bluuebunny/crossref_metadata_2025 huggingface dataset:
Applicability of HLB system in selecting emulsifiers for emulsion polymerization of vinyl chloride
Authors: Testa F. , Vianello G.
Published: June 2010

The choice of the proper emulsifier in the emulsion polymerization of vinyl chloride is very complicated since it greatly affects not only the reaction proceeding but also the physical‐chemical and technological properties of the final product. Greth and Wilson successfully applied in the emulsion polymerization of styrene and vinyl acetate the choosing method of emulsifiers based on their HLB value. The scope of this work was to ascertain if the HLB system could be employed in the emulsion polymerization of vinyl chloride which, due to several features, is different from that of styrene and vinyl acetate. By blending together pairs of emulsifiers of different HLB values it was possible to prepare three series of emulsifier blends covering a wide range of HLB values. The most important properties of the emulsion polymerization of vinyl chloride, i.e., conversion rate, latex stability, particles size, and distribution were plotted against HLB values of emulsifier blends. No bell‐shaped curves were obtained, as should be expected, but the properties considered seemed to depend rather upon the amount of the blend component that strongly affects the polymerization, i.e., Empicol and Na‐laurate. It may be that the poly (vinyl chloride) insolubility in its monomer changes the properties of the latex particle so that it does not follow the emulsification laws on which the HLB system is based.
The characterization of monodisperse polystyrene latices
Authors: Shaw J. N.
Published: June 2010

Four monodisperse polystyrene latices, containing particles of diameter ca. 2400 Å, were prepared using hydrogen peroxide and potassium persulfate as initiators and sodium dodecanoate, sodium mono‐dodecyl phosphate, and dodecylamine hydrochloride as emulsifiers. These latices were characterized by electron microscopy, gas adsorption, and microelectrophoresis. The results obtained by the first two techniques indicated that the particles were essentially nonporous rigid spheres. Electrokinetic procedures were used to characterize the ionogenic groups on the latex particles. In addition to the emulsifier molecules, other groups, namely carboxylic acid groups, were found to be present on all of the latices, irrespective of the nature of the initiator or umulsifier used to produce them, Electrophoresis also revealed that the emulsifiers could be removed from the latex dispersions by dialysis, leaving systems with these carboxyl groups as an integral part of the particle surfaces. By electrokinetics, the surface pK value of these unknown acid groups was 4.64. It was also established by radiochemical methods, combined with microelectrophoresis, that sodium dodecanoate was removable by dialysis from polystyrene latices. Before dialysis the concentration of the free emulsifier was below the critical micelle concentration. The latter experiments also suggested that the construction of adsorption isotherms from electrokinetic data is of doubtful validity. The integral carboxyl groups were probably produced by polymer oxidation during polymerization.
Studies of adsorption onto synthetic latices
Authors: Brodnyan John G. , Kelley E. Lloyd
Published: June 2010

Despite the importance of reactions at the polymer‐water interface of synthetic latices very little work has been reported on the adsorption of surfactants or water‐soluble macromolecules at this site. In the studies reported here the adsorption isotherms of sodium lauryl sulfate onto polystyrene and poly(n‐butyl methacrylate) and of hydroxyethyl cellulose onto poly(n‐butyl methacrylate) are shown to be of the Langmuir type. Other water‐soluble macromolecules and latex substrates were studied at a single macromolecule content and a single latex solids level. The effective surface area of the sodium lauryl sulfate molecule, at the critical micelle concentration, was found to be 58.5 Å2 for both polystyrene and poly(n‐butyl methacrylate). This is in good agreement with results obtained by soap titration. The adsorption of macromolecules is strongly influenced by macromolecule type as well as by the latex substrate, i.e., the type of surfactant on the latex surface as well as the polymeric composition of the latex.
Displacement of hydrophilic colloids from particle interfaces
Authors: Kreider R. W.
Published: June 2010

The viscosity increase observed when hydrophilic colloids are added to latex/pigment systems indicates strong interaction between particles and macromolecules. The interaction is caused by partial adsorption of the macromolecule with a segment free to expand to a nearby particle to form a rigid network. Attempts were made to displace macromolecules from PVAc copolymer and pigment particles. Displacement of the hydrophilic colloid from the particles into the water phase reduced shear stress as demonstrated by flow curves obtained with the Haake Rotovisco. Rheological measurements with the latex serums obtained by ultracentrifuging and reconstruction of the latex aqueous phases confirmed that the abnormal viscosity increase in the latex is caused by link formation. Nonionic surfactants are amphipathically adsorbed at the particle interface and the macromolecules appear to hydrogen bond to the surfactant hydrophile. Segments of the macromolecules remain free, however, to project into the water phase and form linkages. Post‐addition of anionic surfactants from an homologous series produced marked rheological changes in latex/pigment systems. The disarrayed existence of the macromolecules in the water phase produces flow curves that are consistent with those of the hydrophilic colloid dissolved in water.
The helical structure of a β‐D‐1,3‐xylan
Authors: Atkins E. D. T. , Parker K. D.
Published: June 2010

A structure determination is described of a naturally occurring non‐cellulosic polysaccharide which is found in the cell wall of some siphoneous green algae. The structure consists of three β‐1,3‐linked xylan polymer chains intertwining, each helical chain having exactly six residues in a pitch of 18.36 Å. The evidence is in favor of right‐handed helices with stoichiometrically bound water. There is a novel interchain hydrogen bond system at the center of the structure.
Simulation of the gel structure of regenerated cellulose film
Authors: Haskell V. C.
Published: June 2010

There is a growing body of experimental evidence that regenerated cellulose in the gel state is like a random network of microfibrils perfused by water. If this is true, the properties of both the gel and dried structures should be profoundly influenced by the geometrical properties of the network. In this work a computer program was developed with which a random interconnected network of linear structural elements could be generated. During collapse of the network in the thickness direction, which simulated drying, new junctions were formed which could lock in strains imposed on the structure during drying. From the results geometric explanations were proposed for the dimensional instability of cellulose film in varying humidities, for the mechanical behavior of the film, and for the effect of softening and of crosslinking on film properties.
An approach to biosynthesis of organic superconductors
Authors: Kagan Norman E.
Published: June 2010

As a striking similarity exists between the structures of the proposed organic superconductors and certain naturally occurring products of biological activity, it seems reasonable to ask whether Nature has already utilized this phenomena in a living system or whether she might be induced to do so. One test of this hypothesis would be to establish an artificial environment whereby a selective advantage is given to those organisms which show signs of macroscopic superconductivity. An experiment will be described in which bacteria are screened and bred for traits such as heightened conductivity and diamagnetism in an attempt to evolve cells with these properties.
Dipole moments and molecular structure of copolymers IV: Study of methyl acrylate‐methyl methacrylate copolymers
Authors: Kotera Akira , Shimomura Kazuko , Shima Mikiko
Published: June 2010

The dielectric properties of methyl acrylate‐methyl methacrylate copolymers in benzene solutation have been measured, and it was found that the value of the average orientation polarization, Po, Av. of a monomer unit in the copolymers increases with an increase in the methyl acrylate content of the copolymers, e.g. from 37.4 cc. (for the copolymer in which the mole fraction of methyl acrylate, x, is 0.0605) to 40.9 cc. (for the copolymer in which x is 0.788) at 20°C. A theoretical treatment concerning the relation between the average orientation polarization and the detailed structure of a polar‐polar copolymer has been developed, and the variation in value of PoAv. of the copolymer has been discussed in view of the detailed arrangement of monomer units in the copolymer molecule.
Supermolecular organization of as‐spun fibers form melts of crystalline polyolefines
Authors: Baranov V. G. , Volkov T. I. , Farshyan G. S. , Frenkel Ya
Published: June 2010

When polymers are converted into films or fibers, the crystallizing melt is subject to considerable jet stretching and the cooling of the melt proceeds under complex temperature conditions. The occurrence of the temperature and the rate gradients can profoundly affect the tupermolecular organization of the final polymer system. The investigation of the supermolecular organization of polyethylene and polypropylene fibers and films shows that practically in all cases the polymer contains spherulites elongated transversally to the direction of the stretching of the crystallizing melt. The value of the spherulite radius and the degree of its flattening are definitely associated with quite different components of the formation process. Thus, the value of the spherulite radius is inversely porportional to jet stretching, while the change in temperature conditions (e.g. the melt temperature or the cooling conditions) shift the hyperbolae R = f(ϕ) downwards or upwards. The factors Musing the formation of flattened spherulites are analyzed. Probably in the case of thin fibers the major factor is the occurrence of the two temperature gradients while in the case of films it is the mechanical field of the longitudinal rate gradient.
Steady‐state flow properties of poly(ethylene terephthalate) melts
Authors: Gregory D. R. , Watson M. T.
Published: June 2010

Steady‐state flow properties of poly(ethylene terephthalate) melts as a function of Temperature (T), shear rate (γ), and inherent viscosity (I.V.) were determined. An Instron capillary rheometer was used to obtain data on wall shear stress (τW) vs. γ for poly(ethylene terephthalate) (PET) at temperatures of 265 to 295°C. The polymer samples investigated covered an inherent viscosity range of 0.35 to 0.82, corresponding to a weight‐average molecular weight range of 23,000 to 70,000. Capillaries used in this investigation covered the range of 10 to 67.5 in length/diameter (L/D) values. End‐effect corrections (n) estimated by Bagley's method were small with n < 1 over the entire shear rate range covered (50–24,000 sec.−1). Flow curves showed (1) that over the shear rate range of about 50 to 1000 sec.−1, the flow behavior of PET was nearly Newtonian, i.e., log‐log plots of τW vs. γ were linear with slopes of about 1, and (2) that over the shear rate range of 1000 to 24,000 sec.−1, the flow behavior of the polymer was slightly pseudoplastic. Using Mendelson's shear rate‐temperature superposition scheme with an additional shifting to a single reference I.V. level, we were able to shift all the data to a single master curve of log (aTb τ γ), where aT and b are the shift factors for temperature and molecular weight, respectively.
Specific volume and viscosity of polyolefin melts
Authors: Rudin A. , Chee K. K. , Shaw J. H.
Published: June 2010

A simple, inexpensive method is described for the measurement of specific volumes of thermoplastic melts during extrusion at low shear stresses. Data for several polyolefins agree closely with specific volumes obtained by dilatometry or compression measurements on static melts. Data can be obtained at a variety of temperatures more rapidly than by dilatometry. The method described yields specific volumes essentially at atmospheric pressure, but extension to higher pressures and the measurement of compressibilities is possible, with more complicated apparatus. Simultaneous measurements can be also made of apparent shear rates, and these can be converted to absolute shear rates, and viscosities, by application of standard techniques. The simple procedure described does not permit the concurrent measurement of useful apparent shear and volume viscosities because the initial state of the system reflects operational as well as polymer properties. It is suggested that an extension of the present method would provide such data.
Untersuchung von vinylpyridinium‐verbindungen. I. IR‐ und nmr‐spektroskopische untersuchung
Authors: Mielke I. , Ringsdorf H.
Published: June 2010

3‐ and 4‐vinylpyridinium compounds were prepared and investigated by infrared and NMR‐spectroscopy. The spectroscopic data can be used to explain the polymerization behavior of the monomers.
Distribution of ultraviolet stabilizers in crystalline polypropylene
Authors: Frank H. P. , Lehner H.
Published: June 2010

The distribution of Tinuvin 328 [2‐(2′‐hydroxy‐3,5′‐di‐tert‐amyl phenyl)benzo‐triazole] in isotactic polypropylene was studied by means of ultraviolet microscopy. Whereas Tinuvin 328 is uniformly dispersed in noncrystalline polypropylene (atactic or molten isotactic polymer) a certain distribution pattern is generated in the course of crystallization; the details of this pattern depend on a number of factors such as rate of cooling, fraction of noncrystalline polymer, etc. The main feature of the distribution pattern is that Tinuvin 328 is accumulated in the noncrystalline regions within and between polypropylene spherulites and rejected by crystalline regions.
The influence of structure and other factors on molecular motions in solid polymers from 4°K TO 300°K
Authors: Sauer J. A.
Published: June 2010

Semicrystalline, as well as amorphous, polymers frequently develop some measure of molecular mobility at temperatures well below their melting temperature, Tm, or their glass transition temperature, Tg. In these polymers, one or more damping or internal friction peaks are usually found to occur in the low temperature region from 4°K to 300°K. The magnitude, and temperature position, of these maxima are dependent upon the structure of the polymer, its mode of preparation and past history, and the local environment of the moving units. For purposes of discussion, the observed relaxation processes may be classified, on the basis of their temperature location at low measuring frequencies (∼1 Hz) as δ‐processes, those occurring below 80°K; γ‐processes, those occurring in the temperature range from 80°K to about 240°K; and β‐processes, those occurring from about 200°K to above 300°K. Various examples will be given of polymers that show significant δ, γ, and β‐processes and the influence of structure, structural substitution, crystallinity and low molecular weight diluents will be illustrated.

The extent to which relaxation behavior can be correlated to macroscopic ductility and fracture toughness is discussed. It is noted that the lowest temperature δ‐relaxations arise primarily from reorientational and/or wagging motions of pendant methyl, ethyl, and phenyl side chains and, as such, have little bearing on macroscopic impact strength. The intermediate temperature γ‐processes arise from reorientational motions, of short side chain sequences or from local motion of main chain sequences. Some degree of main chain mobility. appears to be an essential requisite if ductility and toughness are to be realized. The higher temperature β‐processes in the 200°K t o 300°K range arise from motion of polar side groups, from motion of short chain sequences involving water complexes, or from large‐scale motions associated with the Tg of the amorphous regions. In the latter instance, the β‐process i s accompanied by a large increase in ductility and impact strength and this feature is utilized in polyblends and copolymers to raise the fracture toughness of otherwise brittle polymers.
Effect of tension and temperature on crystalline polymer texture
Authors: Station W. O.
Published: June 2010

A variety of annealing treatments at elevated temperatures have been characterized by a specific infrared absorption assigned to the folded chain segments in polyethylene terephthalate fibers. The higher the annealing temperature, the more regular is the chain folding introduced into the fiber. When a fiber is free to contract, it will have a much larger amount of refolding than one which is held at constant length. Stretching is able to prevent refolding at low temperatures but in these experiments stretching was not able to prevent refolding at the highest temperature.

By comparing the above infrared results with small angle X‐ray diffraction and broadline nuclear magnetic resonance techniques, it is now possible to give validity to the interpretation that chain folds are major contributors to the long period.

The external tension applied to a fiber during an annealing treatment will determine the internal shrinkage tension caused by the molecules during subsequent reheating. If chain refolding is allowed to occur during annealing, the potential for subsequent shrinkage and the amount of internal shrinkage tension are lowered, and higher temperatures are required to activate additional shrinkage. It thus appears that a major contributor to shrinkage and shrinkage tension in an oriented fiber is the refolding of molecules during thermal activation.
Thermodynamic properties of liquids, including solutions. III. Solutions of polymers, especially poly(viny chloride)
Authors: Huggins Maurice L.
Published: June 2010

A new theory of solution thermodynamics is outlined. The energy and enthalpy are related to the contacting areas of the chemically different kinds of molecular segments, the energy per unit contact area for each kind of contact, and an equilibrium constant. Departures of the entropy of mixing from the classical Raoult's law relationship result from differences in the volumes of solvent and solute molecules, from departures from perfect randomness of mixing, and from the concentration dependence of the orientational randomness of the bonds in the molecules. Simple equations for these relationships have been tested. Quantitative agreement is usually obtained.

Examples are given of applications of the theory to polymer solutions. Application to poly(vinyl chloride) solutions has not yet been made, but the appropriate procedures and methods for determining the parameters are discussed.
Studies on the initiation of the emulsion polymerization of vinyl chloride
Authors: Liegeois J. M.
Published: June 2010

In another paper it was shown that the decomposition reaction of persulphate is equilibrated, and the initial rate of decomposition in a borax buffered solution was determined. Here we have measured the decomposition rate of persulphate in the presence of vinyl chloride at a pressure lower than the vapor pressure. It is found that the initiation which takes place in the aqueous phase proceeds at a rate equal to the initial rate of decomposition found without vinyl chloride. Experiments were done at two different pH and we found an increase of both the decomposition rate and the rate of reaction of vinyl chloride from pH 13 to pH 9.
Effect of initiator end groups and trichlorethylene units on the dehydrochlorination of solution polymerized poly(vinyl chloride)
Authors: Park G. S. , Skene C. L.
Published: June 2010

High proportions of initiator end groups are incorporated into poly(vinyl chloride) when the monomer is polymerized in solution. The rate of thermal dehydrochlorination of these polymers increases linearly with the number of initiator end groups and varies with the type of initiator. The effectiveness of the end groups for causing dehydrochlorination is in the ratio, lauroyl peroxide: isopropyl peroxydicarbonate: benzoyl peroxide: azoisobutyronitrile: 9.7:5.8:4.4:1.6. It is suggested that the low stability of the benzoyl peroxide polymer could be due to the incorporation of phenyl groups while primary radical transfer might decrease the stability in the lauroyl peroxide and isopropyl peroxydicarbonate initiated polymers. High conversion polymers have greater stability than low conversion ones. Transfer polymers produced in the presence of trichloroethylene have much lower stability and this is attributed to both copolymerized CHClCCl2 groups and unsaturated end groups.
Branching structure and thermal stability of poly(vinyl chloride)
Authors: Suzuki T. , Nakamura M. , Yasuda M. , Tatsumi J.
Published: June 2010

Low molecular‐weight model compounds structurally related to polyvinyl chloride undergo thermal changes in considerably different manners depending on their molecular structures. For example, 3‐chloro‐4‐ethyl‐n‐hexane is far more stable than 3‐chloro‐3‐ethyl‐n‐pentane when heated under nitrogen. This suggests that the type of atom attached to the tertiary carbon at the sites of branching in polyvinyl chloride would play an important role in the thermal degradation of the polymer. Results of the present study using polyvinyl chloride and varieties of model compounds indicate that most, if not all, of the tertiary carbons in the polyvinyl chloride molecules carry hydrogen atoms rather than chlorine atoms. It is furthermore shown that the number of branchings does not affect the thermal stability to any significant extent. It thus seems conceivable that the branching structures of polyvinyl chloride do not contribute to the initiation of the thermal decomposition, at least under the ordinary processing conditions.
New plasticizers for poly(vinyl chloride)
Authors: Zeinalov B. K. , Radzhabov D. T. , Mekhtieva F. A.
Published: June 2010

The results of the research of the synthesis and plasticizing properties of symmetrical and mixed esters of ethyleneglycol (“Plastiazans‐1, 25, and 30”), obtained on the basis of various fractions of synthetic fatty and natural naphthenic acids, and their application in the production of polymeric materials are reported.
Polymerization of vinyl chloride in the presence of chain transfer agents. Ii. Polymerization in the presence of small quantities of propionaldehyde
Authors: Ryska M. , Kolinsky M. , Lim D.
Published: June 2010

The influence of additions of propionaldehyde (0.001–0.1 mole/liter) on the kinetics of a homogeneous polymerization of vinyl chloride in solution at temperatures of 25, 30, and 35°C was investigated. The additions cause an increase of the polymerization rate and an anomalous dependence of the polymerization degrees on the quantity of the transfer agent. The phenomena in question are discussed from the point of view of the capability of propionaldehyde to reactivate the less active types of radicals. Besides the reactivation of primary and monomer radicals, a reactivation of polymer radicals is also considered.
Adsorption characteristics of water‐soluble polymers at aqueous‐organic liquid interfaces
Authors: Glass J. E.
Published: June 2010

Adsorption characteristics of water‐soluble polymers, as denoted by interfacial tension measurements, were investigated at aqueous‐organic liquid interfaces via the volume ‐drop and pendant‐drop techniques. Interfacial results obtained from both studies parallel the alkanol adsorption data of Bartell and Davis. If surface tension data are included in the comparison, discrepancies with respect to the alkanol data are observed; macromolecular aqueous solution surface pressures are substantially lower than corresponding interfacial pressures at aqueous‐hexane boundaries. Minute amounts of organic impurities in the air phase effect surface pressures approximate with aqueous‐hexane boundary data. The observations reflect a lesser degree of unfolding and surface occupation at the aqueous‐air interface than at high energy aqueous‐organic boundaries.

Poly(ethylene oxide) possesses a random conformation in bulk benzene solutions and a highly ordered structure in aqueous solutions. An inquiry into boundary conformational effects was undertaken via pendant‐drop studies of PEO adsorption at the common interface from both benzene and aqueous phases. Despite different conformations in two media with different solvating characteristics equivalent interfacial pressures were obtained. Interfacial pressure equilibrium attainment was achieved more rapidly from the aqueous phase. Additional hexane‐water and aqueous‐air boundary studies show the faster equilibrium attainment rate to be related more to the ability of the benzene phase to rapidly orient interfacial polymer segments than to conformational effects.
Extrusion degradation of a high molecular weight polystyrene
Authors: Goetze K. Peter , Porter Roger S.
Published: June 2010

Mechanochemical research has been extended to the study of the magnitude and mechanism for the capillary shear degradation of a narrow distribution and high molecular weight polystyrene (Mw 1,800,000). An Instron Capillary Rheometer was used to perform the experiments over the temperature ranges from 164° to 250°C. The change in molecular weight distribution was evaluated by calibrated gel permeation chromatography. The maximum shear stress employed was 8.8 × 106 dynes/cm2. It was confirmed‐as previously found with a lower molecular weight polystyrene‐that degradation could be induced at high stress at temperatures where it would not occur inclusively due to thermal forces. The activation energy of the shear degradation was +27 kcal/mole with a sign and magnitude consistent with degradation induced principally by thermal forces but distinctly augmented by mechanical energy. For the first time the effect on degradation of capillary entrance angle and reservoir conditions has been examined.
Application of gpc to studies of the viscose process. III. Effect of various treatments of rayon print cloth on the molecular weight distribution of cellulose
Authors: Dyer John , Phifer Lyle H.
Published: June 2010

Gel permeation chromatography (GPC) has been used to determine the molecular weight distribution of cellulose in rayon print cloths. The fabrics were made from a regular and a high wet modulus rayon with staple length of 1 9/16 inches in an 80 × 80, 31 × 41 singles construction. The effects of various treatments of the print cloths including bleaching exposure to UV and abrading on the yarn properties and the molecular weight distribution were determined.

With chemical treatments, the changes in the molecular weight distribution in both warp and fill were similar. The chemical reactions with the fabric immersed in solution were fairly uniform throughout the yarn and in the filaments. In this group, bleaching drastically reduced the average molecular weight.

Degradation due to abrasion and flexing was severe. Results indicate that the larger molecules are particularly susceptible to mechanical degradation. The detritus from abrasion of the high wet modulus and the regular rayons had similar, relatively narrow molecular weight distribution.

The changes in yarn properties and distribution on washing were primarily the result of mechanical damage. Heating at 400°F for 30 min substantially changed the staining characteristic of cross sections of the yarns. The molecular weight distribution width increased on heating and for these samples, the weight average molecular weight determined from GPC was significantly greater than the value determined viscosimetrically.
Chemi‐mechanical pulping of hardwoods using ammonia vapor
Authors: Peterson R. C. , Strauss R. W.
Published: June 2010

Previous investigations have shown that treatment with gaseous ammonia makes wood into an easily deformable material while in a plasticized condition. In many ways the action of ammonia is similar to water or steam except that it is a more efficient plasticizer. Thus at sufficiently high pressures (100‐150 psig) ammonia not only solvates the lignin, hemi‐cellulose, and amorphous cellulose but enters the crystalline cellulose region as well. Much effort has been devoted to studying the overall plasticization of wood and treated wood properties for whole wood forming applications. The concept of defibering wood while in an ammonia plasticized condition has not been investigated.

Conventional wood chips treated with ammonia vapor were fiberized in an Asplund pressurized refiner to produce chemi‐mechanical pulps with properties similar to the conven‐tional cold soda process. When ammonia is used alone the pulps are relatively dark colored. Pretreatment with SO2 vapor improves both the brightness and physical properties of the pulp.

The possible implications of this novel processing technique to both high yield and conventional pulping are discussed.
The separation of oligosaccharides on cellulose gels
Authors: Chitumbo K. , Brown W.
Published: June 2010

The synthesis of tightly cross‐linked cellulose gels in bead form is described. Their ability to separate low molecular weight polyethylene oxides as a function of molecular size is demonstrated.

With cellulose‐80 and water as eluant, chemisorption was found with the cellodextrins at chain lengths greater than three units. Weak adsorption was found for the xylodextrins and mannodextrins in the comparable size interval. The results suggest that an exact structural correspondence between adsorbent and adsorbate is necessary for the adsorption of oligosaccharides to cellulose.

With DMSO as eluant, the separations are determined by a partitioning bearing a direct relationship to the liquid‐liquid partitioning coefficient in thin layer chromatography.
Viscosity and the prolate ellipsoid model applied to low molecular weight cellulose triacetate fractions
Authors: Swenson Harold A. , Carlson John A. , Kaustinen Hilkka M.
Published: June 2010

Cellulose triacetate of molecular weight 5,600, obtained by acetolysis, and separated into 15 fractions by preparative permeation chromatography, was analyzed for intrinsic viscosity, number average, and weight average molecular weight. Glucose pentaacetate, cel‐lobiose octaacetate, and cellotriose hendecaacetate are also included in the analysis. The axial ratios of a prolate ellipsoid calculated from the viscosity of the low DP CT A fractions, when compared to a molecular model and to the fully extended contour length, confirm the persistence length found by viscosity theory at high molecular weight levels. A long plateau region of slope 0.28 to ca. DP 8, is found in the log‐log [n] versus DPn plot. The curve then rises sharply to slope ca. 2.0 at DPn 10 and declines again to slope ca. 0.9 above DP 30. A close correspondence is found with the hydrodynamic predictions of Peterlin [5, 16] for short‐chain wormlike or inflexible polymers. Plots of R2/DPn versus DPn for CTA and CA show that coil randomness is apparently not achieved before DP 400. No change in viscosity was detectable for CTA of DP 50, when increasing amounts of nonsolvent isopropyl alcohol were added to 1,2‐dichloroethane, short of the precipitation point.
Distribution of substituents in partially acetylated cellulose
Authors: Björndal Håkan , Lindberg Bengt , Rosell Karl‐Gunnar
Published: June 2010

The distribution of substituents in a partially acetylated cellulose (DS 2.4) has been determined. 0‐Acetyl groups were replaced by 0‐methyl groups by using methylsulphinyl sodium and methyl iodide on a product, in which the original free hydroxyl groups had been protected by reaction with methyl vinyl ether. The methylated sugars obtained on acid hydrolysis of this product were converted into alditol acetates and analyzed by GLC‐mass spectrometry.
Preparation and water absorptive capacity of sodium cellulose carboxylate
Authors: Godsay M. P. , Gupta V. N. , Lafond R. L. , Macdonald D. M.
Published: June 2010

Sodium cellulose carboxylate was prepared by oxidation of cellulose with gaseous nitrogen dioxide followed by treatment with buffer at pH 7.0. The oxidation reaction rate increased with higher initial gas flow rates, higher total weights of nitrogen dioxide and with nitrogen dioxide pressures higher than 1 atmosphere. Moisture acts as a weak catalyst but is also responsible for loss of nitrogen dioxide by formation of nitrogen acids. Sodium cellulose carboxylate absorbs much more water than cellulose. It is formed without loss of fibrous character or gel formation and with high water absorptivity only if an efficient buffer is used at pH 6.5 to 7.0. Higher pH levels lead to gel formation; lower pH levels lead to impaired absorptivity. Salt formation rate appears to be a diffusion controlled process which is highly sensitive to localized depletion of buffer solution. Use of NaOH in place of buffer does not give the highly absorbent salt. Gelation occurs instead. The diameter of 6‐carboxy cellulose fibers prepared from softwood pulp increases about 90% during the pH 7.0 buffer treatment.
A proposed new mechanism for catalyzed and uncatalyzed graft polymerization onto cellulose
Authors: Gaylord Norman
Published: June 2010

Graft copolymerization of polar vinyl monomers onto cellulose in the presence of oxidizing agents, ceric ion, and radiation has been presumed to be solely the result of propagation from radical sites generated on the cellulose. The uncatalyzed polymerization and graft copolymerization of methyl methacrylate in the presence of cellulose and water has been presumed to involve the formation of a cellulose‐water‐monomer complex with the resultant generation of a covalently bonded monomer radical which then propagates in the usual manner. The formation of grafted alternating copolymer from the radiation induced polymerization of styrene‐acrylonitrile and butadiene‐acrylonitrile, the radical catalyzed polymerization of styrene‐methyl methacrylate and styrene‐acrylonitrile‐ZnCl2 as well as the uncatalyzed polymerization of butadiene‐methyl methacrylate in the presence of cellulose and water indicates the participation of comonomer charge transfer complexes in the graft copolymerization. It is proposed that cellulose acts as a complexing agent for the activation of acceptor monomers and as a matrix for the alignment of acceptor monomer complexes (A*−A‐cellulose‐water) and donor‐acceptor comonomer complexes (D+−A‐cellulose‐water). Polymerization of the complexes is initiated spontaneously or by radicals generated on the cellulose although the latter do not become incorporated into the polymer chain. Graft copolymerization results from termination of the growing polymer chains on cellulose by insertion into aldehyde groups.
Graft copolymerization to cellulose by mutual irradiation
Authors: Guthrie J. T. , Huglin M. B. , Phillips G. O.
Published: June 2010

The mutual irradiation technique in vacuo has been used to study the grafting (G) of styrene to regenerated cellulose film in a dioxan/water medium and the simultaneous homopolymerization (H). The initial rates RG and RH are both found to be directly proportional to the concentration of styrene, but the ratio of the rate constants kP2/kt is ca. 105 times greater in grafting than in homopolymerization (58 cf. 3.3 × 10−4 1. mole−1 sec−1). Bimolecular termination is indicated in both cases by the observed dependences of RG and RH on (intensity)0.5. The degrees of grafting utilized to determine RG were shown to be apparent values only, since extraction of ungrafted cellulose yielded products in which the true degrees of grafting were all some ten times greater.

From ESR spectra of cellulose irradiated in air a value of 1.6 was derived for G (radical) and there was some evidence of scission. Corresponding spectra of cellulose irradiated in vacuo gave G(radical) = 2.9, but no evidence of scission. The radical, formed by hydrogen abstraction, was shown to be located at the C1 atom. However, evidence for scission in cellulose irradiated (in the presence of dioxan/water) in vacuo and in air was provided by measurements of intrinsic viscosity, values of 13.5 and 24.6, respectively being derived for G(scission).
Morphology and kinetics of growth of supermolecular structures in molten polyoxymethylene and mixtures with other substances
Authors: Mihajlov M. , Nedkov E.
Published: June 2010

The results of an investigation of the morphological changes and kinetics of supermolecular structure growth in a thin film of supercooled melt of polyoxymethylene diacetate under the influence of small amounts of organic low molecular, oligomeric, and polymeric compounds and their mixtures have been summarized. A relationship has been found between morphology and kinetics of the supermolecular structure growth and their dependence on the crystallization temperature, chemical structure, and admixture concentration. A possible model of the formation and growth of the supermolecular structures and the influence of the admixtures is presented.
Formation of supermolecular structures of semicrystalline polymers under molecular orientation
Authors: Baranov V. G. , Frenkel' S. Ya. , Gromov V. I. , Volkov T. I. , Zurabian R. S.
Published: June 2010

The effect of stretching on the process of structure formation in fiber spinning and film extrusion and in isothermal crystallization of crosslinked polyethylene has been investigated. It has been shown that the stretching forces (jet stretching) in these systems cause the formation of spherulites flattened with respect to the stretching direction. As a rule, the spherulite radius decreases while the degree of flattening increases with the jet stretching. Thermodynamic analysis of the kinetics and morphology of the spherulite growth during stretching enabled us to interpret these effects and to establish relationships connecting the degree of flattening of the spherulites with the characteristics of molecular orientation in the melt. Taking into account the changes in the conformational entropy of the deformed macromolecule (or the network) in the course of nucleation and crystal the deformed macromolecule (or the network) in the course of nucleation and crystal growth it is possible to explain not only the effect of the spherulite flattening but also the formation of tilted crystals and other peculiarities of crystallization taking place with the occurrence of molecular orientation. A general picture is given of the effect of a mechanical field on the morphology of the crystallizing polymers at various degrees of stretching.
Pore size distribution in swollen macroporous cation exchangers determined from electrolyte uptake and by electron microscopy
Authors: Krska F. , Dusek K.
Published: June 2010

The dependence of the equilibrium electrolyte uptake by macroporous styrene‐divinylbenzene cation exchangers on the external concentration of electrolyte has been studied and distribution functions for the concentration of counterions (exchange groups) in the resin have been calculated using deviations from the Donnan law. The distribution functions for macroporous resins have two maxima: a narrow maximum at higher concentrations of the exchange groups is characteristic of the gel phase, and its position is the same for different cation exchangers; the maximum at low concentrations of the exchange groups corresponds to the macropores, and its position and shape depend on the manner of preparation of the resin. On the assumption of alamellar shape of the pores, the distribution of the macropore sizes has been calculated and compared with the distribution obtained by electron microscopy in dry and swollen states. For cation exchangers with pores not too large, the agreement was quite good; however, the exclusion of the electrolyte in large pores is already negligible, so that the uptake method cannot detect pores of large sizes (> 2000 Å).
Change of spherulitic structure in melt‐crystallized polymer fibers and films during uniaxial stretching
Authors: Bezruk L. I. , Lipatov Yu. S.
Published: June 2010

As revealed by electron‐microscopic studies, the morphology of melt‐crystallized polymer films and fibers subjected to the ultimate degree of orientation, is characterized by layer‐like organization of lamellar crystals (paracrystalline structure). If the direction of the long axes of the macromolecules in crystallites coincides with the texture axis, the morphological orientation of paracrystalline layers is orthogonal to the stretching direction. Partial transformation of a spherulite into a “microneck” can lead to flattening of spherulites.
The influence of morphology on submicrocrack formation in oriented crystalline polymers
Authors: Kuksenko V. S. , Gezalov M. A. , Slutsker A. I. , Yastrebinsky A. A. , Zakrevsky V. A.
Published: June 2010

The supermolecular structure of oriented crystalline polymers and the submicrocracks created in them under mechanical loading were studied by small‐angle x‐ray diffraction.

Most of these polymers consist of fibril‐like formations disposed along the polymer orientation axis, and ranging in thickness from tens to hundreds of angstroms. Crystalline and amorphous regions alternate along the fibrils with periods of hundreds of angstroms. Amorphous regions are mechanically weak. The weakest amorphous regions are torn under loading along the axis of orientation, and submicrocracks are formed. Interlayer rupture occurs by a chain mechanism of successive decomposition of stressed molecules. This process is initiated by free radicals formed at primary thermofluctuation ruptures of macromolecules and is terminated on the amorphous interlayer boundaries. Submicrocracks have the form of disks with transverse dimensions which practically coincide with the fibril thickness. Thus the specific morphology of an oriented crystalline polymer determines the course of development of the fracture from the initial stage.
Chemical potential of KCI and its ion constituents in concentrated protein salt solutions
Authors: Pfister H. , Pauly H.
Published: June 2010

In order to obtain information about the thermodynamic state of simple salts in living cells we measured the mean activity coefficients of KCl and the “apparent” single ion activity coefficients of K+ and Cl‐ in concentrated bovine serum albumin‐KCl solutions and bovine hemoglobin‐KCl solutions and in water soluble fractions of the cytoplasm of calf liver cells, using the EMF method with ion‐exchange membrane electrodes. The protein concentration range extended up to 45% by weight with neutral salt concentration of about 0.1 mole/kg H2O. The pH value varied from 3.5 to 9.8.

Allowing for the effect of site binding and for nonsolvent water, the results show that the “electrostatic” mean activity coefficient of KCl decreases linearly with the equivalent concentration of the polyions. The effect is small, since, in a 0.1 M KCl solution with 20% protein, the activity coefficient of KCl is only 10 to 20% lower than in the pure 0.1M KCl solution.

The meaning of the measured “apparent” single ion activity coefficients is discussed briefly. The results are compared with the predictions of the Marcus‐Katchalsky‐Alexandrowicz theory and of the Oosawa theory.
Solution behavior of homopolymers and random copolymers of l‐methionine and s‐ethyl‐l‐cysteine
Authors: Fougnot Christine , Jozefonvicz Jacqueline
Published: June 2010

Synthesis and conformational studies of polypeptide homopolymers and random copolymers of L‐methionine and S‐ethyl‐L‐cysteine are reported. Syntheses were carried out by sodium methoxide initiation of the N‐carboxyanhydrides of the α‐amino‐acids dissolved in nitrobenzene. The polymers were studied in solution by classical techniques: optical rotatory dispersion, viscometry, light scattering, and spectrophotometry. The effect of the solvent composition on the helix‐random coil transition for poly (L‐methionine) indicates that this polypeptide is still about 60% helical in pure dichloroacetic acid (DCA). Similar behavior of random copolymers containing 60% or more of L‐methionine is observed. The infrared spectra indicate the “β‐structure” of poly (S‐ethyl‐L‐cysteine) and random copolymers rich in S‐ethyl‐L‐cysteine. The influence of solvent composition on the conformational behavior of these polymers is slight. Weight‐average molecular weight and radius of gyration have been determined in pure DCA. In the case of poly (L‐methionine) the experimental observations agree with the interrupted‐helix model.
Fluorimetric investigations of interactions with macromolecules in solution
Authors: Killmann Erwin , Bittler Rolf
Published: June 2010

Blancophor dyes show a considerable increase in fluorescence yield upon adsorption onto poly(vinyl pyrrolidone). A fluorometric method was used for the quantitative determination of adsorption in polymer‐dye solutions. The adsorption isotherms differ from Langmuir adsorption behavior, and an adsorption isotherm is derived by taking into account the electrostatic repulsion potential of the adsorbed Blancophor ions. Adding foreign electrolytes causes a decrease in the electrostatic potential, which is independent of the species of salt, and is characterized by the Debye‐Hückel shielding parameter. The macromolecule with adsorbed ions represents a good model for a polyelectrolyte having the capability of altering or readjusting its charge density. Macromolecular sizes measured by various methods are related to the effective potential on the surface of the macromolecule. The expansion of the poly(vinyl pyrrolidone) molecule caused by the electrostatic repulsion of the adsorbed Blancophor ions was investigated by viscosity and light‐scattering measurements. Relationships among charge on the macromolecule and screening by added salt ions, on the one hand, and the molecular weight, the end‐to‐end distance, and the second virial coefficient, on the other hand were found and interpreted.
NMR relaxation and solvation equilibrium in the ternary system CCl4‐polymethylmethacrylate‐benzene
Authors: Lütje Hans
Published: June 2010

In the ternary system CCl4‐PMMA‐benzene, benzene is preferentially adsorbed in the solvation shell of the polymer. One solvation equilibrium constant allows a satisfactory description of the preferential solvation for a large range of solvent compositions. The nuclear magnetic relaxation time T1 of benzene protons was measured for different values of the polymer concentration. The measurements are compared with analogous measurements in the system C6D6‐PMMA‐C6H6 where no preferential solvation is to be expected. For the system CCl4‐PMMA‐benzene the resulting dimensionless solvation equilibrium constant is K = c32c10/c12c30 = 2.5 ± 0.5 where c10 is the CCl4 concentration in the “free” solvent; c30 is the benzene concentration in the free solvent; c12 and c32 are the concentrations of CCl4 and benzene in contact with the polymer chain, respectively.