a mixture of many components is applied to a solution of homologous polymers. It is found that the concentration dependence of the turbidity is intimately related to that of the osmotic pressure. The molecular weight distribution does not have any influence on the concentration dependence of the turbidity.

Macromolecular Compounds. CCXCII Polyisobutylene

Abstract An explanation of the chemical constitution of macromolecular substances has to a great extent been made possible by the preparation and study of various homologous series of polymers. In these investigations, the relations between the average degrees of polymerization and the physical properties of the particular substances concerned were studied. As a result of these studies, it was found that the unusual physical properties of macromolecular substances, such as toughness, elasticity, swelling in liquids, and above all, the colloidal nature of their solutions, are dependent on the size and form of their macromolecules, and not on a special micellar structure, as had been so widely assumed previously. It has been found possible to prepare a complete series of homologous polymers, starting with the low members, and passing through the hemicolloids and mesocolloids, to the highest molecular members, the eucolloids, by polymerization of vinyl derivatives under various conditions. It has not been found possible, however, to prepare a complete series of homologous polymers from all vinyl derivatives. At present, for example, there are still no known eucolloid members of polyindenes and of polyanetholes. On the other hand, in the polymerization of styrene, vinyl chloride, acrylic esters and vinyl acetate, it has been found possible to prepare, by the proper choice of conditions during polymerization, members extending from hemicolloids to eucolloids. An analogous complete series of homologous polymers can be prepared from polyisobutylenes. In this case it is possible, by the choice of various catalysts, to obtain polymerized products extending from the lowest to the highest degrees of polymerization. The hemicolloid members of this series are used technically as lubricating oils; the mesocolloid and eucolloid products are of importance in other ways because of their rubberlike properties.

Isoprene and Rubber. Part 44. Viscosity Measurements of Squalene and Hydrosqualene Solutions

Abstract The physical properties of highly polymerized substances, which are composed of fiber molecules, depend on the lengths of the chains of these fiber molecules. Thus tensile strength, elasticity, tendency to swell in solvents, and above all viscosity, are dependent on the length of chain of the particular substance. Among the substances, the properties of which vary thus, are rubber, gutta-percha, and balata. Since the length of fiber molecules can vary within wide limits, such physical properties as those mentioned above show wide variations in the case of rubber, gutta-percha, and balata. This is evident for example by a comparison of the properties of unmasticated rubber, which consists of long fiber molecules of a degree of polymerization of 2000, with the properties of masticated rubber, the greatly dissociated molecules of which have a degree of polymerization of only 500. The determination of the length of the fiber molecules is therefore of great importance in the case of highly polymerized substances. It has already been proved in past experiments with members of a series of homologous polymers, i. e., of substances the macromolecules of which have the same basic structure and differ only in length, that the molecular weights can be determined from viscosity measurements. This determination is based on the fact that there is a general relation between the specific viscosity and the length of the dissolved molecules, which can be expressed by the formula:

Isoprene and Rubber. Part 41. The Hydrogenation of Rubber and Balata

Abstract Viscosity measurements of dilute solutions of rubber and of balata led to the following values for the size and form of the molecules of these hydrocarbons. It is therefore not a question of definition whether the particle sizes shown above are to be regarded as the molecular or the micellar weights of these substances, for here the concept of molecular weight has the same significance as in the case of lower molecular substances, i. e., the molecule comprises the sum of all atoms combined by normal, i. e., homopolar atoms. The only difference between low and high molecular substances is that low molecular substances are composed of molecules of uniform size, whereas high molecular substances are a mixture of homologous polymers, so that the values above refer to average molecular weights. These results, which explain the nature of colloidal solutions of rubber, are at variance with the views of most investigators of colloids, who ascribe a micellar structure to the rubber particles, and in this way explain the property which rubber has of forming colloidal solutions. This makes clear why until very recently explanations of the constitution of rubber have been open to question among these particular investigators themselves. In order to lend further support to our opinion, the reduction of rubber and balata and low molecular homologous polymeric hydrocarbons was undertaken from certain points of view, as shown in the work which follows.

Isoprene and Rubber. Part 33. End Groups in Rubber

Abstract In a recent work, Pummerer, Ebermeyer, and Gerlach attempted to identify end members in the rubber molecule by ozone decomposition, and in this way to determine the molecular weight of rubber by chemical means. In this connection they say: The basis for the validity of the conclusions derived from the cleavage fragments on the average length of the rubber chain is that this hydrocarbon contains no structurally foreign impurities, but is built up of homogeneous molecules, though of perhaps different lengths. Pummerer abandons his earlier view, according to which rubber is composed of a uniform base molecule, in favor of concepts held by me for years on the constitution of rubber and other high polymeric substances. As was first proved for synthetic products and as shown for balata and rubber, these substances consist of a mixture of similarly constituted molecules of various lengths and therefore of a mixture of homologous polymers. Pummerer has now adopted this concept, but on the other hand he does not agree on the question of the molecular weight.