bluuebunny/crossref_metadata_2025 huggingface dataset:
The effect of chemical composition on selected physical properties of linear polymers
Authors: Izard E. F.
Published: April 2003

A review of the data available in the literature and new data reported in this paper show that in any homologous series of condensation polymers there is a uniform change in the melting point as the hydrocarbon content of the polymer is increased. If all such series are treated as copolymers of the simplest modifying element and polyethylene and the composition expressed on a mole fraction basis, the data when presented graphically show that the melting points of any such series passes through a minimum at some intermediate composition. The position of the minimum as well as the depth of the minimum is dependent on the polarity of the modifying group. This survey has included aliphatic polyesters, aromatic polyesters, polysulfides, cellulose derivatives, and polyamides. Some of the series are complete enough to show a definite minimum with compositions on either side of the minimum with higher melting points. In some compositions based on the very highly polar groups, such as amides, the series is not complete enough to establish the complete shape of the curve, but the indications are strong that the minimum does exist.
Polyelectrolytes. X. Shear dependence of viscosity in aqueous solutions of poly‐4‐vinyl‐N‐n‐butylpyridinium bromide
Authors: Strauss Ulrich P. , Fuoss Raymond M.
Published: April 2003

Apparent viscosities of aqueous solutions of polyvinylbutylpyridinium bromide (DP = 2000), after correction for instrument constants, are linear in average rate of shear in the capillary viscometer. If a non‐Newtonian solute in a Newtonian solvent is assumed, the rather complicated experimental viscosity‐pressure curves at various concentrations may be summarized by the simple expression ηsp./C = z∞ (1 − αz∞β)where z∞ is ηsp./C extrapolated to zero rate of shear and β is the average velocity gradient.
Some new butadiene copolymers
Authors: Marvel C. S. , Fukuto T. R. , Berry James W. , Taft W. K. , Labbe B. G.
Published: April 2003

Copolymers of butadiene with 2‐ethoxyethyl acrylate, 2‐ethoxyethyl methacrylate, tetrahydrofurfuryl acrylate, acrylic acid, and methacrylic acid have been prepared and evaluated as rubbers. The 2‐ethoxyethyl acrylate copolymer has good low temperature properties. The methacrylic acid copolymer has unexpectedly good oil resistance, but the low temperature properties are poor. The acrylic acid copolymers show fair oil resistance and good low temperature properties. Both acrylic acid and methacrylic acid copolymers with butadiene show unexpectedly good tensiles.
Control of dust in solution for turbidimetry
Authors: Thurmond Carl D.
Published: April 2003

Dust‐free polymer solutions have been prepared with the aid of special equipment which is described.
A new tool for determination of the stage of polymerization of thermosetting polymers
Authors: Sofer George A. , Hauser Ernst A.
Published: April 2003

Studies of the change of attenuation and velocity of longitudinal ultrasonic waves with proceeding polymerization of thermosetting plastics have revealed that this new technique may permit rapid determination of the stage of polymerization under various conditions. The ultrasonic equipment used for these tests is described in detail. On the basis of results so far obtained, future possibilities for the application of this new technique in studying polymerization reactions are outlined.
The elasticity of polythene melts
Authors: Hoff E. A. W.
Published: April 2003

The elasticity of polythene melts was measured with a resonance method by inducing shear oscillations in the region about 30 cycles/second at small shear amplitudes. The experiments covered a temperature region of 130° to 230°C. and a range of (osmotic) molecular weights from 12,000–64,000. Shear moduli of the order 105 to 105 dyne cm.−2 were observed and a single relaxation time appeared sufficient to characterize the mechanical behavior of the polythene melts at a given temperature. The variation of mechanical parameters with temperature and molecular weight is brought into relation with known data on the amount of chain branching.
Further studies by light scattering of amylose aggregates. Particle weights under various conditions
Authors: Paschall Eugene F. , Foster Joseph F.
Published: April 2003

Decreases in particle weight of amylose on aging in neutral and in alkaline aqueous solution are demonstrated by measurements of turbidity as a function of concentration. This further verifies that the previously reported turbidity drops are a consequence of disaggregation of an unusual type of aggregate. The same particle weights are obtained, in the case of aggregated samples, at pH 4 and in normal KOH. Anomalies arise in dilution series carried out in neutral solution and in solutions at pH 4 in the case of amyloses of low degree of aggregation, and a probable explanation is given. Samples can be partially stabilized in a given state of disaggregation by rendering the solution alkaline, and normal dilution series curves result. Disaggregation of the “native” aggregates continues along with retrogradation, and the retrograded aggregates are broken down readily by alkali. This leads to a method of disaggregation based on retrogradation followed by solution in 0.5 N KOH.
Stability of the vulcanized cross link in butyl rubber: Theory and application
Authors: Zapp R. L. , Ford F. P.
Published: April 2003

It has been determined analytically that, when a Butyl vulcanizate softens during exposure to high temperature, the disulfide cross links between polymer chains break down to thiol groups. Of all the accelerator types, tellurium derivatives of dithiocarbamic acids impart the greatest inherent resistance to this reversion. Such a mechanism of breakdown, however, suggested the use of oxidizing agents to reform the disulfide cross linkage, and four metallic peroxides or dioxides have been found effective. These are CaO2, PbO2, MnO2, and SrO2. Barium peroxide is too stable to be an effective oxidizing agent while magnesium peroxide expels oxygen too rapidly for an effective retarder. Other types of organic and inorganic oxidizing agents have not proved beneficial. The fact that an oxidizing action is responsible for retardation of reversion has been demonstrated by the fact that the corresponding mono‐oxides of calcium, strontium, lead, and manganese do not perform in the same manner. In rubber technology the stabilization of vulcanized materials by oxidizing agents is novel, and it appears applicable only in the case of Butyl whose low unsaturation offers greater resistance to oxidation of the chain proper. When CaO2 is added to diene type rubbers such as Buna S, Buna N, and natural rubber the common oxidative effects are accelerated. With the Buna rubbers the hardening action is more rapid, while with natural rubber a softening followed by a hardening action is promoted.

A practical illustration of this principle of retarding reversion of Butyl vulcanizates by oxidizing agents has been presented. It has been demonstrated in the laboratory that the service life of automotive tire curing bags made from Butyl can be prolonged by the addition of these metallic dioxides or peroxides to the compound.
Rates of thermal degradation of polystyrene and polyethylene in a vacuum
Authors: Madorsky Samuel L.
Published: April 2003

When heated in a vaccum at 325° to 375°C., polystyrene yields mainly the monomer and some dimer, trimer, tetramer, etc., indicating that the breaks in the molecular chains occur largely at the ends. Polyethylene, under similar conditions, but at a some‐what higher temperature, yields fragments of an average molecular weight of about 700, indicating that the molecular chains break, mostly at random positions. A study was made of rates of thermal degradation of these two polymers by measuring rates of loss of weight of samples by means of a very sensitive tungsten spring balance enclosed in a vaccum. The samples were limited to 5–6 mg. in order to avoid spattering during degradation. Rate curves plotted against per cent loss of weight by volatilization indicate that in the case of polystyrene the process is intermediate between a zero and first order reaction, while in the case of polyethylene, the process approximates a first order reaction. Activation energies were calculated on the basis of rates of degradation at various temperatures. The values thus obtained for polystyrene and polyethylene are 58 and 68 kilocalories, respectively.
Preparation of 1,3,5‐trivinyl‐2,4,6‐trichlorobenzene and its copolymerization with styrene
Authors: Ross Sidney D. , Markarian Moushy
Published: April 2003

1,3,5‐Trivinyl‐2,4,6‐trichlorobenzene has been prepared and its copolymerization, at low weight percentages, with styrene has been studied by following the change in viscosity of the polymerizing systems as a function of time. The copolymerization was studied as a function of the concentration of the trivinyl compound (0.5–2 weight per cent) at two temperatures and two benzoyl peroxide concentrations. The gelation times and per cent styrene polymerized at gelation were estimated. In addition, the copolymerization of 1,3,5‐trivinyl‐2,4,6‐trichlorobenzene with styrene was compared with that of 1,4‐divinyl‐2,3,5,6‐tetrachlorobenzene and 1,3‐divinyl‐2,4,5,6‐tetrachlorobenzene, both with styrene. The infrared and ultraviolet spectra of the three cross‐linking agents were determined. The ultraviolet spectrum of 1,4‐divinyl‐2,3,5,6‐tetrachlorobenzene provides a basis for explaining its greater reactivity in copolymerization with styrene.
Ratio of tensile strength to melt viscosity for high polymeric materials
Authors: Boyer Raymond F.
Published: April 2003

The ratio of tensile strength of a polymer at 25°C. to its melt viscosity at some elevated temperature in the fabrication range is suggested as a quantitative figure of merit for commercial polymers. This ratio goes through a very sharp maximum as a function of molecular weight. The height of the maximum drops sharply with increasing molecular weight heterogeneity, although the location of the maximum along the molecular weight scale is unchanged. This behavior follows because tensile strength depends on number‐average, and melt viscosity on weight‐average, molecular weight. The possible role of non‐Newtonian behavior on these conclusions is discussed. Finally it is shown that the ratio of tensile strength to melt viscosity for a plasticized polymer increases exponentially with plasticizer content.
Reactivity ratios of some monomer pairs
Authors: Haas Howard C. , Simon Myron S.
Published: April 2003

To continue the study of the effect of structure on reactivity, an experimental investigation of the free radical copolymerization behavior of eight monomer pairs has been made. The monomer pairs include: vinyl acetate‐methyl vinyl ketone; vinyl acetate‐1,3‐acetoxybutadiene; acrylonitrile‐1,3‐acetoxybutadiene; methylacrolein‐acrylonitrile; vinylsulfonic acid‐methyl methacrylate; 2,5‐dichlorostyrene‐2,5‐dimethylstyrene; vinyl acetate‐fumaryl chloride; and styrene‐fumaryl chloride.
Redox recipes. VII. A recipe with ferric versenate, hydrazine, and hydroperoxide as activating system (veroxazine recipe)
Authors: Kolthoff I. M. , Meehan E. J.
Published: April 2003

A new initiating system, named the “Veroxazine” system, for the copolymerization of butadiene (75)–styrene (25) is described. Ferric versenate is reduced by hydrazine to the ferrous complex which in turn reacts with hydroperoxide to produce the radicals which initiate polymerization. At 5°C., with 5 parts of K‐fatty acid soap, 0.1 part of Diox D, 0.1 part of N2H4·H2SO4, 0.0615 part of sodium hydroxide (to give free hydrazine base from the salt), 0.0005 M ferric iron (equivalent to 0.036 part ferric nitrate nonahydrate per 100 parts monomers), 0.0005 M versene, 1 part of K4P2O7 and 0.3 part sulfole, 70% conversion is reached in 12 hours. The rate of conversion can be varied within wide limits by changing the concentration of ferric iron, versene, or hydrazine. Typical conversion–time data at 5°C. with K‐fatty acid soap, 0.1 Diox D, and 1 part of K4P2O7 are summarized below.

Fe(III)
V
N2H4·H2SO4, part
Conversion, %

1
2
4
8
12 hrs.

0.005
M
0.002
M
0.1
14
25
47
90
—

0.002
M
0.001
M
0.1
11
22
44
75
—

0.001
M
0.0008
M
0.1
9
19
32
64
85

0.0005
M
0.0005
M
0.1
6
16
28
48
70

0.0003
M
0.0002
M
0.1
4
10
19
38
53

0.001
M
0.0005
M
0.4
17
31
52
92
—

0.001
M
0.0005
M
0.2
15
27
40
81
—

0.001
M
0.0005
M
0.1
11
21
33
62
83

0.001
M
0.0005
M
0.05
6
14
27
47
66

With a given concentration of ferric iron the maximum rate is found with a molar concentration of versene slightly smaller than that of ferric iron. The excess of ferric iron over versene is kept in aqueous solution as the complex with pyrophosphate. The addition of potassium pyrophosphate up to one part increases the rate of conversion and yields a normal latex free from precoagulation. In the absence of pyrophosphate a viscous latex subject to precoagulation is obtained. The effects of kind and amounts of soap, of free acid or base, of kind and concentration of hydroperoxide, kind and concentration of mercaptan, of oxygen, of methanol, and of shortstops have been investigated. Veroxazine recipes which give from 55 to 70% conversion in 12 hours at −5°C. are described.
Vapor pressures of methyl methacrylate and styrene
Authors: Bywater S.
Published: April 2003

The vapor pressures of monomeric styrene and methyl methacrylate have been measured over a wide range of temperatures. The data are compared with values in the literature where this is possible.
Thermodynamics of high polymer solutions. VI. The compatibility of copolymers
Authors: Scott Robert L.
Published: April 2003

It is evident that a copolymeric mixture, if sufficiently heterogeneous in chemical composition and molecular weight, may separate into two or more distinct phases. The conditions for thermodynamic stability of a single‐phase system have been investigated using the modified Flory‐Huggins equations for heterogeneous polymer mixtures. The equation for a “spinodal hyper‐surface” serves as a sufficient, but not always necessary, condition for phase separation. With certain simplifying assumptions, this reduces to the requirement that two or more phases must exist if:

where M̄w is the weight average molecular weight, ρ is the density of the high polymer, xk is the mole fraction (or volume fraction) of chains with the same chain‐average chemical composition, represented by the “solubility parameter” δk, and δ is the average δ for the whole mixture. For a typical case (M̄w = 100,000, ρ = 1, T = 300°K), the standard deviation in δ cannot exceed 0.055. Since for a typical copolymer the possible range of δ (from 100% of one monomer to 100% of the other) may be 0.5–1.0 δ‐units, we conclude that most copolymers must be reasonably homogeneous in chemical composition; the over‐all composition of one chain cannot differ greatly from that of another in the same phase.
Polysoaps. IV. Dissolution phenomena of a poly‐4‐vinylpyridine derivative
Authors: Strauss Ulrich P. , Assony Steven J. , Jackson Earl G. , Layton Lionel H.
Published: April 2003

A polysoap was prepared from poly‐4‐vinylpyridine by quaternizing 43.4% of the pyridine nitrogens with ethyl bromide and 46.7% with n‐dodecyl bromide. Temperatures considerably higher than 25°C. were necessary to bring the polysoap into solution; but, once prepared, the solutions remained stable when cooled to 25°C. Viscosities measured just after the polymer had dissolved were irreproducible. On further heating, the viscosity decreased, eventually reaching a constant value which was reproducible. The viscosity decreases of three portions of a 0.5% solution was followed at 45°C., 55°C., and 65°C., respectively, and it was found to be fastest at the highest at the highest of these temperatures and slowest at the lowest. The final values reached at all three temperatures were approximately the same. These results are consistent with the assumption that the initially irreproducible viscosities are due to clusters of polysoap molecules which have not had enough time to break up. Prolonged heating is necessary to produce complete dissolution into individual molecules. Once reproducibility was attained it was shown that the polysoap exhibited essentially the same viscosity and solubilization characteristics as had previously been observed for polysoaps derived from poly‐2‐vinylpyridine.
Ultramikroskopische beobachtungen an polystyrollösungen
Authors: Breitenbach J. W. , Duch E.
Published: April 2003

Das Streulicht von Polystyrollösungen in Benzol, Methyläthylketon und Cyclohexan kann auch bei ausreichender Knäuelgrösse und genügender Verdünnung im Spaltultramikroskop nicht aufgelöst werden. Die in Lösungsmittel‐Fällungsmittelgemischen auftretenden Ultramikronen sind wahrscheinlich schon Molekelaggregate. Das ultramikroscopische Bild der Fällung von Polystyrol aus Benzol mit Methanol wird beschrieben.
Les possibilités de la diffusion des rayons X aux petits angles dans l'etude des grosses molécules
Authors: Guinier A.
Published: April 2003

Les progrès récents réalisés dans la technique et dam les différentes théories de la diffraction des réactions‐X à faible angle sont analysés de façon critique en vue d'examiner les possibilités pratiques qu'ils offrent dans les recherche sur les macromolécules et les miceues.
Fitting of polymer distributions of molecular weight by the method of moments
Authors: Herdan G.
Published: April 2003

As an alternative method to fractionating the polymer into portions of different molecular weight, in order to obtain the distribution of molecular weights, the method of fitting by statistical moments is proposed. It is shown how from a knowledge of differen order, utilising the inequalities between such averages and their relation to the dispersion of molecular weight, estimates of the distribution function can be obtained: (A) under the assumption of a standard form for the distribution function; (B) without such an assumption, but building up the approximation from a standard form as the norm function and its derivatives; (C) without using any standard form of distribution at all. Numerical examples of the fitting procedures accompany the exposition.
Effects of the ionizable components in cast phenoplasts
Authors: Harris Thomas G. , Neville Harvey A.
Published: April 2003

The various stages employed in the production of a phenolformaldehyde cast resin are discussed. It is assumed that the chains formed during the condensation stage undergo a rearrangement upon acidification to yield roughly spherical, stabilized micelles. These micelles are concentrated by dehydration until coalescence begins. At this point the chains again rearrange and the resin becomes the continuous phase. Pronounced changes in the properties of the system are observed at this critical point. The effects produced by undercondensation, overcondensation, overdehydration, etc. are mentioned briefly. The ionizable components, by determining the interfacial pH during the curing stage, are shown to be directly related to the rate of cure, stability, color, light transmissibility, etc. of the cured casting. Transparent castings are expected only when an ionizable component of the proper refractive powers is oriented at the interface. An examination of the immediately available data provides a lead to the future changes that can be expected as aging progresses.
The changes induced in sodium desoxyribonucleate by dilute acid
Authors: Reichmann M. E. , Bunce Barbara H. , Doty Paul
Published: April 2003

Light scattering and viscosity studies have been made on solutions of sodium desoxyribonucleate in 0.2 M NaCl adjusted to pH values of 6.5, 3.0, and 2.6 by dialysis in order to prevent contact with more concentrated acid. It is found that the molecular weight (7,700,000) is the same under these three conditions and remains so when the acid solutions are adjusted to pH 6.5. Upon lowering the pH the molecular size decreases due to increased coiling, but returns to its original value upon reneutralization. At pH 2.6 the mean radius of the molecule is less than half the pH 6.5 value. It is argued that these observations invalidate the existing evidence for degradation or disaggregation accompanying the appearance of new titratable groups. However, it is likely that most of the amino groups have not been titrated at pH 2.6 at the ionic strength employed here. Consequently the possibility remains that the stability at pH 2.6 is a consequence of a hydrogen‐bonded structure that is still largely intact.
Polymerization in bulk at high pressures
Authors: Klaassens K. H. , Gisolf J. H.
Published: April 2003

In this paper an apparatus is described for polymerizing monomers in bulk up to a pressure of 10000 atmospheres and in which the polymerizing substance can be heated and the temperature of the substance measured. Styrene shows an explosive reaction at 10000 atmospheres and at about 70°C. Indene polymerizes slowly when heating at 10000 atmospheres and shows an explosive reaction at 175°C. Both compounds give a solid polymer. Crotonaldehyde heated at 10000 atmospheres gives a brittle, high‐melting polymer. Coumarone and some chlorinated ethylenes carbonize when heated at 10000 atmospheres. Butyraldehyde polymerizes to a solid product which rapidly reverts to butyraldehyde.
Sur l'étude des mélanges de protéines au moyen de la lumière diffusèe
Authors: Guinand Sylvanie , Labeyrie Françoise , Tonnelat Jacques
Published: April 2003

Molecular weights of lactoglobuline and trypsin, as determined at pH 6.8, agree with the data generally admitted. However the molecular weight of trypsin in 1/100 M hydrochloric acid solution in the absence of salts, is two to three times lower than the value received in buffered solution at pH 6.8. With the purpose of detecting any combination or polymerization reaction, the study of mixtures showed that no conclusion may be obtained from the values of diffused light intensity at 90° when the diffusion diagram is not rigorously symmetrical.
Determination of molecular weight of polyvinylpyrrolidone
Authors: Frank H. P. , Levy Gabor B.
Published: April 2003

The molecular weight of selected polyvinylpyrrolidone samples was determined by light scattering and by osmotic pressure in methanol. The corresponding limiting viscosity numbers were also determined, as well as the limiting viscosity number of the same samples in water. The data relating to the methanolic system conform with theory and the values for K and α in [η] = KMα were determined. The data relating to aqueous solutions do not show such conformity but an unexplained dependence on the degree of homogeneity of the samples. Nevertheless some empirical constants were deduced which may aid in industrial practice in which aqueous viscosity measurements are usual.
The reaction of cellulose acetate with acetic acid and water
Authors: Hiller L. A.
Published: April 2003

Reaction curves for the simplest of cellulose acetylation systems; namely, the homogeneous reaction of secondary cellulose acetates with acetic acid and water, were studied. These reactions were found to be slow and complex, consisting of two interdependent simultaneous reversible second‐order processes. The faster process represented the reaction of primary hydroxyl and acetyl groups, while the slower process represented the reaction of the two secondary hydroxyl and acetyl groups. Equilibrium and rate constants and initial and final concentrations of hydroxyl and acetyl groups were calculated for the two simultaneous reactions. Equilibrium constants for the primary groups favored acetylation, while equilibrium constants for the secondary groups favored deacetylation. Final equilibrium was not affected by the presence of sulfuric acid. On the other hand, rate of reaction was increased in the presence of sulfuric acid, indicating catalysis by this reagent. The reaction mechnanism outlined above was confirmed by comparing primary hydroxyl group contents calculated from acetylation results with primary hydroxyl group contents measured by means of the tritylation reaction. Energies of reaction and energies of activation were calculated. Energies of reaction were low, indicating that equilibrium for this process is very nearly temperature independent. Energies of activation were in agreement with energies of activation for esterifications of simple alcohols, from which it was concluded that the acetylation and deacetylation of secondary cellulose acetates in homogeneous solution is but another example of general acid catalyzed esterification with carboxylic acids and general acid catalyzed hydrolysis of fatty acid esters. Degradation of the cellulose chain molecule was followed throughout these studies and energies of activation for this reaction were calculated. These energies of activation were higher than those for the acetylation reactions. It was concluded that degradation is more severe at higher temperatures for a given change in acetyl group substitution. Initial determination of equilibrium and rate constants for acetic acid acetylation of cellulose acetate has been carried out. It is suggested that through use of such procedures as tritylation analysis, which isolates the reaction of the primary groups from the secondary groups, improved values for these constants may be achieved.
Influence of concentration on the viscosity of sodium thymonucleate solutions
Authors: Callanan M. Joan , Carroll William R.
Published: April 2003

A viscometer to which variable pressures may be applied is shown to be convenient for measuring viscosities of sodium thymonucleate (NaTN).

The viscosities of solutions of NaTN investigated vary with velocity gradient. All of the solutions obey the empirical equation:

where p is the average pressure on the solutions during the outflow time, t. A is used to calculate what are believed to be characteristic relative viscosities.

The viscosity of solutions of alcohol precipitable NaTN is found to depend on the concentration according to the equation:

Our preparation of NaTN gives values of 11.1 dl./g. and 0.24 for [η] and k″, respectively.

The viscosity of NaTN solutions not easily precipitable depends on the concentration according to the equation:

Our values for [η] and k′ are 21.8 dl./g. and 0.26, respectively.

The viscous behavior of NaTN is discussed in the light of modernP polymer theory.
An experimental study of the influence of various factors on the time dependent nature of diffusion in polymers
Authors: Park G. S.
Published: April 2003

The kinetics of the sorption and desorption of methylene chloride by cellulose acetate and polystyrene have been studied by following the increase in mass of a polymer sheet suspended from a quartz spring in an atmosphere of the vapor. A tenfold change in the molecular weight of polystyrene does not alter the sorption rate, but a slight increase in rate is obtained when the molecules of this polymer are given a large unidirectional orientation in the plane of the polymer sheet. In agreement with other work, a considerable increase in both sorption and desorption rate is obtained by increasing the pressure of the solvent vapor. Previously it had been shown that a plot of the mass of sorbed vapor against the square root of the time has a slope that increases with time. It was shown that this peculiar characteristic of the sorption kinetics could not be accounted for by a purely concentration dependent diffusion coefficient, and it was suggested that it might be due either to a slow response of the diffusion coefficient to change in solvent concentrationor to the stresses set up between the swollen and unswollen parts of the polymer. Here it is shown that neither hypothesis alone will account for all the observed effects of the thickness of the polystyrene or cellulose acetate sheet upon the sorption and desorption kinetics. Sorption experiments on polymer sheet already containing some dissolved solvent do not show this peculiar characteristic of increasing slope when the concentration difference between the start and the end of the experiment is small, but when this is large very peculiar curves are obtained. The effects can be reconciled with either of the proposed mechanisms. Measurements of the changes in area during sorption and desorption have been measured on polystyrene sheet and these lend support to the strain hypothesis but also indicate that some plastic, as well as elastic, deformation of the polymer takes place during sorption.
A theoretical investigation of the influence of molecular relaxation and internal stress on diffusion in polymers
Authors: Crank J.
Published: April 2003

Recent experiments have indicated that the diffusion properties of a penetrant‐polymer system may change with time as diffusion proceeds. It is thought that two possible explanations of these time effects are slow changes of polymer structure accompanying diffusion and internal stresses exerted by one part of the polymer sheet on another as it swells. Two theoretical models are set up in order to express these effects quantitatively. The first model is essentially that in terms of which mechanical and other properties of polymers are commonly discussed, involving the concept of an instantaneous change of diffusion coefficient when the concentration changes, followed by a slow drift toward an equilibrium value. The second model expresses the effect of stresses set up between the outer swollen layers and the unattacked center of a polymer sheet during sorption. These stresses are slowly relieved as the diffusion proceeds, leading to a time‐dependent diffusion coefficient. The main features of diffusion behavior are established by calculation and the models are shown to account for the various types of sorption and desorption curves observed experimentally under different conditions, e.g., for sheets of different thicknesses and for different ranges of penetrant concentration. As examples, sorption and desorption curves calculated from the first model are shown to agree reasonably well with experimental curves for the methylene chloride‐polystyrene system. The rate of sorption and of the associated change in area of the sheet are accounted for by the second model. The presence of internal stresses also provides an explanation for the observation that there may be an appreciable interval of time during which a thin sheet takes up more penetrant than a thicker one under corresponding conditions. On the other hand, it is the slow structural changes which cause the rate of sorption to be not always inversely proportional to the square of the thickness of the sheet. It is concluded that both polymer relaxation and internal stresses play a part in determining diffusion behavior. The particular experimental results examined can be accounted for if the half‐life of the slow structural changes is comparable with that of the sorption experiment itself, and if the internal stresses change the diffusion coefficient by a factor of two or three.
Studies on hydroxyethylpolyvinyl alcohol
Authors: Cohen Saul G. , Haas Howard C. , Slotnick Herbert
Published: April 2003

Hydroxyethylated polyvinyl alcohols (HEPVA's) containing 12, 19, and 35% combined ethylene oxide were prepared by a heterogeneous reaction between dry polyvinyl alcohol (PVA) and liquid ethylene oxide. Another sample containing 18% was prepared by a more nearly homogeneous reaction in the presence of water. These derivatives may be analyzed satisfactorily by the modified zeisel method of Morgan. The properties of the HEPVA's are briefly described. Reaction of HEPVA with p‐toluenesulfonyl chloride showed that secondary hydroxyls were tosylated along with the primary and that the two reactions cannot be separated kinetically. This method, useful in estimating the primary hydroxyl content of hydroxyethylcellulose, cannot be applied to HEPVA. The stability of the tosylates indicated, however, that in derivatives containing up to 35% combined C2H4O2 ca. 1/2 ethylene oxide per vinyl alcohol unit, no polyethylene glycol chains were present and all combined ethylene oxide existed as individual hydroxyethyl groups distributed along the PVA backbone. Introduction of ethylene oxide into PVA increased the reactivity of residual secondary hydroxyls toward chemical reagents by destroying the normal high degree of hydrogen bonding and making adjacent domains more accessible for reaction. Very noticeable differences in properties were observed between HEPVA's prepared under differing conditions of heterogeneity. Two such polymers of similar ethylene oxide content showed quite different extents of reactions, susceptibility toward swelling agents, and x‐ray diffraction diagrams. These differences are attributed to a more random distribution of hydroxyethyl groups along the PVA backbone in the product of the more homogeneous reaction which leads to a more disordered system.
A color reaction involving vinyl chloride containing polymers and pyridine
Authors: Wechsler Harry
Published: April 2003

When a dilute pyridine solution of vinyl chloride polymers or copolymers is heated and a few drops of alcoholic hydroxide are added to the hot solution, a dark brown color develops. The response of vinyl chloride polymers in this reaction is much more intense than that of most other organic compounds, probably due to the conjugated double bonds produced in the main chain through the loss of hydrogen chloride. In addition to straight degradation of the polymer, the formation of an isocyanine dye is suggested by a mechanism which, besides pyridine and the polymer, involves the alkali alkoxide as a reactant.
Polymerization of methyl methacrylate by its polymer
Authors: Melville H. W. , Watson W. F.
Published: April 2003

Addition of its polymer causes methyl methacrylate to polymerize. The extent of polymerization is linear with time of reaction to at last 5% conversion at 60–90°C. The rate of polymerization is proportional to the first power of the concentration of added polymer and independent of its molecular weight. The molecular weight of the polymer formed increases with increase in reaction temperature. No polymerization caused by polymer occurred with the other polymer/monomer systems tested. The rate and nature of the initiating reaction are discussed.
Adsorption of high polymers from solution on to solids. I. Adsorption of polystyrene on charcoal
Authors: Hobden Joan F. , Jellinek H. H. G.
Published: April 2003

Rates of adsorption from solution on to charcoal and adsorption isotherms have been determined for unfractionated and fractionated polystyrene samples. The rates and extent of adsorption increase with decreasing solvent power and decreasing molecular weight. The rate curves of the fractionated samples show two distinct steps. Langmuir's adsorption equation is obeyed. Mechanisms of adsorption are discussed.
Mechanism of the crystallization of high polymers
Authors: Schuur G.
Published: April 2003

In this article a conception of the mechanism of crystallization is given, on the basis of which, it is suggested the origin of spherulites might be explained. A tentative explanation of several related phenomena is based on the new concept. Crystallites are conceived to be small collections of strongly oriented polymer which, on fusing, exhibit marked shrinking in the direction of orientation. Particles of amorphous material therefore stretch out in a certain direction during crystallization, as the result of which there is substantial contraction in the other directions. This is termed “auto‐orientation.” As the growing crystallite has to be fed from surrounding material, an orienation is initiated in the latter at right angles to the first crystallite. As a result of this orientation, crystallites are formed there which are oriented Perpendicular to the first crystallite. In their turn, these crystallites induce orientation in the surroundings and in this way crystallization becomes autocatalytic in character. Spherulites owe their origin to the fact that the various sectors in a symmetrical spherical order mutually cancel out their stretching and shrinking tendencies. In highly crystalline polymers with rapid nuclear formation there first comes into existence numerous radomly oriented nuclei which proliferate to small crystallites. Wherever these small crystallites come to be arranged in a suitable position, their relative tensions will be cancelled out and they will grow into a spherulite. Simultaneously small crystallites which are in an unfavorable position will be consumed by the growing spherulite, or else oriented in the correct direction and incorporated. As spherulites commonly measure from 10 to 50 microns, compensation between the tensions of the various sectors has to take place at long distance. At higher temperatures, compensation is as a rule found at short distances, i.e., crystallites which are at right angles to each other are in close proximity. Therefore “spherulites” varying individually come into existence as the crystallites are subject to other influences in addition to auto‐orientation. At very low temperatures the primary small crystallites are too stable to develop into spherulites. The mechanism of crystallization as thus conceived implies that the melting point of a polymer depends not only upon the dimensions and perfection of the crystallites, but also upon the specific arrangement of the crystallites, i. e., the degree in which they stabilize each other by a mutual compensation of tensions. It also helps to explain the following facts which have been noted in experiments performed with natural rubber: (1) The typical S‐shape of the crystallization curve and the constancy of the product of induction period and maximum rate of crystallization. (2) The fact that natural rubber always crystallizes under nonequilibrium conditions. (3) The failure of rubber in latex to crystallize and the fact that the rate of crystallization in films produced from latex is poorly reproducible.
The electrostatic free energy of polyelectrolyte solutions. I. Randomly kinked macromolecules
Authors: Katchalsky A. , Lifson S. , Mazur J.
Published: April 2003

(1) The electrostatic free energy of randomly kinked, ionized, macromolecules was calculated for polyelectrolyte solutions of finite ionic strenght. A detailed analysis of the charging process and the reference state of the free energy is given. The mutual electrostatic repulsion of the fixed charges on the macromolecule is the main part of the electrostatic free energy. Its calculation is based on two main assumptions: the validity of Kuhn's statistics and of Debye's approximation. (2) The electrostatic contribution per macromolecule to the free energy of the solution is found to be Fe = (v2ϵ2/Dh)ln {1 + (6h/κh)}, where v is the number of charged groups per polymolecule, ϵ the unit of charge, D the dielectric constant, κ Debye's inverse radius, based on the number of free ions in solution, h the end‐to‐end distance of the charged molecule, and h0 the corresponding end‐to‐end distance in and uncharged reference state. (3) Activity coefficients of free ions in polyelectrolyte solutions have been derived from the theory. The calculated values compare favorably with the activity coefficients from measurements on Donnan distribution of salt.
Peroxides from autoxidized methyl oleate and linoleate as initiators in the preparation of butadiene‐styrene synthetic rubber
Authors: Swern Daniel , Coleman Joseph E. , Knight H. B. , Zilch K. T. , Dutton H. J. , Cowan J. C. , Gyenge J. M.
Published: April 2003

In the dextrose‐free recipe at 41°F. for the copolymerization of butadiene and styrene, using 6 × 10−4 mole of initiator per one hundred grams of monomers, methyl oleate peroxide (MOP) and methyl linoleate peroxide (MLP) gave higher polymerization rates and conversions than cumene hydroperoxide (CHP), and they gave as high rates of conversion as p‐menthane hydroperoxide (PMHP). In the peroxide‐dextrose recipe at 122°F., at both low and high dextrose levels, only about one‐half as much MOP (1.5 × 10−4 mole) as CHP or PMHP was employed on a molar basis to achieve the same conversion and polymerization rate. In the low dextrose‐redox recipe at 41°F., using 6 × 10−4 mole of initiator per one hundred grams of monomers, MLP gave slightly higher conversions than CHP or PMHP, but in the amine recipe at 41°F., MLP gave lower conversions.
Polymeric chain transfer reactions. Polymerization of some vinyl monomers in the presence of vinyl polymers
Authors: Hayes Robert A.
Published: April 2003

The polymerization of certain vinyl monomers in the presence of some vinyl polymers leads to the formation of a chemical bond between the resulting two polymers. A study of the efficiency of this graft copolymerization process under various conditions in emulsion has been made and the following conclusions drawn. An increase in the catalyst concentration and temperature of polymerization increases the efficiency, while the addition of dodecyl mercaptan decreases it. The list of the monomers used in the order of decreasing activity toward graft copolymerization is vinyl chloride, vinyl acetate,and styrene. A list of polymers in order of decreasing susceptibility to graft copolymerization is polyvinyl chloride, polyacrylonitrile, polyvinyl a cetate, and polystyrene.
Orientation processes in synthetic crystalline polymers in terms of morphology
Authors: Keller A.
Published: April 2003

A new approach to orientation processes is proposed in terms of the morphology of crystalline polymers. Our present knowledge of the morphology of unoriented crystalline polymers is summarized, and the process of orientation is visualized as an alignment and pulling out of the submicroscopic and microscopic structural units. The various stages of this process are discussed and it is found that in this way several anomalous and hitherto unexplained orientation effects frequently described in the literature can be accounted for. The phenomenon of preferential tilt of the chains with respect to the fiber axis can now be explained in general terms. Peculiarities in the drawing‐relaxation process, and the special case of perpendicular orientation, also substantiated by recent experiments, follow naturally from the new model.
Etat de nos connaissances sur la biréfringence d'écoulement des solutions de macromolécules
Authors: Cerf Roger
Published: April 2003

Les résultats classiques concernant les solutions de particules rigides sont brièvement rappelés (théorie de l'orientation). L'éxpérience a montré que la théorie avait une valeur quantitative. On examine ensuite en détail le cas où la particule est déformable. Cette question s'est considérablement clarifiée au cours des dix dernières années. La nature de l'effet présenté est déterminée essentiellement (1) par l'intensité des fluctuations de forme de la molécule et (2) par la durée de vie d'une configuration donnée. Il en résulte que le phénomène peut ětre dans certains cas extrěmes (1) un effet d'orientation analogue à celui que présentent les solutions de particules rigides, (2) un effet de déformation pure complètement différent du précédent. Dans le cas général il y a superposition des deux effets. Pour une molécule donnée il peut y avoir passage continu de l'effet (1) à l'effet (2) lorsqu'on modifie la valeur de la viscosité du solvant. On considère en particulier le cas des solutions de hauts polymères. Les théories pour les deux effets (1) et (2) mentionnés ci‐dessus, ainsi que pour le cas intermédiaire, permettent de comprendre dans une large mesure les phénomènes présentés par ces solutions. Il existe un critère expérimental permettant de déceler si l'effet présenté par une solution donnée est principalement un effet d'orientation ou un effet de déformation. Il est possible de relier les grandeurs observées à des coefficients moléculaires, au moins dans les deux cas extrěmes mentionnés ci‐dessus. Du point de vue expérimental il est intéressant de coupler les mesures de biréfringence d'écoulement avec des mesures de viscosité spécifique, viscosité statique et dispersion de la viscosité (ondes de cisaillement de fréquence ultra‐sonique). On indique finalement sur quelles bases générales une théorie pour les molécules en chaǐnes pourrait ětre développée.
Flow birefringence in solutions of macromolecules: Effect of fluctuations of the shape of the molecule
Authors: Cerf Roger
Published: April 2003

A treatment is given for the Brownian deformation of an elastic sphere which permits extension of the theory of the Maxwell effect of solutions of elastic spheres to arbitrary values of the ratio of the time of establishment θ′, of a preferential orientation to the deformation relaxation time θ of the sphere. For large values of η0/ηi the (ratio of solvent viscosity to internal viscosity) the effect reduces to the simple deformation effect described in previous papers. For decreasing values of η0/ηi the deformation effect is gradually replaced by the orientation effect (orientation of elongated configurations). The influence of the intensity of the fluctuations as measured by the mean square value δ02 of the deformation coefficient is discussed. Values of δ0 are given for a series of polystyrene samples of increasing molecular weight. The theory is in qualitative agreement with experimental results on solutions of chain molecules and leads in particular to a new interpretation of the data for thymonucleic acid. The incompatibility of the Kuhn and Kuhn dumbbell theory with experimental results is discussed in more detail than in previous papers.
Les lois de la diffusion de la lumière du point de vue de leur application à l'études des macromolécules en solution étendue
Authors: Sadron Ch.
Published: April 2003

Dans cet exposé qui constitue simplement une brève revue critique l'auteur résume rapidement les résultats classiques de la théorie de la diffusion de la lumière par les solutions macromoléculaires étendues et souligne les hypothèses simplificatrices qui ont permis les calculs. Il examine en particulier le cas où les dipǒles élémentaires ne sont plus isotropes et montre les conséquences importantes des nouveaux résultats obtenus.

Il s'attache en particulier à l'examen du cas important où la solution contient des macromolécules en chaǐne linéaire et résume les plus récentes tentatives qui tendent à traiter les configurations réelles de la molécule et non plus celles d'un “random flight” fictif.
Polymer association. I. Osmotic pressure of solutions of mixed acidic and basic polymers
Authors: Morawetz H. , Gobran R. H.
Published: April 2003

Methyl methacrylate was copolymerized with small amounts of methacrylic acid or dimethylaminoethyl methacrylate. The molecular weight of the basic copolymer calculated from osmotic pressure data in butanone and benzene gave consistent results. The molecular weight of the acidic copolymer was obtained from osmotic pressures of pyridine solutions, but in butanone and particularly in benzene strong molecular association was observed. Osmotic pressures of mixtures of the two copolymers in butanone at 30.2 and 50.1 and in benzene at 49.7°C. were determined. The reduced osmotic pressure plots were linear but indicated the persistence of molecular associations to the highest dilutions at which osmotic pressures could be measured. A thermodynamic analysis of the data showed that under certain conditions the activity of one or the other polymer component decreases with increasing concentration of the mixture.