bluuebunny/crossref_metadata_2025 huggingface dataset:
Molecular weight and long‐chain branching distributions of some polybutadienes and styrene–butadiene rubbers. Determination by GPC and dilute solution viscometry
Authors: Kraus Gerard , Stacy C. J.
Published: April 2003

A method described for the determination of molecular weight and long‐chain branching distributions of polymers requires no prior knowledge of the functional relation between branching frequency and molecular weight. It is based on preparative fractionation and viscometric and gel‐permeation chromatographic measurements on both fractions and whole polymer. The technique is applied to several polybutadienes and butadiene‐styrene copolymers differing widely in method of synthesis and pattern of long‐chain branching.
Dilute solution characterization of polyfluoroalkoxyphosphazenes
Authors: Hagnauer G. L. , Schneider N. S.
Published: April 2003

Results from the dilute solution characterization of polyfluoroalkoxyphosphazenes in Freon ether (E2) solutions are reported. Anomalous viscosity data suggest that polymer aggregation sometimes occurs in E2 and may be caused by the presence of relatively few anomalous polar groups on the polymer backbone. Since small amounts of acetone added to the E2 solutions inhibit aggregate formation, samples are also characterized in an E2‐acetone mixed solvent. Light scattering and osmometry indicate that E2 and E2‐acetone (9.09% by volume) are theta solvents for the polymers. High molecular weights (M̄w < 3 × 106) and unusually broad molecular weight distributions (M̄w/M̄n < 16) are found. One polymer is fractionated by extracting solutions in 1,1,2‐trichloro‐1,2,2‐trifluoroethane with acetone. Although the samples are highly polydisperse, intrinsic viscosities correlate with number‐average molecular weights satisfying the Mark‐Houwink relation with the exponent a ≈ 1/2. The z‐average mean‐square radius of gyration increases linearly with molecular weight so that 〈S2〉g/M̄w ≈ 0.098. Because of the large polydispersity and unknown form of the distribution function, a quantitative interpretation of characterization results relating dilute solution parameters to polymer skeletal structure is not possible. The tentative conclusion is that the fluoroalkoxy‐substituted phosphazene polymers are relatively linear and therefore that the broad distribution of molecular weights must be due to some polymerization mechanism other than branching.
Structure of unsaturated polyester resins crosslinked with styrene as studied by raman spectroscopy
Authors: Koenig J. L. , Shih Peter T. K.
Published: April 2003

An unsaturated polyester resin and the styrene‐crosslinked polyester were studied with laser Raman spectroscopy. Following the polyesterification reaction, Raman measurements showed that the polyester contained 55% fumarate and 45% maleate unsaturation. Additionally, the glycol fragment was indicated to exist as the gauche isomer. The 1213 cm−1 line is assigned to the glycol‐ester linkage and can be measured to follow the conversion to polymer. After the crosslinking reaction, styrene was found to copolymerize preferentially with the fumarate unsaturation. There was no evidence of forming long‐chain polystyrene crosslinks. Our results indicate that, after crosslinking, 41% of the fumarates have reacted with styrene and there is an average of two styrene molecules in each link.
Conductivity of some semiconducting polyazophenylenes
Authors: Heleskivi J. , Löfgren B.
Published: April 2003

The electrical conductivity of a series of semiconducting polyazophenylenes was studied as a function of temperature and molecular weight in the temperature range 293–493°K and for molecular weights between 9500 and 62800. The compounds studied included poly‐2,4‐diminotoluene and poly‐2,5‐diaminotoluene. The temperature dependence of conductivity obeys the exponential law σ = σ0 exp {–Ea/kT}. All of the compounds studied show a break in the conductivity curve at a temperature of about 380°K with the slope of the curve greater at temperatures above 380°K. The activation energies Ea determined from the higher slopes are in the range 0.63–0.89 eV, and the corresponding σ0 values are in the range 10−4‐10° (ohm‐cm)−1. Both Ea and σ0 show a tendency to increase with increasing molecular weight such that the compensation law was valid. Activation energies and σ0 values determined from the (smaller) slope below the temperature of the break point showed a tendency to decrease with successive measurements on new samples. This indicates some kind of orientation effect, and conclusions concerning the properties of the material on basis of results below the break point are therefore difficult.
Sorption of propane and propylene in polyethylene
Authors: Santos Marcos Luiz Dos , Leitão Dorodame Moura
Published: April 2003

Measurements are reported of the solubility and concentration of propane and propylene in polyethylene, at temperatures from −30°C to +30°C and pressures from 1.68 to 3.52 atm. Solubility of both gases in polymer depends on penetrant activity. Henry's law is not obeyed at high values of the penetrant activity, i.e., in the vicinity of the condensation point of the gas. The interaction between the solvent and the polymer is independent of pressure and a function of temperature. The propylene‐polyethylene interaction seems to reach a maximum at 10°C within the range investigated. A physical mechanism, based on opposite effects of temperature upon polymer and penetrant, is suggested to explain the results.
Melting behavior of isotactic polystyrene
Authors: Lemstra P. J. , Kooistra T. , Challa G.
Published: April 2003

The melting behavior of isotactic polystyrene, crystallized from the melt and from dilute solutions in trans‐decalin, has been studied by differential scanning calorimetry and solubility measurements. The melting curves show 1, 2, or 3 melting endotherms. At large supercooling, crystallization from the melt produces a small melting endotherm just above the crystallization temperature Tc. This peak originates from secondary crystallization of melt trapped within the spherulites. The next melting endotherm is related to the normal primary crystallization process. Its peak temperature increases linearly with Tc, yielding an extrapolated value for the equilibrium melting temperature Tc° of 242 ± 1°C as found before. By self‐seeding, crystallization from the melt could be performed at much higher temperature to obtain melting temperatures as high as 243°C, giving rise to doubt about the value of Tc° found by extrapolation. For normal values of Tc and heating rate, an extra endotherm appears on the melting curve. Its peak temperature is the same for both melt‐crystallized and solution‐crystallized samples, and independent of Tc, but rises with decreasing heating rate. From the effects of heating rate and partial scanning on the ratio of peak areas and of previous heat treatment on dissolution temperature, it is concluded that this peak arises from the second one by continuous melting and recrystallization during the scan.
Interdependence of enthalpic and entropic contributions to the second osmotic virial coefficient
Authors: Wolf B. A.
Published: April 2003

The interdependence of the enthalpic contribution A2, H and the entropic contribution A2, s to the second osmotic virial coefficient for a given polymer‐solvent system has been investigated from the experimental and the theoretical point of view. Experimentally, the following common facts were observed for various systems at temperatures and pressures below the critical values for the solvent. Both the isobaric and isothermal dependences can be approximated over relatively wide ranges of A2, H by linear relations with a slope deviating only slightly, but in a characteristic manner from a value of −1. When the temperature is increased at constant pressure one moves along an isobar towards higher A2, H; when the pressure is increased at constant temperature, one moves along an isotherm in the opposite direction, i.e., towards lower A2, H. Theoretically this behavior can be described in a qualitative manner, starting from a relation derived by Patterson and Delmas on the basis of the Prigogine corresponding‐states theory. The reasons for the lack of quantitative agreement are discussed.
Measurement of surface area of polymer shavings
Authors: Salloum Robert J. , Eckert Roger E.
Published: April 2003

A modified BET apparatus has been developed to measure the surface area of polymer samples in the range 0.2–3.0 m2. The sample holder is designed to permit easy entry for bulky samples, such as polymer shavings, which cannot be loaded through a capillary or exposed to the high temperature required to seal glass. Other apparatus modifications, which allow the accurate measurement of surface area, include the addition of a dibutyl phthalate differential manometer in conjunction with a pressure reservoir. Corrections for the dead volume, nonideality of nitrogen, and the thermal gradient in the sample holder are developed. Calibrations of the equipment with inorganic samples of known areas from 1.81 to 11.8 m2 gave highly accurate values of 1.74 to 11.6 m2. Results on high‐density polyethylene shavings showed precision in determinations and very close agreement in the value of 49.7 for C in the BET equation with the published value, 47.7.
Proposed GPC and intrinsic viscosity analyses of randomly crosslinked polymers having primary distributions of the schulz‐zimm form
Authors: Shultz A. R.
Published: April 2003

A mathematical treatment is presented for the gel‐permeation chromatographic and intrinsic viscosity behavior of randomly crosslinked polymers having primary molecular weight distributions of the Schulz‐Zimm form. Kimura's serial solution of the integro‐differential equation derived by Saito for randomly crosslinked polymers is employed for the distribution function. The intrinsic viscosity of a molecule containing i crosslinks is assumed related to that of a linear molecule of the same number of units through [η]br/ = gi½[η]l where gi = (Rbr2)i/Rl2 = {[1 + (i/6)]½ + (4i/3π)}−½. Rbrand Rl denoting the root‐mean‐square radii of gyration of branched and linear chains of the same mass. It is also assumed that GPC elution is controlled by the hydrodynamic volumes of the molecules. Representative calculation results are displayed for polymers with a narrow primary distribution and the “most probable” primary distribution. Results for the latter polymers are compared with those previously obtained by a somewhat different mathematical approach.
Crazing of polystyrene containing two rubber balls: A model for ABS plastics
Authors: Matsuo M. , Wang Tsuey T. , Kwei T. K.
Published: April 2003

In order to study the crazing behavior in rubber‐toughened glassy polymers, polystyrene samples containing two rubber balls of the same diameter with varying separations have been prepared. They were subjected to simple tension, and their crazing behavior was observed. When the two balls are close together, the craze‐initiation stress is considerably lower than that of single‐ball samples. With increase in the distance between the two balls the craze‐initiation stress increases at first almost linearly and levels off when l/d reaches about 1.45, where l and d are the center‐to‐center distance and the diameter of the balls, respectively. When l is sufficiently small, the crazes are seen to develop extensively at the inner surfaces of the balls and finally bridge with each other. The crazes bridged between the balls expand largely in the plane perpendicular to the applied load.
Multiple melting transitions in natural rubber
Authors: Kim Hyo‐gun , Mandelkern L.
Published: April 2003

Detailed studies of the fusion of natural rubber, following isothermal crystallization, has revealed a hitherto undetected low temperature transition which depends on the crystallization temperature. This transition is shown to be a melting phenomenon which is not caused by any polymorphic structural changes. It can be attributed to the formation of less stable crystallites which develop as the transition progresses.
Polymorphism in polymers. I. The equilibrium melting temperature of two crystalline modifications of trans‐1,4‐polyisoprene
Authors: Flanagan R. D. , Rijke A. M.
Published: April 2003

Dilatometric, calorimetric, and dissolution studies have been made of two crystalline modifications of trans‐1,4‐polyisoprene in order to determine their equilibrium melting temperatures. This parameter is of fundamental importance in the formal treatment of polymorphism in crystalline polymers. A consistent set of thermodynamic parameters has been derived for both crystalline modifications. The equilibrium melting temperature of the polymorph, which was previously observed to melt from carefully crystallized bulk material at 64°C, was calculated to be at least 82.4°C. The other form, which melts from the bulk at 74°C, has an equilibrium melting temperature of 79.5 ± 0.5°C. The trans‐1,4‐polyisoprene, crystallized by stirring n‐butyl acetate solutions at 49°C, was found by x‐ray diffraction to be in the first form and melts at 81.2 ± 0.5°C when very slow heating rates are applied. This melting temperature is very close to the independently derived equilibrium melting temperature and lends support to the possibility that extended chain crystals are present in these solution crystallized crystals. Using the newly found melting temperatures of the two crystalline modifications it can be derived from the free energies of fusion that the first crystalline form is more stable at temperatures above approximately 66°C, whereas the other form is more stable below this temperature.
Dynamic mechanical behavior of lightly crosslinked networks of poly(n‐butyl methacrylate) and poly(n‐butyl acrylate) in the rubberlike region
Authors: Hrouz J. , Janáček J.
Published: April 2003

An investigation was made of the dynamic mechanical behavior in the rubberlike region of poly(n‐butyl methacrylate) (PBuMA) and poly(n‐butyl acrylate) (PBuA) networks lightly crosslinked with ethylene dimethacrylate to concentrations from 10−6 to 10−4 mole/cm3. The measurements were carried out by use of an apparatus for low‐frequency forced vibrations working in the frequency range 2.5 × 10−4 to 1 Hz. With parameters c1 and c2 of the Williams‐Landel‐Ferry equation, obtained from data in the main transition region, the data did not reduce in the rubberlike region for the poly(butyl methacrylate) networks; the spread of the deviations decreases with increasing concentration of the crosslinking agent. Superposition could be achieved in all cases when a shift factor was used on the vertical axis. At sufficiently low reduced frequencies and at high temperatures the storage compliance decreases in both series of polymers with increasing concentration of the crosslinking agent as expected. At higher reduced frequencies and at higher temperatures of measurement, however, anomalous behavior was observed with uncrosslinked samples having a lower compliance than those crosslinked to a very low degree. This finding was explained as due to very long relaxation times of the untrapped entanglements present in the noncrosslinked polymer, which are absent in the same polymer crosslinked already to very low degrees. The retardation spectra of both PBuMA and PBuA exhibited secondary relaxation mechanisms which were shifted by four logarithmic decades toward higher retardation times in comparison with the primary retardation maximum.
Fracture behavior in nylon 6 fibers
Authors: Lloyd B. A. , Devries K. L. , Williams M. L.
Published: April 2003

A reaction rate model of fracture in polymer fibers is described. This model assumes that bond rupture is governed by absolute reaction rate theory with a stress‐aided activation energy. It is demonstrated that the key in obtaining good agreement between the model and experiment lies in taking proper account of the variation of stress on the tie‐chain molecules. The more taut chains rupture first, and the load is redistributed among the remaining unruptured tie chains. The effect of varying the temperature both in the model and in experiments on fracture in fibers is explored. Good agreement between predictions of the model and experiment is possible only with an undeterstanding of the distribution in stress on the tie chains. The distribution in stress on the chains was experimentally determined by monitoring the kinetics of bond rupture with electron paramagnetic resonance (EPR) spectroscopy. Temperature is found to have two effects on macroscopic strength. (1) The thermal energy aids the atomic stress in breaking the atomic bonds; as a consequence the rate of bond rupture of a family of bonds under a given molecular stress is increased. In this respect temperature might be viewed as decreasing the “strength” of a bond. (2) Temperature also serves to “loosen” the molecular structure and in this way modify the distribution in stress on the tie chains. To explain bond rupture and macroscopic fracture behavior quantitatively, account must be taken of both effects.
Theoretical analysis of sorption of a binary solvent in a polymer phase. I. Occurrence and character of inversion in preferential sorption
Authors: Živný A. , Pouchlý J.
Published: April 2003

Osmotic and sorption equilibria in the system polymer–binary solvent can be represented with advantage in coordinates (u1, v3), where v3 is the volume fraction of the polymer and u1 gives the composition (volume fraction) of the binary solvent in the polymer phase. The coexistence lines and osmotic isobars are plotted; the former are used to read the preferential sorption ε of one of the solvent components in the polymer. The newly formulated equilibrium condition for the preferential sorption is applied to the Flory–Huggins theory extended by the ternary interaction parameter χT. This is used as a starting point for analyzing the conditions under which inversion of preferential sorption takes place, i.e., the sign of ε changes. The existence of inversion and the course of the inversion line in the v3 versus u1 plot are affected in a decisive manner by the extent to which the effect of the mutual interaction of solvent components prevails over the effect of the relative difference between their molar volumes and of the difference in strength of their interaction with the polymer. The effect of the ratio of molar volumes upon the preferential sorption increases with the concentration of the polymer, so that for v3 not too far from unity the component having the smaller molecule is necessarily sorbed preferentially. If, therefore, both types of small molecules are not of the same size, the inversion vanishes for large v3 even in systems where it actually occurs if v3 is small. On the contrary, the same effect can in other cases have as its consequence an inversion at moderate values of v3, even if it does not appear as v3 approaches zero; a similar effect can also be produced by a nonzero value of the interaction parameter χT. The neighborhood of the inversion line can have a “divergent” or a “convergent” character, depending on whether the component being preferentially sorbed is that present in excess. The former case is observed with negative and the latter for the positive values of the binary solvent–solvent interaction parameter χ12. The inversion with the divergent neighborhood has not yet been confirmed experimentally, owing to the small number of systems investigated.
Theoretical analysis of sorption of a binary solvent in a polymer phase. II. Occurrence of maxima and minima in the curve of total sorption
Authors: Pouchlý J. , Živný A.
Published: April 2003

It has been shown that sorption equilibrium in the system polymer–mixed solvent and the total sorption as one of its manifestations can be derived from osmotic equilibrium. The equilibrium relation for the dependence of the osmotic pressure II (as the potential for total sorption) on the composition of the ternary polymer‐containing phase also includes the preferential sorption ε. This complication leads to difficulties in the analysis of the dependence of II on composition: for this reason, analysis has been limited to the case of a very dilute polymer phase. If preferential sorption is neglected, the occurrence of an extremum on the curve representing the dependence of the total sorption on the composition of the mixed solvent is affected by the Flory‐Huggins parameters as in the occurrence of an inversion in preferential sorption, with the exception that in the former case the difference in the molar volumes of the solvent components contributes a term smaller by a factor of two. In the general case, however, the contribution of preferential sorption to the osmotic pressure (which has always a negative sign) also plays its role. Consequently, while total sorption, at a low preferential sorption and at a large positive value of the solvent–solvent interaction parameter χ12, can exhibit a maximum, a larger preferential sorption can overcompensate the effect of the parameter χ12, so that a minimum appears. The coexistence of a minimum with a maximum on the same curve is possible in some cases with positive χ12. The latter theoretical predictions have not yet been confirmed experimentally. At a negative χ12 the extremum is always a minimum.
Studies on crystalline forms of nylon 6. II. Crystallization from the melt
Authors: Kyotani Mutsumasa , Mitsuhashi Shigenobu
Published: April 2003

The relative amounts of the α and the γ crystalline forms of nylon 6 obtained from the melt under different crystallization conditions have been studied by an x‐ray diffraction procedure by comparison with a calibration curve obtained from the diffraction of standard samples. The weight fraction of the α form decreases with increasing crystallization temperature and that of the γ form increases. Growth of the α form is predominant in crystallization at 100°C and of the α form at 200°C. The amount of the α form tends to increase on annealing at 200°C for specimens crystallized at any temperature.
Bulk modulus and density of polyethylene to 30 kbar
Authors: Heydemann P. L. M. , Houck J. C.
Published: April 2003

The results of bulk modulus and density measurements on low‐density polyethylene to 30 kbar are presented. From these data the pressure coefficient dTt/dp of the glass transition temperature is obtained, and a comparison is made with data calculated from Pastine's theoretical equation of state for polyethylene.
Side‐chain crystallinity. IV. Mechanical properties and transition temperatures of copolymers of methyl methacrylate with higher n‐alkyl acrylates and N‐n‐alkylacrylamides
Authors: Jordan Edmund F. , Riser George R. , Artymyshyn Bohdan , Pensabene John W. , Wrigley A. N.
Published: April 2003

Mechanical properties were correlated with glass transition temperatures for a series of random copolymers of methyl methacrylate with comonomers selected from the higher n‐alkyl acrylates and N‐n‐alkylacrylamides. The plasticizing comonomers were the n‐butyl, 2‐ethylhexyl, n‐octadecyl, and oleyl acrylates, and the N‐n‐butyl‐, N‐n‐octyl‐, N‐n‐octadecyl‐, and N‐oleylacrylamides. The complete range of compositions was investigated. However, the bulk of the data was obtained on compositions in the glassy region below the onset of the vitreous transition. In this region it was found that the decrease in tensile and flexural moduli and strengths with increase in internal plasticizer for all of the systems was directly proportional to the decrease in Tg. It was concluded that the additive contribution to the free volume made by each side‐chain methylene group was alone responsible for the magnitude of the rate of change of properties. However, polar contributions of the amide group to stiffening the main chain exceeded those of the ester, so that the amides were less efficient plasticizers. An empirical equation was derived which described, with fair accuracy, the decrease in the mechanical parameters with composition for the amorphous copolymers. It was reasonably successful in predicting properties even into the composition range where the ambient testing temperature corresponded to or exceeded the transition temperature. In this transition region an accelerated decrease in the magnitude of the physical properties was observed. All samples exhibited brittle fracture except those tested in the transition region. Here the strain was largely irrecoverable flow. Side‐chain crystallinity did not interfere significantly with the mechanical properties because moduli and strengths had already decayed to small values near the compositions where crystallinity commenced. Non‐random copolymers of vinyl stearate and methyl methacrylate showed no internal plasticization, apparently because of macrophase aggregation.
Effect of the reference chain dimensions in the molecular theory of viscoelastic behavior of polymer networks
Authors: Ilavský M. , Hasa J. , Havlíček I.
Published: April 2003

Mooney's version of the molecular theory of polymer networks has been generalized to the case when the external strain applied in the isotropic state is different from that at network formation. As in the theory of equilibrium behavior of the polymer networks, this generalization allows inclusion in the viscoelastic functions of effects connected with the temperature dependence of internal energy of the chains and with the strain effect of the solvent. From viscoelastic functions thus generalized, it is possible to derive a relation for calculation of the monomeric friction coefficient. It also suggests the possibility of superposing data obtained at various temperatures, degrees of swelling, and condition of network formation.
Characterization of polymers under large deformation. I. Repeated chemical stress relaxation of vulcanized rubbers
Authors: Kusano Takae , Murakami Kenkichi
Published: April 2003

In this investigation, repeated chemical stress relaxation measurements were carried out to observe the relaxation behavior at large deformation. It was found that the repeated chemical stress relaxation curves were affected by both measurement temperature and the extension ratio of rubber. It was suggested on the basis of the results that temperature and mechanical stimulus have a similar effect on the stress relaxation curves. Thus we propose the following Arrhenius type equation for high extension ratios:

where α is the extension ratio and A, B are constants determined experimentally. On the other hand, from this equation and the usual Arrhenius equation, a universal equation for the extension ratio and the temperature was derived as follows:

where, T0 is voluntary temperature. The curves obtained by this equation were quite consistent with those obtained experimentally at different temperatures and extensions at large deformation.
Photopolymerization with the use of titanocene dichoride as sensitizer
Authors: Kaeriyama Kyoji , Shimura Yukio
Published: April 2003

Titanocene dichloride sensitized photopolymerization of vinyl ethers and styrene but did not polymerize methyl methacrylate and vinyl acetate. In the case of 2‐chloroethyl vinyl ether, polymerization started rapidly some time after the color of the liquid had changed from orange to green. Polymerization was also achieved by heating the monomer at 60°C after stopping the irradiation at the end of the induction period. On the basis of the reactivity of the monomers and the effect of additives, polymerization is considered to proceed cationically. In case of the polymerization of styrene, conversion increased linearly with time. The k/kt value of 6.3 × 10−5l./mole‐sec obtained for the polymerization of styrene agrees well with the value reported for radical polymerization. The agreement of the value and ineffective inhibition of polymerization in the presence of pyridine indicates the polymerization follows a radical mechanism. Copolymerization of styrene (M1) and 2‐chloroethyl vinyl ether (M2) proceeded radically, and the reactivity ratios were r1 = 2.5 and r2 = 0.6.
Long branching in poly(vinyl acetate) and poly(vinyl alcohol). III. Kinetic study of the branching reaction in the radical polymerization of vinyl acetate
Authors: Nozakura Shun‐Ichi , Morishima Yotaro , Murahashi Shunsuke
Published: April 2003

The branching reaction in the radical polymerization of vinyl acetate was studied kinetically. Branching occurs by polymer transfer as well as terminal double‐bond copolymerization. The chain‐transfer constants to the main chain (Cp,2) and to the acetoxy methyl group (Cp,1) on the polymer were calculated on the basis of the experimental data described in the preceding paper giving Cp,2 = 3.03 × 10−4, Cp,1 = 1.27 × 10−4 at 60°C, and Cp,2 = 2.48 × 10−4, Cp,1 = 0.52 × 10−4 at 0°C. Chain transfer to monomer is important with respect to the formation of the terminal double bond. The total values of transfer constants to the α‐ or β‐position in the vinyl group and the acetoxymethyl group in vinyl acetate was determined to be 2.15 × 10−4 at 60°C. The transfer constant to the acetyl group in the monomer (Cm,1) was also evaluated to be 2.26 × 10−4 at 60°C from the quantitative determination of the carboxyl terminals in PVA. These facts suggest that the chain‐transfer constant to the α‐ or β‐position in the monomer (Cm,2) is nearly equal to zero within experimental error. Copolymerization reactivity parameters of the terminal double bond were also estimated. In conclusion, it has become clear that the formation of nonhydrolyzable branching by the terminal double‐bond reaction can be almost neglected, and hence that the long branching in PVA is formed only by the polymer transfer mechanism. On the other hand, a large number of hydrolyzable branches in PVAc are prepared by the terminal double‐bond reaction rather than by polymer transfer.
Organolithium cleavage of aliphatic polyethers, polysulfides and polyimines
Authors: Vandenberg E. J.
Published: April 2003

Organolithium compounds and other Group IA organometallics cleave high molecular weight poly(alkylene oxides) very rapidly at room temperature in dilute benzene solution. This reaction also works on a dimeric polyepoxide such as bis(2‐n‐butoxyethyl)ether and much less readily on a monomeric one as 1,2‐dimethoxyethane. On the other hand, a simple aliphatic monoether such as di‐n‐butyl ether is not cleaved under conditions several orders of magnitude more drastic than were effective on the polyethers. The mechanism for this facile polyether cleavage is proposed as a β‐elimination in which the organolithium is greatly activated by chelation with the main‐chain oxygen atoms of the polyether. This cleavage method has been used broadly on high molecular weight polyethers to obtain quantitative yields of hydroxyl‐ended, amorphous, and crystalline polyethers (Mn = 500–10,000), many of which cannot be made by direct polymerization. Aliphatic polysulfides and an N‐substituted aliphatic polyamine cleave by this same method to, respectively, mercapto‐ended and secondary amine‐ended polymers. The mechanism aspects of these results are discussed.
Theoretical reaction kinetics of reversible polymerization with a linear time dependence of the rate constant
Authors: Huang Ching‐Rong , Wang Huei‐Hsiung
Published: April 2003

The theoretical kinetics of reversible polymerization of a live polymer solution is studied. The initiation, transfer, and termination reactions are assumed to be negligible. An analytic solution in a closed form is obtained which gives the transient monomer concentration after perturbation of the polymer system. The disturbance is assumed to impose a linear change of the depropagation rate constant with respect to time. It is more realistic physically than the assumption of a sudden change of rate constants. Also discussed in the paper is the application of the solution to cases which have a nonlinear change of the rate constant.
Preparation and thermal degradation of polyperfluorobut‐2‐yne
Authors: Jackson J. A.
Published: April 2003

Polyperfluorobut‐2‐yne has been prepared by the fluoride ion‐catalyzed polymerization of hexafluorobut‐2‐yne. The thermal stability of the polymer was monitored by TGA and DTA in air, argon, and vacuum environments. The major breakdown route appears to be depolymerization into fragments of lower molecular weight. Copolymerization of the acetylene with fluoroolefins was attempted; however, homopolymerization of the acetylene occurred at a far greater rate than the copolymerization reaction.
Preparation and properties of polymers from aryl cyclic sulfonium zwitterions
Authors: Schmidt D. L. , Smith H. B. , Yoshimine M. , Hatch M. J.
Published: April 2003

A new class of zwitterionic monomers were prepared in which the positive and negative sites are cyclic sulfonium and phenolate. Thermal polymerization occurs by phenolic anionic attack upon the aliphatic carbon α to the sulfonium sulfur. Polymerization proceeds with ring opening and net loss of charge to form nonionic polymers. The monomeric zwitterions are generally hydrated, crystalline solids that are soluble in water or alcohol. Chlorination of the aromatic portion of the molecule yields nonhydrated species. The polymerizations of 1‐(4‐hydroxy‐3‐methylphenyl)tetrahydrothiophenium hydroxide inner salt (dihydrate) and 1‐(3,5‐dichloro‐4‐hydroxyphenyl)tetrahydrothiophenium hydroxide inner salt were studied. The latter monomer gave a polymer with M̄n of 46,000 when a nucleophile was present as an initiator. The physical properties of this polymer were determined. Cyclization appears to be the main mechanism of termination in the polymerization of zwitterions.
Radical terpolymerization of sulfur dioxide, hexene‐1, and methyl acrylate or methyl methacrylate
Authors: Iino Masashi , Seki Kiichiro , Matsuda Minoru
Published: April 2003

The radical terpolymerization of sulfur dioxide, hexene‐1, and methyl acrylate has been investigated, and from the dilution effects on composition of the terpolymer it would seem reasonable to rule out the possibility of the participation of the charge‐transfer complex in the propagation process. We have also carried out terpolymerization of sulfur dioxide, hexene‐1, and methyl methacrylate and obtained a terpolymer having the block nature.
γ‐Radiation‐initiated post‐polymerization of methacrylic acid in the solid state
Authors: Lando J. B. , Semen J.
Published: April 2003

The solid‐state postpolymerization of slowly crystallized methacrylic acid was studied at 0°C with 60Co γ‐radiation as the initiator. The yield, molecular weight, molecular weight distribution, and stereosequencing of the polymer product were determined as a function of polymerization time. The narrow molecular weight distribution and the linear dependence of molecular weight on polymer yield were attributed to a polymerization mechanism characterized by both independent chain propagation and essentially no termination step. The overall polymerization rate was substantially faster than that reported previously for shock‐crystallized monomer, a result which was attributed to termination by the occlusion of propagating radicals at defects in the shock‐crystallized monomer. Although largely atactic, the polymer synthesized in the solid state contained a secondary kind of stereosequencing; the meso triad probability was highest at the end of the chain, where propagation had initiated and decreased continuously with chain growth. The gradient in stereosequencing along the chains was attributed to defects that were introduced into the monomer crystals by the growing polymer chains.
Alternating copolymer of butadiene and ethylene. I. Copolymerization by TiCl4–R3Al catalyst systems
Authors: Furukawa Junji , Hirai Ryuichi
Published: April 2003

Alternating copolymerization of butadiene and ethylene was investigated by the TiCl4−R3Al system as catalyst with the use of toluene solutions of monomers of various compositions or by introducing a 1:1 gaseous mixture of both monomers into the reaction system. It was found that the copolymer composition is much influenced by the monomer composition or by the flow rate of monomer. Copolymers containing sequences of alternating monomer arrangement are formed by the polymerization of a monomer mixture having a butadiene: ethylene ratio of 4:1. A suitable catalyst for the alternating copolymerization was found to consist of R3Al−TiCl4 at a ratio of 2. The addition of amine was found to modify the catalyst to favor the alternating copolymerization but was accompanied by a decrease in catalyst activity.
Radiation‐induced heterogeneous polymerization of ethylene in the presence of ethyl alcohol
Authors: Wada Takeshi , Watanabe Terutaka , Takehisa Masaaki
Published: April 2003

The radiation‐induced heterogeneous polymerization of ethylene in ethyl alcohol was carried out in a reactor with a capacity of 100 ml under the following reaction conditions: temperature, 24 ± 3°C; pressure, 200–400 kg/cm2; amount of ethyl alcohol, 30–70 ml; dose rate, 3.7 × 104−1.05 × 105 rad hr. The effects of amount of ethyl alcohol, pressure, and dose rate on the rate of polymerization at the steady state, the amount of polymerized monomer, the molecular weight of polymer, and the number of polymer chains were studied compared with the results obtained in the polymerization in tert‐butyl alcohol. It was found that there is an acceleration period in the early stage of reaction followed by a steady state. The rate of polymerization was maximum when about 50 ml of ethyl alcohol was used. The molecular weight of polymer increased with a decrease in the amount of ethyl alcohol. The dependences of pressure (p) and dose rate (I) on the rate of polymerization at steady state (Rs) and the molecular weight of polymer (M̄n) were expressed as follows; Rs ∝ p0.74, M̄n ∝ p0.3−0.4, Rs ∝ I0.9 and M̄n ∝ I−0.1 −0.0. The results were analyzed by a kinetic treatment based on a reaction mechanism containing both first‐and second‐order terminations. The rate constant of first‐order termination by radical occlusion was considerably larger than that in the polymerization in tert‐butyl alcohol, because the affinity of ethyl alcohol for polyethylene is smaller than that of tert‐butyl alcohol. It was found that chain transfer to ethyl alcohol takes place easily and the G value of ethyl alcohol for initiation is larger than 1.5.
Molecular weight distributions in radiation‐induced polymerization. VII. γ‐ray‐induced polymerization of “wet” styrene in the solid state
Authors: Westlake John F. , Huang Robert Y.
Published: April 2003

In the present paper kinetic and molecular weight distribution results are reported for the γ‐ray‐initiated polymerization of styrene in the solid state. “In‐source” polymerization over the temperature range −35°C to −55°C and post‐polymerization at −35°C have been investigated for “wet” styrene samples (water concentration ≈ 10−3 mole/l.). An interesting feature of the solid‐state polymerization of styrene is the bimodal nature of the molecular weight distribution. On a qualitative basis the results resemble those obtained previously for the polymerization of rigorously dried (“dry”) styrene. However, there are noticeable differences on a quantitative basis resulting from the considerable difference in the water content between wet and dry samples. On the basis of these studies, the kinetic and molecular weight distribution data have been interpreted as being indicative of polymerization occurring simultaneously via free‐radical and cationic mechanisms.
Catalytic action of calcium acetate and the manganese acetate–sodium acetate mixture in the pre‐esterification of dimethyl terephthalate with ethylene glycol
Authors: Dimov K. , Terlemezyan E.
Published: April 2003

Products of pre‐esterification of dimethyl terephthalate with ethylene glycol at various times carried out with two catalysts, i.e., calcium acetate and a mixture of manganese and sodium acetates, were studied. Thin‐layer chromatography was used to follow the fundamental reaction and determine the type and degree of oligomerization. It was established that the manganese–sodium acetate mixed catalyst is more efficient both with regard to pre‐esterification and oligomerization.
Oxidized polyethylenimine
Authors: Haas Howard C. , Schuler Norman W. , Macdonald Ruby L.
Published: April 2003

Polyethylenimine (PEI) has been oxidized with aqueous hydrogen peroxide to yield a hygroscopic, water‐soluble, slightly basic, yellow polymeric solid (OPEI) containing about 25% oxygen. Some chain degradation accompanies oxidation. The nature of the product varies somewhat with preparative conditions. OPEI, in the presence of strong alkali, reduces silver salts and peptizes a portion of the silver. By use of infrared, ultraviolet, and proton magnetic resonance spectroscopy together with qualitative testing, OPEI has been found to contain carboxyl groups, unoxidized primary amine groups, tertiary amine oxide, small amounts of aldehyde and nitrone groups, and a considerable amount of secondary amide. The probable reaction sequence is: PEI → dialkylhydroxylamine → nitrone → oxazirane → rearranged product. Oxazirane groups appear to be absent, as well as oxime, nitro, nitrite, and nitrate. The groups which reduce silver salts are not known with certainty but are probably of the hydroxylamine type. The carboxyl content of OPEI is associated with the lower molecular weight species which are present.
Effect of the excluded volume on specific rate of combination reactions between polymer radicals
Authors: Ito Katsukiyo
Published: April 2003

The specific rate kD for reaction between polymer radicals is formulated when the potential of average force on the basis of the excluded volume affects the motion of the polymer radicals. This rate is given by \documentclass{article}\pagestyle{empty}\begin{document}$ k_D = Fk_S \left( {{\rm with}\ {F} = \sum\limits_{s = 0}^\infty {{{[ ‐ 2(\alpha ^2 ‐ 1)]} \mathord{\left/ {\vphantom {{[ ‐ 2(\alpha ^2 ‐ 1)]} {(s + 1)^{{3 \mathord{\left/ {\vphantom {3 2}} \right. \kern‐\nulldelimiterspace} 2}} }}} \right. \kern‐\nulldelimiterspace} {(s + 1)^{{3 \mathord{\left/ {\vphantom {3 2}} \right. \kern‐\nulldelimiterspace} 2}} }}} } \right) $\end{document} where kS is specific rate of reaction between radical chain ends and α is the average expansion of the polymer arising from the long‐range effects. The effect of the excluded volume reduces kD. F depends on the degree of polymerization of the polymer radical when α ≠ 1. These results are discussed in terms of the experimental data for very low polymer concentrations.
Sulfur‐containing polymers. V. Preparation of polyoxycarbonylsulfenamides by polycondensation of bis(oxycarbonylsulfenyl chlorides) with diamines
Authors: Kobayashi Norio , Fujisawa Tamotsu
Published: April 2003

Polyoxycarbonylsulfenamides (POSA) have been prepared by interfacial polycondensation of bis(oxycarbonylsulfenyl chlorides) with diamines. The polymers obtained ranged in physical form from crystalline solids to resinous materials depending on the kind of both bis(oxycarbonylsulfenyl chlorides) and diamines used. Some of the polymers gave transparent pliable films from chloroform solution. The polymer films decomposed with liberation of carbonyl sulfide on being subjected to ultraviolet radiation.
Benzophenone/triethylamine‐photoinitiated polymerization of methyl acrylate
Authors: Sandner M. R. , Osborn C. L. , Trecker D. J.
Published: April 2003

Benzophenone‐sensitized photopolymerization of methyl acrylate was shown to be remarkably enhanced by the addition of small amounts of triethylamine. This was attributed to the efficient formation of an electron‐transfer complex between photoactivated benzophenone and ground‐state amine. Ketyl and amine free radicals derived from this complex were postulated to be the chain‐initiating species. Quantum yield experiments indicated that methyl acrylate itself was also a quencher of the benzophenone triplet state.
Polymerization of α‐methylstyrene by n‐butyllithium in tetrahydrofuran
Authors: Bitsenko M. I. , Podolsky A. F. , Khvostik G. M. , Sokolov V. N.
Published: April 2003

The kinetics of polymerization of α‐methylstyrene by n‐BuLi (labeled with C14 and unlabeled) has been studied in tetrahydrofuran at −78°C. The catalyst n‐BuLi was used as a complex of n‐BuLi in THF and a hexane solution of n‐BuLi. Contrary to expectations, the relative polymerization rate and the catalyst consumption were higher when a hexane solution of n‐BuLi was used. Experimental molecular weights of the polymers greatly exceeded those calculated for the case of complete catalyst consumption. The polymers exhibited low polydispersity, and when a hexane solution of n‐BuLi was used, the molecular weight distribution was bimodal. The rate of initiation for the case of polymerization α‐methylstyrene with a hexane solution of n‐BuLi as a catalyst was much higher than in the polymerization of α‐methylstyrene with the use of the complex of n‐BuLi in THF as in situ catalyst. Experimental data confirm the preferable interaction of α‐methylstyrene with associated n‐BuLi in the presence of THF. The complex which was formed as a result of such interaction is an active centers of polymerization.
Photoinduced ionic polymerization. II. Cationic polymerization of α‐methylstyrene in the presence of tetracyanobenzene
Authors: Irie Masahiro , Tomimoto Setsuko , Hayashi Koichiro
Published: April 2003

The dependence of the rate of polymerization on light intensity and the stereoregularity of the polymer was studied to elucidate the propagation and termination mechanisms of the photoinduced cationic polymerization of α‐methylstyrene in the presence of tetracyanobenzene in methylene chloride. The rate of polymerization was proportional to the light intensity. The polymer is highly syndiotactic, and the stereoregularity is similar to that of polymers obtained by radiation‐induced cationic polymerization. The initiation mechanism was also studied by electron spin resonance, by which the anion radical of tetracyanobenzene formed from a photoexcited complex between α‐methylstyrene and tetracyanobenzene was observed. The cation radical of α‐methylstyrene, counterpart of the anion radical, is believed to initiate the polymerization.
Copolymerization of styrene and diethyl fumarate with ZnBr2. IV. Comparison between photoinitiation and electroinitiation
Authors: Davies D. H. , Phillips D. C. , Smith J. D. B.
Published: April 2003

A comparative analysis of photoinitiation and electroinitiation can help elucidate initiation processes in donor‐acceptor charge‐transfer copolymerization. The technique has been applied to the zinc bromide‐catalyzed copolymerization of styrene and diethyl fumarate in methanol. The photocopolymer product was analyzed by GPC, NMR, and elemental analysis. The results showed that 1:1 copolymers were formed initially, but changes occurred in both the kinetics and products after the early stages of the reaction. Significant correlations found between the two initiation methods included the initial kinetic order with respect to the initiating process and the effect on product yield of equivalent increases in total initiation energy. The limiting value of zinc bromide for both initiation methods was found to be the same. The data obtained support the contention that the copolymerization proceeds through a donor–acceptor process and that photoactivation of the preformed complex, inducing electron transfer, is a likely initiation process.
Copolymerization of styrene and diethyl fumarate with zinc bromide. III. Electroinitiation at low current densities
Authors: Phillips D. C. , Smith J. D. B. , Davies D. H.
Published: April 2003

The electroinitiated preparation of equimolar copolymers of styrene and diethyl fumarate is described. The reaction medium consisted of these monomers dissolved in a methanol–zinc bromide solution. Rates of polymerization increased with increasing applied current and the copolymer yield increased linearly with the total number of Faradays transferred. The copolymer composition is 1:1 and is essentially invariant with the degree of conversion (<15%), electroinitiation rate, and monomer feed ratios. A reaction mechanism involving donor–acceptor complexes and electroinitiated excitation of these complexes at the electrode is postulated.