bluuebunny/crossref_metadata_2025 huggingface dataset:
Microstructure of the copolymers of methyl methacrylate with other methacrylates obtained by radical and anionic copolymerizations in tetrahydrofuran
Authors: Yuki Heimei , Okamoto Yoshio , Shimada Yoshiki , Ohta Koji , Hatada Koichi
Published: April 2003

Monomer reactivity ratios r1 and r2 were determined in the copolymerizations of methyl methacrylate (MMA, M1) with 1, 1‐diphenylethyl (DPEMA), α,α‐dimethylbenzyl (DMBMA), tert‐butyl (t‐BuMA), diphenylmethyl (DPMMA), phenyl (PhMA), and 1‐naphthyl (NpMA) methacrylates (M2) in tetrahydrofuran (THF) by azobisisobutyronitrile (AIBN) at 60°C and butyllithium (n‐BuLi) at −78°C. The reactivities of the monomers were explained in terms of the polar effect of the ester groups in both copolymerizations. All the copolymers isolated in low yields were converted to PMMA either directly or by copoly(MMA—methacrylic acid) to determine the triad tacticities of the copolymers. Coisotactic parameters σ12 and σ21 were determined by assuming the terminal model statistics. The σ21 values always accorded to the σ21 values within experimental error, and in radical copolymerizations they were between isotactic parameters σ11 and σ22 of the homopolymerizations of MMA and M2 monomers. In anionic copolymerizations, however, the σ12 = σ21 values varied, depending on the M2 monomers. In copolymerization with DPEMA the values were less than both σ11 and σ22 with DMBMA they were between σ11 and σ22, with DPMMA, nearly equal to σ11, and with PhMA and NpMA, greater than both σ11 and σ22. The application of these parameters to copolymerizations performed at high conversion was also investigated.
Radiation‐induced grafting polymerization by the anionic mechanism
Authors: Kabanov V. Ya. , Aliev R. E.
Published: April 2003

The radiation‐induced grafting polymerization of phenylacetylene and 2‐methyl‐5‐vinylpyridine (2M‐5VPy) onto low‐density polyethylene has been investigated under strict identical conditions, using crude and thoroughly dried monomers. In the case of thoroughly dried monomers, the radiation‐induced grafting is performed by the combined (radical + anionic) mechanism. The kinetics of radical and anionic grafting of 2M‐5VPy are investigated in detail. The activation energies are 4.8 ± 0.3 and −2.7 ± 0.3 kcal/mole for the radical and anionic grafting, respectively. The initial rate of grafting is approximately proportional to the dose rate to the 0.47 ± 0.03 and 0.92 ± 0.03 power for the radical and anionic grafting, respectively. The initial rate of grafting is approximately proportional to monomer concentration to the 1.55 ± 0.05 and 2.1 ± 0.05 power for the radical and anionic grafting, respectively. These data conform to the contribution of the anionic mechanism in a thoroughly dried system. The mechanism of radiation‐induced anionic grafting is discussed.
Radiation‐induced addition reaction of carbon tetrachloride onto 1,2‐polybutadiene
Authors: Okamoto Hidemasa , Adachi Shoichi , Iwai Tadashi
Published: April 2003

The γ‐ray‐induced addition reaction of carbon tetrachloride onto syndiotactic 1,2‐polybutadiene film and liquid 1,2‐polybutadiene was carried out at room temperature. In the film gelation was pronounced and the rate of addition increased as the crystallinity of the polymer decreased. In the liquid gelation, which makes the polymer insoluble in carbon tetrachloride, did not take place, although a definite crosslinking reaction was noticed. In this case the appearance of the product changed from a viscous liquid to a white powder as the reaction proceeded. Its structure was compared with that of chlorinated 1,2‐polybutadiene. The addition of carbon tetrachloride to the vinyl group in liquid 1,2‐polybutadiene caused an anti‐Markownikoff‐type reaction and was accompanied by an unexpectedly large vinyl depletion in the polymer. The total decrease in the vinyl group was found to be much larger than that brought about by the addition of carbon tetrachloride. This discrepancy was attributed to a cyclization and crosslinking reaction ascribed to the vinyl group bound by the main chain. Cyclization and crosslinking were less noticeable in the chlorination than in the carbon tetrachloride.
Mechanism of radiation‐induced addition reaction of carbon tetrachloride onto liquid 1,2‐polybutadiene accompanied by cyclization
Authors: Okamoto Hidemasa , Adachi Shoichi , Takada Kiyoshi , Iwai Tadashi
Published: April 2003

Effects of irradiation conditions were investigated in the γ‐ray‐induced addition reaction of carbon tetrachloride onto liquid 1,2‐polybutadiene. The rate of addition reaction was proportional to the dose rate, and its apparent activation energy was 1.4 kcal/mole in the range of ca. 20–80°C; the G values for the addition of carbon tetrachloride and vinyl consumption were high. The addition reactions of methyl isobutylate, isopropyl amine, and bromotrichloromethane to liquid 1,2‐polybutadiene by γ rays were studied to compare with carbon tetrachloride. Methyl isobutylate and isopropyl amine were added much more slowly. On the other hand, in bromotrichloromethane the rate of addition reaction was much faster but cyclization was less pronounced than in carbon tetrachloride. On the basis of these results a mechanism of a radical chain reaction which includes the addition of carbon tetrachloride, cyclization, and crosslinking, is proposed.
Copolymerization of 1,6‐anhydro‐ß‐D‐galactopyranose and 1,6‐anhydro‐ß‐D‐mannopyranose derivatives
Authors: Ito Hiroshi , Marousek Vladimir , Schuerch Conrad
Published: April 2003

1,6‐Anhydro‐2,3,4‐tri‐O‐(p‐methylbenzyl)‐ß‐D‐galactopyranose (TXGal,M1) has been copolymerized with 1,6‐anhydro‐2,3,4‐tri‐O‐benzyl‐ß‐D‐mannopyranose (TBMan,M2), the products characterized by NMR, specific rotation, and viscosity, and the reactivity ratios calculated. The reactivity ratios r1 = 0.37 ± 0.15 and r2 = 38 ± 4 indicate that the anhydromannose derivative is about 100 times as reactive as that of anhydrogalactose. A comparison of glucose, mannose, and galactose copolymerizations suggests that the reactivity differences of the three propagating cations are comparatively small and the reactivity differences of the monomers large. This result is consistent with a mechanism proposed earlier. Methyl substitution on the aromatic rings of the p‐xylyl groups inhibits the initiation process significantly relative to benzyl, but propagation only slightly.
Kinetics of the copolymerization of styrene with small quantities of divinylbenzenes
Authors: Kwant P. W.
Published: April 2003

The study of copolymerization of styrene with small amounts (≤0.04 wt %) of divinylbenzenes (DVB) offers advantages over similar studies made at high DVB concentrations. A simple set of equations can be used to describe the kinetics of copolymerization at low DVB concentrations. Experimental data show that the copolymerization constants (r2) for the copolymerization of the first double bonds of m‐ and p‐DVB (monomer 1) with styrene (monomer 2) are 0.85 and 0.43, respectively. In contrast to findings at higher DVB concentrations these constants do not change during the first half of the polymerization. After 50% conversion an autoacceleration effect reduces the selectivity of the growing polystyrene radical. The copolymerization constants for the second double bonds of m‐ and p‐DVB during the first half of the polymerization are estimated as 1.
Thermal decomposition products of a chlorinated aromatic polyamide
Authors: Chatfield D. A. , Einhorn I. N. , Mickelson R. W. , Futrell J. H.
Published: April 2003

Products from the thermal decomposition of a chlorinated aromatic polyamide fabric are described for conditions of pyrolysis and flaming and nonflaming oxidative degradation. Volatile degradation products were identified by gas chromatography‐mass spectrometry (GC‐MS) and the condensible fraction, by infrared (IR) spectroscopy, high‐pressure liquid chromatography (HPLC), and MS. Nonvolatile char was characterized by IR and elemental analysis. Twenty‐one compounds were identified as volatile products from pyrolysis at 550°C; the condensible material contained ammonium chloride and at least 22 organic compounds. From volatile compounds produced in flaming oxidative degradation 21 compounds were identified, of which CO, CO2, and H2O were prominent. Nonflaming oxidative degradation at 400 and 550°C produced 11 and 21 volatile identifiable compounds, respectively, and results from experiments at the higher temperature compared favorably with results from the flaming experiments. By comparison of data from this work with those from unchlorinated analogs (described in an earlier article), it is concluded that the incorporation of chlorine into the polymeric structure lowers the temperature for the onset of thermal degradation and alters the type and concentration of thermolytic products. The major degradation products can be explained by a mechanism similar to that proposed for aromatic polyamides with the exception of the formation of substantial amounts of ammonium chloride. It is proposed that the latter is formed by an initial acid‐catalyzed hydrolysis reaction which is followed by deammoniation or by an intermolecular process that involves an isoimide intermediate.
Analysis of the products of thermal decomposition of an aromatic polyamide fabric
Authors: Chatfield D. A. , Einhorn I. N. , Mickelson R. W. , Futrell J. H.
Published: April 2003

The thermal degradation of an aromatic polyamide was studied under conditions of pyrolysis and oxidative degradation at 550°C and of flaming combustion. Techniques described elsewhere were used to determine the volatile compounds quantitatively by gas chromatography‐mass spectrometry (GC–MS). The condensible material and the solid residue were characterized by infrared spectroscopy and MS, and in pyrolysis experiments 28 compounds were identified (CO, CO2, H2O, and C6H5CN were the primary products). Collectively, these compounds accounted for 79% of the sample weight loss. The remaining 21% was a condensible material that contained at least 17 compounds; the two major components were 1,3‐dicyanobenzene and 3‐cyanobenzoic acid. Most of the nitrogen content of the polymer remained as involatile residue. This study was sufficiently detailed to obtain a mass balance between the composition of the original polymer and the sum of the observed pyrolysis products. The major products observed in pyrolysis experiments supported a mechanism that involved the cleavage of an aromatic‐NH bond and the loss of H2O to form aromatic nitriles. Hydrolysis of the amide linkage, followed by decarboxylation of the product acid, accounted for the high concentrations of CO2 observed. Oxidative degradation at 450°C yielded ten identifiable compounds and an additional 19 volatile compounds were formed at 550°C. The condensible fraction, which contained at least 20 compounds, was similar in composition to the fraction collected from the pyrolysis experiments. The sum of the carbon content from the two major volatile products of oxidative degradation (CO and CO2) and from the solid residue quantitatively accounted for the carbon content in the original sample. Flaming combustion studies revealed a markedly different product distribution than was observed under nonflaming conditions, especially in regard to the higher‐molecular‐weight species.
Polymerization of t‐butyl thiirane. II. Polymerization of enantiomerically enriched monomer. Mechanism of stereoelective process
Authors: Dumas Philippe , Spassky Nicolas , Sigwalt Pierre
Published: April 2003

The kinetics of enantiomerically enriched t‐butyl thiirane was studied. The stereoelectivity and the kinetic behavior are not changed when a monomer of an initial enantiomeric composition lower than a defined limit value is used. When the enantiomeric composition is higher than this value, the stereoelectivity increases. In agreement with kinetic results, a mechanism is proposed involving, in a first step, the complexation of monomer on preexisting sites of the initiator with formation of highly selective chiral active species on which propagation occurs.
Synthesis and properties of polyurethanes derived from bis‐N‐hydroxyimides and diisocyanates
Authors: Kurita Keisuke , Imajo Hidetomo , Iwakura Yoshio
Published: April 2003

Polyurethanes were synthesized by polyaddition reaction of bis‐N‐hydroxyimides and diisocyanates. The reactions were carried out in an aprotic polar solvent such as dimethylacetamide or N‐methyl‐2‐pyrrolidone, and the polymers with inherent viscosities of up to 1.32 dl/g were obtained. These polyurethanes were found to exhibit high reactivity toward nucleophiles such as water and amines, which brought about rapid reduction of viscosity. The stabilities against heat and exposure to sunlight were also studied.
Polymerization of diacetylenes in multilayers
Authors: Tieke B. , Lieser G. , Wegner G.
Published: April 2003

A series of amphiphilic diacetylene monocarbonic acids was synthesized, and their ability to form monolayers at the air–water interphase was investigated. Acids with total number of C atoms ≥20 and mp >45°C form surface states suitable to be used for buildup of multilayers by the Langmuir–Blodgett technique. Using the LB technique, multilayers of defined thickness were built up on quartz substrates. The multilayers were polymerized by exposure to a UV light source according to the mechanism of solid‐state polymerization of diacetylenes without destruction of the layer structure and with retention of the packing in the individual layers. Thus well‐defined polymer multilayers were obtained. The monomer and polymer multilayers were characterized by UV spectra, x‐ray small‐angle diffraction, and interference microscopic and electron microscopic techniques. The polyconjugated backbones of the polymer chains are all stretched out in the plane of the substrate but not over macroscopic dimensions because the multilayers have a crystalline domain structure. The polymer multilayer films are quite stable under ambient conditions.
2,4‐Dimethyl‐3‐pentanone‐sensitized photopolymerization of vinyl monomers
Authors: Encina M. V. , Lissi E. A.
Published: April 2003

The initiation quantum yield in the bulk photopolymerization of vinyl monomers sensitized by 2,4‐dimethyl‐3‐pentanone has been measured for several monomers. The results obtained were interpreted in terms of a mechanism that considers singlet and triplet photocleavage of the ketone, competing with the quenching by the monomer. The quenching process does not lead to free radicals that can initiate the polymerization.
Thermotropic liquid crystalline polymers. I. Cholesterol‐containing polymers and copolymers
Authors: Shibaev V. P. , Platé N. A. , Freidzon Ya. S.
Published: April 2003

An approach to the creation of thermotropic cholesterol‐containing liquid crystalline polymers by the chemical binding of cholesterol molecules with side chains of comblike polymers is presented. This type of structure permits a decrease in the steric hindrances provided by the backbone chains for the purpose of realizing the liquid crystalline state. A number of new cholesteric esters of poly(N‐methacryloyl‐ω‐aminocarbonic acid)s (PChMAA‐n) with different side‐chain lengths (n = 2–11) as well as a series of copolymers of ChMA‐n with n‐alkylacrylates and n‐alkylmethacrylates have been synthesized. The experimental evidence of liquid crystalline structure formation in these polymers in glass, viscoelastic, and fluid states is discussed. Molecular and supermolecular structures of cholesterol‐containing comblike polymers have been studied and the model of macromolecular packing in the liquid crystalline state is proposed. It is shown that the existence of a layered order of side methylene groups together with ordering of cholesterol groups is necessary to the production of the liquid crystalline state in these polymers.
Photooxidation of polybutadiene: Quenching of excited triplet states of αβ‐unsaturated carbonyls
Authors: Hargreaves J. S. , Phillips D.
Published: April 2003

The quenching of the triplet states of several model αβ‐unsaturated ketones and that produced by thermal oxidation of polybutadiene by the triplet quencher cyclooctadiene at low temperatures has been studied by quantum yield and phosphorescence decay‐time methods. Both the Perrin and Inokuti–Hirayama relationships were tested and a typical exchange interaction distance for half‐quenching of R0 = 12 ± 1 Å was obtained for both models on all compounds studied.
Polymerization of acetylenes catalyzed by rhenium carbonyl halides
Authors: Tsonis Christos P. , Farona Michael F.
Published: April 2003

The homogeneous catalyst Re(CO)5X (X = Cl, Br) was found to promote the homopolymerization of terminal alkynes at elevated temperatures. Detection and structure characterization of low‐molecular‐weight products provided evidence of the formation of a metal–acetylide species as the initiator of polymerization, and propagation occurs by a series of insertion reactions of coordinated alkynes into metal–carbon bonds of the growing chain. Evidence of the active forms of the catalyst comes from studies on gas evolution, catalyst derivatization, and copolymerization reactions. The final polymers have a linear, polyconjugated macrostructure, and the formation of aromatic species was not detected in these reactions.
Small‐angle x‐ray scattering from solution of rodlike particles with length distribution
Authors: Ishimuro Yoshitaka , Hamada Fumiyuki , Nakajima Akio
Published: April 2003

The scattering function of rods with a constant radius, 8 Å, and a length distribution of the Schulz–Zimm type was calculated on a computer as a model of helical synthetic polypeptide. The influence of length and length distribution on the scattered intensity of small‐angle x‐ray scattering was clarified. As length grows and length distribution broadens it is difficult to obtain reliable values of molecular weight and radius of gyration from a Zimm plot. The influence of length distribution on the mass per unit length, Mq, and the radius of gyration of the cross section, 〈S〉1/2, from the Guinier plot of the cross‐sectional factor decreases as the length increases, and reliable values of Mq and 〈S〉1/2 can be obtained even for rods with wide distribution for rods more than 600 Å long. In particular, it is pointed out that the value of 〈S〉1/2 is little influenced by length and length distribution.
Radiation crosslinking of polymethylhydrogensiloxane containing methoxy groups
Authors: Nishide Shinko , Shimizu Harumichi
Published: April 2003

The bulk viscosity of polymethylhydrogensiloxane containing methoxy groups (PMHS‐A) was measured before and after irradiation. The gel point was then determined from the variation of viscosity by irradiation by comparing it with methoxy‐free polymethylhydrogensiloxane (PMHS‐B) and polydimethylsiloxane blocked by methoxyldimethylsilyl (PDMS‐C) or trimethylsilyl (PDMS‐D). The following results were obtained: (1) The G value of crosslinking by irradiation is 167, 52, 25, and 3 for PMHS‐A, PMHS‐B, PDMS‐C, and PDMS‐D, respectively. (2) The scission of the SiOCH3 bond is easier than that of the SiH, SiCH3, or SiCH2H bond. The SiOCH3 bond is PMHS‐A is severed from SiO· and ·CH3 to induce chain reactions at the initial stage by irradiation. (3) It was confirmed that the commercial PMHS is at present free of methoxy groups. To replace the hydrogen of SiH in the commercial PMHS with methoxy groups heat treatment with methanol was performed by which the G value of crosslinking was increased.
High‐conversion polymerization. IV. A definition of the onset of the gel effect
Authors: Dionisio J. , Mahabadi H. K. , O'Driscoll K. F. , Abuin E. , Lissi E. A.
Published: April 2003

The gel effect in free radical polymerization of vinyl monomers has been recognized as the result of the increased viscosity of the reaction solution of polymer in monomer, which causes a decrease in the rate of the termination reaction. This effect manifests itself as an increase in the rate of polymerization over that rate to be expected in its absence. Definition of the onset of the gel effect has become necessary for several purposes. Previously, it has been common to define the onset phenomenologically, i.e., in terms of the increase in the rate of polymerization. It is proposed here that the onset of the gel effect is best defined on a fundamental basis, i.e., as occurring at that conversion at which the rate of segmental diffusion of the polymeric radicals equals the rate of their translational diffusion. Experimental evidence is presented that shows that the small minima predicted by this definition do exist for both rates and degrees of polymerization. Measurements of the viscosities of solutions of polymers in their monomers suggest that the polymer concentrations at which the “chain‐entanglement” phenomena are observed are the same as those for the onset of the gel effect for styrene, methyl methacrylate, and butyl methacrylate.
Kinetics of the hydrolysis of linear poly[(acylimino)‐ethylenes]
Authors: Kem Kenneth M.
Published: April 2003

The kinetic variables associated with the hydrolysis of linear poly[(acylimino)ethylenes] by acid and base have been studied. As anticipated, both reactions follow conventional second‐order rate laws and are essentially irreversible. This stoichiometry and the unexpectedly rapid rate of the acid hydrolysis have been useful in the preparation of partly deacylated poly[(acylimino)ethylenes]. The desired degree of deacylation can be accurately obtained by the relative amount of acid and hydrolyzable amide functionality. The effects of the reaction temperature and nature of the acyl group on the reaction rate have been determined and an unusual relationship between rate and molecular weight was uncovered. The reactions are compared with the hydrolyses of corresponding monomeric tertiary amides and the potential utility of the products is discussed.
Polymer morphology and random chain scission of nylon 66
Authors: Kachi H. , Jellinek H. H. G.
Published: April 2003

Nylon 66 films with varying spherulite size but almost constant percentages of crystallinity were prepared (melt method). These films were degraded by NO2 over a range of temperatures from 35 to 65°C. Random chain scission took place except in the initial stages at low temperatures at which some crosslinking occurred. Observation of the films with the extent of degradation under polarized light revealed that dark bands developed around and also inside spherulite boundaries that became wider with the extent of degradation. This indicates that amorphous material is formed during random chain scission; the spherulites remained practically intact, however. The experimental chain scission rate constants did not change essentially with spherulite diameter until small diameters were reached, at which time the rate constants increased noticeably. Degradation can be accounted for by chain scission in amorphous and interfacial regions; in the latter the rate constants increased with this area and in addition main chain links were weaker in fold regions, due to strain energy, than normal ones in amorphous regions. The energy of activation for chain scission was compatible with a predominantly diffusion‐controlled process.
Thermally reversible polymer systems by cyclopentadienylation. I. A model for termination by cyclopentadienylation of olefin polymerization
Authors: Kennedy Joseph P. , Castner Kenneth F.
Published: April 2003

The reaction between tert‐butylchloride (t‐BuCl) and dimethylcyclopentadienylaluminum (Me2AlCPD) was studied as a model for initiation by the tert‐butyl cation (t‐Bu⊕) and termination by cyclopentadienylation by the Me2Al(CPD)Cl⊖ counteranion of isobutylene polymerization. All reaction products formed in this model system have been identified and quantitatively determined. A comprehensive scheme that indicates pathways to these products was developed (scheme III). It is proposed that the predominant product, tert‐butylcyclopentadiene (t‐BuCPD), arises in the collapse of the t‐Bu⊕‐Me2Al(CPD)Cl⊖ ion pair, mainly by CPD⊖ transfer to the tert‐butyl cation. The minor products are neopentane (t‐BuMe) and isobutylene (i‐C4H8), which are probably formed, respectively, by Me⊖ transfer to and proton loss from the t‐butyl cation. Cyclopentadienylation selectivity increases by lowering the temperature and extrapolation of results suggests 100% cyclopentadienylation at −55°C. The t‐BuCl/Me2AlCPD ratio strongly influences the overall reaction pathway. The reaction is first order in t‐BuCl with ΔEa of ca. 7 kcal/mole (1,2‐dichloroethane or chlorobenzene solvents, +24 to −29°C). Indirect evidence indicates that the kinetic product of cyclopentadienylation is 5‐t‐BuCPD and that this isomer cannot be tert‐butylated; that is, the initiation of 5‐t‐BuCPD polymerization by t‐Bu⊕ is sterically unfavorable. Detailed analysis of the chemistry and kinetics of the t‐BuCl/Me2AlCPD model system holds important clues to the controlled polymerization of olefins leading to macromolecules with cyclopentadiene (CPD) termini.
Studies on the optical active alternating copolymer of benzofuran or 1,3‐cyclooctadiene with acrylic monomers
Authors: Kobayashi Eiichi , Furukawa Junji , Nagata Shiro
Published: April 2003

In the presence of an optical active amyloxyaluminum or menthoxyaluminum chloride the asymmetric‐induction alternating copolymerization of benzofuran or 1,3‐cyclooctadiene and acrylonitrile or methacrylonitrile was investigated. The sign of optical rotation of copolymers was positive or negative, depending on the kind of catalyst used. The optical activity of copolymers of benzofuran and acrylonitrile attains a maximum value at an equimolar composition. The highest specific rotation [α]D of copolymers of benzofuran and acrylonitrile prepared in the presence of stoichiometric amount of (—)‐menthoxyaluminum dichloride with respect to acrylonitrile was about −8°. The stereo‐structure of acrylonitrile unit may be controlled by the optical active aluminum compound onto which a strong coordination of acrylonitrile may occur.
Photopolymerization of methyl methacrylate using hydrogen peroxide as the photoinitiator
Authors: Ghosh Premamoy , Sengupta Pranab Kumar , Mukherjee Nikhileswar
Published: April 2003

Photopolymerization of MMA with the use of H2O2 as the photoinitiator under visible light at 30°C was studied. Kinetic features in bulk monomer and in the presence of different diluents differ significantly. Usual free radical kinetics with square‐root dependence of rate on initiator, indicating bimolecular termination of chain radicals, were observed for bulk polymerization. On dilution with various solvents polymerization was found to be retarded to different (usual and more than usual) extents, the observed monomer exponent value being much higher than unity in many cases. This deviation from normal kinetics has been interpreted in terms of the predominance of degradative initiator transfer in the diluted systems.
A study of the cationic solid‐state polymerization of 1,3,5‐trithiane
Authors: Żuk Aleksander , Jȩczalik Jerzy
Published: April 2003

The effect of various reaction parameters, such as temperature, catalyst, and concentration, on the cationic‐initiated polymerization of 1,3,5‐trithiane in solid state was studied and the apparent activation energies were estimated. A simple mathematical formula to describe the observed kinetic curves is proposed. The features observed are interpreted in terms of disordering a crystal structure during polymerization.
Volume and conformation. II. Homopolypeptide chains
Authors: Zanotti G. , Spadon P. , Del Pra A.
Published: April 2003

A conformational analysis of two homopolypeptides, poly‐L‐proline and polyglycine, has been carried out with a method based on the van der Waals molecular volume change as a function of internal rotation angles about the nonrigid bonds. The results indicate that the structures with large van der Waals volume are all reasonable structures.
Mechanism of inhibitory action of metal bis(dialkylethylene)dithiolates. II. Interaction of Ni‐bis(diphenylethylene)dithiolate with hydroperoxides
Authors: Ivanov S. K. , Kateva J.
Published: April 2003

During the oxidation of tetraline or cumene, initiated with α,α′‐azobisisobutyronitrile (AIBN) in the presence of Ni‐bis(diphenylethylene)dithiolate (NiDT), induction periods can be observed, proving the interaction between tetralylperoxy and cumylperoxy radicals on the one hand and the metal helate on the other. During the initiation of the oxidation process of tetraline by tetralylhy‐droperoxide and of cumene by cumylhydroperoxide in the presence of NiDT, prooxidation effects in the beginning of the oxidation are observed. The measured stoichiometric coefficients of inhibition (ƒ) depend on the concentration of NiDT. During the absorption of oxygen, an effect of oscillation is observed. The decomposition of tetralylhydroperoxide under the influence of NiDT runs with consumption of the scavenger of free radicals, N‐phenyl‐β‐naphtylamine (PNA), moving the homolytical character of the reaction. A mechanism of the decomposition of hydroperoxides in the initial stage in the presence of NiDT is proposed.
γ‐radiation‐induced crosslinking of polystyrene
Authors: Shimizu Yuichi , Mitsui Hiroshi
Published: April 2003

The γ‐radiation‐induced crosslinking of polystyrene was studied at 30–100°C in vacuo with a dose rate of 6.35 × 105 rad/hr. The amount of hydrogen formation increased with increasing irradiation time, and the rate of the formation decreased with the time. The results were well described by the zero‐order formation kinetics with respect to the hydrogen concentration combined with the first‐order disappearance. The apparent rate constant for the formation of hydrogen increased somewhat with rising irradiation temperature, and the one for the disappearance was little affected by the temperature. The gel fraction increased with the time by the irradiation beyond the critical time for incipient gel formation, and the rate of gel formation decreased with the time. The gel formation was retarded by rising irradiation temperature, and only a little gel fraction was observed at 100°C. The G values for the crosslinking and main‐chain scission were obtained from the gel data by using the Charlesby–Pinner equation. On the basis of these results, the mechanism of the γ‐radiation‐induced crosslinking of polystyrene was discussed.
Heat‐resistant polymers containing thianthrene analogs units. I. Polyimides
Authors: Niume K. , Nakamichi K. , Takatuka R. , Toda F. , Uno K. , Iwakura Y.
Published: April 2003

Polyimides that contained thianthrene and dibenzo‐p‐dioxins units were synthesized. The tricyclic fused rings were successfully incorporated by polymerizing the diamines of the units with aromatic tetracarboxylic dianhydrides. The resulting polyamic acids were converted to polyimides by thermal cyclodehydration. The influence of the tricyclic units on the properties of the polyimides has been investigated. Polyimides that contained dibenzo‐p‐dioxins (ODP) exhibited sufficient thermal stability but were insoluble even in concentrated sulfuric acid. The introduction of a methyl group did not produce an appreciable increase in solubility. Thianthrene polyimides were considerably less stable than the equivalent polymers derived from open‐chain diamine, 4,4′‐diaminodiphenyl sulfide but were partly soluble in acid solvents. The results are discussed in terms of packing the polymer molecules.
Kinetics and mechanism of the cationic polymerization of tetrahydrofuran in solution. THF–CH2Cl2 and THF–CH2Cl2/CH3NO2 systems
Authors: Matyjaszewski Krzysztof , Słomkowski Stanisław , Penczek Stanisław
Published: April 2003

Cationic polymerization of tetrahydrofuran (THF) in CH2Cl2 solvent and in mixed CH2Cl2/CH3NO2 solvent was initiated with 1,3‐dioxolan‐2‐ylium cations with AsF and SbF anions. Dissociation constants of the polytetrahydrofuranium ion pairs into ions were measured (e.g., KD = 1.5 × 10−5M at 25°C and [THF]0 = 7.0M; CH2Cl2 solvent) and were found to be more than 100 times lower than in CH3NO2 solvent at the same [THF]0 and temperature. The rate constants k and k, measured for degrees of dissociation ranging from 0.03 to 0.35 in CH2Cl2, were the same within an experimental error of measurements (±15% of the value of kp). Dependence of k( = k = k) on the dielectric constant was a monotonous function in three different solvents, namely, CCl4, CH2Cl2, and CH3NO2, which covered a large range of dielectric constants of the medium (from D = 5 to D = 22) and degrees of dissociation of the macroion pairs, α (from 0.03 to more than 0.70). Thus a decrease in the dielectric constant increases the rate constant k in the whole range of studied polarities of the medium. This result confirms an earlier conclusion that the rate constant of propagation does not depend on the state of aggregation of ions and k = k.
Linear polythioesters. II. Products of interfacial polycondensation of 1,4‐di(mercaptomethyl)‐naphthalene, 1,5‐di(mercaptomethyl)naphthalene, and a mixture of 1,4‐ and 1,5‐di(mercaptomethyl)‐naphthalene with terephthaloyl and isophthaloyl chlorides
Authors: Podkoscielny Wawrzyniec , Charmas Władysław
Published: April 2003

New polythioesters of naphthalene derivatives produced by interfacial polycondensation of 1,4‐di(mercaptomethyl)naphthalene and 1,5‐di(mercaptomethyl)naphthalene and their mixture with isophthaloyl and terephthaloyl chlorides were obtained. To define the optimal conditions of interfacial polycondensation the following factors that influence the process were studied: the ratio of the aqueous phase to the organic (water–benzene), the concentration of the hydrochloride acceptor, the contribution of emulsifier and catalyst, and the temperature of the reaction. Yield for all reaction products and the reduced viscosity of phenol–tetrachloroethane soluble in the mixture were found. The structure of polythioesters with high‐value reduced viscosity and good yield was determined by elementary analysis, infrared (IR) spectra, and x‐ray analysis; the glassy temperature, initial decomposition, and maximum velocity of decomposition were obtained by thermogravimetric analysis (TGA); and the thermal, mechanical, and electrical properties of the polythioesters were determined. Their molecular weight was not measured because of their low solubility. The good yields, short process time, and good chemical and thermal properties of the polymers showed that the interfacial polycondensation method could be effective in obtaining polythioesters by using aliphatic–aromatic dimercaptans of naphthalene with terephthaloyl and isophthaloyl chlorides.
Synthesis of polyimides from 2,5‐di(carboxymethyl)terephthalic dianhydride and diamines
Authors: Ueda Mitsuru , Takahashi Masayoshi , Hishiki Shohei , Imai Yoshio
Published: April 2003

A new six‐membered tetracarboxylic dianhydride, 2,5‐di(carboxymethyl)terephthalic dianhydride, was synthesized in six steps, starting with pyromellitic dianhydride. The polyimides were prepared from dianhydride and diamines in a two‐step procedure. The polyamic acids, which were formed in the first step by the ring‐opening polyaddition in DMAc, had inherent viscosities of 0.1–0.7 and were converted to the polyimides by thermal cyclodehydration. These polyimides were insoluble in organic solvents. Thermogravimetric analysis (TGA) in air and nitrogen atmospheres revealed that rapid decomposition began above 400°C for aromatic polyimides.
Rate of spontaneous deactivation of styryl and α‐methylstyryl carbanions
Authors: Okamoto Akio , Watanabe Eiichi , Mita Itaru
Published: April 2003

The deactivation of α‐methylstyryl and styryl carbanions followed by spectral change and titration was studied kinetically. First‐order rate constants were obtained for the deactivation of oligo‐α‐methylstyryl lithium, disodium, and dipotassium in tetrahydrofuran and of polystyryl potassium in varying degrees of polymerization in benzene that contained a small amount of tetrahydrofuran and n‐hexane. It was observed that the addition of cryptate [222] exerts a significant effect on the system of oligo‐α‐methylstyryl disodium in tetrahydrofuran. The effect of dilution, degree of polymerization of the polymer, and counterions on the rate of deactivation of carbanions was discussed.
Monolayer properties of mixtures of poly(n‐stearyl methacrylate), poly(n‐lauryl methacrylate), and their corresponding copolymers
Authors: Yoshikawa Satoshi , Ueno Minoru , Meguro Kenjiro
Published: April 2003

The monolayer properties of poly(n‐stearyl methacrylate), poly(n‐lauryl methacrylate), and their mixtures at various ratios of the two polymers have been studied from the measurements of their surface pressure–area isotherms at air–water interface. The monolayer properties of their mixtures have been compared with those of their corresponding copolymers. The results show that the isotherms of the mixed monolayers have two break points at higher pressures than that of poly(n‐lauryl methacrylate). This suggests that the mixtures may form more stable films that consist of separate phases of the two homopolymers, although each phase may contain a small amount of the other. The isotherms of the copolymer monolayers indicate a phase transition from liquid condensed to solid film between 50 segment mole % and 70% poly(n‐stearyl methacrylate). The monclayer of these copolymers has properties that differ from those of the corresponding mixtures of two pure homopolymers and is more compatible than the mixtures of pure homopolymers.
Coenzyme models. 15. A polymeric model system for the NADH‐dependent dehydrogenase enzymes
Authors: Shinkai Seiji , Tanake Kenji , Ide Toyoko , Manabe Osamu
Published: April 2003

Copolymers of 4‐vinylpyridine (4‐VP) and N‐(p‐vinylbenzyl)‐1,4‐dihydronicotinamide (VNicH) were synthesized, and a carbonyl substrate (benzil) was reduced to alcohol in an aqueous ethanol solution in the absence and presence of metal ions (Zn2+ and Ni2+) as part of a model study of NADH‐dependent enzymes. The reduction rates by VNicH in polymers were four to seven times greater than that of the corresponding monomeric analog (N‐benzyl‐1,4‐dihydronicotinamide). Added metal ions catalyzed the reduction by VNicH‐29 (VNicH content, 29 mole%) but inhibited the reduction by VNicH‐9 (VNicH content, 9 mole%). It was suggested that metal catalysis occurs only when metal ions are bound closely near the dihydronicotinamide moiety.
Diffusion‐controlled reaction. V. Effect of concentration‐dependent diffusion coefficient on reaction rate in graft polymerization
Authors: Imre Kaya , Odian George
Published: April 2003

The effect of diffusion on radiation‐initiated graft polymerization has been studied with emphasis on the single‐ and two‐penetrant cases. When the physical properties of the penetrants are similar, the two‐penetrant problem can be reduced to the single‐penetrant problem by redefining the characteristic parameters of the system. The diffusion‐free graft polymerization rate is assumed to be proportional to the v power of the monomer concentration C, in which the proportionality constant a = kpR/k, where kp and kt are the propagation and termination rate constants, respectively, and Ri is the initiation rate. The values of v, w, and z depend on the particular reaction system. The results of our earlier work were generalized by allowing a non‐Fickian diffusion rate, obtained from an extension of the Fujita free‐volume theory, which predicts an essentially exponential dependence on the monomer concentration of the diffusion coefficient, D = D0 [exp(δC/M)], where M is the saturation concentration. It was shown that a reaction system is characterized by the three dimensionless parameters v, δ, and A = (L/2)[aM(v−1)/D0]1/2, where L is the polymer film thickness. Graft polymerization tends to become diffusion controlled as A increases. Larger values of δ and v cause a reaction system to behave closer to the diffusion‐free regime. The transition from diffusion‐free to diffusion‐controlled reaction involves changes in the dependence of the reaction rate on film thickness, initiation rate, and monomer concentration. Although the diffusion‐free rate is w order in initiation rate, v order in monomer, and independent of film thickness, the diffusion‐controlled rate is w/2 order in initiator rate and inverse first‐order in film thickness. The dependence of the diffusion‐controlled rate on monomer is dependent in a complex manner on the diffusional characteristics of the reaction system.
Kinetics of vinyl fluoride polymerization
Authors: Raucher Daniel , Levy Moshe
Published: April 2003

Vinyl fluoride was polymerized, at low temperatures and pressures, by photo‐ and γ‐ray initiation. The kinetics of this heterogeneous polymerization reaction was studied and a general scheme was proposed to explain the experimental results. The scheme is based on the assumption that the main site of the polymerization is in the “polymer phase.” The solvent used determines the rate of the reaction by its effect on the swelling of the polymer. The degree of polymerization is determined mainly by transfer reactions.
Thermal stability of homo‐ and copolymers of vinyl fluoride
Authors: Raucher Daniel , Levy Moshe
Published: April 2003

The thermal stability of poly(vinyl fluoride) (PVF) was studied by thermal gravimetry and mass spectrometry (TGA and TGA–MS). In low‐molecular‐weight polymers a two‐step decomposition pattern was observed. It consisted of the dehydrofluorination to a polyene chain followed by decomposition of the resulting polyene at higher temperatures. Copolymers of vinyl fluoride–vinyl acetate (VF–VAc) and vinyl fluoride‐vinyl chloride (VF–VCl) showed a simultaneous evolution of hydrofluoric acid and acetic acid and hydrofluoric acid and hydrochloric acid, respectively. This suggests that after the elimination of the weakest link a spontaneous elimination of neighboring HF molecules takes place.
The effect of frequency on the plasma polymerization of ethane
Authors: Morita S. , Bell A. T. , Shen M.
Published: April 2003

The plasma polymerization of ethane has been studied in the frequency range of from 50 Hz to 13.56 MHz. The rate of polymer deposition is strongly dependent on frequency, with significantly higher rates being observed at frequencies below 6 MHz. The effects of frequency can be interpreted in terms of a mechanism that assumes that polymer is formed by the reaction of surface free radicals, created by the bombardment of the growing polymer by charged species, with gas phase free radicals, formed by collisions of energetic electrons with monomer molecules.
Kinetic study of the γ radiolysis of polyethylene
Authors: Mitsui Hiroshi , Shimizu Yuichi
Published: April 2003

A kinetic study was made of the formation of hydrogen and trans‐vinylene unsaturation in the radiolysis of polyethylene induced by γ rays with a dose rate of 6.35 × 105 rad/hr at 30–100°C in vacuo. The rates of the formation of hydrogen and trans‐vinylene unsaturation were described by the zero‐order formation kinetics with respect to each concentration combined with the first‐order disappearance. The apparent rate constant for the formation of hydrogen increased gradually with rising irradiation temperature to give the activation energy of 0.6 kcal/mole. On the other hand, those for the disappearance of hydrogen and the formation and disappearance of trans‐vinylene unsaturation were almost independent of temperature. The G values for crosslinking and main‐chain scission were obtained from the gel data by using the Charlesby‐Pinner equation, and the activation energy of 1.5 kcal/mole was given for both of them. On the basis of these results the reactions induced by γ rays in solid polyethylene were discussed.
Photoinitiated cationic polymerization by dialkylphenacylsulfonium salts
Authors: Crivello J. V. , Lam J. H. W.
Published: April 2003

Dialkylphenacylsulfonium salts in which the anions are of the general type BF, AsF, PF, and SbFare a new class of useful photoinitiators for cationic polymerization. On irradiation these salts underwent reversible ylid formation with the simultaneous generation of strong Brϕnsted acids. The photoinitiated cationic polymerization of a number of monomers with dialkylphenacylsulfonium salts demonstrated the utility of these new photoinitiators.
Anionic copolymerization of optically active α‐methylbenzyl methacrylate and trityl methacrylate. I. Reactivity of monomers
Authors: Ohta Koji , Okamoto Yoshio , Hatada Koichi , Yuki Heimei
Published: April 2003

The monomer reactivity ratios were determined in the anionic copolymerization of (S)‐ or (RS)‐α‐methylbenzyl methacrylate (MBMA) and trityl methacrylate (TrMA) with butyllithium at −78°C, and the stereoregularity of the yielded copolymer was investigated. In the copolymerization of (S)‐MBMA (M1) and TrMA (M2) in toluene the monomer reactivity ratios were r1 = 8.55 and r2 = 0.005. On the other hand, those in the copolymerization of (RS)‐MBMA with TrMA were r1 = 4.30 and r2 = 0.03. The copolymer of (S)‐MBMA and TrMA prepared in toluene was a mixture of two types of copolymer: one consisted mainly of the (S)‐MBMA unit and was highly isotactic and the other contained both monomers copiously. The same monomer reactivity ratios, r1 = 0.39 and r2 = 0.33, were obtained in the copolymerizations of the (S)‐MBMA–TrMA and (RS)‐MBMA–TrMA systems in tetrahydrofuran (THF). The microstructures of poly[(S)‐MBMA‐co‐TrMA] and poly‐[(RS)‐MBMA‐co‐TrMA] produced in THF were similar where the isotacticity increased with an increase in the content of the TrMA unit.
Solid‐state polymerization of long‐chain vinyl compounds. II. Effect of molecular arrangement on polymerizability of octadecyl acrylate
Authors: Shibasaki Yoshio , Fukuda Kiyoshige
Published: April 2003

To clarify the effect of a molecular arrangement of long‐chain monomers on polymerizability, γ‐ray‐initiated postpolymerization of polymorphic crystals of octadecyl acrylate and the melt has been investigated. According to thermal, x‐ray, and infrared (IR) analyses octadecyl acrylate exhibit three crystalline modifications similar to, but different in transition behavior from, those of octadecyl methacrylate. The α‐form is stable in the range of 19–32°C (mp) and at lower temperatures the β‐form is stable, whereas the sub‐α‐form appears transiently in α → β transition. The monomer molecules in triclinic packing (α‐form) show little tendency to polymerize, whereas those in hexagonal packing (β‐form) have high polymerizability that increases with temperature. The polymerizability in the molten state at fairly high temperatures is rather low, however. Thus the polymerization rate, saturated conversion, and polymer molecular weight exhibit maxima just above the melting point of α‐form. It is concluded that the hexagonal packing of monomer molecules with particular orientation in the layered structure and rotational freedom around the molecular axis, together with some conformational freedom of functional group, is favorable to the polymerization reaction. In addition, the mechanism of polymerization in the layered structure is discussed, assuming a cone‐type distribution for the polymerization probability.
Chemical modification of polymers. XII. Control of triboelectric charging properties of polymers by chemical modification
Authors: Gibson Harry W. , Bailey F. C. , Mincer Joseph L. , Gunther Wolfgang H. H.
Published: April 2003

Chemical modification of polymers leads to changes in triboelectric charging properties which are proportional to the degree of conversion. This contrasts to physical mixtures in which the surface energy causes one component to dominate the surface, hence the charging properties. Relationships between molecular structure and triboelectric charging have been deduced from the results. Thus the direction of change of triboelectric charging on chemical modification is governed by the nature of the reaction and the magnitude of the change is governed by the extent of reaction.