bluuebunny/crossref_metadata_2025 huggingface dataset:
Polyamides from trans‐4‐octen‐1,8‐dioic and trans‐2‐trans‐6‐octadien‐1,8‐dioic acids
Authors: Lanzetta N. , Maglio G. , Marchetta C. , Palumbo R.
Published: April 2003

Novel polyamides from trans‐4‐octen‐1,8‐dioic acid (4‐OD) and trans‐2‐trans‐6‐octadien‐1,8‐dioic acid (2,6‐ODD) ad linear aliphatic diamines or piperazine were prepared in good yields by low‐temperature polycondensation. The polymers obtained were investigated by infrared spectroscopy, x‐ray diffraction, and differential scanning calorimetry. Polyamides from 4‐OD show high molecular weights and crystallinities and Tm above 500°K, whereas those from 2,6‐ODD are very weakly crystalline and decompose without melting in nitrogen at temperatures higher than 550°K. DSC studies revealed in the case of 4‐OD polymers with odd diamines, a multiple peak phenomenon in the melting region, strongly dependent from the heating rate. Some hypotheses consistent with this behavior are briefly discussed, and it is concluded that the phenomenon arises from melt recrystallization occurring during the DSC scan.
Radiation‐induced polymerization of glass‐forming systems. IV. Effect of the homogeneity of polymerization phase and polymer concentration on temperature dependence of initial polymerization rate
Authors: Kaetsu Isao , Ito Akihiko , Hayashi Koichiro
Published: April 2003

The effect of homogeneity of polymerization phase and monomer concentration on the temperature dependence of initial polymerization rate was studied in the radiation‐induced radical polymerization of binary systems consisting of glass‐forming monomer and solvent. In the polymerization of a completely homogeneous system such as HEMA–propylene glycol, a maximum and a minimum in polymerization rates as a function of temperature, characteristic of the polymerization in glass‐forming systems, were observed for all monomer concentrations. However, in the heterogeneous polymerization systems such as HEMA–triacetin and HEMA–isoamyl acetate, maximum and minimum rates were observed in monomer‐rich compositions but not at low monomer concentrations. Furthermore, in the HEMA–dioctyl phthalate polymerization system, which is extremely heterogeneous, no maximum and minimum rates were observed at any monomer concentration. The effect of conversion on the temperature dependence of polymerization rate in homogeneous bulk polymerization of HEMA and GMA was investigated. Maximum and minimum rates were observed clearly in conversions less than 10% in the case of HEMA and less than 50% in the case of GMA, but the maximum and minimum changed to a mere inflection in the curve at higher conversions. A similar effect of polymer concentration on the temperature dependence of polymerization rate in the GMA–poly(methyl methacrylate) system were also observed. It is deduced that the change in temperature dependence of polymerization rate is attributed to the decrease in contribution of mutual termination reaction of growing chain radicals to the polymerization rate.
Copolymerization of 1,6‐anhydroglucose and 1,6‐anhydromaltose derivatives
Authors: Lindenberger William H. , Schuerch Conrad
Published: April 2003

The copolymerization of 1,6‐anhydro‐2,3,4‐tri‐O‐(p‐methyl‐benzyl)‐β‐D‐glucopyrnose [TXGL, M1] with 1,6‐anhydro‐2,3‐di‐O‐benzyl‐4‐O‐(2,3,4,6‐tetra‐O‐benzyl‐α‐D‐glucopyranosyl)‐β‐D‐glucopyranose [HBMA, M2] has been studied as a method of producing dextrans of controlled composition with a linear backbone and randomly distributed single glucose units as side chains. Copolymers of intrinsic viscosities ranging from 0.51 to 0.05 dl/g are produced. The copolymerization appears to follow classical copolymerization theory but is affected adversely by the low reactivity of the maltose derivative. Reactivity ratios have been calculated for runs catalyzed by 10 mole‐% and 20 mole‐% phosphorus pentafluoride (PF5): r1 = 1.91 ± 0.35, r2 = 0.28 ± 0.25 and r1 = 2.21 ± 0.15, r2 = 0.21 ± 0.10, respectively.
Cationic copolymerization of 2‐vinyl‐1,3‐dioxane with styrene and 1,3‐dioxolane
Authors: Okada Masahiko , Uno Masaaki , Sumitomo Hiroshi
Published: April 2003

Copolymerization of 2‐vinyl‐1,3‐dioxane with styrene and 1,3‐dioxolane was carried out in methylene chloride at 0°C with triethyloxonium tetrafluoroborate as an initiator. Random copolymers were obtained from both of these monomer pairs, but attempted copolymerization of 2‐vinyl‐1,3‐dioxane with 3,3‐bis(chloromethyl)oxetane under similar conditions resulted in the homopolymer of the latter monomer. There were three structural units of 2‐vinyl‐1,3‐dioxane in these copolymers as in its homopolymer: the “ester” unit, which was formed by vinyl addition with hydride shift followed by ring‐opening rearrangement, the “vinyl” unit produced by ring‐opening reaction, and the unit with a pendant 1,3‐dioxane ring formed by simple vinyl addition. The fractions of the ester and vinyl units to the total 2‐vinyl‐1,3‐dioxane units in the copolymer of 2‐vinyl‐1,3‐dioxane with styrene decreased with decreasing 2‐vinyl‐1,3‐dioxane content. On the contrary, the fraction of the vinyl unit in the copolymer of 2‐vinyl‐1,3‐dioxane with 1,3‐dioxolane increased slightly with decreasing 2‐vinyl‐1,3‐dioxane content, while that of the ester unit decreased. The reactivities of the propagating species are discussed on the basis of these results.
Anionic copolymerization of isocyanates with ketenes
Authors: Dyer Elizabeth , Sincich Eugene
Published: April 2003

Diphenyl‐, phenylethyl, and phenylmethylketene have been copolymerized with phenyl isocyanate by use of sodium naphthalene in dimethylformamide (DMF) at −45°C. Reactivity ratios of phenyl isocyanate (r2) with diphenylketene (r1) were r1 = 0.10, r2 = 0.29; with phenylethylketene (r1) were r1 = 1.6, r2 = 0.10; and with phenyl methyl ketene (r1) were r1 = 4.8, r2 = 0.02. The same initiator and solvent system were used for homopolymerization of phenylethylketene and copolymerization with m‐chloro‐, p‐chloro‐, p‐methoxy‐, and m‐methoxyphenyl isocyanate as well as with phenyl isocyanate. Molecular weights ranged from 1740 to 4000. The effect of substituents on the order of isocyanate incorporation into the copolymer was m‐Cl = p‐Cl > m‐MeO > H > p‐MeO. Phenylethylketene was also copolymerized with m‐methoxyphenyl, p‐methoxyphenyl, and p‐tolyl isocyanate in tetrahydrofuran (THF) at −78°C. Molecular weights ranged from 2800 to 10,500. The least reactive isocyanate was incorporated into the copolymer to a greater extent in this solvent than in the more polar DMF. DTA showed the presence of crystallinity only in polymers of high isocyanate content. The ketenes copolymerized less readily with alkyl isocyanates, such as ethyl, n‐butyl, n‐hexyl, and cyclohexyl isocyanate, than with the aromatic isocyanates when sodium naphthalene was used in either DMF or THF.
Synthesis of block copolymer with polystyrene and nylon units
Authors: Shimura Yukio , Ikeda Noboru
Published: April 2003

Bis‐ε‐aminocaproylaminocaproylhexamethylenediamine (I) was synthesized as an analog of 6‐nylon pentamer diamine, and its incorporation into block copolymers was studied with the use of α,ω‐dihydroxyl, α,ω‐bisdimethylchlorosilyl, and α,ω‐diepoxy polystyrene. In the course of the experiments, the stability and the reactivity of 4,4′‐diphenylmethane diisocyanate and tetramethylene diisocyanate in aprotic dipolar solvents were examined by infrared spectroscopy. The only usable solvent, N‐methylpyrrolidone, was found still inadequate for the synthesis involving I, diisocyanate, and α,ω‐dihydroxyl polystyrene. A block copolymer having Mn = 18,000 was obtained by the reaction of I and α,ω‐diepoxy polystyrene. All Tg values of the block copolymers were above 90°C, higher than for polystyrenes with corresponding molecular weight.
Alternating copolymer of styrene–acrylonitrile obtained with vanadium‐based complex catalyst in presence of monomers
Authors: Deshpande A. B. , Rajan C. R. , Kapur S. L.
Published: April 2003

Vanadium‐based catalyst complexes prepared in the presence of monomers have been used for the copolymerization of styrene and acrylonitrile. VOCl3–Al(i‐C4H9)3 catalyst system seems to yield an alternating copolymer. The copolymers are easily soluble in DMF and have low softening points.
Semiconducting polymers based on charge‐transfer complexes. II. Crystal structure of poly‐N‐4‐[4‐(methylthio)phenoxy]butyrylethylenimine
Authors: Summers James W. , Litt Morton H.
Published: April 2003

Of the two electron‐donor‐containing polymers whose synthesis was described in Part I of this series, one was crystalline. This polymer, which contains (methylthio)phenoxy electron‐donating groups on the side chains of an N‐acyl‐substituted polyethylenimine, could be indexed in a triclinic unit cell of dimensions a = 4.35 Å, b = 24.0 Å, c = 12.7 Å, and α = β = γ = 90°. The polymer has the side chains alternating on each side of the polymer backbone. They extend to form at 24.0 Å repeat in that direction. The thickness of the ribbonlike molecule is 4.35 Å, while the repeat distance along the polymer backbone is 12.7 Å, which includes four monomer units.
Stereospecific polymerization of acetaldehyde by R2AlOR′ catalyst
Authors: Yasuda H. , Fujita K. , Yamamoto S. , Tani H.
Published: April 2003

Stereospecific polymerization of acetaldehyde was examined by using four possible purified diethylaluminum butoxides, (Et2AlOBu)2 [Bu = n‐, i‐, sec‐, or tert‐Bu], as catalyst. These catalysts gave isotactic polyacetaldehyde quantitatively irrespective of the degree of branching of the butyl group, only when an optimum amount of water (about 0.03 mole/mole of catalyst) was added to the purified acetaldehyde monomer. Quite similar results were obtained for organozinc catalysts. These results indicate that water is an indispensable cocatalyst in the polymerization reaction with organoaluminum and zinc catalysts. An novel coordinate cationic mechanism was proposed for the stereospecific polymerization of acetaldehyde with organoaluminums, based on the above phenomena and on the inactivation of the catalyst by forming a complex with a strong Lewis base.
Characterization of networks from the peroxide cure of polybutadiene. II. Kinetics and sol–gel
Authors: Hergenrother William L.
Published: April 2003

The kinetics of cure of polybutadiene with molecular weights varying from 12,500 to 92,000 g/mole and containing 23–93% of 1,2 microstructure were investigated at two levels of dicumyl peroxide and two temperatures. The relative rates of termination were determined as a function of vinyl content and of reactive additives. Sol‐gel measurements showed that molecular weights between crosslinks of less than 100 g/mole could be obtained. Network formation was found to be a polymerization process in which each free radical formed started only one crosslink chain. However, at high initiator levels chain scission did occur during cure.
Thermal degradation of poly(vinyl chloride). II. Degradation mechanism based on decomposition energetics
Authors: Gupta V. P. , St. Pierre L. E.
Published: April 2003

On the basis of the measured activation energies for radical and HCl generation in four poly(vinyl chlorides) of controlled structures, an overall mechanism of degradation is proposed. The mechanism is a chain reaction involving a β‐chloro elimination from a radical‐containing polymer molecule. Molecules containing tertiary CCl bonds are shown to undergo a fast initiation. Those containing tertiary CH bonds are also demonstrated to be highly unstable, but the instability is not associated with the initiation step.
Evaluation of mass transfer rate during Ziegler‐Natta propylene polymerization
Authors: Keii Tominaga , Doi Yoshiharu , Kobayashi Hiromu
Published: April 2003

Mass transfer which affects the rate of propylene polymerization with titanium trichloride–triethylaluminum, has been evaluated by use of a new method developed for this heterogeneous reaction. The polymerization was carried out with the usual flask reactor equipped with a paddle stirrer; the rate of gas absorption into the polymerization slurry was proportional to stirring speed and the reciprocal of the total amount of polymers produced. It has been confirmed that the polymerization rate separated from the absorption rate is purely kinetic (propagation), and an effective physical process, such as monomer transfer through a polymer film covering the catalyst surface, no longer exists.
Polymerization of vinyl chloride in the presence of precipitants. II.
Authors: Arita Koichiro , Stannett V. T.
Published: April 2003

The kinetics of the radiation‐induced polymerization of vinyl chloride in the presence of precipitants has been successfully described by a one‐parameter equation as follows,

where ϕ0 is initial monomer volume fraction, X is conversion, t is time, and k is reaction constant. The equation was confirmed for extensive conditions of temperatures and monomer concentrations in the case of polymerization in methanol. The degree of polymerization was related with the reaction constant k, initial monomer volume fraction ϕ0, monomer chain transfer constant Cm, conversion X, and the initiation rate I as follows,

The factors which determine the value of the reaction constant k were elucidated through measurements of the reaction constant k and the degree of polymerization DPn.
Thermomechanical behavior of a polyphenylimide‐quinoxaline
Authors: Augl Joseph M. , Booth Hubert J.
Published: April 2003

Linear polyphenylimide‐quinoxalines (PPIQ) can be crosslinked by isothermal heat treatment in an inert atmosphere. To show this, three polyphenylimide‐quinoxalines were prepared which differed only in molecular weight and polymer chain endings. Apparent activation energies of thermal crosslinking were then obtained from the rates of change of Tg as a function of time and temperature. The values (60 kcal/mole) were essentially the same as those for the thermal degradation of the same polymer in vacuum. Differences in polymer molecular weight had a distinct effect on the rates of change of Tg but the polymer chain ends seemed to have a lesser effect than previously observed on polyphenylquinoxalines (PPQ). Nevertheless, the rate of change in Tg is greater for PPIQ than for PPQ of a similar molecular weight. This indicates that the imide portion of the polymer chain leads to faster crosslinking under isothermal conditions.
Crystallization‐induced reactions of copolymers. I. Ring‐size isomerization of poly(ester acetals)
Authors: Lenz R. W. , Martin E. , Schuler A. N.
Published: April 2003

The isomerization reactions of five‐ and six‐membered acetal rings in copolyesters containing these structures along the backbone were studied both in the melt and in the semicrystalline solid state. For the latter, isomerization of the solid copolymer at a temperature well below the melting point was in a direction opposite to that expected from the data for the acetal ring equilibration in a homogeneous melt. This apparent anti‐equilibrium behavior was rationalized on the basis of the continuous removal of the five‐membered ring units by crystallization during the reaction, thereby forcing the reaction in the direction controlled by the ability of that unit to crystallize, irrespective of the normal thermodynamic properties of the reaction itself. The probable requirements to be met for the operation of this type of crystallization‐induced reaction are discussed.
Stereostructure of oligomeric polyisoprenyllithium in tetrahydrofuran
Authors: Lachance P. , Worsfold D. J.
Published: April 2003

The oligomer of polyisoprenyllithium, 2,5,5‐trimethylhexen‐2‐yllithium, formed from tert‐butyllithium and one molecule of isoprene in benzene has a structure similar to that of higher members of the series and also similar properties. In THF only one stereoisomer is stable, and an attempt is made to determine its stereostructure. The lithium compound was converted at low temperature to the acid, and this by a series of steps in which the structure was monitored to the acid's parent hydrocarbon 3,6,6‐trimethyl‐3‐heptene. This was then compared with a synthesized sample of this hydrocarbon of known structure. In this way it was shown that the original lithium compound had a cis configuration in tetrahydrofuran solution.
Photocopolymerization of methacryloyl‐L‐valine methyl ester with maleic anhydride
Authors: Nishihara Koji , Suzuoka Akihiro , Sakota Naokazu
Published: April 2003

Methacryloyl‐L‐valine methyl ester (MAVM) and maleic anhydride (MAn) were photopolymerized without initiator in dioxane at 35°C. Copolymer having a 1:1 molar ratio of the monomers was obtained regardless of both molar ratio of monomers in the feed and polymerization time. The circular dichroism (CD) spectrum of the copolymer before and after hydrolysis showed the induction of asymmetric centers into the polymer main chain. Spectroscopic and kinetic studies suggested the alternating and stereoregular copolymerization of MAVM and MAn, in which a charge transfer complex with a 1:1 molar ratio of monomers participated.
Transfer reactions in radical polymerization of styrene in acetone–chloroform mixture
Authors: Kaloforov N. Ya. , Borsig E.
Published: April 2003

The study of chain‐transfer reactions in thermal and AIBN‐initiated polymerization of styrene is aimed at the determination of transfer constants to the solvents at 60°C. For thermal polymerization the transfer constants Cs to acetone, chloroform, and chloroform mixed with acetone are 3.2 × 10−5, 4.1 × 10−5, and 4.4 × 10−5, respectively. In the case of AIBN‐initiated polymerization, the transfer constant of chloroform in the mixture acetone–chloroform is Cs = 3.3 × 10−4. All these transfer constants are average values. It has been found that neither acetone nor chloroform satisfies the Mayo equation in the presence of transfer agent very well. These anomalies can be explained by assuming a complexation phenomenon. The changes in the polarity and resonance are taken into account. It is considered that in the chain‐transfer reactions under investigation, the association or complex‐forming ability of solvent and monomer or polymer play a role. In studying the chain‐transfer reaction in the acetone–chloroform solvent mixture another phenomenon affecting the determination of the chain transfer constant is assumed. This phenomenon consists in formation of associates in which both solvents participate.
Organometallic polymers. XXIV. Synthesis and copolymerization behavior of h6‐(2‐phenylethyl acrylate) tricarbonylchromium
Authors: Pittman Charles U. , Marlin Gary V.
Published: April 2003

The monomer h6‐(2‐phenylethyl Acrylate) tricarbonylchromium (PEAC) was synthesized and copolymerized in solution at 70°C with styrene, methyl acrylate, acrylonitrile, and 2‐phenylethyl acrylate, azobisisobutyronitrile being used as the initiator. In ethyl acetate solvent the relative reactivity ratios were crudely approximated. The copolymers all exhibited binodal molecular weight distributions, the high molecular weight node probably resulting from branching. The h6‐benzenetricarbonylchromium unit decomposed when exposed to sunlight or ultraviolet light both in air and under N2. In air, Cr2O3 was initially formed within copolymer films. Several unsuccessful attempts were made to prepare h6‐(2‐phenylethyl acrylate)tricarbonylmolybdenum, (III), the molybdenum analog of PEAC, from arenes and both Mo(CO)6 and (CH3CN)3Mo(CO)3. These reactions are described.
Aging and degradation of polyolefins. III. Polyethylene and ethylene–propylene copolymers
Authors: Decker Christian , Mayo Frank R. , Richardson Harold
Published: April 2003

Rates of oxygen absorption and formation of oxidation products were determined in γ‐initiated oxidations of thin films of high‐ and low‐density polyethylene, atactic and isotactic polypropylene, and of three ethylene–propylene copolymers. Radiation yields G for O2 absorbed and formation of hydroperoxides depend on dose rates and decrease sharply with increasing ethylene content of the copolymers and moderately with increasing crystallinity of any base polymer. G values for dialkyl peroxide and carbonyl formation, and therefore for chain initiation and termination, do not change much with polymer composition and crystallinity and not at all with dose rates. A few experiments with atactic polypropylene and an amorphous ethylene–propylene copolymer, initiated by di‐tert‐butylperoxy oxalate, indicate that 37 mole‐% of ethylene in the polymer increases the efficiency of initiation and the tendency toward crosslinking.
Polymerization of styrene by poly(bisphenol a 4,4′‐azobis‐4‐cyanopentanoate)
Authors: George M. H. , Ward J. R.
Published: April 2003

A free radical initiator, poly(bisphenol A 4,4′‐azobis‐4‐cyanopentanoate) (BPA), containing more than one azo group per molecule, was used to polymerize styrene in N,N‐dimethylformamide (DMF) at 60°C. Polymerization rates were measured gravimetrically or dilatometrically, and the molecular weights of the isolated polystyrenes were determined viscometrically, both before and after hydrolysis. BPA has a relatively low initiator efficiency of 0.28. The activation energy and velocity constant at 60°C for decomposition of BPA per azo group in DMF were found spectroscopically to be 105.9 kJ/mole and 2.08 × 10−5 sec−1, respectively. The molecular weights of unhydrolysed polystyrenes increased with increasing conversion and a theory is developed to explain these results.
Mechanism of charge‐transfer polymerization. V. Photopolymerization and photocyclodimerization of N‐vinylcarbazole in the N‐vinylcarbazole–oxygen–solvent system
Authors: Tada Kazuhiro , Shirota Yasuhiko , Mikawa Hiroshi
Published: April 2003

Photochemical reactions of N‐vinylcarbazole (VCZ), studied in various solvents, were profoundly influenced by the atmosphere. In the deaerated system radical polymerization of VCZ occurred in various solvents, e.g., tetrahydrofuran, acetone, ethyl methyl ketone, acetonitrile, methanol, sulfolane, N,N‐dimethylformamide (DMF), or dimethyl sulfoxide (DMSO). By contrast, when dissolved oxygen was present, cyclodimerization of VCZ occurred exclusively to give trans‐1,2‐dicarbazole‐9‐yl‐cyclobutane in such polar, basic solvents as acetone, ethyl methyl ketone, acetonitrile or methanol. In stronger basic solvents, i.e., sulfolane, DMF, or DMSO, simultaneous radical polymerization and cyclodimerization of VCZ proceeded, the ratio of the cyclodimerization to the radical polymerization decreasing in the order, sulfolane > DMF > DMSO. In dichloromethane, on the other hand, cationic polymerization of VCZ occurred irrespective of the atmosphere. It is suggested that oxygen acts as an electron acceptor to the excited VCZ, electron transfer occurring in polar solvents from the excited VCZ to oxygen to give transient VCZ cation radical. The effect of solvent basicity on the photocyclodimerization of VCZ is discussed.
The influence of fine structure on the pyrolysis of cellulose. I. Vacuum pyrolysis
Authors: Basch A. , Lewin M.
Published: April 2003

The effects of crystallinity, orientation and degree of polymerization on the vacuum pyrolysis of cellulose have been investigated. Natural, modified and manmade celluloses were characterized and the kinetics of their pyrolysis at 251°C studied. The high‐temperature pyrolysis of these samples was also investigated by means of DSC and TGA. At 251°C all of the samples showed a rapid, initial weight loss followed by a linear (weight loss)1/2 versus time dependency. Both the initial weight loss and the subsequent reaction rate were dependent upon the crystallinity of the sample. The reaction rate was shown to be inversely proportional to (DP)1/2 and related to the orientation. Effects of crystallinity and orientation could also be seen in the DSC thermograms and in the apparent energies of activation. Results are interpreted in terms of probable mechanisms of the uncatalyzed pyrolysis of cellulose.
Heat‐resistant polymers containing bipyridyl units. II. Polyamide‐imides
Authors: Kurita Keisuke , Williams Roy L.
Published: April 2003

Polyamide‐amic acids containing bipyridyl units were prepared by polymerization of various bipyridyl diamines with trimellitic anhydride acid chloride. These polymers were converted to polyamide‐imides by thermal cyclization. The resulting polyamide‐imides exhibited very good solubility in organic solvents.
Polymerization of propadiene. IV. Kinetics and mechanism of polymerization under the influence of rhodium(I) complexes
Authors: Scholten J. P. , Van Der Ploeg H. J.
Published: April 2003

The kinetics and mechanisms of propadiene polymerization under the influence of [Rh(CO)2Cl]2, Rh(CO)2P(C6H5)3Cl, Rh(CO)3Cl are reported. The reaction rates are first‐order in Rh(CO)2P(C6H5)3Cl and Rh(CO)3Cl and half‐order in [Rh(CO)2Cl]2. They are second‐order in the substrate for Rh(CO)3Cl and [Rh(CO)2Cl]2 and first‐order for Rh(CO)2P(C6H5)3Cl. The data are interpreted in terms of a common intermediate mechanism. The formation of this common intermediate is the rate‐determining step. A solvent effect is also discussed.
Thermodynamic interactions in polymer systems by gas–liquid chromatography. III. Polyethylene–hydrocarbons
Authors: Schreiber H. P. , Tewari Y. B. , Patterson D.
Published: April 2003

Thermodynamic interaction parameters have been calculated from gas–liquid chromatographic measurements for linear and branched polyethylene interacting with selected hydrocarbons. The values of the interaction parameter χ are substantial in spite of chemical similarities between the polymer and low molecular weight hydrocarbon species, a fact attributed to significant differences in the respective thermal expansion coefficients. A systematic increase of χ is observed in going from branched to linear polyethylene systems. The thermal expansion coefficients of these polymer homologs therefore may not be identical. The present χ values differ substantially from those reported in earlier literature. The comparison confirms suspicions that some older data, based on equilibrium sorption experiments, were erroneously low because of an underestimate in the reduced melting temperature of polymer in the presence of excess solvent.
Pulsed NMR study of molecular motion in the uncured diglycidyl ether of bisphenol‐A
Authors: Larsen David W. , Strange John H.
Published: April 2003

The diglycidyl ether of bisphenol‐A, an uncured epoxy resin, has been studied by pulsed NMR. Values of the proton relaxation times T1, T1p, and T2 have been measured over the temperature range from −160 to 200°C. The resin was studied in its monomeric form and in two mixtures containing higher oligomers. The relaxation times are interpreted in terms of the molecular motion in the resins. The motion responsible for relaxation in the solid monomer form is thought to be methyl group reorientation at low temperatures and general molecular motion at high temperatures. The motions are characterized by activation energies of 5 kcal/mole and 33 kcal/mole, respectively. The solid mixtures exhibit similar effects to the monomer, but an additional relaxation mechanism is observed which is attributed to segmental motion. This motion is characterized by an activation energy of 12–15 kcal/mole. The self‐diffusion coefficient was measured in the liquid monomer, and the activation energy for self‐diffusion is found to be 11 kcal/mole.
Carbon‐13 NMR of ethylene‐1–olefin copolymers: Extension to the short‐chain branch distribution in a low‐density polyethylene
Authors: Randall James C.
Published: April 2003

As model polymers for isolated short‐chain branches in low‐density polyethylene, a series of ethylene–1‐olefin copolymers was examined by use of 13C NMR at 25.2 MHz. An array of 13C resonances was observed that could be associated independently with methyl through amyl branches. The 13C chemical shifts became insensitive to branch length with hexyl and longer branches. Assignments of the various carbon resonances associated with branching were accomplished by using off‐resonance decoupling techniques and the behavior of alkane chemical shifts previously observed by other investigators. The ratio of certain backbone and branch resonances could be used to establish the short‐chain branch distribution in a low‐density polyethylene.
Statistical thermodynamics of ABA block copolymers. II
Authors: Leary David F. , Williams Michael C.
Published: April 2003

A microstructural model for the phase‐separated states of ABA triblock copolymers is proposed. It postulates the simultaneous existence of three phases: pure A, pure B, and a mixed region. Incorporation of the mixed region distinguishes this treatment from all other theories and is responsible for considerable flexibility in the model without increased numbers of parameters. Calculations of free energy changes required to establish specific microstructures permit the prediction of a favored one from among five possibilities: discrete spheres of A (or B), discrete cylinders of A (or B), and lamellae.
Strain‐induced crystallization of natural rubber. III. Reexamination of axial‐stress changes during oriented crystallization of natural rubber vulcanizates
Authors: Luch D. , Yeh G. S. Y.
Published: April 2003

In order critically to evaluate the previous morphological interpretations of stress relaxation during oriented crystallization, a reexamination was made of the relaxation behavior of the same oriented natural rubber material used for the x‐ray investigation in Part II of this series. Our results were found to be in qualitative agreement with previously published reports. Comparison of stress‐relaxation rates at low temperatures for samples with strains of 200% or more with crystallization rates at room temperature by others for similar elongations indicates a dual nature in the strain‐induced crystallization process. This conclusion is in full agreement with the indication of dual crystalline morphologies, namely, fibrillar and lamellar, for both electron microscopy and x‐ray investigations on highly stretched samples reported in Parts I and II. Examination of stress‐relaxation data in light of morphological evidence for oriented crystallization indicates that caution must be exercised in attaching morphological significance to the Avrami exponent n obtained from stress‐relaxation or crystallization data.
Dynamic light scattering of polyethylene. I. Introduction and experimental procedures
Authors: Hashimoto T. , Prud'homme R. E. , Keedy D. A. , Stein R. S.
Published: April 2003

An apparatus and procedures are described for the observation of the light‐scattering changes during the periodic vibration of a polymer film sample. The relationship between static and dynamic scattering experiments is discussed as are the means for interpreting such experiments in terms of spherulite deformation and statistical theories. The performance of the apparatus is illustrated with some experiments on a medium‐density polyethylene sample.
Heat capacity of molten polymers
Authors: Bares Vera , Wunderlich Bernhard
Published: April 2003

Heat capacities of molten polyethylene, polypropylene, poly‐1‐butene, polystyrene, and poly(methyl methacrylate) were measured over a wide range of temperature by using a differential scanning calorimeter. The upper limit of temperature was established for each polymer at about 10°K below the beginning of thermal decomposition. For poly‐1‐butene and poly(methyl methacrylate) the solid‐state heat capacity was also measured starting from room temperature. Several samples of each polymer were used so that average values of heat capacities could be established (reported in 10°K intervals). The data revealed for all polymers a nearly linear increase of heat capacity with increasing temperature over the whole temperature range investigated.
Notes on polymer hydrodynamics
Authors: Fujita Hiroshi
Published: April 2003

The sedimentation of an unperturbed polymer chain in dilute solution is reformulated by using Burgers' method, in which the no‐slip boundary condition on the surface of each chain element is taken into account approximately. It is shown that the forcevelocity proportionality relation employed so far as the basis of theoretical developments in polymer hydrodynamics can be justified as a first approximation to the no‐slip condition. The derived expression for the translational friction coefficient ft is a complex function of n and a/b, where n is the number of chain elements in a single molecule and a/b is the ratio of the Stokes radius of a chain element to the effective bond length. Three special cases corresponding mathematically to b = ∞ (no hydrodynamic interaction), a ≪ b (Kirkwood‐Riseman theory), and b = 2a (touching‐sphere model) are examined in detail. Finally, it is shown that when a/b = 0.2360, our ft varies linearly with n1/2 over the entire range of n.
Approach to generalization of concentration dependence of zero‐shear viscosity in polymer solutions
Authors: Dreval V. E. , Malkin A. Ya. , Botvinnik G. O.
Published: April 2003

The possibility of constructing zero‐shear viscosity master curves valid for the entire range of concentration for a large number of polymer solutions in different solvents independent of molecular weight and the nature of the solvent is considered. The results obtained show that the parameters characterizing the individual macromolecular chain., viz., the dimensions of the polymer coil and the rheological effectiveness of segmental interactions, are significant in determining the viscosity of polymer solutions from very dilute to highly concentrated ones. The relation between the parameter of rheological interaction and characteristics of polymer solutions such as the flexibility of the polymer chain and the Flory‐Huggins parameter is discussed. This permits one to separate the influence of the energy and entropy factors on the concentration dependence of zero‐shear viscosity.
Synthesis and characterization of poly(p‐phenylene pyromellitamic acid)
Authors: Tsimpris C. W. , Mayhan K. G.
Published: April 2003

Poly(p‐phenylene pyromellitamic acid)s were synthesized over the weight‐average molecular weight range 8,000 to 22,000. The polymers were recovered as amorphous powders composed of 3–4 × 1–2 μ platelets 0.1–0.2 μ thick containing 20–30% associated solvent. Consumption of reactants and attainment of the ultimate molecular weight of the polymer were found to occur within the first few minutes of reaction. The polymers were characterized by scanning electron microscopy; ultraviolet, visible, near‐infrared, and infrared spectroscopy; x‐ray analysis; viscometry; and light‐scattering photometry. The intrinsic viscosity–molecular weight relation for the polymer in DMF was \documentclass{article}\pagestyle{empty}\begin{document}$ [\eta ] = 25.2 \times 10^{ - 4} \bar M_w^{0.56} $\end{document}.
Mark‐Houwink relations for linear polyethylene in 1‐chloronaphthalene and 1,2,4‐trichlorobenzene
Authors: Wagner Herman L. , Hoeve C. A. J.
Published: April 2003

The parameters in the Mark‐Houwink relationship, [η] = K′M̄va, for linear polyethylene in 1‐chloronaphthalene and 1,2,4‐trichlorobenzene at 130°C have been estimated. They were found by measuring the limiting viscosity numbers of a series of fractions with molecular weights ranging from less than 10,000 to almost 700,000. The results are for 1‐chloronaphthalene, [η] =0.0555 M̄v0.684 (with a standard error of 0.0064 in K′ and 0.010 in a) and for 1,2,4‐trichlorobenzene, [η] = 0.0392M̄v0.725 (with a standard error of 0.00703 in K′ and 0.015 in a), where [η] is expressed in ml/g. The unperturbed end‐to‐end distance calculated from the viscosity‐molecular weight data agrees with the theoretically expected value.
Creep failure in highly oriented nylon 6 fibers
Authors: Narisawa I. , Kondo T.
Published: April 2003

Creep failure in oriented nylon 6 fibers has been studied. The results suggest that the variations in the lifetime under various loading histories are inherent, but statistical, characteristics of the material itself. The treatment of experimental data by a stochastic theory shows that the creep failure can be regarded as a nucleation process. An interpretative analysis of the structural changes during creep indicates that the nucleation is brought about by bond rupture in the amorphous regions of the fiber structures.
Electrical properties of carbon black in an SBR–wax matrix
Authors: Bueche F.
Published: April 2003

The resistivity and dielectric constant for carbon black (5–12 vol‐%) in a nonconducting matrix have been measured over the range 20–90°C and dc to 2–105 Hz. Styrene–butadiene rubber dissolved in tetracosane (22 parts SBR to about 70 parts wax) constituted the matrix. Wide variations in resistivity and dielectric constant with temperature and/or frequency were observed. A theory is presented to explain the experimental observations. It correctly predicts the qualitative features of the experimental results but its predictions are not quantitatively accurate.
Interpretation of boundaries in the pressure–temperature diagram for liquid tellurium and their relationship to the melting‐curve maximum
Authors: Vezzoli G. C.
Published: April 2003

Research on liquid tellurium is reviewed and interpreted in an effort to obtain a consistent picture of the effect of pressure and temperature on the structure and properties of tellurium in the liquid state. Electrical resistance experiments on liquid tellurium support the existence of reaction boundaries in the p–T diagram. The boundaries are believed to identify stages in the reaction whereby the 2‐coordinate covalent chain structure transforms to a 3‐coordinate covalent network structure which eventually dissociates with pressure and temperature into a metallic system. The increasing liquid density associated with the molecular reaction is given as the cause of the maximum on the P–T melting curve. The melting curve maximum in tellurium is shown to be related to maxima in selenium and sulfur. Quenching tellurium from different liquid fields, delineated by reaction boundaries, resulted in materials with different x‐ray spectra.
Random‐coil dimensions and dipole moments of propylene–vinyl chloride copolymers
Authors: Mark J. E.
Published: April 2003

Mean‐square unperturbed dimensions 〈r2〉0 and dipole moments 〈μ2〉 have been calculated for propylene–vinyl chloride copolymers by means of rotational isomeric state theory. The calculations indicate that for these chain molecules 〈mu;2〉 is much more sensitive to chemical sequence distribution than is 〈r2〉0, a conclusion in agreement with results of previous studies of ethylene–propylene copolymers and styrene‐substituted styrene copolymers. In the case of propylene–vinyl chloride chains, both 〈r2〉0 and 〈μ2〉 are most strongly dependent on chemical sequence distribution in the case of copolymers which are significantly syndiotactic in stereochemical structure. At equimolar chemical composition, increase in average chemical sequence length generally increases 〈r2〉0 but decreases 〈μ2〉. Under some conditions, values of these statistical properties go through a minimum with increase in the reactivity ratio product r1r2, thus complicating the use of experimental values of these properties in the characterization of chemical sequence distributions in these copolymers.
Diglycidyl ether of bisphenol‐A with 4,4′‐methylenedianiline: A pulsed NMR study of the curing process
Authors: Larsen David W. , Strange John H.
Published: April 2003

The curing process, during which the monomeric diglycidyl ether of bisphenol‐A is cured with 4,4′‐methylenedianiline, has been studied by pulsed NMR. Values of the proton relaxation times T1, T1ρ, and T2 have been measured as a function of time as the resin system cures at constant temperature. The relaxation times are interpreted in terms of the decrease in general molecular motion which results from the cure. Plots of correlation frequency versus time for the constant‐temperature cure were constructed for three temperatures. It is shown that these three plots can be represented by a reduced curve. With certain simplifying assumptions, the shape of this reduced curve. With certain simplifying assumptions, the shape of this reduced curve can be accounted for in terms of the chemical rate constant and an exponent relating molecular weight to viscosity. The activation energy for the cure is estimated to be 11.7 kcal/mole.
Ionic thermal current study of the α′ process in poly(hexamethylene adipamide)
Authors: Chatain D. , Gautier P. , Lacabanne C.
Published: April 2003

The ionic thermoconductivity (ITC) method has been used to study the α′ transition in the polyamide \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm \hbox{--}\rlap{--} [NH(CH}_{\rm 2} )_6 {\rm NH}\hbox{---} \rm CO(CH_2 )_4 {\rm CO\hbox{--}\rlap{--} ]}_{{\rm x}} $\end{document} (nylon 66). Depending on the thermal history of the sample, the maximum of the thermocurrent peak attributed to the α′ relaxation is found somewhere between ca. 45°C and ca. 66°C; on one heating, it shifts to higher temperatures. The high sensitivity and resolving power of the ITC method permit resolution of this peak into four elementary “pure” activated processes, with constant activation energies in the relevant temperature range. Each of the four corresponding relaxation times follows an Arrhenius law, with a well‐defined characteristic temperature T0 = 83°C at which all these relaxation times are equal. When this last result is interpreted in the light of Eyring's or Bauer's theory, it gives a linear relation between “apparent” activation entropy and activation enthalpy of the elementary processes. The characteristic temperature T0 is independent of the thermal history of the sample, and the temperature shift of the thermocurrent maximum can be interpreted by the observed variation of the relative intensities of the elementary processes, without modification of their other characteristic features.
Lamellar thickening in polyethylene single crystals annealed under low and high pressure
Authors: Roe Ryong‐Joon , Gieniewski C. , Vadimsky R. G.
Published: April 2003

Single crystals of linear polyethylene, prepared from a dilute xylene solution, were annealed below their melting temperature under atmospheric and 6 kbar pressure. In order to preserve the identity of the single crystals, they were suspended in an inert solvent medium, silicone oil and ethanol, during annealing. Examination of the annealed crystals under an electron microscope revealed development of numerous reorganization centers consisting of a central, elongated hole surrounded by a raised edge. Characteristics of these holes, especially their location and orientation, were interpreted in terms of the molecular packing that existed prior to the annealing and the mechanism of molecular reorganization that occurred during the annealing. The effect of high pressure was primarily to flatten out the crystals and to increase the number of reorganization centers, but the height of the raised edges remained about the same irrespective of the applied pressure. The present study also showed examples pointing to the importance of differentiating the annealing behavior of monolayer crystals from that of multilayer crystals.
Stress relaxation upon cessation of steady flow and the overshoot effect of polymer solutions
Authors: Stratton Robert A. , Butcher Allan F.
Published: April 2003

The basis for obtaining the steady‐state compliance from stress relaxation upon cessation of steady flow (SRUCSF) data is derived. Measurements on three polymer solutions of differing molecular weight, polydispersity, and degree of entanglement coupling show good agreement between results from SRUCSF and creep‐recovery experiments in both linear and nonlinear viscoelastic regions. The stress overshoot phenomenon is interpreted in terms of a change in entanglement spacing upon imposition of a shearing field. The phenomenon is analyzed in terms of a relaxation time for re‐entanglement, which is found to be much longer than the relaxation time of the shear stress upon cessation of steady flow.
Morphology of uniaxially oriented poly(ethylene terephthalate)
Authors: Mocherla K. K. , Bell J. P.
Published: April 2003

The morphological character of uniaxially oriented poly(ethylene terephthalate) (PET) films was investigated as a function of draw ratio. Dynamic mechanical, infrared, and crystallite‐size measurements were made on the samples. In addition, selective degradation experiments and molecular weight determinations were employed. The dynamic mechanical measurements indicated a sharp decrease in irregular folds for draw ratios of 3.0 and higher, which also coincided with the essentially complete disappearence of regular folds (from the 988 cm−1band in the infrared spectra) in unannealed samples. Infrared studies of drawn samples annealed under different conditions gave evidence in support of a structure in which the chains are stretched out. Apparent crystallite‐size measurements showed a sudden increase in length of the crystals in the direction of the draw beyond a draw ratio of 3.0. Molecular weight measurements showed a large increase in average chain length in the residue after selective degradation of amorphous material and folds; undrawn and slightly drawn samples gave a much lowerMn. Based on these observations, it is postulated that for higher draw ratios and present drawing conditions, the crystals are of the straight chain type, somewhat similar to the fringed‐micelle crystal concept.
Determination of copolymer composition by Raman spectroscopy
Authors: Boerio F. J. , Yuann J. K.
Published: April 2003

The application of laser‐Raman spectroscopy to the analysis of copolymers of glycidyl methacrylate (GMA) with methyl methacrylate (MMA) and styrene is discussed. For both copolymer systems the line near 1451 cm−1, assigned to the methylene bending mode, was found to be a useful reference. Lines characteristic of each monomer were identified. The intensities of these lines were found to be linearly related to the composition of the copolymers when normalized against the 1451 cm−1 reference. The line near 1730 cm−1, assigned to the carbonyl stretching mode, was also found to be a useful reference for the copolymers of methyl methacrylate and glycidyl methacrylate.
Vapor sorption by filled/reinforced resins. I. General behavior and interpretation
Authors: Clark‐Monks Colin , Ellis Bryan
Published: April 2003

The sorption behavior of particulate‐filled resin composites is discussed and related to several different models. A thermodynamic analysis of the sorption is presented in the form of a cycle for the changes in Gibbs free energy. From such an analysis it is possible to set up a scale of relative adhesion between filler and resin matrix. It is shown that the scale depends on the sorbate, but use of this scale will rate the adhesion between resin and filler in the correct relative order.
Molecular energetics of the epitaxial crystallization of polyethylene on alkali halide substrates
Authors: Mauritz K. A. , Baer Eric , Hopfinger A. J.
Published: April 2003

A series of energy calculations have been carried out in order to describe the epitaxial crystallization of polyethylene from solution in terms of molecular interactions. The total energy has been computed as the sum of electrostatic, dispersion, and repulsion contributions. The potential energy associated with a section of a planar‐zigzag polyethylene chain has been determined for various orientations and positions above three different planar alkali halide substrates. Inspection of the energy surfaces as a function of the spatial degrees of freedom reveals that the minimum energy orientation of the chain is that for which it is parallel to the substrate [(001) cleavage plane] and aligned in the 〈110〉 direction on the surface, a result in accordance with available experimental evidence. Specifically, the chain preference is to position itself along rows of positive ions, whereas alignment along rows of negative charge appears energetically unfavorable. The mode of chain orientation is virtually independent of lattice matching criteria. Dispersionrepulsive forces have been found to be most sensitive to orientation and greater in magnitude than the electrostatic forces.