bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis of phosphorus‐containing poly‐o‐acylamideoximes from polyacrylonitrile
Authors: Carraher Charles E. , Wang Long‐Shyong
Published: April 2003

The synthesis of phosphorus‐containing poly‐O‐acylamideoximes from polyacrylonitrile has been accomplished by the reaction sequence:
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Reaction is believed to occur at the NH2 nitrogen as well as at the oxime group, but reaction is not believed to occur at both groups in the amide oxime unit. Inclusion of the phosphorus moiety occurs in the medium to high range.
Preparation and polymerization of N‐(1,1‐dimethyl‐3‐hydroxybutyl) acrylamide and N‐(1,1‐dimethyl‐3‐hydroxybutyl)methacrylamide
Authors: Hoke Donald I.
Published: April 2003

The syntheses of N‐(1,1‐dimethyl‐3‐hydroxybutyl)acrylamide and the corresponding methacrylamide by reduction of the oxobutyl acrylamides are described. These monomers are colorless liquids which are soluble in water and many organic solvents. They polymerize readily to form homopolymers and copolymers with other vinyl monomers. The preparation of polymers containing these repeating units by reduction of polymers of diacetone acrylamide and diacetone methacrylamide is also described.
Snake‐cage redox polyelectrolytes based on anion‐exchange resins
Authors: Kessick M. A.
Published: April 2003

Redox polyelectrolytes are described where the polyphenols hydroquinone, pyrogallol, and catechol were absorbed as counterions by a strong base anion‐exchange resin in the hydroxide form, and then polymerized by refluxing in 1:1 mole ratio with formaldehyde in aqueous solution, thus producing a “snake‐cage” configuration. The redox capacities of the resins were determined by oxidation with iodine/iodide solution, and found to approach theoretical at between 5.1 and 5.4 meq/g. The rate of oxidation was found to be controlled by diffusion within the particles. Fe3+ was unsatisfactory as an oxidant, owing to the exclusion effect by the fixed positive charges in the resin matrix. At low pH the resin beads were light to reddish brown in the reduced form, black in the oxidized form. The resins, especially that based on catechol, showed much greater stability in 1N NaOH solution than simple polyphenol–formaldehyde condensation polymers.
Electroinitiated polymerization of vinylic monomers in polar systems. III. Polymerization of acrylates and methacrylates in alcohol solutions
Authors: Albeck Michael , Relis Joseph
Published: April 2003

Methyl, ethyl, and n‐butyl acrylates and methacrylates are polymerized by electroinitiation in methanol–, ethanol–, and n‐propanol–electrolyte mixtures in which the monomers are soluble whereas the polymers obtained are insoluble. The technique of changing the polarity of the electrodes described earlier was used. The relationships between molecular weights and polymer yields as function of current density, initial monomer concentration and dielectric constant of the solvent are described. A kinetic scheme for the initiation, propagation, and termination is given.
Hydrodimerization in liquid ammonia
Authors: Rosen H. , Levy M.
Published: April 2003

The hydrodimerization of acrylonitrile (M1), ethyl acrylate (M2), and α‐methyl acrylonitrile (M3) in liquid ammonia by Na amalgam was studied. It was found that the concentration of phenol, as protonating agent, affects the rate of electron transfer from the amalgam to the monomer. This was explained by assuming the active species to be the protonated monomer complex MH+. Cross hydrodimerization rate constants were measured for the three monomers. The values of the ratios obtained were: k11/k12 = 0.89, k22/k21 = 0.39, k11/k13 = 5.8, k33/k31 = 0.12, k22/k23 = 1.7, k33/k32 = 0.36.
1,4 polymerization of isoprene by titanate catalyst systems
Authors: Horne Samuel E. , Carman Charles J.
Published: April 2003

Titanates are versatile in the 1,4 polymerization of isoprene. The (R′O)4Ti/RAlCl2 catalyst gives either cis‐ or trans‐1,4‐polyisoprene, depending on the nature of both the titanate and the solvent. Primary titanates give cis‐1,4‐polyisoprene in both aliphatic and aromatic solvents. Secondary titanates give cis‐polyisoprene in aliphatic solvents, and trans‐1,4‐polyisoprene in aromatic solvents. Tertiary titanates give trans‐polyisoprene in both aliphatic and aromatic solvents. A mechanism is postulated which takes into consideration the role of the solvent. ESR studies of the various titanate–RAlCl2 catalysts were made; the paramagnetic structures are related to polymerization mechanisms.
Structure and property relationships in ethylene–vinyl acetate copolymers
Authors: Salyer I. O. , Kenyon A. S.
Published: April 2003

The effects of vinyl acetate content on crystallinity of ethylene–vinyl acetate (E/VA) copolymers were investigated by x‐ray diffraction and differential thermal analysis (DTA). The values of these parameters obtained from DTA were found to agree quantitatively with data calculated from x‐ray, probability equations, and copolymer theory. The melting points of the crystalline copolymers, and the molar amounts of vinyl acetate to produce a completely amorphous rubber corresponds exactly to that predicted by the Flory theory. The random character expected in E/VA copolymers is thereby confirmed. The physical properties of E/VA copolymers of all ranges of compositions and crystallinity were determined. Depending directly upon vinyl acetate content, the copolymers changed progressively from highly crystalline polyethylene to semicrystalline polyethylene, a completely amorphous rubber, a soft plastic with a glass transition near room temperature. Properties which were correlated with copolymer composition include: crystallinity, melting point, density, modulus, tensile strength, glass transition, and solubility. Finally, the effect on crystallinity and physical properties of replacing the acetoxy group in E/VA with the smaller, highly polar hydroxyl group (ethylene—vinyl alcohol copolymer) was also investigated.
Reactions of some organic peroxides with triphenylphosphine and sodium dialkyl phosphites
Authors: Jarvie A. W. P. , Moore C. G. , Skelton D.
Published: April 2003

The reactions of the allylic peroxides ascaridole, cyclohexadiene endoperoxide, and α‐phellandrene peroxide with triphenylphosphine follow an SNi'‐type mechanism. In contrast, the acyclic allylic compounds, allyl tert‐butyl peroxide, α‐cumyl cyclohexenyl peroxide, and tert‐butyl cyclohexenyl peroxide apparently react with triphenylphosphine by a free‐radical mechanism. The saturated cyclic peroxide dihydroascaridole, in which there is no possibility of an allylic rearrangement, gives with triphenylphosphine a mixture of olefinic alcohols. Di‐n‐butyl peroxide is readily cleaved by sodium dialkyl phosphites, but sterically hindered peroxides do not react under similar conditions. Reaction can, however, take place at the oxygen adjacent to a large group if a smaller substituent is present on the other oxygen atom.
Kinetic study of ethylene polymerization with chromium oxide catalysts by a radiotracer technique
Authors: Zakharov V. A. , Ermakov Yu. I.
Published: April 2003

The quenching of polymerization with a chromium oxide catalyst by radioactive methanol 14CH3OH enables one to determine the concentration of propagation centers and then to calculate the rate constant of the propagation. The dependence of the concentration of propagation centers and the polymerization rate on reaction time, ethylene concentration, and temperature was investigated. The change of the concentration of propagation centers with the duration of polymerization was found to be responsible for the time dependence of the overall polymerization rate. The propagation reaction is of first order on ethylene concentration in the pressure range 2–25 kg/cm2. For catalysts of different composition, the temperature dependence of the overall polymerization rate and the propagation rate constant were determined, and the overall activation energy Eov and activation energy of the propagation state Ep were calculated. The difference between Eov and Ep is due to the change of the number of propagation centers with temperature. The variation of catalyst composition and preliminary reduction of the catalyst influence the shape of the temperature dependence of the propagation center concentration and change Eov.
Polysulfone–polydimethylsiloxane block copolymers
Authors: Noshay A. , Matzner M. , Merriam C. N.
Published: April 2003

Alternating block copolymers have been synthesized from dihydroxyl‐terminated polysulfone and bis(dimethylamine)‐terminated polydimethylsiloxane oligomers. The products are soluble, amorphous, and transparent, and display excellent thermal and hydrolytic stability. Elastomeric and rigid compositions can be prepared by varying oligomer molecular weight. Copolymers made with oligomers of ≥ 5000 molecular weight are two‐microphase systems which display glass transition temperatures at −120°C and at +160°C, and therefore have a wide useful temperature range.
Novel aliphatic polymers containing imide ring. I. Polyspiroimide based on methanetetraacetic acid
Authors: Lee Lester T. C. , Pearce Eli M. , Hirsch Stephen S.
Published: April 2003

High molecular weight polyspiroimides have been prepared by reacting diamines with the dianhydride of carboxymethanetetraacetic acid in polar organic solvents. Alternatively, thermal condensation of the preformed salt made from equimolar amounts of diamine and methanetetraacetic acid (MTA) can be used. These all‐aliphatic polyimides are soluble in certain organic solvents, and possess good thermal‐oxidative stability.
Characterization of the collagen–vinyl graft copolymers prepared by the ceric ion method. I. Solution properties
Authors: Rao K. Panduranga , Joseph K. Thomas , Nayudamma Y.
Published: April 2003

Graft copolymerization of vinyl monomers on to collagen was carried out by the ceric ion method. The grafted vinyl polymer chains were isolated by both acid and enzymatic hydrolysis of the collagen backbone in order to characterize the graft copolymers. Proof of grafting was obtained through the detection of amino acid endgroups in the grafts isolated by both the methods. The grafts isolated gave the characteristic blue color normally associated with the presence of amino acids. The presence of amino acid endgroups was further confirmed by dinitrophenylation of the isolated grafts. The absorption spectra of the dinitrophenylated(DNP) grafts showed absorption maximum in the ultraviolet region of 340–360 mμ, characteristic of DNP‐amino acids. Soluble collagen grafted with polyacrylamide(PAA) formed fibrils on heating to 37°C at neutral pH but, unlike the native collagen, these fibrils did not redissolve on cooling at 2°C. These results show that the redispersion property of soluble collagen was impaired, probably by attachment of the PAA side chains to the collagen molecule. The turbidimetric titration behavior of the grafts, their general behavior of swelling in different solvents, and the intrinsic viscosity of the copolymers in mixed solvents also provided additional proof of grafting.
Grafting of methyl methacrylate and its derivatives onto blood
Authors: Kojima Kuniharu , Iwabuchi Susumu , Kojima Koichi , Tarumi Niro , Masuhara Eiichi
Published: April 2003

The grafting of vinyl monomers by tri‐n‐butylborane to blood has been investigated. The infrared spectra indicated that the monomers were grafted onto blood components. The grafting seems to occur onto blood proteins, mainly onto hemoglobin. The presence of water was essential to the grafting. The hydrolysis of the graft suggests that basic amino acids in the blood proteins, such as lysine and histidine, play an important role in the grafting.
Crosslinking and structural changes of cellulose fibers
Authors: Nikonovich G. V. , Usmanov Kh. U.
Published: April 2003

The supermolecular structure of various cellulose fibers modified with crosslinking reagents has been investigated by electron microscopy methods. The density, degree of crystallinity (DC), and length changes in alkaline solutions were measured for the modified celluloses. The samples treated with monofunctional analogs of the crosslinking reagents as well as the fiber preparations containing linear and network polymer were also investigated. Three main problems are suggested for the discussion: (1) the general regularities of the structural changes in cellulose in the process of crosslinking; (2) the specific features of the structural changes, as observed in different cellulose samples; (3) the relation between the degree of modification, the type of modifying reagent, and the structure of the crosslinked cellulose. The characteristic structural changes, i.e., the increase in the thickness of fragments, the specific cogged edges, the increase in the lateral dimensions of structural elements all seem to be most representative in native cellulose fibers and are perfectly well distinguished. Similar changes are found in viscose fibers but are less clearly defined. Crosslinking proceeds rather uniformly through the whole of the fiber cross section. It appeared to be most evident when the cross sections are treated with solvents, or when etched in gaseous discharge. Only in cases when the modification is performed in nonaqueous solutions does the reaction proceed mainly in the peripherial regions of the fiber. In fibers subjected to strong swelling, crosslinking results in a real increase in the lateral dimensions of the microfibrils, with the layer thicknesses remaining the same. As a rule, the modification does not imply significant changes in the fiber surface. The crystallite size decreases in the process of crosslinking. This appears to be peculiar to viscose fibers, especially to those subjected to crosslinking in the swollen state. The degree of crystallinity and density of the fibers decrease sharply, which seems to be especially evident in epichlorohydrin‐modified samples. Cellulose structure remains unchanged when linear or network polymer forms in the fiber or when the samples are treated with monofunctional reagents. Changes in properties and structure of cellulose caused by crosslinking are most apparent if elongation of the fibers in alkaline solution before and after the modification is compared.
Quantitative treatment of the dye partition method of analysis of surfactants and of ionic groups in high polymers
Authors: Mandal B. M. , Palit S. R.
Published: April 2003

A quantitative treatment of the extraction of ionic dyes from aqueous solutions into organic solvents of low dielectric constant by surfactants or polymers with ionic groups having a charge opposite to that of the dye ion, is presented. The assumption is made that the extracted species are ion‐paired in the organic phase. Based on this, a graphical extrapolation method is suggested for the quantitative estimation of ionic groups in polymers. Theoretically, the method should yield quantitative results irrespective of polymer chain length and character. This method of analysis does not require any calibration data.
Mechanism of propagation and degenerate chain branching in the oxidation of polypropylene and polyethylene
Authors: Zolotova N. V. , Denisov E. T.
Published: April 2003

Samples of polypropylene with adjacent and isolated hydroperoxide groups have been prepared. The rate constants of free‐radical formation from solid hydroperoxides were measured by the inhibitor method. It was found that the free radicals yielded by adjacent hydroperoxide groups are formed more rapidly. The main reaction of free‐radical formation in oxidized polypropylene is of the type: ROOH + ROOH → RO + H2O + RO2˙. The average yield of free radicals from polypropylene hydroperoxide is 2–4%. Oxygen has no effect on the yield of free radicals. However, the pressure of oxygen Po2 affects the rate of degenerate chain branching in polypropylene. The number of adjacent hydroperoxide groups and the rate of initiation increase with Po2. Consequently, a reaction of the type, R˙, + RH → RH + R˙, plays an important part in transport of free valence through solid polymer. This reaction is very fast in polyethylene, and no adjacent hydroperoxide groups are formed. The free radicals from polyethylene hydroperoxide are found to form by a reaction of the type: ROOH → RO˙ + HO˙.
Low‐temperature polyesterification in the presence of tertiary amines
Authors: Vinogradova S. V. , Vasnyev V. A. , Mitaishvili T. I. , Vasil'yev A. V.
Published: April 2003

Several variations of catalysis (nucleophilic and general basic) responsible for the lowtemperature polyesterification in solution have been investigated. The type of catalysis which predominates depends on the chemical structure of the initial reagents and the reaction conditions. Increasing basicity of the tertiary amine and increasing acidity of the bisphenol promote the general base catalysis.
Side‐chain crystallinity. III. Influence of side‐chain crystallinity on the glass transition temperatures of selected copolymers incorporating n‐octadecyl acrylate or vinyl stearate
Authors: Jordan Edmund F.
Published: April 2003

The influence of side‐chain crystallinity on the glass transition temperatures of selected copolymers was investigated. The copolymers were selected, in part, from those whose crystallinity was treated in the preceding paper. These included the lower amorphous acrylate esters, such as methyl, ethyl, n‐butyl, and 2‐ethylhexyl acrylates, together with methyl methacrylate and acrylonitrile, each copolymerized with n‐octadecyl acrylate over the range of composition. The decline in the glass transition temperature was linear with increasing weight fraction of n‐octadecyl acrylate for all systems in the composition range where the copolymers were essentially amorphous. The extrapolated Tg for the amorphous state of poly(n‐octadecyl acrylate), and for amorphous poly(oleyl acrylate), was close to −111°C. This coincided with a value previously obtained by an extrapolation of data on homologs. Beyond a critical fraction of octadecyl acrylate (0.3 to 0.5), developing side‐chain crystallinity in n‐octadecyl acrylate raised the glass temperature steadily for all systems, up to a value of 17‐C, obtained for the crystalline homopolymer. Crystallinity did not develop in stiff copolymers until Tg was about 30°C below the melting point of the most perfect crystals. In compositionally heterogeneous copolymers incorporating vinyl stearate, blocks of crystalline units appeared to be dispersed in a glassy matrix of amorphous co‐units. An empirical equation was derived which fitted the experimental data for random copolymers, over all composition ranges, with fair accuracy.
Analysis of polymerization rates in radical polymerization with primary radical termination of some methacrylates
Authors: Ito Katsukiyo
Published: April 2003

Polymerization rates in polymerizations with primary radical termination of ethyl methacrylate, β‐phenylethyl methacrylate, β‐methoxyethyl methacrylate, and phenyl methacrylate initiated by 2,2'‐azobis‐(2,4‐dimethylvaleronitrile) at 60°C were analyzed by using a simple linear equation. The values obtained of kti/kikp (where kti is the primary radical termination rate constant, ki is the rate constant of addition on to monomer of primary radical, and kp is the propagation rate constant) on these analyses are discussed on the theoretical base.
Stereospecific polymerization of butadiene in the presence of isobutylene
Authors: Veruović Budimír
Published: April 2003

The polymerization of isobutylene–butadiene monomer mixtures by a cobalt‐containing catalytic system (cobaltous acetylacetonate–diethylaluminum chloride–water) yields a homopolymer mixture consisting of polyisobutylene and polybutadiene. It is assumed that the polymerization of both monomers proceeds according essentially identical reaction mechanisms, i.e., isobutylene polymerizes cationically and butadiene follows a coordination‐cationic mechanism.
Anionic bulk polymerization of α‐methylstyrene. Stopping of polymerization due to vitrification and equilibrium in bulk
Authors: Mita Itaru , Okuyama Hiroshi
Published: April 2003

Anionic living polymerization of α‐methylstyrene containing a small amount of THF (less than 10%) was studied at temperatures between −30°C and 50°C. At any temperature studied, a certain quantity of monomer remained without further polymerization. The effect of temperature and THF content on the final state was completely different in low and high temperature regions; at temperatures lower than ca. 20°C, the final monomer concentration decreased with increasing polymerization temperature and THF content. This is explained by the concept of “stopping of polymerization due to vitrification” of the polymerizing mixture. In fact, the final reaction mixture is really glassy in most cases and the red color of living polymer buried in the glass is discolored only very slowly when exposed to air. Detailed analysis of the results showed that the vitrification stopping holds only approximately. At temperatures higher than ca. 30°C, a normal equilibrium between propagation and depropagation holds, and the final monomer concentration increased with temperature. It is, however, far less than the equilibrium monomer concentration obtained in solution polymerization at the same temperature, and it increased appreciably with the increase in THF content. It is shown that the behavior of the equilibrium for the whole concentration range can be explained satisfactorily by a thermodynamic theory of ternary mixture.
Aminimides. XII. Synthesis, homo‐ and copolymerization studies of trialkylamine N‐acryloyl or N‐methacryloyl glycinimides and β‐aminopropanimides
Authors: Culbertson B. M. , Freis R. E. , Grote D.
Published: April 2003

Some representative examples of a new family of aminimide monomers, i.e., trialkylamine N‐acryloyl or N‐methacryloyl glycinimides and β‐aminopropanimides have been prepared and studied. These are the first examples of a possible large family of primary aminimide monomers. With radical initiators, the acryloyl and monosubstituted methacryloyl monomers readily homopolymerize. The disubstituted methacryloyl aminimides do not homopolymerize under the same conditions. All of the new monomers copolymerize with styrene, methyl methacrylate, and n‐butyl acrylate. The various polymers were characterized by IR, DTA, TGA, GPC and inherent viscosities. When heated (160°C) the polymers liberate amine and crosslink in the presence of active hydrogen moieties to give resins with carbamate, urea, allophonate, etc., residues. When no active hydrogens are available during heating, polymers can be prepared with pendent primary isocyanate groups. This preliminary work shows these monomers to be highly useful for preparing a wide variety of reactive copolymers.
Thermodynamic properties of epoxy reaction systems
Authors: Aleman J. V.
Published: April 2003

Enthalpy, entropy, and Gibbs free energy of epichlorhydrin, bisphenol A, and epoxy resins from specific heat data obtained experimentally in a DuPont 900 differential thermal analyzer are described. The epoxy resin used has a second‐order transition temperature around −15°C and a chain rigidity of 50.6 cal/g.
60Co‐initiated copolymerization of styrene with vinyl acetate
Authors: Niezette Joseph , Desreux Victor
Published: April 2003

The kinetic behavior of the 60Co‐initiated copolymerization at 25°C of styrene with vinyl acetate at 1100 and 2000 rad/hr was studied. As in the case of thermal and photochemical copolymerizations of these monomers, the growing chains are particularly rich in styrene units, and the overall rate is affected by a diluent effect due to the vinyl acetate monomer. However, in the case of the radiation copolymerization, this effect is partially counterbalanced by an increase of the initiation rate with the vinyl acetate concentration; the polymerization rate curve shows a maximum at a vinyl acetate molar fraction of 0.25. This effect is due to the very different free radical yields of these two monomers. The experimental results may be understood on the basis of a kinetic scheme which involves an energy transfer process from the excited vinyl acetate molecules to the styrene monomer and a termination reaction of the growing chains by very short styrene radicals when the mixture is rich in vinyl acetate.
Polymerization of vinyl chloride by the Ti(O‐n‐Bu)4–AlEt3–epichlorohydrin catalyst system
Authors: Suzuki Yuji , Saito Mitsutaka
Published: April 2003

The polymerization of vinyl chloride was carried out by using a catalyst system consisting of Ti(O‐n‐Bu)4, AlEt3, and epichlorohydrin. The polymerization rate and the reduced viscosity of polymer were influenced by the polymerization temperature, AlEt3/Ti(O‐n‐Bu)4 molar ratios, and epichlorohydrin/Ti(O‐n‐Bu)4 molar ratios. The reduced viscosity of polymer obtained in the virtual absence of n‐heptane as solvent was two to three times as high as that of polymer obtained in the presence of n‐heptane. The crystallinity of poly(vinyl chloride) thus obtained was similar to that of poly(vinyl chloride) produced by a radical catalyst. It was concluded that the polymerization of vinyl chloride by the present catalyst system obeys a radical mechanism rather than a coordinated anionic mechanism.
Studies on formaldehyde condensation resins. XII. Gelation theory for tetrafunctional amino resins
Authors: Uragami Tadashi , Oiwa Masayoshi
Published: April 2003

General kinetic equations for the gelation reaction of tetrafunctional amino monomer with formaldehyde are formulated according to Case's gelation theory. The ratio of the rate constant of the condensation reaction to that of the addition reaction is evaluated by applying a theoretical kinetic equation to the experimental measurements. The ratio of the rate constant for addition of an imino group to that for an amino group is also determined by combining the kinetic equation, stoichiometric relation, and expression for the gel point. The total yield of resin, the yield of sol, and the number‐average molecular weight of the sol fraction are discussed.
Studies on formaldehyde condensation resins. XIII. Gelation of acetoguanamine–formaldehyde resin
Authors: Uragami Tadashi , Oiwa Masayoshi
Published: April 2003

The gelation reaction of acetoguanamine with formaldehyde was investigated in the light of the gelation theory for tetrafunctional amino resins described in the previous paper. The gel time and extents of reaction of formaldehyde, amino groups, and imino groups varied with the molar ratio in the feed, but values of K (the ratio of the rate constant for condensation to that for addition) and k (the ratio of the rate constant for addition of the imino group to that of the amino group) were nearly constant. When the catalyst concentration was increased, the gel time, extents of reaction of each functional group, and the values of K and k varied; in particular K increased markedly. From the results of varying the molar ratio and concentration of acidic catalyst, it was found that the number of methylol groups per molecule of acetoguanamine at the gel point was influenced by the reaction conditions but the number of methylene linkages per molecular of acetoguanamine was nearly constant at about 0.6, regardless of reaction conditions. The number‐average molecular weights up to the gel point varied with the reaction conditions, but at the gel point they were all nearly constant at about 385.
Lamellar and interlamellar structure in melt‐crystallized polyethylene. II. Lamellar spacing, interlamellar thickness, interlamellar density, and stacking disorder
Authors: Kavesh S. , Schultz J. M.
Published: April 2003

Measurements of the small‐angle scattering power and the degree of crystallinity in melt‐crystallized high‐density polyethylene have been used to evaluate the “amorphous” density in situ by the relation,

where V is the irradiated volume and ḡ(S) is the “slit‐smeared” absolute intensity. The amorphous density is a function of sample history and is always higher than the extrapolated melt density. After slit‐height correction, and within the experimental error, the ratio of the two observed long periods is 2:1 at all temperatures (25‐‐126°C). The lamellar thickness and the average interlamellar spacing are obtained from the degree of crystallinity and the first corrected long period. At increasing temperatures between 25°C and 110°C, the lamellae become thinner while the interlamellar zone expands by almost half. Over this range the changes are reversible with temperature. Above 110°C, both the lamellae and the interlamellar region expand with temperature. The thickening is partially reversible upon recooling. Other results obtained include measurements of stacking disorder and of microstructural changes with crystallization temperature and with time at ambient temperature.
Structure and optical activity of a crystalline modification of isotactic poly‐(S)‐4‐methyl‐1‐hexene
Authors: Bassi I. W. , Bonsignori O. , Lorenzi G. P. , Pino P. , Corradini P. , Temussi P. A.
Published: April 2003

The results of an x‐ray and polarimetric study of a crystalline modification (form I) of isotactic poly‐(S)‐4‐methyl‐1‐hexene are reported and discussed. The x‐ray fiber spectra of this polymer are practically indistinguishable from those of isotactic poly‐(R)‐(S)‐4‐methyl‐1‐hexene. Although the crystal structure of the latter can be described on the basis of helices of different screw sense packed in a P4 space group, the crystal structure of poly‐(S)‐4‐methyl‐1‐hexene is better described on the basis of a P1 space group. The conclusion of the x‐ray investigation, that in the crystals of the optically active polymer an equal number of right‐handed and left‐handed helices must be present, is supported by the polarimetric measurements, which have shown that the polymer in the crystalline form I possesses a rather low rotatory power.
Side‐chain relaxation in stereoregular poly(isobutyl methacrylate)
Authors: Ochiai Hiroshi , Shindo Heisaburo , Yamamura Hitoshi
Published: April 2003

The effects of stereoregularity on the low‐temperature relaxation processes were studied by dynamic mechanical measurements on isotactic and syndiotactic polyisobutyl methacrylates (iso‐PiBMA and syn‐PiBMA). The α, β, and γ relaxation processes were observed in both stereoregular forms. Both the α, and β loss peaks were at lower temperatures for iso‐PiBMA than for syn‐PiBMA. The γ loss peak was observed at about −155°C at 30 Hz for both forms, and the apparent activation energy of this process was same for both samples within experimental error (6.7 ± 0.5 kcal/mole). It was reduced from these results that the α and β processes are both considerably influenced by the isotactic configuration but the γ process is not.
Occurrence of rippling during the deformation of oriented polyethylene
Authors: Robertson Richard E.
Published: April 2003

Rippling is another mode, in addition to kink‐band formation, by which oriented polyethylene can deform and results in a profuse and irregular waviness in the fibrils. For the medium‐density and high‐density polyethylenes investigated, rippling tended to occur only at strain rates below about 1 min−1 at 25°C. Above this rate, kink bands tended to form. It is suggested that rippling results from easy slip between the fibrils of the oriented polymers and from the resistance of the fibrils to shortening under a compressive stress. The applied shear stress is reduced by the easy slip to a simple compression along the fibrils, and this distorts the fibril into the series of waves that constitutes rippling. Stress–strain measurements confirm that fibril slip is considerably easier under the rates at which rippling occurs than at the rates at which kink bands form.
Effect of pressure in capillary flow of polystyrene
Authors: Penwell Richard C. , Porter Roger S.
Published: April 2003

Several corrections possibly required for capillary flow are based on the existence of a linear relationship between the pressure drop along the capillary and the length‐to‐diameter ratio at a given temperature and shear rate. Recently, the appearance of nonlinearities in this relationship has created some concern as to the cause of this behavior. The occurrence and an explanation of the nonlinearities for polystyrene form the basis of this study. A narrow‐distribution, low molecular weight (20,400) polystyrene was tested in eight capillaries at temperatures of 140 and 160°C to initiate the discussion of the nonlinearity in a ΔP (pressure) versus L/D (length/diameter of capillary) plot. The sample exhibits negligible extrudate swelling at all pressures which reinforces the idea that pressure is influencing the flow. The pressure dependence of viscosity is determined using the equivalent expression of the WLF equation derived from free volume theory. Justification for its use is presented. A pressure correction, representing the increased shear stress necessary for flow of the higher viscosity material, is found to linearize the ΔP versus L/D data. A narrow‐distribution, high molecular weight polystyrene (670,000) is subjected to a similar analysis at 165°C by using nine capillaries. The situation is quite different, as the high molecular weight sample is not nearly as ideal as the low molecular weight polystyrene.
Dielectric and rheo‐optical properties of some ethylene‐carbon monoxide copolymers
Authors: Phillips P. J. , Wilkes G. L. , Delf B. W. , Stein R. S.
Published: April 2003

Studies were made on films of copolymers of ethylene with 0.5 and 1.0 mole‐% carbon monoxide. The carbon monoxide appeared negligibly to affect the degree of crystallinity, melting point, morphology, and dynamic mechanical spectra. Infrared dichroism showed that the orientation of the carbonyl groups was comparable with that of the crystalline CH2 groups and indicated that the carbonyl groups are at least partially within the crystals. This is confirmed by x‐ray measurements which indicate an expansion of the a‐axis spacing and by an appreciable increase in the height of the α dielectric loss peak which has been assigned to crystalline motion. This α loss peak moves to a lower temperature with increasing carbonyl content, while the γ dielectric loss peak moves to higher temperatures. Activation energies of 25, 35, and 15 kcal/mole for the α, β, and γ peaks, respectively, were independent of carbonyl content and comparable with values for oxidized polyethylene.
Segmental motion in polyoxymethylene
Authors: Crist B. , Peterlin A.
Published: April 2003

The proton spin‐lattice relaxation times (T1) of melt‐crystallized, solution‐crystallized, and solid‐state‐polymerized polyoxymethylene (POM) were measured between −60 and +150°C. The three types of samples each have a pronounced T1 minimum near room temperature which is a high‐frequency manifestation of the γ process. From the quantitative dependence of the relaxation intensity on crystallinity as well as from the absolute magnitude of the relaxation times, it is concluded that the γ process in POM arises from hindered rotation of noncrystalline chain segments. The relation between the relaxation times and the long period indicates that these noncrystalline segments constitute disordered lamellar surface layers, the thickness of which depends on thermal history of the material. The temperature dependence of the motion of the relatively thin surface layers of solution crystallized POM is quite straightforward. The γ process in the bulk‐crystallized material involves cooperative motion, however, leading to temperature‐dependent kinetic parameters.
Size‐distribution analysis of polymer latex systems by use of the extrema in the angular light‐scattering pattern: II. The polarization ratio
Authors: Wallace Thomas P.
Published: April 2003

Previously, the angular positions of the extrema of the polarization ratio have been utilized in light‐scattering studies as a method of particle‐size analysis under the assumption of monodisperse, spherical particles. Since the consequences of the existing finite polydispersity on this method of analysis was not assessed, the results are questionable. This work is concerned with (1) reporting the quantitative effects of a finite polydispersity on the method of analysis, (2) pointing out previous misuse of the method, and (3) revising the method of analysis to include polydispersity and the exact Mie calculations. The method will then permit the characterization of a scattering system in terms of a modal diameter and a distribution‐width parameter by utilizing prepared diagrams for a particular relative refractive index.
Polymerization mechanisms and stereosequence distributions: A monomer–dimer model
Authors: Pyun Chong Wha , Fox Thomas G
Published: April 2003

A polymerization mechanism in which monomers and dimers add to a growing polymer chain with different rate constants and different stereospecificity is considered. A fraction of the dimers are in isotactic placement internally, and low conversion to polymer is assumed. The stereosequence distribution generated by this monomer–dimer model is calculated and found to be non‐Markovian in general. A method of determining kinetic parameters of the mechanism from experimentally obtained placement sequence probabilities and related experimental tests for the applicability of the mechanism are also described. A few ramifications of the general monomer–dimer model are then discussed. A case of special interest is the one in which all the dimers have a single internal tacticity, a model recently proposed by Blumstein, et al., for a polymerization involving the surface of certain aluminosilicate minerals. For the case where all dimers are isotactic, it is found that although the propagation of consecutive syndiotactic placements alone is simple Markovian, the overall stereosequence distribution is non‐Markovian. Another special case of interest is the limiting case with dimers only in the feed. This case turns out to correspond to a special case of the cyclopolymerization mechanism proposed previously by Reinmöller and Fox. Although the tacticity distribution of the placements created by the head (or tail) monomer units alone of the dimers is Bernoullian, the composite stereosequence distribution is again non‐Markovian.
Dynamic mechanical and dielectric relaxations of polystyrene below the glass temperature
Authors: Yano Okimichi , Wada Yasaku
Published: April 2003

Dynamic mechanical and dielectric properties of various kinds of polystyrene, including bulk‐polymerized, monodisperse, isotactic, and thermally degraded samples, have been measured below the glass temperature to 4°K. Five relaxation processes are found, designated β, γ, γ′, δ, and ε in order of descending temperature. The β peak (350°K at 10 kHz) is attributed to the local oscillation mode of backbone chains and the γ′ peak (180°K at 10 kHz) to rotation of phenyl groups. The δ peak (100°K at 10 kHz) is observed only in dielectric properties of the bulk‐polymerized sample and is assigned to weak polar bonds, such as oxygen bonds in the chain. The δ peak (55°K at 10 kHz) which is prominent in dynamic mechanical properties is interpreted in terms of lattice defects due to a syndiotactic diad inserted between isotactic sequences in a chain or vice versa. The ε peak (ca. 25°K at 10 kHz) is first reported in the present work, but the mechanism involved is not yet clear.
Investigation of cooperative kinetics on reactions of functional groups on polymer chains
Authors: Goldstein B. N. , Goryunov A. N. , Gotlib Yu. Ya. , Elyashevich A. M. , Zubova T. P. , Koltzov A. I. , Nemirovskii V. D. , Skorokhodov S. S.
Published: April 2003

The kinetics of aminolysis of 1,2;3,4‐meso‐erythritol dicarbonate and 1,2;3,4;5,6‐mannitol, sorbitol, and dulcitol tricarbonates by n‐butylamine in dimethylformamide solution was investigated. The dicarbonate and tricarbonates are considered respectively as models of dyads and triads in the poly(vinylene carbonate) chain. The theoretical kinetic curves for the dimer and the trimers were calculated by solution of kinetic equations and close agreement with experiment was obtained. A version of the Monte‐Carlo method was developed to provide a model for the reaction process by a computer calculation including the neighboring group effect in enhancing reactivity. The theoretical curve for a trimer coincides with the experimental one. These results confirm the accelerating influence of the unreacted neighboring groups. For the polymeric chain the experimental and calculated curves deviate for conversions beyond 10%. This indicates an additional polymer effect, which is as yet unexplained.
Fractionation during crystallization
Authors: Sadler D. M.
Published: April 2003

Extensive gel‐permeation chromatography (GPC) results are presented which reveal in much more detail than hitherto the effects of fractionation during the crystallization of polyethylene from solution. It is suggested how these results may be used to assess the affects of fractionation on the production of single crystals. In addition the results are compared with the fractionation which would be expected assuming the crystals to be in equilibrium with the solution. It was found that the results can be explained very well on this basis. A discussion of this rather unexpected result is included.
Formation of spherulites in polyamides. V. “odd‐odd” polyamides
Authors: Magill J. H.
Published: April 2003

The crystallization of a series of “odd‐odd” polyamides has been examined for a variety of fusion conditions and crystallization temperatures. Diverse kinds of spherulites and other crystalline structures have been formed in these nylon polymers by direct crystallization from the melt and by melt‐seeding techniques. The structures formed in this way have been characterized primarily with the aid of optical microscopy. In this series of polymers, characteristic textural features yield a fairly unified pattern of crystallization behavior. Crystalline aggregates are formed near the respective melting points of these polymers. In very thin sections (ca. 0.1μ), plateletlike crystals of high crystallinity exhibit optical and diffraction behavior characteristic of single crystals.
Adsorption of polymers at the solution–solid interface. V. Styrene–methyl methacrylate copolymers on carbon
Authors: Hopkins A. , Howard G. J.
Published: April 2003

The adsorption of a series of block and random styrene–methyl methacrylate copolymers on an animal charcoal and on Graphon has been studied. On charcoal, adsorption decreases with increase of molecular weight because of the inability of larger coils to penetrate into the adsorbent. An analysis is presented which requires that coils undergo considerable distortion on adsorption in pores. The adsorption of random copolymers on Graphon is also in reverse order of molecular weight; this effect may be due to particle bridging leading to the formation of interparticle “pores.” The relative affinity of the styrene and methyl methacrylate residues is different on charcoal and Graphon, respectively; on both surfaces, however, relatively few of the more active residues are required for adsorption. Block and random copolymers are adsorbed to different extents which depend on the nature of the adsorbent surface.
Adsorption kinetics in the polyethylenimine–cellulose fiber system
Authors: Kindler William A. , Swanson John W.
Published: April 2003

The rate of adsorption of fractionated polyethylenimine (PEI) from water onto regenerated cellulose fibers was studied as a function of the polymer diffusion coefficient. Differences in polymer molecular weight, salt concentration, and pH were employed to vary the diffusion coefficient which was measured independently by a free‐diffusion technique. The sorption rate was measured at the same conditions and found to increase with decreasing molecular weight, increasing polymer concentration, decreasing salt concentration, and increasing pH. A simplified rate equation based on diffusion control with Langmuirian adsorption in stirred solution was developed by utilizing the concept of a Nernst diffusional film. The equation was successful in predicting the relationship between adsorption rate and diffusion coefficient for most cases studied. It was found, however, that a very large barrier to mass transfer retards the adsorption rate. For the system studied it was concluded that this barrier is a result of diffusion into and subsequent adsorption onto the internal porous structure of the cellulose.
Electron microscopy of drawn polypropylene
Authors: Sakaoku K. , Peterlin A.
Published: April 2003

Extremely thin polypropylene films formed by evaporation of dilute solutions floating on water, thin films deposited on Mylar or on carbon‐coated Mylar, and bulk samples were deformed; after etching with aqua regia or chromic acid, the surfaces were studied by electron microscopy of surface replicas. At small draw ratio, microfibrils with lateral dimensions of about 200 Å, originating in micronecks at crack boundaries of the original crystal lamellae, were obtained in isolated areas exhibiting maximum local strain separated by large regions of much less deformed material. With increasing draw ratio the necked regions grow, the old structure gradually being reduced to smaller and smaller islands until it disappears completely. The inhomogeneity of strain in adjacent bundles of microfibrils creates a great many longitudinal voids with more or less disoriented microfibrils bridging the gaps. The regular arrangement of crystalline blocks of rather uniform length and width can be occasionally seen on surface replicas of drawn samples, and much better on dark‐field electron micrographs of drawn and annealed thin membranes. In the latter case the blocks are very uniform and have similar dimensions along and perpendicular to the axis of the microfibril. The evidence from the electron micrographs, together with previous small‐angle x‐ray scattering data, supports Peterlin's molecular model for plastic deformation of crystalline polymers.
Molecular morphology of cellulose
Authors: St. John Manley R.
Published: April 2003

Native celluloses of various biological origins, as well as regenerated celluloses were examined by electron microscopy after suitable dispersion. In all cases the specimens were found to be composed of a common filamentary unit which is rectangular in cross section and has the approximate dimensions 35 × 20 Å. It is suggested that these are the basic morphological units of cellulose; they are therefore called protofibrils. For protofibrils of regenerated cellulose it is shown that: (1) the molecular contour length greatly exceeds the protofibril length, (2) the mass of the protofibril corresponds to that of a single molecule, and (3) the protofibril length increases with molecular weight. Additionally, high resolution electron micrographs of native and regenerated protofibrils show an apparent axial texture with a periodicity of about 40 Å. From these observations and the knowledge that the molecular chain axis is aligned parallel to the protofibril axis, a model of the protofibril is deduced. The model consists of a ribbon which is pleated on itself so as to form a planar zigzag structure of rectangular cross section. This supersedes a previously proposed model of circular cross section. The structure is composed of a single folded, chain, arranged so that the short extended segments between the folds are parallel to the protofibril axis. The protofibril is thus regarded as the morphological expression of the cellulose molecule. Microfibrils and protofibrils often exhibit kinks, the angle between the kinked portions being 120°. This phenomenon is satisfactorily explained by the protofibril model and in fact provides good support for it. Finally, various properties of cellulose are considered in relation to the model. By contrast with the earlier crystalline–amorphous concepts of cellulose fine structure, it is suggested that protofibrils are completely crystalline structures, and that the properties of cellulose may be understood by considering processes that occur at the level of the protofibril as a unit.