bluuebunny/crossref_metadata_2025 huggingface dataset:
Conformational freedom of polyamide chains above the melting point
Authors: Carfagna Cosimo , Vacatello Michele , Corradini Paolo
Published: April 2003

The melting behavior of diamides of general formula (n‐CpH2p+1)CONH(CH2)qNHCO(nCpH2p+1) has been investigated by differential scanning calorimetry (DSC). The close similarity of the melting behavior of these low molar mass compounds with that of polymeric amides is discussed in terms of restricted conformational disorder in the amorphous state, due to the high degree of retention of hydrogen bonding.
Copolyamides from adipic and truxillic acids: Synthesis and characterization by direct pyrolysis in the mass spectrometer
Authors: Caccamese S. , Foti S. , Maravigna P. , Montaudo G. , Recca A. , Luderwald I. , Przybylski M.
Published: April 2003

The synthesis of a series of polyamides and copolyamides containing α‐truxillic and adipic units in the chain is reported. The thermal degradation of these polymers was investigated by direct pyrolysis in the ion source of a mass spectrometer. Thermal degradation reactions were followed directly by this method by detecting the thermal‐ and electron‐impact‐induced fragments. The results obtained show a good correlation between the intensity of mass peaks characteristic of truxillic and adipic moieties and the composition of the copolyamides, as ascertained by elemental analysis. This is an important result since it shows the potential of the direct pyrolysis method in the analysis of copolymers. Relevant information on the relative thermal stabilities of the polymers investigated has been also obtained.
Grafting of acrylamide onto methyl cellulose by persulfate ion
Authors: Bardhan Krishna , Mukhopadhyay Sailes , Chatterjee Satya. R.
Published: April 2003

Acrylamide was grafted onto methyl cellulose backbone by using potassium persulfate as initiator in aqueous solution, and variables affecting the copolymerization were studied. It was found that efficiency of grafting was maximum at an initiator concentration of 3.7 × 10−4 mole/l. Grafting was found to increase steadily with increase in monomer/polymer ratio and with temperature up to 40°C.
Radiation‐induced grafting of hexafluoroacetone to polyethylene
Authors: Clark Chester F. , Silverman Joseph
Published: April 2003

Although hexafluoroacetone is not polymerized by ionizing radiation, it is shown that γ‐irradiation of hexafluoroacetone dissolved in polyethylene films produces a graft with a G value of 500 and, therefore, a kinetic chain length of 200. The effects of dose rate (0.021–3.55 Mrad/hr), temperature (21–53°C), and pressure (1.5–6.2 atm) on the graft rates have been measured. Also the effect of temperature (21–53°C) on the postirradiation grafting reaction and on the physical properties of the grafted films have been investigated. Together with solubility, diffusivity, infrared, and EPR data, the results lead to the following mechanism:

equation image

The first step represents production of secondary alkyl radicals in the polyethylene by irradiation of the polymer–monomer system. The second step involves the linkage of the monomer to the radical site to form the alkoxy radical. Since it cannot add to another monomer unit, this radical abstracts a hydrogen atom from an adjacent polyethylene chain in the third step. Radical R· can then continue the kinetic chain. Radical combination and radical–impurity reactions terminate the chain. The graft may be unique in that it is the only one we have found in which a pendant group containing only one monomer unit is attached by a chain reaction. At dose rates up to 0.215 Mrad/hr, the grafting was linear with time and proportional to the 0.73 power of the dose rate at 21°C and to the 0.81 power at 53°C. The reaction is insensitive to increases in dose rate above 0.215 Mrad/hr where diffusivity measurements show the reaction to be diffusion‐controlled. The rate of reaction increased 10% when the temperature was increased from 21 to 53°C. While there was significant postirradiation grafting reaction at 21°C, there was none at 53°C. The results do not fit the equations of reaction‐controlled steady‐state graft‐polymerization kinetics. The deviations arise from an observed increase in monomer solubility in the film with increasing graft combined with low diffusivity of the monomer in polyethylene, and the presence of a radical‐scavenging impurity which terminates the kinetic chain with the appearance of a relatively stable radical. EPR data suggests that the impurity is a trace of oxygen which may be produced radiolytically.
Studies on propagating species in cationic polymerization of styrene derivatives by acetyl perchlorate or iodine. III. Effect of salt on cationic copolymerization of styrene derivatives with vinyl ethers by acetyl perchlorate
Authors: Higashimura Toshinobu , Yamamoto Kenji
Published: April 2003

A common‐ion salt, tetra‐n‐butylammonium perchlorate, was found to affect the monomer reactivity ratios in the cationic copolymerization by acetyl perchlorate of styrene with p‐methylstyrene and of 2‐chloroethyl vinyl ether with p‐methylstyrene, but not those for the copolymerization of 2‐chloroethyl vinyl ether with isobutyl vinyl ether. In the copolymerization of p‐methylstyrene with styrene or with 2‐chloroethyl vinyl ether, the addition of the common‐ion salt in a polar solvent shifted the monomer reactivity ratios to those in a less polar solvent. The molecular weight distribution analysis of the copolymer suggested that the addition of the common‐ion salt depresses the dissociation of propagating species. Therefore, it was concluded that a propagating species with a different degree of dissociation shows a different relative reactivity towards two monomers. The nature of propagating species was also discussed on the basis of the common‐ion effect on the monomer reactivity ratios in various solvents.
Regular copolyamides. I. A facile method for the preparation of diamine‐oxamides
Authors: Chang H. J. , Vogl O.
Published: April 2003

α,ω‐Diamine‐oxamides with 2–12 CH2 groups between the two amino groups were obtained by the reaction of the diamines and diethyl or dimethyl oxalate. Diethyl oxalate is added slowly to a substantial excess of diamine in the proper solvent over a period of time under controlled temperature conditions. All variables are very important for each individual diamine in order to obtain optimal conversions to the diamine‐oxamides under the most favorable conditions. Diamine‐oxamides were obtained in approximately 80% yield with only small amounts (5–10%) of the corresponding polyoxamides as the side product. Diamine‐oxamides from diamines with less than six methylene groups are water‐soluble. All diamine‐oxamides show an alternation of their melting points and are useful intermediates for the preparation of regular copolyoxamides.
Vinylhydroquinone. IV. Preparation and polymerization behavior of 2‐methyl‐5‐vinylhydroquinone derivatives
Authors: Iwabuchi Susumu , Kojima Kuniharu , Nakahira Takayuki , Uchiyama Takashi , Sakata Junji , Shimizu Hisashi
Published: April 2003

As in the case of vinylhydroquinone (I), its alkyl‐substituted derivative, 2‐methyl‐5‐vinylhydroquinone (II) was found to copolymerize with methyl methacrylate by tri‐n‐butylborane in cyclohexanone at 30°C. II was prepared from the O,O′‐bisether compound, 2‐methyl‐5‐vinyl‐O,O′‐bis(1′‐ethoxyethyl)hydroquinone (III). The monomer reactivity ratios (M2 = II) were determined to be r1 = 0.37 and r2 = 0. No homopolymerization proceeded under the same conditions. Ordinary free‐radical initiators, such as azobisisobutyronitrile and benzoyl peroxide, were not effective in the homopolymerization of II. 1:1 Copolymers were obtained from II and maleic anhydride by using tri‐n‐butylborane as an initiator. The copolymers exhibited no definite melting range and decomposed at 370–375°C endothermally (DSC). The polymerization behavior of III was also investigated. Although tri‐n‐butylborane did not initiate the homopolymerization of the monomer, azobisisobutyronitrile was capable of initiating the homopolymerization and copolymerization of III. The monomer reactivity ratios (M1 = styrene) were determined to be r1 = 0.83 and r2 = 0.18. The ratios gave the following Q and e values; Q = 0.15 and e = −2.2.
Synthesis and polymerization of N‐(p‐vinylbenzyl)‐3‐carbamoyl‐1,4‐dihydropyridine and redox behavior of the oligomer
Authors: Tsuchida Eishun , Hasegawa Etsuo , Ohno Hiroyuki
Published: April 2003

In order to prepare a soluble dihydropyridine‐type redox polymer, N‐(p‐vinylbenzyl)‐3‐carbamoyl‐1,4‐dihydropyridine was synthesized and characterized by elemental analysis, infrared spectroscopy, and nuclear magnetic resonance spectroscopy. The polymerization of the vinyl monomer in N,N‐dimethylformamide or chloroform was also studied. Only oligomers were obtained by radical polymerization. The reduction of various compounds by the oligomer thus prepared was examined in heterogeneous or homogeneous solution.
Measurement of particle size distribution in the discrete phase of high‐impact polystyrene. I. Errors in direct coulter counter techniques
Authors: Craig T. O. , Quick R. M. , Jenkins T. E.
Published: April 2003

The published Coulter Counter method for measuring particle size distribution of the discrete phase in rubber‐modified polystyrene is shown to be subject to serious limitations, especially when the data generated are used to compute discrete phase volume fractions. The source of error is time‐dependent swelling of the particles in DMF which is used to isolate them from the polystyrene matrix for the counting operation.
Measurement of particle size distribution in the discrete phase of high‐impact polystyrene. II. An improved coulter counter procedure
Authors: Craig T. O. , Quick R. M. , Jenkins T. E.
Published: April 2003

An improved Coulter Counter procedure is described for determining the size distribution and volume fraction of the elastomeric discrete phase in high‐impact polystyrene. The method isolates the discrete phase from a dispersion of the whole polymer in DMF by centrifugation and redisperses the discrete phase in an aqueous surfactant solution, thus allowing the particles to deswell and resume the dimensions they had in the polystyrene matrix. By measuring a Coulter Counter size distribution on the aqueous dispersion, a discrete‐phase volume fraction can be reliably derived for the original impact polystyrene. The method is rapid and precise.
Preparation and some properties of nylon 46
Authors: Gaymans R. J. , Van Utteren T. E. C. , Van Den Berg J. W. A. , Schuyer J.
Published: April 2003

Nylon 46 was synthesized from the salt of 1,4‐diaminobutane and adipic acid. High molecular weight polymers could be obtained by reaction for 1 hr at 215°C in a closed system and at least for 1 hr in vacuo at a temperature in the range 290–305°C. The reactions at 290°C were found to have taken place in the solid state and those at 305°C in the melt. The highest molecular weights (M̄w ca. 45,000) were obtained by reaction at 290°C with a nylon salt with a pH of 7.8–8.0. The molecular weight characteristics were studied with end‐group analysis, viscometry, light scattering, and ultracentrifugation. The polymers were found to be gel‐free and monodisperse (M̄w/M̄n ∼ 1.15). Films could be cast from formic acid. From x‐ray diffraction patterns, measured on such films, spacings of 3.74 and 4.30 Å were calculated, whereas a long period of 66 Å was also found. The infrared spectra showed all the usual amide bands of even–even polyamides. The melting temperature was found to vary between 283 and 319°C, depending on the thermal history of the sample. Water absorption measured on a cast film showed this to be very hygroscopic (7.5% at 65% RH), while a highly crystalline sample absorbed only little water (1.6% at 65% RH).
Water‐soluble copolymers containing N‐vinylcarbazole
Authors: Mulvaney J. E. , Chang Daniel M.
Published: April 2003

Water‐soluble or dispersable copolymers of N‐vinylcarbazole (VCbz) with sodium N‐acryloylsulfanilate (SAS), or sodium styrene‐sulfonate (SSS), or N,N,N‐triethyl‐N‐[2‐(methacryloxy) ethyl]‐ammonium iodide (TAI), or N,N,N‐trimethyl‐(p‐vinylbenzyl)ammonium chloride (TVBA) were prepared by using a radical initiator. VCbz and SAS were copolymerized in N,N‐dimethylacetamide. Copolymers containing more than 49% SAS were water‐soluble. In the case of VCbz and SSS, copolymerization was also carried out in DMAN to yield water‐soluble copolymers when the SSS content was greater than 36%. VCbz–TAI and VCbz–TVBA were similarly copolymerized in DMAN to give water‐soluble polymers when the TAI content was greater than 58% or the TVBA content was 60%. In addition, a copolymer of VCbz and methyl acrylate was partially hydrolyzed with NaOH in tetrahydrofuran to yield a water‐dispersable polymer.
Copolymers of vinylcyclohexane with styrene: Peculiarity of thermal behavior, parameters of crystal structure, and structural transitions
Authors: Kharas G. B. , Kleiner V. I. , Stotskaya L. L. , Karpacheva G. P. , Krentsel B. A. , Nechitailo N. A. , Dzyubina M. A. , Litvinov I. A. , Artamonova S. D.
Published: April 2003

Thermal behavior, the parameters of crystal structure, and the structural transitions of copolymers of vinylcyclohexane with styrene were studied. Heating in air of the copolymers and of mechanical mixtures of homopolymers results in thermooxidative destruction. For all samples, the oxidation starts at 210–220°C. The antioxidant effect on thermal stability of copolymers was studied. Differential thermal analysis (DTA) data were used to determine the melting points of homopolymers and crystal copolymers. The method of x‐ray diffraction on large scattering angles was used to determine the dimensions and type of unit cells, the degree of crystallinity, the dimensions of the coherent scattering regions (the dimensions of crystallites) of copolymers of various compositions, and to compare them to the parameters of the structure of polyvinylcyclohexane and polystyrene. Information on molecular motion intensity and structural transitions in homopolymers and copolymers with changing temperature was obtained by the spin‐probe technique.
Radiation‐induced oxidation of solid poly(ethylene oxide). I. Experimental results
Authors: Decker Christian
Published: April 2003

γ‐Initiated oxidations of solid poly(ethylene oxide) (PEO) have been carried out at ambient temperatures and the dependence of the rate of oxygen consumption on rate of initiation, O2 pressure, and crystallinity has been determined. At 25°C, the radiation yield G for O2 absorbed is 117–281, depending on dose rate, and decreases moderately with increasing crystallinity. The principal oxidation products are formate and hemiformal groups, hydroperoxides, and some volatile compounds, mainly formaldehyde and carbon dioxide. The rates of O2 consumption and formation of products and chain scission are little affected by a change of the temperature in the range −23 to +55°C except for hydroperoxide, the formation of which requires an activation energy of 4 kcal/mole. Experiments with 2,6‐di‐tert‐butyl‐p‐cresol show that essentially all of the initiating PO2· radicals escape cage termination; G value for formation of the initiating peroxy radicals was estimated from the inhibition period to be 5.0 ± 0.3.
Optical properties and conformations of asymmetric polyamides derived from optically active trans‐1,2‐cyclopropanedicarboxylic acid
Authors: Overberger C. G. , Shimokawa Y. , Montaudo G.
Published: April 2003

Optical properties and conformations, in solution, of optically active polyamides derived from (+)(S)‐trans‐1,2‐cyclopropanedicarboxylic acid with secondary diamines such as trans‐2,5‐dimethylpiperazine (DMPIP), piperazine (PIP), or N,N′‐dimethylethylenediamine (DMED) have been investigated and compared with the corresponding diamide model compounds. The results suggest that the rigid DMPIP and PIP polyamides may exist in ordered conformations in 2,2,2‐trifluoroethanol (TFE) and tetramethylene sulfone (TMS), while reversible conformational transitions to highly extended forms may be induced by the addition of methanesulfonic acid (MSA). In MSA/TMS mixtures, a change in the optical properties, and thus possibly in the conformations, can be observed around 0.5 mole fraction of MSA. A study of CD at higher temperature indicates that the conformations of the DMPIP and PIP polymides tend to be randomized on heating in TMS and probably also in MSA. No evidence for salt effects on conformation has been observed. Possible ordered conformations have been proposed.
Energy transfer and radical formation in the system poly(methyl methacrylate)–2‐methyltetrahydrofuran
Authors: Torikai Ayako , Kinugawa Kazuhisa , Kuri Zen‐Ichiro
Published: April 2003

ESR spectra of γ‐irradiated poly(methyl methacrylate) (PMMA) at 77°K and the effect of additives have been studied. γ‐Irradiation of PMMA containing a small amount of 2‐methyltetrahydrofuran as an additive at 77°K gives MTHF radical. Yields of MTHF radical increase with increasing MTHF concentration and reach a plateau value, and are independent of photobleaching with visible light. Yeilds of polymer radical are reduced by the addition of MTHF. Some elementary processes for the MTHF radical formation are proposed on the basis of the experimental results.
Soluble bimetallic μ‐oxoalkoxides. VII. Characteristics and mechanism of ring‐opening polymerization of lactones
Authors: Hamitou A. , Ouhadi T. , Jerome R. , Teyssié Ph.
Published: April 2003

The ring‐opening polymerization of unsubstituted lactones by Al2Zn and Al2Co(II) μ‐oxoalkoxides in homogeneous organic phase is described. Under these conditions, the chain propagation is very fast and proceeds without transfer or termination reactions. The composition and structure of the main products resulting from the first polymerization steps have been determined, and fit with a monomer insertion mechanism into the aluminum‐alkoxide bonds of the catalyst.
Oligomérisation anionique de l'ethylène. I. Etude cinétique
Authors: Magnin Henri , Rodriguez Firmin , Abadie Marc , Schué François
Published: April 2003

A kinetic study of ethylene oligomerization in hexane, in the presence of n‐BuLi–TMEDA complexes, allowed us to suggest a new mechanism for anionic ethylene oligomerization. n‐BuLi and n‐Bu(CH2CH2)Li species have the same reactivity. The RLi–TMEDA complex in a 1‐to‐1 stoichiometry is the active species. The following kinetic equation has been established:

It reflects the intervention of associated species (n‐BuLi–TMEDA)2 as well as the influence of the concentration of the complexing agent on the kinetics of oligomerization.
Copolymerization of anhydroglucose and anhydromannose derivatives: Structure, reactivity, and conformational analyses
Authors: Kobayashi Kazukiyo , Schuerch Conrad
Published: April 2003

Phosphorus pentafluoride‐catalyzed copolymerization of 1,6‐anhydro‐2,3,4‐tri‐O‐(p‐methylbenzyl)‐β‐D‐glucopyranose (TXGL, monomer G) and 1,6‐anhydro‐2,3,4‐tri‐O‐benzyl‐β‐D‐mannopyranose (TBMN, monomer M) appears to follow classical copolymerization theory. Reactivity ratios calculated by the procedure of Mayo and Lewis were rG = 0.90 ± 0.08, rM = 11.5 ± 0.80, from which sequence distributions were calculated. A conformational analysis of anhydro sugar polymerization is presented to explain differences in reactivity of monomers and their derived cations in polymerization and copolymerization. The polymers and copolymers were characterized by viscosity, 1H‐ and 13C‐NMR spectroscopy, optical rotation, and circular dichroism. The reaction gives stereoregular polymers as have other polymerizations and copolymerizations of this class.
Copolymerization of propylene oxide and carbon disulfide with diethylzinc–electron‐donor catalyst
Authors: Adachi Nobuo , Kida Yasuji , Shikata Kazuo
Published: April 2003

Copolymerization of propylene oxide with carbon disulfide was studied by using a catalyst consisting of diethylzinc (ZnEt2) and various electron donors. Tertiary amines, tertiary phosphines, and hexamethylphosphoric triamide were the effective donors for the copolymerization, but ZnEt2–water, alcohol, and primary or secondary amines having high activities for the homopolymerization of propylene oxide were not effective for the copolymerization of propylene oxide and carbon disulfide. The copolymers obtained were of low molecular weight and had a monomer unit ratio (CS2/PO) of 0.5–0.7. In addition, a considerable amount of 1,3‐oxathioran‐4‐methyl‐2‐thion was isolated as a by‐product.
Soluble bimetallic μ‐oxoalkoxides. IX. ε‐caprolactone and β‐propiolactone block copolymerization
Authors: Hamitou A. , Jerome R. , Teyssié Ph.
Published: April 2003

The fast and living ring‐opening polymerization of lactones by bimetallic μ‐oxoalkoxides in homogeneous organic phase has led to successful block copolymerization. The catalyst is coordinatively associated in organic media; however, interaction with lactones can induce, following their nature, different rearrangements of the catalytic aggregates, depending on the nature of these lactones. Consequently, ε‐caprolactone and β‐propiolactone block copolymers are quantitatively obtained only in the presence of a completely dissociated catalyst.
Regular copolyamides. II. Preparation and characterization of regular aliphatic copolyoxamides
Authors: Chang H. J. , Vogl O.
Published: April 2003

Regular copolyoxamides were prepared from diamine‐oxamides and aliphatic diacid chlorides by interfacial and solution polymerization. Interfacial polymerization is preferred with diamineoxamides where the diamine portion has two to six methylene groups and the diamine‐oxamides are readily soluble in water. Regular aliphatic polyoxamides from diamine‐oxamides are readily soluble in water. Regular aliphatic polyoxamides from diamine‐oxamides with more than six methylene groups in the diamine portion of the molecule are better prepared by solution polymerization in dimethyl acetamide. Regular aliphatic oxamides are soluble in trifluoroacetic acid and hexafluoroisopropanol and show a considerable alternation of the melting point behavior in the diamine portion of the polyamides with up to five methylene groups. Copolyoxamides with two and four methylene groups melt higher than the copolyoxamides with three and five methylene groups. Aliphatic copolyoxamides/adipamides melt at approximately 260°C and show a steady decrease in melting points to about 220°C for polyoxamides with twelve methylene groups.
Stereoelective cationic polymerization of propenyl ether by asymmetric catalysts
Authors: Higashimura Toshinobu , Hirokawa Yoshitsugu
Published: April 2003

In order to elucidate the possibility of stereoelective cationic polymerization (asymmetric selective polymerization) of olefinic monomers, racemic cis‐ and trans‐1‐methylpropyl propenyl ether and racemic 1‐methylpropyl vinyl ether were polymerized by asymmetric alkoxyaluminum dichlorides. In the polymerization of racemic cis‐1‐methylpropyl propenyl ether with (−)‐menthoxyaluminum dichloride in toluene at −78°C, the polymer obtained showed a positive optical activity, and the residual monomers were converted by BF3OEt2 into a polymer having a negative optical activity. Thus, the stereoelective polymerization of racemic cis‐1‐methylpropyl propenyl ether was beyond any doubt attained in homogeneous cationic polymerization. In the polymerization of the trans isomer by the same catalyst, an optically active polymer was hardly formed. In the polymerization of racemic 1‐methylpropyl vinyl ether which has no β‐methyl group, stereoelectivity was not observed at all. The cis‐1‐methylpropyl propenyl ether did not produce an optical active polymer in the polymerization catalyzed by (S)‐1‐methylpropoxyaluminum dichloride or (S)‐2‐methylbutoxyaluminum dichloride under the same polymerization conditions.
Isothermal degradation of poly‐2,2′‐(m‐phenylene)‐5,5′‐bibenzimidazole
Authors: Lerner N. R.
Published: April 2003

The isothermal degradation of poly‐2,2′‐(m‐phenylene)‐5,5′‐bibenzimidazole in vacuo has been studied. Measurement of the increase in pressure with time, coupled with infrared analysis, was used to determine the distribution of the degradation products. Processes A and B with different second‐order rate laws were determined to be significant in the temperature range of 550–700°C. Process A leads to the formation of equimolar quantities of hydrogen and ammonia and has an activation energy of 68 kcal/mole. Process B leads to the production of HCN, NH3, and H2 in the ratio of 1:1:2.5 and has an activation energy of 77 kcal/mole. The activation energies and the rate laws are consistent with a mechanism in which the initial degradation step is the bimolecular reaction of two aromatic rings.
Dimerization of methylstyrenes by acetyl perchlorate and trifluoromethanesulfonic acid
Authors: Nishii Hideo , Higashimura Toshinobu
Published: April 2003

Ring‐substituted methylstyrenes (p‐, m‐, and o‐methylstyrenes) in conjunction with acetyl perchlorate (AcClO4) or trifluoromethanesulfonic acid as catalysts gave their linear unsaturated dimer in high yield in benzene at temperatures from 50 to 70°C. In particular, the yield of o‐methylstyrene dimer was as high as 90% in the AcClO4 catalysis at 50°C. The dimer yield depended on solvent and catalyst. The terminal structures of the dimers and higher oligomers were analyzed by NMR spectroscopy. Oligomers with a cyclic terminal structure increased in the products at higher temperature. The dimer yield was improved by codimerizing p‐methylstyrene with less reactive m‐methylstyrene or styrene with AcClO4 catalyst. The dimers obtained partly consisted of linear unsaturated codimers.
Polysalt complexes of poly(crown ethers) and sodium carboxymethylcellulose
Authors: Varma A. J. , Smid J.
Published: April 2003

Insoluble polysalt complexes are formed on mixing aqueous solutions of poly(vinylbenzo‐18‐crown‐6) (P18C6) and sodium carboxymethylcellulose (CMC) in the presence of certain salts. Potassium salts are especially effective, converting the neutral P18C6 into a polycation which then interacts with sodium CMC. Nearly quantitative precipitation can be achieved at low KCl concentration (ca. 0.005M) for a crown/carboxylate ratio of approximately 5, while for 0.1–0.2M KCl the precipitation is close to completion at a crown/CMC ratio of about 2. The precipitates solubilize again on addition of water or concentrated KCl. Precipitation also occurs with CsCl but not with NaCl. Potentiometric measurements were carried out to determine the complex formation constant of the three alkali ions to P18C6. Their values can be used to rationalize the observed phenomena. Charge equivalence appears to play an important role in the formation of the polysalt complexes.
Polymérisation anionique des diènes. V. Configurations des oligopolyisoprènyl–lithium en milieu benzènique et en présence de dioxanne. Étude par résonance magnétique protonique: Haute résolution (RMP‐HR)
Authors: Salle Robert , Gole Jean , Pham Quang‐Tho
Published: April 2003

By PMR, three dioxane–Li+ complexes have been detected for the oligopolyisoprenyl–lithium–dioxane mixtures in benzene solution. The (4‐1) living end isomerizes into the cis configuration when the sample temperature or the dioxane concentration is increased, but the isomerization phenomenon is reversible only if dioxane/Li+ ratios are smaller than unity. The specificity of the vinyl addition (86%), mainly (4‐3) (70%), due to the stronger negative charge at the Cγ carbon atom is effective only at low temperature (+15°C). At higher temperature, because of the steric hindrance of the methyl group, this stereospecificity decreases.
Influence of the solvents on the γ‐ray polymerization of acrylic acid. I.
Authors: Laborie Francoise
Published: April 2003

Bulk polymerization of acrylic acid is controlled by linear plurimolecular H‐bonded aggregates of the monomer. It is proved that it is not the precipitating medium that is responsible for the accelerated rate of the polymerization, but the presence of the H‐bonded plurimolecular aggregates. It has been shown that the presence of the previously formed polymer is important, as it gives a matrix effect which allows the monomer aggregated to be stabilized by associating with the polymer. In polymerizing acrylic acid solutions, two types of solvents have been characterized: first, the polar solvents which do not destroy the H‐bonded aggregates up to high dilutions. Then, in the presence of hydrocarbons or chlorinated solvents, 10–20% of the solvents dissociate the aggregates. A very striking parallelism is observed between the polymerization kinetics and the associated form of the monomer.
Polymers with potential pharmaceutical properties: Fixation of histamine on the macromolecular chain of polyisoprene
Authors: Pinazzi C. , Rabadeux J. C. , Pleurdeau A.
Published: April 2003

The fixation of histamine [2‐(4‐imidazolyl)ethylamine] along or at the end of the chain of a low molecular weight 1,4‐polyisoprene prepared by an anionic process has been studied, and the structure of the resulting polymers determined in comparison with those of organic model molecules similarly obtained.
Superacid polymers: Synthesis and analysis of AlCl3–sulfonic acid resin complexes
Authors: Magnotta V. L. , Gates B. C.
Published: April 2003

Crosslinked poly(styrenesulfonic acid) beads in contact with AlCl3 vapors at 115°C reacted to give HCl and a complex incorporating S, Al, and Cl in the ratio 2:1:2. Electron microprobe x‐ray analysis showed that the complexes were distributed uniformly throughout the polymer structure, which consisted of 200 Å microspheres surrounded by a labyrinth of pores. The polymer is a very strong proton donor, comparable to the superacid solution SbF5 + FSO3H. Its structural and acidic properties are inferred to be similar to those of the complex formed from AlCl3 and H2SO4.
Use of ESR to investigate formation of free radicals on compounding rubbers with carbon blacks
Authors: Jamroż M. , Kozłowski K. , Sieniakowski M. , Jachym B.
Published: April 2003

An ESR method was used to investigate the formation of free radicals during rubber mastication and filling of rubber with various carbon blacks. The ESR spectra of natural rubber and styrenebutadiene rubber with various carbon blacks are of a complex character. A narrow component line is superimposed on the much broader signal line of carbon black. The changes in this narrow spectral line with plasticization time and with carbon black content in the rubber–filler system result from interactions between the rubber macromolecules and filler particles.
Synthesis and solution properties of poly(2‐methylproline)
Authors: Overberger C. G. , Jon Y. S.
Published: April 2003

The resolution of 2‐methylproline and the assignment of absolute configuration to the stereoisomer has been carried out. The L‐enantiomer was obtained from the fractional crystallization of the quinine salt of (−)‐N‐carbobenzoxy‐2‐methylproline and the D‐enantiomer from the collected filtrates. The (−)‐2‐methylproline was assigned the L‐configuration by means of the Clough‐Lutz‐Jirgensons method. Polymers were obtained in bulk from the N‐carboxyanhydrides. Although polymers obtained from different solvents exhibited different solubility properties, subsequent spectral studies indicated that this effect was not due to a large conformational change as in the polyproline case. Spectral evidence suggests that poly(2‐methylproline) (P2MP) exists as a polyproline type II helix.
Alternating ethylene–alkyl acrylate copolymers. I. polymer preparation
Authors: Logothetis A. L. , McKenna J. M.
Published: April 2003

High molecular weight alternating ethylene–ethyl acrylate copolymers were prepared by using boron trifluoride to complex the acrylate ester. The polymerizations were run under mild conditions (25–50°C, 6–20 atm ethylene) in dichloromethane or dichloroethane solution with free‐radical initiation. At lower ethylene pressures or at less than stoichiometric levels of BF3, the polymers are acrylate‐rich. This is due to ethyl acrylate homopolymerization competing with the copolymerization reaction. The effect of other polymerization variables is also discussed.
Zur kopolymerisation: Axiomatische formulierung eines mathematischen modells, das memory 3 programm—anwendungen
Authors: Mot̨oc Ioan , Holban Stefan , Ciubotariu Dan
Published: April 2003

This paper presents an axiomatic mathematical model for binary copolymerization reactions. The FØRTRAN program entitled MEMØRY 3 is described. This program implements the Monte Carlo version of the axiomatic model, computing the most probable sequence distribution. Finally, a concrete copolymerization process is studied and good results are presented.
Copolymerization of 2‐hydroxypropyl methacrylate with alkyl acrylate monomers
Authors: Gaddam N. B. , Xavioir S. F. , Goel T. C.
Published: April 2003

2‐Hydroxypropyl methacrylate has been copolymerized with methyl acrylate, ethyl acrylate, n‐butyl acrylate, and methyl methacrylate in bulk at 60°C using benzoyl peroxide as initiator. The compositions of copolymers have been determined by the estimation of the hydroxyl group by acetylation process. The copolymerization parameters have been determined by conventional scheme of copolymerization.
Grafting onto wool. I. Ceric ion‐initiated grafting of poly(methyl acrylate) onto wool
Authors: Misra B. N. , Chandel P. S.
Published: April 2003

Poly(methyl acrylate) has been grafted onto wool by using ceric ion as redox initiator in an aqueous medium. Initiation by ceric ammonium nitrate (CAN) was carried out in the presence of nitric acid of varying concentration at 35, 45, and 50°C for a period of 1.5 or 3 hr. Percent grafting was found to be dependent on concentrations of acid and monomer, reaction time, and temperature. Above 45°C, a considerable amount of homopolymer was formed; at 35°C, very little grafting of poly(methyl acrylate) was observed. Nitric acid catalyzed the reaction and a concentration of 0.17–0.19M HNO3 was found suitable.
Grafting onto wool. II. BPO‐initiated grafting of polystyrene
Authors: Chandel P. S. , Misra B. N.
Published: April 2003

Grafting of polystyrene (PS) onto wool has been carried out in aqueous medium by use of benzoyl peroxide (BPO) as initiator in the presence of an acetic acid–pyridine mixture which acted as a pH modifier. Percent grafting was found to be dependent on concentration of acetic acid and pyridine, concentration of monomer, concentration of BPO, and reaction temperature. The role of pH modifier upon BPO‐initiated grafting is established by the observation that no grafting occurred when one of the components of the pH modifier was absent.
Preparation and properties of solvent‐soluble bridged polybiphenylenes and related copolymers
Authors: Hayama Shigeru , Niino Shogo , Sakamoto Akira
Published: April 2003

A solvent‐soluble polybiphenylene with a single hetero atom in the chain (a bridged polybiphenylene) was prepared according to the synthetic procedure for a solvent‐soluble poly(4,4′‐biphenylene). In addition, a related copolymer was similarly prepared by the addition of the MMA monomer in the reaction system. The thermal properties and viscosity behavior of each product were influenced by the hetero atom, especially by the introduction of MMA component in the chain. Each viscosity curve (ηsp/c vs. c) shows an anomalous peak at a specific concentration (0.3–0.002 g/100 ml DMF), depending upon the atomic group. The ηsp/c value for each homopolymer was not over 0.1 except in the neighborhood of the anomalous peak, while those for copolymers became 3–4 times larger than values for corresponding homopolymers. It is obvious that the viscosity of each copolymer increases due to an increase in flexibility due to introduction of the MMA units in the chain, since little difference in molecular weights is found between homopolymers (16,000–15,000) and copolymers (10,000–12,000).
Reactivity ratios for acrylonitrile–phenyl acrylate copolymerization systems
Authors: Miller Andrzej , Szafko Jerzy
Published: April 2003

Reactivity ratios for various acrylonitrile–phenyl acrylate systems have been determined for radical copolymerization at 60°C in dimethylformamide. The values of the ratios calculated by the linear graphical method of Kelen and Tüdös were as follows: r1 = 0.46 ± 0.02 and r2 = 0.36 ± 0.04 for acrylonitrile–phenyl acrylate, r1 = 0.73 ± 0.02 and r2 = 0.80 ± 0.02 for acrylonitrile–p‐cresyl acrylate, r1 = 0.33 ± 0.03 and r2 = 0.9 ± 0.02 for acrylonitrile–p‐chlorophenyl acrylate, r1 = 0.82 ± 0.03 and r2 = 1.02 ± 0.03 for acrylonitrile–p‐bromophenyl acrylate, r1 = 1.12 ± 0.05 and r2 = 1.16 ± 0.05 for acrylonitryle–o‐chlorophenyl acrylate, and r1 = 1.26 ± 0.05 and r2 = 0.86 ± 0.05 for acrylonitrile–m‐chlorophenyl acrylate. The dependence of reactivities of the monomers upon their chemical structure was discussed.
Equilibrium cyclotrimerization of n‐butyraldehyde
Authors: Hashimoto Kazuhiko , Sumitomo Hiroshi , Kawase Sanshiro
Published: April 2003

n‐Butyraldehyde was cyclotrimerized by using boron trifluoride etherate as an initiator at −10 to 25°C under various conditions, e.g., in methylene chloride, in toluene, and without adding solvent. An equilibrium between the monomer and its cyclic trimer was observed, the equilibrium constant being highly dependent on not only the reaction temperature and the kind of solvents, but also the initial monomer concentration. A consistent interpretation for the results was obtained by the thermodynamic treatment of the equilibrium system as a nonideal solution composed of the monomer, its cyclic trimer, and solvent, in consideration of the intermolecular interactions between any two components.
Study of energy transfer to solvent in radiation graft polymerization of styrene onto polyethylene
Authors: Rabie Abdelgawad , Odian George
Published: April 2003

The radiation‐initiated graft polymerization of styrene onto polyethylene was studied to determine whether energy transfer to diluent was responsible for the previously observed high orders of dependence of the grafting rate on monomer concentration. n‐Octane was used as the diluent instead of benzene. If energy transfer from excited polyethylene to benzene were present, it should not be with n‐octane. The percent swelling of polyethylene by various n‐octane–styrene mixtures was determined. The compositions of various n‐octane–styrene mixtures absorbed inside polyethylene were determined by ultraviolet and refractive index measurements and found to be richer in styrene than the corresponding mixtures in which the polyethylene had been placed. The graft polymerization rates were determined at 0.000761, 0.0371, and 0.213 Mrad/hr and plotted against the inside styrene concentrations on a log‐log scale to yield the kinetic orders of dependence of rate on monomer as 2,3, and 3, respectively. It was concluded that energy transfer to diluent was not responsible for the high‐order dependence observed.
Photodegradation of polyethylene in the presence of ferric chloride
Authors: Ogiwara Yoshitaka , Kimura Yuji , Osawa Zenjiro , Kubota Hitoshi
Published: April 2003

Effects of ferric chloride (FeCl3) on photodegradation of high‐density polyethylene (PE) were investigated by using ESR and infrared spectrometry. In the system with irradiation at light of λ > 220 nm, PE irradiated at 77°K yielded an 8‐line spectrum, the intensity of which was markedly weakened by using FeCl3 with the sample, indicating a distinct depression of radical formation. On the other hand, PE with the use of FeCl3 yielded radicals under irradiation only with light of λ > 300 nm, showing a singlet spectrum with a line width of 15 gauss. For photooxidized PE, almost the same effect of FeCl3 was observed. On irradiation at room temperature, PE samples with and without FeCl3 showed a singlet spectrum with line widths of 15 and 25 gauss, respectively. On the other hand, the unsaturated double bond contained in a small amount in PE sample was observed by infrared study to be decreased with photoirradiation; however, the decrease was sharply depressed with the addition of FeCl3 to the sample. The degradation of carbonyl group in a photooxidized sample was markedly affected by photoirradiation, and the decay was obviously reduced for the sample on addition of FeCl3. It is concluded that FeCl3 works upon photodegradation of PE to enhance the Norrish type II reaction and to accelerate the formation of unsaturated double bond in the chain.
Adsorption of polymers at the solution–solid interface. XIII. Adsorption and steric stabilization with styrene–2‐vinylpyridine copolymers
Authors: Howard G. J. , McGrath M. J.
Published: April 2003

Random and block copolymers of styrene and 2‐vinylpyridine, covering the full range of composition, have been synthesized. The adsorption of these polymers from trichloroethylene solution on to precipitated silica has been studied and their ability to impart colloidal stability to the silica dispersions also investigated. Estimates of the layer thickness of adsorbed copolymers have been made. Polystyrene is not adsorbed from trichloroethylene and does not stabilize dispersions of precipitated silica. A random copolymer having 1% 2‐vinylpyridine units is adsorbed but shows very little steric stabilization. Random copolymers of 2‐vinylpyridine content greater than 10% and AB block copolymers of more than 6% 2‐vinylpyridine behave very similarly in respect both of the quantity adsorbed and in their ability to stabilize silica suspensions. Layer thickness does not seem to depend on copolymer composition. Random copolymers with low to intermediate 2‐vinylpyridine contents are better steric stabilizers in trichloroethylene than are the corresponding copolymers of methyl methacrylate with styrene: this is attributed in part to the longer sequences of adsorbable units in the vinylpyridine copolymers.
Adsorption of polymers at the solution–solid interface. XIV. Adsorption and steric stabilization with styrene–acrylonitrile copolymers
Authors: Howard G. J. , McGrath M. J.
Published: April 2003

The adsorption of random copolymers of styrene and acrylonitrile of azeotropic composition from their trichloroethylene solutions onto precipitated silica exhibits a maximum at intermediate molecular weights. These copolymers are able to stabilize dispersions of some, but not all, grades of precipitated silica; here, too, a maximum effect is found at intermediate molecular weights. Copolymers are partially desorbed by ethyl cyanide, which destabilizes silica dispersions. Block copolymers of low acrylonitrile contents do not stabilize well but, when preadsorbed, affect the behavior of subsequently adsorbed random copolymers. In particular, high molecular weight random copolymers flocculate the pretreated silica; silica with grafted polyacrylonitrile chains may also be flocculated by these copolymers.
Light‐induced decay of free radicals in wool keratin
Authors: Shatkay A. , Weatherall I. L.
Published: April 2003

The kinetics of free radicals created by blue light in wool keratin are interpreted in terms of two decay processes: a first‐order decay occurring spontaneously even in the dark, and another first‐order decay directly proportional to the light intensity. This interpretation is supported by an analysis of previous experimental results and by more direct new experimental evidence.
Effect of pressure on free‐radical copolymerization kinetics. I. A concept of additivity of partial molar volumes of activation
Authors: Van der Meer R. , German A. L. , Heikens D.
Published: April 2003

A short review of the effect of pressure on copolymerization kinetics shows the necessity of simple models for a better understanding of activation volumes. Therefore, a simple concept, possibly generally valid for free‐radical polymerization, is proposed, based on the assumption that molar volumes of activation can be expressed as an addition of a characteristic radical and a monomer contribution, regardless of the combination involved. The scheme may facilitate the visualization of the transition state and contribute to the understanding of reaction mechanisms of radical polymerizations. Ethylene–vinyl acetate copolymerization at 62°C with tert‐butyl alcohol as solvent agrees with the proposed scheme, appearing from the pressure independence of the product of reactivity ratios at the different levels (35,600, and 1200 kg/cm2). Implicitly it can be shown that an ethylene monomer contributes about 2 cm3/mole more to the activation volumes of the propagation reactions than does the vinyl acetate monomer, whereas for the radicals the difference of the respective contributions to the activation volumes is opposite in sign.
Polymérisation anionique des diènes. VI. Microstructure des polybutadiène et polyisoprène par résonance magnétique protonique à 250 MHz et mécanismes de propagation
Authors: Salle Robert , Pham Quang‐Tho
Published: April 2003

Analysis by 250‐MHz proton magnetic resonance (PMR) allows more precise examination of the microstructure of anionic polyisoprenes and polybutadienes obtained in the presence of organo‐alkali metals. Besides vinyl addition, the propagation of contact ion pairs in dioxane solvent gives a mixture of cis and trans products with isoprene, whereas only trans product is obtained with butadiene. The presence of 1,4‐trans‐polyisoprene appears to be inconsistent with the cis configuration of the polyisoprenyllithium living end in dioxane or tetrahydrofurane media. In taking into account the existence of complexation phenomena, it was suggested that propagation mechanisms should involve a transition state which should begin with the trans configuration before isomerization into the more stable cis configuration. For the free ions, the living end of the carbanion should be entirely trans.
ESR studies of the radiation‐induced multiple graft polymerization
Authors: Omichi Hideki , Araki Kunio
Published: April 2003

The radiation‐induced multiple‐graft polymerization was studied by an ESR method. When methyl methacrylate vapor was introduced onto preirradiated polyethylene already grafted with styrene, the second step of grafting of methyl methacrylate occurred mainly in the polyethylene portion. The kinetic treatment proved that the termination rate constant kt of methyl methacrylate decreased with the amount of styrene grafted in advance. On the other hand, when styrene vapor was introduced onto polyethylene grafted with methyl methacrylate, only radicals of poly(methyl methacrylate) decreased. In this case, the second step of grafting of styrene occurred in the poly‐(methyl methacrylate) portion which covered the whole surface of the polyethylene powder. When monomer vapors were alternately introduced onto preirradiated polyethylene powder, the second step of grafting occurred at the growing chain end of the first monomer.
Synthesis of oligoesters and polyesters from oxalic acid and ethylene glycol
Authors: Alksnis A. , Deme Dz. , Surna J.
Published: April 2003

High molecular weight poly(ethylene oxalate) with fiber‐forming properties was obtained from oxalic acid and ethylene glycol. The process was carried out on two stages in the melt. A new method was used for aliphatic oligoester synthesis in the melt, because the decomposition of oxalic acid takes place in the presence of glycol. The process was carried out at low temperatures with azeotropic water removal. Investigations of the polycondensation of oxalic acid and ethylene glycol with a compound forming a heteroazeotrope with water showed that the process is subject to the general laws of the polycondensation in melt: it depends on the ratio of initial components, presence of accelerating compounds, etc. However, the reaction time of polycondensation was dependent on the stirring intensity. High molecular weight poly(ethylene oxalate) was obtained by oligomer polycondensation in the melt. Thorium carbonate and tin dichloride were used as catalysts.
High‐conversion polymerization. II. Influence of chain transfer on the gel effect
Authors: Cardenas J. N. , O'Driscoll K. F.
Published: April 2003

Kinetic equations are presented which describe the course of a free‐radical polymerization carried to high conversion when chain transfer to monomer or to other low molecular weight agents is important. Calculations are presented which show that the influence of chain transfer to monomer can greatly affect the rate of polymerization and the molecular weight averages when a polymerization is subject to autoacceleration because of the gel effect.