bluuebunny/crossref_metadata_2025 huggingface dataset:
Polymerization of phenyl‐substituted butadienes by metal alkyl catalysts
Authors: Stille J. K. , Vessel Eugene D.
Published: April 2003

Heterogeneous Ziegler‐type catalysts polymerize 2‐phenyl‐1,3‐butadiene to form low molecular weight polymers. The polymer prepared with a 3:1 catalyst ratio of aluminum triisobutyl to titanium tetrachloride contains 80–90% cis‐1,4‐units and the polymer formed by the 1:1 catalyst has 60–70% cis‐1,4‐structure. No trans‐1,4‐ or 3,4‐units are found in any of the polymer samples and the remaining unsaturation is attributed to 1,2‐polymerization. Both Ziegler‐type catalysts and butyllithium are ineffective for the polymerization of 2,3‐diphenyl‐1,3‐butadiene.
Microscopic studies of Mylar film and its low molecular weight extracts
Authors: Giuffria Ruth
Published: April 2003

Mylar polyester film has some low molecular weight material which may be extracted by various organic solvents as well as oil. This extract crystallizes in different crystal forms depending upon conditions of crystallization. Regardless of the crystal form, the Mylar extracts act alike on a hot stage, subliming without melting at 300°C. to form a sublimate which will melt sharply at 322°C. This characteristic behavior, as well as its crystallization from chloroform, forms a basis for microscopic identification of very small quantities of low molecular weight Mylar. The presence of a sublimate of low molecular weight material from raw Mylar film and the complete absence of any sublimate from extracted Mylar film makes possible rapid differentiation between raw and extracted films. This sublimate has characteristics similar to those of low molecular weight material obtained by solvent extraction. There exist in Mylar film minute areas of different refractive index which make a definite contribution to the haze level of the film. These areas are assumed to be different in crystallinity than the matrix in which they exist.
Polymer fractionation by precipitation chromatography
Authors: Jungnickel J. L. , Weiss F. T.
Published: April 2003

The precipitation chromatography method of Baker and Williams has been found to have advantages in efficiency and ease of operation over other methods for fractionation of polymers. Good fractionations according to molecular weight have been obtained on several polymers of widely different molecular weight distributions, including samples of polystyrenes and of a high molecular weight polyolefin.
Studies on amylose and its derivatives. Part II. Light‐scattering and viscosity studies on amylose acetate in dilute solution
Authors: Cowie J. M. G.
Published: April 2003

Amylose acetate has been fractionated and the solution properties of the fractions studied in two solvents. Weight‐average molecular weights have been determined in nitromethane by the light‐scattering method, and measurements of viscosity as a function of shear stress have been made in chloroform and nitromethane. The Ree‐Eyring flow theory has been used to describe non‐Newtonian behavior which was detected in samples with [η] > 2.0. The parameters in the Mark‐Houwink equation are [η] = 1.10 × 10−5M̄0.87 in CH3NO2 and [η] = 1.06 × 10−5M̄0.92 in CHCl3. The Kratky‐Porod chain model has been found to be most useful in describing the hydrodynamic behavior and indicated that the molecule is much stiffer than the vinyl polymers but more flexible than the cellulose derivatives. The existence of a helical form has been discussed, and it is thought probable that this is the basic form in solution.
Sorption and diffusion in crystalline elastomers. Part I. Solubility of isomeric hydrocarbons in stretched rubber
Authors: Barrie J. A. , Platt B.
Published: April 2003

The solubility coefficients of n‐ and isobutane for stretched crosslinked natural rubber have been measured for simple elongations of 0–400% in the temperature range 30–50°C. To minimize the effect of penetrant on the degree of crystallinity, regions of low concentration were chosen. The sorptive capacity of the rubber was not significantly altered by elongation until the extension was sufficient to permit crystallization to take place. For both stretched and unstretched samples temperature—hysteresis effects were absent and Henry's law was obeyed. The data indicate that the difference in solubility between stretched and unstretched rubber can be taken as a measure of the degree of crystallinity. A slight decrease in the solubility over extended periods of time was attributed to a corresponding slow increase in the degree of crystallinity. The dependence of the degree of crystallinity on temperature and elongation was well represented by that deduced from Flory's theory of strain‐induced crystallization.
A versatile osmometer for polymer gels and solutions with applications to cellulosic gels
Authors: Pennings A. J. , Prins W.
Published: April 2003

An osmometer is described which is capable of measuring swelling pressures of polymer and polyelectrolyte gels up to 200 atm., as well as measuring osmotic pressures of solutions down to approximately 0.1 mm. H2O pressure. For the latter, use can be made of the deswelling of a solvent swollen gel that occurs when it is placed in contact with the polymer solution. In this case no semipermeable membrane is required. Useful thermodynamic information regarding the network structure of gels can be obtained, which in the case of polyelectrolytes cannot be obtained through vapor phase measurements. Measurements on a gel obtained by crosslinking cellulose acetate in solution allow the determination of the elastic free energy and the degree of swelling q0 at which the coiling chains are relaxed, if Huggins' parameter in the expression for the free energy of mixing is known. If the degree of swelling q is not too far removed from q0, it is shown that the “rubber elasticity” theory of networks holds, and yields the number of crosslinks in the gel. Pressure measurements of a cellulose gel in water and in alkali solutions are presented. The maximum in the swelling pressure at 10% alkali is qualitatively explained with Neale's theory, which considers the cellulose hydroxyl groups to be weakly acidic.
Graft copolymers of p‐isopropylstyrene and methyl methacrylate
Authors: Matlack J. D. , Chinai S. N. , Guzzi R. A. , Levi D. W.
Published: April 2003

The preparation of a completely isopropylated polystyrene by polymerization of p‐isopropylstyrene monomer is described. This polymer was autoxidized in cyclohexane with lauroyl peroxide to give a material of good reproducibility and high purity. Methyl methacrylate was successfully grafted to the polymeric hydroperoxide by using a sugar‐containing recipe. Homopolymer was separated from the graft copolymer by extraction. Evidence for grafting was obtained from solubility and fractionation behavior, as well as from light‐scattering and viscosity measurements.
Second‐order transitions in solutions of cellulose triacetate
Authors: Sharples A. , Swinton F. L.
Published: April 2003

The system cellulose triacetate in chloroform has been studied using the technique of dilatometry, viscometry, and light‐scattering, and it has been observed that although under certain conditions the solutions can be induced to gel, gelation occurs without the change in volume to be expected for a first‐order transition. Two second‐order transitions have been observed however, which are still detectable while the system is in the liquid state. In addition, the transition temperatures have been found to be independent of concentration. An explanation for these unusual effects has been proposed, suggesting that the system contains submicroscopic, partly crystalline aggregates of polymer molecules, whole melting point lies above the temperature range studied. Gelation is considered to take place by a coalescence of these aggregates, and second‐order transitions to occur within the aggregates while the aggregates while the system is in an apparently liquid state.
Differential thermal analysis of high polymers. III. Polyamides
Authors: Ke Bacon , Sisko A. W.
Published: April 2003

Differential thermal analysis has been used to study melting and glass transitions in various homo‐ and copolyamides, as well as crystallite disorientation in nylon monofilaments. Transition temperatures obtained from the thermograms of the commoner polyamides agree well with literature values, but the less common polyamides gave slightly higher melting points. Heats of fusion of polyamides 66 and 610 were obtained from the thermograms by calibration with a calorimetric standard. These values together with the independently determined degree of crystallinity have been used to calculate the true heats of fusion. The thermograms of two series of copolyamides, the adipamide–sebacamides and adipamide–terephthalamides, showed changes in peak shapes, positions, and areas from those of the parent homopolymers. Decrease in crystallinity led to pronounced glass transitions. Two melting peaks observed for certain copolymers are interpreted as evidence for the production of block copolymers, which are favored by the reaction conditions existing in interfacial polycondensations.
Dynamic mechanical behavior of some partially crystalline poly‐α‐olefins
Authors: Woodward A. E. , Sauer J. A. , Wall R. A.
Published: April 2003

Internal friction (Q−1) and dynamic elastic storage modulus have been measured as functions of temperature (80°K. and higher) for partially crystalline samples of poly(pentene‐1) (PP1), poly(3‐methylbutene‐1), (P3MB1), and poly(4‐methylpentene‐1) (P4MP1); a resonance technique at audiofrequencies was used. Two internal friction peaks at 145°K. (γ) and 290°K. (β) and a final upswing in Q−1 at 335–345°K. (α) in conjunction with associated modulus dispersions are exhibited by PP1, the mechanical loss spectrum being similar to that reported previously for poly(butene‐1) except that the final upswing for PP1 occurs at lower temperatures. Both P3MB1 and P4MP1 have small Q−1 damping peaks near 150°K. (γ). The latter polymer also has a peak of considerable magnitude at 335–340°K. (β) and an upswing in Q−1 at 425–435°K. (α). The former polymer shows a broad dispersion commencing at about 320°K. (β). Owing to the absence of a sizable transition below the principal amorphous transition starting at about 325°K., the modulus for P3MB1 exhibits the least variation with temperature in the range of 80–325°K. among the poly‐α‐olefins with aliphatic side chains, including polyethylene and polypropylene, that have been studied by this method. It is suggested that the γ and β loss peaks and associated modulus changes are the consequence of the onset of motion in the amorphous regions, involving small and large number of chain segments, respectively.
Copolymerization of 1‐acrylamido‐1‐deoxy‐Dhyphen;glucitol and of 1‐deoxy‐1‐methacrylamido‐D‐glucitol with various vinyl monomers
Authors: Whistler Roy L. , Goatley James L.
Published: April 2003

Copolymerization characteristics for 1‐acrylamido‐1‐deoxy‐D‐glucitol and of 1‐deoxy‐1‐methacrylamido‐D‐glucitol with various vinyl monomers is given. For the former compounds Q and e values are found to be 0.12 and 0.6 respectively and, for the latter, 0.08 and 1.3. In addition, viscosity, osmotic molecular weights, and solubilities for representative compounds are given.
Molecular weight distribution and branching in butadiene polymers and copolymers
Authors: Cooper W. , Vaughan G. , Eaves D. E. , Madden R. W.
Published: April 2003

Butadiene polymers and copolymers prepared in emulsion and with complex coordination catalysts have been examined by use of light‐scattering, osmometric, viscometric, and fractionation techniques. These polymers are particularly prone to branching, the extent of which has been characterized from light‐scattering and viscometry data. A correlation was obtained between polydispersity and branching, and the lightscattering second virial coefficients of the polymers. The second virial coefficients obtained from osmotic pressure measurements were not greatly affected by the presence of branched polymer. Similar results were obtained on a butadiene–styrene copolymer which was branched by exposure to high energy radiation. Further branching, leading ultimately to crosslinking, occurred on storage of polybutadiene both in the solid polymer and in concentrated solution, the changes being influenced by catalyst residues in the polymer. On the other hand, in dilute solution or on milling in the presence of radical traps, degradation at the branch points occurred. No relationship was observed between branching and the physical properties of the polymer. Butadiene polymers prepared using complex coordination catalysts, possessed, in general, somewhat wider molecular weight distributions than emulsion polymers prepared at 10°C. They were characterized by substantial amounts of low molecular weight polymer and the absence of a high molecular weight tail. The molecular weight of essentially linear fractionated polybutadiene of 93% cis‐1,4‐ content is related to the intrinsic viscosity by [η] (benzene 100 ml. g.−1) = 1.00 × 10−4M0.77. After making corrections for differences in structure and chain stiffness this relationship is in close accord with relationships from other sources obtained on unbranched butadiene polymers.
Spherulites in nylon 610 and nylon 66
Authors: Lindegren C. R.
Published: April 2003

The two types of spherulites in nylon 610 differ in birefringence, melting point, and rate of growth. The rates of growth depend strongly upon the degree of supercooling, and—at least for the positive spherulites—to a small extent on the molecular weight. The rate curve for the positive spherulites has a singular point at 188°C. and appears to have a maximum in the neighborhood of 120°C. Concentric rings were observed in positive spherulites only after crystallization in the temperature range between 188° and 195°C. Positive spherulites formed near 180°C. have maximum birefringence. Negative spherulites were observed only in specimens allowed to crystallize between 205° and 225°C. Three types of spherulites were observed in nylon 66. The large, positive, and highly birefringent spherulites have the same melting point, 273—274°C., as the negative spherulites. The small positive spherulite with normal birefringence melt at 269.5—270°C. Simultaneous growth of all three types of spherulites was observed only between 250 and 255°C.
The mechanism of gelation in the reaction between diisocyanates and polyethylene ethers
Authors: Pearson R. W.
Published: April 2003

When polyethylene ethers which have been prepared in the presence of alkaline catalysts are reacted with diisocyanates, gelation usually takes place and more isocyanate reacts than is required for complete conversion of hydroxyl groups to urethane. These facts are explained by the rapid reaction, in the presence of basic catalysts, of isocyanate with urethane groups to form allophanate and similar structures. A theory relating the extent of isocyanate reaction at gelation to the initial ratio of hydroxyl to isocyanate group has been developed, and compared with the experimental results. The effect of the addition of sodium hydroxide to neutralized polyethylene ether, and of the addition of sodium to n‐butanol, on the reaction of these compounds with diisocyanates has been examined, and the results support the suggested mechanism.
An empirical concept of flow for polyisobutene systems
Authors: Porter Roger S. , Johnson Julian F.
Published: April 2003

Viscosities were measured on 11 polyisobutenes with molecular weight of 224 to 71,000. Measurements were made on cetane and tetralin solutions containing 11.2–100 wt.‐% polymer. Tests were made at 80–135°C. and a t shear rates to 8 × lo6 sec.‐l. Low shear capillary and two types of rotational viscometers were used. The data confirm that polyisobutene systems show an abrupt transition in log viscosity—log molecular weight correlations. This transition occurs near 15,000 for MV where M is Viscosity‐average molecular weight and V is polymer volume fraction. Below a product of 15,000, polyisobutene systems exhibit essentially Newtonian flow and an absence of laminar flow shear degradation to stresses above 2 × 105 dynes/cm.2. In this region the viscosity dependence on molecular weight approaches fist order at higher temperatures and lower polymer concentrations. For polyisobutene systems above the transition near 15,000, low shear viscosities uniformly increased aa the 3.4 power of molecular weight. Systems in this range exhibited large and predictable non‐Newtonian effects and frequently showed laminar flow shear degradation at low rates of shear.
Polybenzimidazoles, new thermally stable polymers
Authors: Vogel Herward , Marvel C. S.
Published: April 2003

Wholly aromatic polybenzimidazoles were synthesized from aromatic tetraamines and difunctional aromatic acids and characterized as new thermally stable polymers. The melt polycondensation of aromatic tetraamines and the diphenyl esters of aromatic dicarboxylic acids was developed as a general procedure of wide applicability. Polybenzimidazoles containing mixed aromatic units in the chain backbone were prepared from 3,3′‐diaminobenzidine, 1,2,4,5‐tetraaminobenzene and a variety of aromatic diphenyl dicarboxylates. Phenyl 3,4‐diaminobenzoate could also be polymerized by melt condensation to give poly‐2,5(6)‐benzimidazole. The polymers were characterized by a high degree of stability, showing great resistance to treatment with hydrolytic media and an ability to withstand continued exposure to elevated temperatures. Most of the polymers were infusible, but some had melting points above about 400°C. Many of the polymers exhibited no change in properties on being heated to 550°C. and showed a weight loss of less than 5% when heated under nitrogen for several hours to 600°C. The polymers were soluble in concentrated sulfuric acid and formic acid, producing stable solutions. Many of the polymers were soluble in dimethyl sulfoxide and some also in dimethylformamide. The inherent viscosities of a number of polymers in 0.5% dimethyl sulfoxide solution ranged from approximately 0.4 to 1.1. The higher polymers could be cast into stiff and tough films from formic acid and dimethyl sulfoxide solutions.
Viscosity and glass temperature relations for polymer‐diluent systems
Authors: Kelley Frank N. , Bueche F.
Published: April 2003

Expressions are derived from free volume considerations which predict the concentration dependence of viscosity and glass temperature for polymer‐diluent systems. Experimental data for several systems were examined and general agreement with theory was found over broad ranges of concentration. Particular emphasis is placed on the limited amount of information required for the application of these expressions to describe the viscous properties of polymer‐diluent systems.
Isolation of the precursor of bacterial cellulose
Authors: Khan A. W. , Colvin J. Ross
Published: April 2003

A method is described for the isolation of the precursor of cellulose microfibrils from ethanol extracts of active cultures of Acetobacter xylinum. Using the capacity to form cellulose microfibrils for an assay procedure, the method employs column chromatography of chloroform extracts of the residues from the ethanol solutions, on silicic acid and Celite followed by magnesium trisilicate (Magnesol) and Celite. A fraction from the second stage contains only one compound, which is capable of forming typical bacterial cellulose microfibrils in the presence of ultrafiltered supernatant of an active culture. The compound contains glucose, an unknown base, and a fatty acid.
The distribution of polysaccharides in wood fibers
Authors: Meier Hans
Published: April 2003

A study was made of polysaccharide distribution in the cell walls of both hardwood fibers and conifer tracheids by means of analysis of fractions obtained through microdissection. Radial sections of about 50 μ in thickness were made through the cambium and the outermost part of the xylem of birch, spruce, and pine woods. In these sections, the successive stages of maturation of the fibers can be distinguished microscopically. Under a polarizing microscope, the optical characteristic of each cell wall layer (M, P, S1, S2, S3) is dependent on the orientation of the cellulose microfibrils in it, and it was therefore possible, with a microdissector, to isolate samples of fibers at different stages of maturation. Samples of about 0.3 mg. of each fiber fraction were hydrolyzed and the sugars present were determined quantitatively. With the use of present knowledge of the chemical composition of the different polysaccharides in wood, the sugar analysis results were converted into polysaccharide contents for each fraction. From these it, was then possible to calcute very roughly the proportions of the different polysaccharides in each cell wall layer. The youngest fibers (M + P fibers) of the three woods studied consist principally of pectic substances (pectic acid, galactan, and arabinan). In birch the S1 layer and the outer part of the S2 layer contain only slightly more cellulose than glucuronoxylan, while the innermost layers of the fiber (around the lumen) contain a large proportion of cellulose. In both sprucc and pine the S1 layers contain about 60% cellulose, between 15 and 20% glucomaiinm, and between 15 and 20% glucuronoarabinoxylan. In the outer part of S2 the cellulose and glucomannan contents increase and the glucuronoarabinoxylan decreases. In the innermost parts of the summer wood tracheids of pine the cellulose content decreases again and the glucurono arabinoxylan content is very high in the S3 layer. In the spring wood tracheids of spruce the composition of the S3 layer cannot be deduced from the present study but there are indications that it is similar to that of summer wood trncheids of pine.
The use of holocellulose to study cellulose supermolecular structure
Authors: Nelson Russell
Published: April 2003

Holocelluloses were prepared from slash pine wood at the 17–19, 4‐6, and 0‐2% lignin levels by the chlorite and chlorine–monoethanolamine methods. The products were compared with respect to carbohydrate composition, nitrate degree of polymerization, x‐ray diffraction peak width, x‐ray crystdlinitg index, mercerization resistance, and alkali solubility. Structural differences among holocelluloses at each lignin level were noted. Thest. wvre attributrd to a deperidencc of x‐ray diffraction peak width on delignification conditioris and to small differences in amount of residual lignin. It was determined that alkali‐resistant, heimictrlluloses interfere with mercerization analyses inasmuch as they diminish diffraction pattern resolution. Taking account of such interference, the swelling behavior of the cellulose in whole wood can be estimated from either type of holocellulose. It is necessary, however, to ensure that all of the lignin is removed and that cellulose degradation is not excessive. The effect of stepwise alkaline extraction of hemicelluloses from the holocelluloses containing 0–2% lignin was followed by x‐ray analyses of the extracted residues after each extraction stage. Narrowing of the 002 diffraction peak width was observed and was found to depend on an alkalicellulose interaction and on hemicellulose reinoval. Reinoval of “polyuronides” has less of an effect on peak width than removal of the “cellulosans.” The hemiceliulosic polysaccharides, araboglucuronoxylan, and glucomannan are discussed in regard to molecular structure, probable relationship to the crystalline cellulose, ease of alkaline extraction, and effect of removal on the cellulose supermolecular structure. Narrowing of the 002 peak width, independent of cause, is considered to represent an increase in crystallite width, in development of the crystal lattice, and in packing perfection of the cellulose chains within and on the surfaces of the crystallites. Structure parameters were estimated for native slash pine cellulose, and these were compared with values found for celluloses isolated from the same species by the conventional acid sulfite and prehydrolysis sulfate processes. This comparison enabled approximation of the direction and magnitude of change effected in the native cellulose structure during pulping.
Infrared spectra of cellulose and related polysaccharides
Authors: Higgins H. G. , Stewart C. M. , Harrington K. J.
Published: April 2003

A comparison has been made between the infrared spectra of native cellulose and those of various closely related materials differing in each instance from cellulose I in one salient feature. These materials have been compared individually with groups of others, each differing from cellulose in a further salient feature. Considered in conjunction with the spectra of a few formally more distant relatives such as tetrahydropyran and the simple alcohols, these empirical comparisons can contribute to an understanding of the influence on the spectrum of hydrogen bonding, hydroxyl groups (through HD exchange and o‐acylsubstitution), the type of anomeric and positional linkage, attachment at a specific carbon atom, the glycosidic link, and degree of polymerization. The comparative spectroscopy of cellulose, laminarin, amylose, and xylan permits correlation between these glucosans for about a dozen of the major bands or groups of bands in the spectra of the amorphous materials between ca. 3 and 13μ. An examination of the spectra of various crystalline modifications of cellulose lends support to various conclusions drawn by previous workers regarding the relationship between these forms. The effects of deuterating native and regenerated cellulose have been taken into account in considering band assignments. The intensity of the strong band near 8.6 μ (1160 cm.−1) is reduced on deuteration, and it is questioned whether this is consistent with its assignment to stretching in the glycosidic link (on the basis of its strong parallel polarization, etc.). The response to deuteration suggests that the band near 9.0 μ (1120 cm.−1) may be an association band of the type observed in primary and secondary alcohols and that the residual band near 8.9 μ (1120 cm.−1) may be identified with the antisymmetric ring‐stretching vibration. The persistence of the strong bands between 9 and 10 μ (1100–1000 cm.−1) after deuteration, acetylation and, in the case of sugars, freeze drying, supports the conventional assignment to CO stretching, perhaps coupled to CC frequencies. The band near 10.1 μ (990 cm.−1) is eliminated on deuteration or hetero‐geneous acetylation of cellulose. These and other facts suggest that it is connected with a vibration which is restricted in the crystallites. The band a t 11.2 μ (893 cm.−1) in cellulose and other β‐linked glucosans is clearly connected with the C(1) group vibration. In much of this work the samples were examined as dispersions in pressed potassium chloride pellets. In the amorphous state the spectra of the smaller molecules resemble those of the corresponding polymers. It was also observed that freeze‐dried samples, dispersed in potassium chloride, showed a slow reversion to the sharp spectrum characteristic of the crystal.
The effect of crystalline structure on the alkaline degradation of cellulose fibers
Authors: Meller Alexander
Published: April 2003

The resistance of cotton cellulose and of sodium borohydride‐reduced hydrocelluloses to boiling 1% sodium hydroxide solution is decreased by ethylamine treatment. In contrast, hydrocelluloses exhibit a greater resistance to hot dilute alkali after ethylamine treatment. This increased hot alkali stability seems to be associated with the reaction between the reducing end group in the terminal glucose units of the cellulose molecules and the amine. Aqueous hydroxylamine–treated hydrocelluloses also show a slightly increased resistance to hot dilute alkali. The ethylamine treatment apparently induces a change in the physical structure of the fibers, “decrystallization” or conversion of cellulose I to cellulose III, depending on the manner in which the amine is removed from the fibers. The amine treatment results in a lower resistance to boiling dilute alkali. On the other hand, the reaction between the reducing end groups and the amine (possibly a condensation reaction) has an opposite effect on hot alkali stability. The net effect, thus, may depend on the relative magnitudes of the opposing effects and on the rate of change in the physical structure of cellulose that takes place during the hot alkali stability test. With hydrocellulose possessing a large number of reducing groups, the effect on hot alkali stability arising from a chemical reaction between the reducing end groups and anhydrous ethylamine is greater than that caused by the change in physical structure (decrystallization and conversion of cellulose I to cellulose III). With cotton fibers and borohydride‐reduced hydrocelluloses that contain a small number of reducing end groups, the effect of “crystallinity” and crystal structure on hot alkali stability seems to be the greater. Immersion in hot water of amine‐treated celluloses and hydrocelluloses increases their resistance to hot dilute alkali. This increased resistance is probably due to a recrystallization which takes place by the action of hot water.
Kinetics of the acid‐catalyzed degradation of cellulose esters
Authors: Rosenthal Arnold J.
Published: April 2003

The acid‐catalyzed degradation rates of cellulose acetate and cellulose propionate in acetic and propionic acids and anhydrides have been determined by repeated viscosity measurements. Relative degradation rates could be estimated with the aid of a standardized curve that related intrinsic viscosity to extent of degradation under the assumption of pseudozero‐order degradation kinetics. Degradation rates were established as functions of temperature and concentrations of water, sulfuric acid, and aliphatic anhydrides. The most surprising result was that the degradation of cellulose acetate passed through a minimum as a function of acetic anhydride concentration, whereas the degradation rate for cellulose propionate always increased with acetic anhydride or propionic anhydride concentrations. A mechanism is offered in terms of steric interaction between ester groups on the cellulose and various acidic species.
Interaction of cellulose with small molecules. II. Ethylenediamine, ethylene glycol, and tetramethylene sulfone
Authors: Wellisch Eric , Hagan Lamont , Marker Leon , Sweeting Orville J.
Published: April 2003

The interactions of cellulose with highly hygroscopic ethylenediamine and ethylene glycol and with the less hygroscopic tetramethylene sulfone have been determined. The measurements are based on the difference between the equilibrium vapor pressure of films containing known percentages of aqueous softener and the equilibrium vapor pressure of the same aqueous softener not perturbed by the presence of cellulose. The equilibrium moisture content of unsoftened cellulose (α), the equilibrium moisture content of the plasticizing molecule (β), and the equilibrium moisture content of the treated cellulose (γ) were measured as a function of relative humidity and of plasticizer content in the film. From these data relative interaction values expressed as p/p0 ratios (partial pressures of water in softened film and in aqueous softener solutions) or as deviation from additivity, δ = α + β − γ, were calculated. An interpretation of the data in terms of the relative affinities of water for softener and cellulose, arid cellulose for water and softener, is given.
The state of solution of technical viscose
Authors: Treiber Erich
Published: April 2003

The state of solution of a technical viscose is of both theoretical and technical interest. The existing assumptions may be divided into two general theories. These two opposing theories are concerned, to put it simply, with whether cellulose xanthate is more or less molecularly dispersed or is only a dispersion of micelles and bigger aggregates. After a short survey of the more essential and newer contributions a particle spectrum for describing the state of solution of a spinnable viscose is proposed. Furthermore, the assumption is made that about 60% of the cellulose may behave as a molecular dispersion, making possible the determination of molecular weight and other molecular parameters. The frequency distribution of micelles, bigger aggregates, and fiber fragments, derived from a stepwise disintegration process, may follow a Gaussian curve. This hypothetical frequency distribution in our particle spectrum is in agreement with known observations. The microscopic particles, affecting technical operations, can be determined directly by particle counting or indirectly by filterability determinations. After mentioning a new technique for obtaining filter values of unusually high accuracy despite the inhomogeneity of the filter materials, some results of filterability tests combined with gel particle counting are reported.
The sorption of polymers on cellulose
Authors: Luce J. E. , Robertson A. A.
Published: April 2003

The sorption of polyvinyl acetate from solution in organic solvents by cellulose fibers has been investigated and found to resemble the sorption of polymers by other porous sorbents. Differences in the extents of sorption from different solvents have been attributed to competition between solvent and polymer molecules for sorption sites, and have been correlated with the Hildebrand solubility parameter. The sorption properties of cellulose fibers which had been subjected to swelling in organic liquids, to solvent‐replacement procedures, and to freeze drying were examined. The extent of sorption measures the degree of swelling and has been correlated with the properties of the swelling liquid.
Gamma‐ray–induced graft copolymerization of styrene onto cellulose and some chemical properties of the grafted polymer
Authors: Kobayashi Y.
Published: April 2003

The γ‐ray–induced graft copolyinerization of cellulose and styrene by preirradiation was studied. (1) The graft copolymerization of cellulose and styrene was accelerated by immersing the cellulose in H202 solution during γ irradiation. The number of active sites such as hydroperoxides was estimated by the ferrous ion method. There is shown a correlation between the number of active sites and the rate of grafting. (2) The acetylation of the grafted cellulose–styrene polymer was carried out. The progress of the reaction was observed from the weight increase and infrared spectra measurement. The reaction proceeded very rapidly owing to the increased swelling of grafted polymer in the treating bath. (3) The acetylation of the cellulose‐styrene polymer was next carried out under more severe conditions. In this case the ccllulose part of the grafted polymer was degraded by acetolysis and only the polystyrene was extracted from the grafted polymer. The viscosity‐average molecular weight of the extracted polystyrene was estimated by viscometry and the degree of polymerization was calculated as 1.98 × l06. This value was compared with the number of the active sites estimated by the ferrous ion method.
The different crystalline modifications of TiCl3, a catalyst component for the polymerization of α‐olefins. I: α‐, β‐, γ‐TiCl3. II: δ‐TiCl3
Authors: Natta G. , Corradini P. , Allegra G.
Published: April 2003

Crystalline TiCl3 is the typical solid component of the catalytic system for the stereo‐specific polymerization of α‐olefins; hence a great interest in the knowledge of its crystal structure arises. Four different crystalline modifications of TiCl3 (α, β, γ and δ) are known to date; three (β, γ, and δ) were first described in our laboratory. A preliminary structural distinction among them can be made in terms of fiber‐shaped (β) and layer (α, γ, and δ) modifications. The crystal structure of the β‐modification can, in fact, be considered as built up by linear macromolecules, while identical bidimensional (planar) macro molecules, packing with different sequences of shifts, between themselves, can originate an α‐, or γ‐, or δ‐TiCl3 crystal. This close structural analogy explains the great similarity in physical and chemical properties of the last three modifications. In the first part of this paper, the most important structural features of α, β, and γ‐modifications are described; in the second, the structure of the most recently discovered δ‐TiCl3 is more deeply analyzed. The presence of diffuse halos instead of sharp reflections in its Debye spectra clearly indicates the presence of a certain structural disorder; mathematical calculations (not fully reported here), based on the alternative assumption of two different statistical models of shift successions between structural layers, have led us to find the most probable succession type. As the possible shifts between adjacent structural layers cannot be different in type, in δ‐TiCl3, from those which take place in the ordered α‐ or γ‐modifications, we can say that, in δ‐TiCl3, the intervention of disorder in shift successions leads to something intermediate (in a statistical sense) between the two stated structures.
Ethylene–propylene copolymerization in the presence of catalysts prepared from vanadium triacetylacetonate
Authors: Natta Giulio , Mazzanti Giorgio , Valvassori Alberto , Sartori Guido , Fiumani Diego
Published: April 2003

Ethylene–propylene copolymerization in the presence of catalysts prepared from vanadium halides was described in our previous papers. Linear, high molecular weight, completely amorphous copolymers, having an ethylene molar content up to 80%, can also be von 0°C weitaus höhere Copolymerausbeuten als bei Raumtemperatur. Die höhere Bruttopolymerisationsgeschwindigkeit bei tiefen Temperaturen ist spezifisch für dieses besonder katalytische System und tritt bei Katalysatoren, die aus Vanadinchloriden dargestellt wurden, nicht auf. Bei −20°C ist die Zusammensetzung der Copolymeren von der Polymerisationsdauer, dem Molverhältnis Al(C2H5)2Cl/VAc3, der Katalysator‐konzentration oder der Gesamtkonzentration der Monomeren unabhängig. Das mittlere Molekulargewicht der Copolymeren nimmt mit steigendem Al(C2H5)2Cl/VAc3Verhältnis und steigender Katalysatorkonzentration ab, was für das Auftreten eines Ubertragungsprozesses zwischen den wachsenden Ketten und den im System vorhandenen organometallischen Verbindungen spricht. Bei konstantem Verhältnis zwischen den Monomerkonzentrationen und zwischen den Katalysatorkomponenten ist die Bruttopolymerisationsgeschwindigkeit in bezug auf die Katalysator‐ und Monomerkonzentrationen von erster Ordnung. Die Reaktivitätsverhältnisse der Monomeren, r(C2H4) = 15.0, r(C3H6) = 0.04, sind zwischen −20°C und +25°C von der Temperatur unabhängig. Das Produkt der beiden Werte (0,6) weist darauf hin, dass eine Abwechslung der Monomereinheiten in den Ketten wahrscheinlicher ist als eine statistische Verteilung, bei der das Produkt dieser Verhältnisse gleich 1 ist.
Kinetics of ethylene–propylene copolymerization
Authors: Natta G. , Mazzanti G. , Valvassori A. , Sartori G. , Barbagallo A.
Published: April 2003

The values of the reactivity ratios for ethylene–propylene and ethylene–1‐butene copolymerization, described in previous papers, and the distribution of monomer units in different length sequences are discussed. In this paper the kinetics of ethylene–propylene copolymerization in the presence of catalysts prepared from trialkylaluminum and vanadium tetrachloride is studied. Having adopted the conditions leading to the formation of catalysts having an activity independent of time, we were able to determine that the copolymerization rate is first order with respect to the catalyst concentration and to the sum of the concentrations of the two monomers. With the total concentration of the monomers constant, the copolymerization rate increases very rapidly as the ethylene concentration increases. The activation energies of the four chain growth reactions of the copolymerization proved to be practically equal.
Stereospecific polymerization of 2‐vinylpyridine
Authors: Natta G. , Mazzanti G. , Longi P. , Dall'Asta G. , Bernardini F.
Published: April 2003

Some metalloorganic or metal amide compounds of very electropositive metals, such as lithium, sodium, beryllium, magnesium, and aluminum, cause the polymerization of 2‐vinylpyridine. Whereas the compounds of beryllium and of aluminum furnish slightly crystalline 2‐vinylpyridine polymers, by using magnesium derivatives it is possible to obtain polymers which are highly crystalline by x‐rays. The results obtained from the systematic study of the polymerization in the presence of amides or of metalloorganic compounds of magnesium are reported. In particular, it has been examined the influence of the monomer/catalyst molar ratio, of the temperature, of the polymerization time, and of the nature of the substituents bound to magnesium, on the course of the polymerization and on the properties of the obtained polymers. Examination by IR spectrography allowed us to conclude that at least a part of the macromolecules contain, as endgroup, the organic groups which were initially bound to the metal in the compounds used as catalyst. The stereospecificity of the process must be ascribed to the possibility of coordination of the catalyst to the monomer molecules entering the growing chain. In fact, the addition of organic Lewis bases to the system, causes the reduction or the disappearence of stereospecificity. The obtained results allowed us to conclude that the stereospecific polymerization of 2‐vinylpyridine takes place by an anionic coordinated mechanism. 4‐Vinylpyridine, in the presence of catalysts which are stereospecific for the polymerization of 2‐vinylpyridine, gives amorphous noncrystallizable polymers. That was ascribed by us to the fact that the nitrogen atom, in the case of 4‐vinylpyridine is too far from the vinyl double bond to form, with the catalyst, an addition complex able to give the same orientation to all the monomer molecules, at the very moment of the polymerization.
Isomorphism phenomena in macromolecules
Authors: Natta G. , Corradini P. , Sianesi D. , Morero D.
Published: April 2003

Through x‐ray and infrared examinations of stereoregular polymers and copolymers of vinylaromatic monomers, the occurrence of chain isomorphism phenomena, together with many cases of a new type of isomorphism between monomeric units, have been proved. Isomorphism of macromolecules, allowing true solid solutions, has been observed when melting and crystallizing mixtures of homopolymers (i.e., isotactic polystyrene) and of crystalline copolymers (i.e., styrene‐p‐methylstyrene) having the same identity period and differing very little in lattice constants. Isomorphism among monomeric units occurs in copolymerizing monomers that have a chemical nature and shape slightly different one from the other, e.g., styrene and o‐fluorostyrene. This allows the formation of crystallizable copolymers in the entire composition range. They show physical properties (lattice constants, melting temperatures, etc.) continuously varying between those of the pure homopolymers. The occurrence of isodimorphism phenomena has been observed in crystalline copolymers obtained from monomers the homopolymers of which have different crystalline structures (e.g., styrene‐p‐fluorostyrene), and also in copolymerizing styrene with monomers (e.g., p‐methyl, p‐chlorostyrene) giving only amorphous homopolymers. In the latter case, of course, the copolymers show crystallinity only in a limited composition range.
The influence of substituents on the properties of crystalline polyhydrocarbons. I. Methyl‐substituted arylpropene and arylbutene polymers
Authors: Price J. A. , Lytton M. R. , Rånby B. G.
Published: April 2003

The new alpha olefins 2‐allyl‐p‐xylene, 4‐allyl‐o‐xylene, 5‐allyl‐m‐xylene, 4‐(o‐tolyl)‐1‐butene and 4‐(p‐tolyl)‐1‐butene were prepared. These olefins, in addition to the known ortho, meta and para allyltoluenes, have polymerized, using aluminum alkyl titanium chloride catalyst, to crystalline polymers. Physical properties of these polymers, both as powder and molded sample, have been studied. Melt temperatures (Tm) and glass transition temperatures (Tg) have been determined using differential thermal analysis, dynamic modulus measurements, and dilatometric measurements; observations on the birefringent melting behavior were also noted. The effects of both olefin chain length and substitution of methyl groups in the ortho, meta, and para position, respectively, on the properties of these polymers have been interpreted according to present concepts. The results are in general agreement with corresponding data for isotactic methyl‐substituted polystyrenes. Substitution in the ortho position raises both transition temperatures considerably, while meta and para substitution cause only smaller effects.
Changes in potential during polymerization in redox systems
Authors: Turska E. , Wisniewski J.
Published: April 2003

The change in potential during emulsion polymerization in a system in which the oxidizing agent is soluble in the disperse phase and the reducing agent in the aqueous phase was studied. The process was also followed by means of an ultraviolet spectrophotometric method. The time‐potential curve was found to be linearly related to the curve depicting the change in monomer concerntration. The experimental data were subjected to mathematical treatment to determine the correlation coefficient and to derive a direct regression equation. In addition, systems containing reducing and oxidizing agents and monomer in a single phase were also studied, and the change in potential during polymerization was determined at various initial monomer concentrations. A relation was established between the results obtained and the polymerization process.
Emulsion polymerization of chloroprene
Authors: Hrabáak F. , Zachoval Ya.
Published: April 2003

The emulsion polymerization of chloroprene was investigated. Determinations were made of the effect of the emulsifier on the polymerization rate in the presence of varying initiators. It has been found that in the case of monomer‐soluble initiators, rosin soap (as compared with mersolate and hydrogenated rosin) has been found to be a strong inhibitor of polymerization. With the objective of ascertaining the optimum conditions of interaction between TETD and the polysulfide bonds of the chloroprene‐sulfur copolymer the rate of rupture of the bonds in relation to the pH of the latex was determined. Polymerization of chloroprene in the presence of various initiator systems of the peroxide‐tertiary amine type was investigated with the use of mersolate as emulsifier. During the course of the polymerization the viscosity of the polymer was determined with the aid of the Vistex method for determining gel formation. On adding 5 wt‐% of carbon tetrachloride in the presence of sodium N,N‐dimethylsulfanilate and benzoyl peroxide, a soluble polymer was obtained, the conversion reaching a value of 100%. Phenyl‐β‐naphthylamine is an inhibitor of peroxide‐induced polymerization but has no inhibiting effect when azobisisobutyronitrile is employed as initiator.
A study of emulsion polymerizations
Authors: Krishan T. , Margaritova M.
Published: April 2003

A kinetic study of the polymerization of methyl methacrylate, vinylidene chloride, and chloroprene in aqueous emulsion has been studied over a wide range of concentrations of emulsifier and initiator. Potassium persulfate, hydrogen peroxide, sodium perborate, benzoyl peroxide, and azobisisobutyronitrile were used as initiators, and the sodium salts of the sulfonic acids of aliphatic hydrocarbons (SA emulsifier) and sodium laurate as emulsifiers. A soap titration method coupled with conductometric titration was employed to determine the number and size of the polymer particles formed at various stages of the polymerization process with respect to the concentration of the substances participating in the latter. The kinetic relations and the data on the particle number and size were discussed from the standpoint of existing views on the mechanism of emulsion polymerization. This led to the conclusion that the principle of discrete particles cannot be applied to polymer particles; i.e., they cannot be considered as microspaces where polymerization takes place independently of each other. The experimental findings indicate that the relations are determined by the overall volume of the emulsifier independently of whether it is in the form of micelles or is on the surface of the polymer particles.