bluuebunny/crossref_metadata_2025 huggingface dataset:
Stereoregularity of polystyrene‐β,β‐d2
Authors: Matsuzaki Kei , Uryu Toshiyuki , Osada Kiyoshi , Kawamura Tokiji
Published: April 2003

The 100‐MHz methine proton spectra of polystyrene‐β,β‐d2 obtained by radical and cationic initiators consisted of four peaks at 2.35, 2.25, 2.17, and 2.03 ppm, the proportion of which changed with polymerization conditions such as catalyst, solvent, and temperature. The spectrum was interpreted in terms of pentad sequences assuming Bernoullian statistics and the stereoregularity was determined. Polystyrene‐β,β‐d2 prepared by radical initiators had a syndiotactic‐rich configuration, independent of polymerization temperature. Polymers obtained by cationic initiators had lower racemic dyads. Cationic polymerization in toluene at 0°C gave a polymer of an almost random configuration. It was revealed that nondeuterated polystyrene of a random configuration can be distinguished from syndiotactic‐rich polystyrene as well as the isotactic polymer by 100 MHz NMR spectroscopy.
Synthesis and properties of poly(2,5‐ethylene benzimidazole)
Authors: Shalaby S. W. , Lapinski R. L. , Turi E. A.
Published: April 2003

Methyl β‐(3,4‐diaminophenyl)propionate, its hydrochloride, and β‐(3,4‐diaminophenyl)propionic acid were prepared and their structures were established. The effect of temperature, time, and pressure on the polymerization of these compounds and the molecular weight and structure of the resulting polymers were examined. Thin films of different polymer samples were prepared by compression molding, and their infrared spectra were used to study their structures. Samples of poly(2,5‐ethylene benzimidazole) formed under typical polymerization conditions were shown by differential scanning calorimetry and x‐ray techniques to be amorphous, and the glass transition temperature ranged between 201 and 240°C. The polymers were shown by thermogravimetric analysis to have good thermal stability, and 29–34% of the original weights remained after heating to 1000°C in nitrogen.
Pyrolysis of poly(vinyl chloride)
Authors: Chang E. P. , Salovey R.
Published: April 2003

A pyrolysis–gas chromatography–mass spectrometric technique has been developed to study the thermal degradation of poly(vinyl chlorides) polymerized at different temperatures. Hydrogen chloride and benzene evolution during successive stages of pyrolysis have been quantitatively determined and correlated to the tacticity and molecular weight of the polymer. It was found that lowering the temperature of polymerization and molecular weight depresses benzene evolution and increases char weight but does not affect the HCl yield. It is suggested that the syndiotactic trans microstructure favored at low temperature of polymerization yields polyenes which cannot cyclize to form benzene. As the molecular weight decreases, the increase in number of vinyl chain ends facilitates pyrolytic crosslinking and char formation.
Novel polyviologens: Photochromic redox polymers with film‐forming properties
Authors: Simon Myron S. , Moore Phylis T.
Published: April 2003

Several novel polyamides containing the N,N′‐dialkyl‐4,4′‐dipyridinium (“viologen”) system were made by interfacial condensation of N,N′‐bis(aminoalkyl)‐4,4,‐dipyridinium salts with di‐, tri‐, or tetrafunctional acid chlorides. These materials are useful redox polymers which turn deeply colored when reduced chemically or electrically, or when exposed to light.
Block and graft copolymers by selective cationic initiation. II. Synthesis and characterization of styrene‐isobutylene block copolymers by use of chlorobrominated alkanes
Authors: Kennedy Joseph P. , Melby Earl G.
Published: April 2003

The synthesis and characterization of a new block copolymer, poly(styrene‐b‐isobutylene) (PSt‐b‐PIB), is described. The synthesis involves the initiation of an isobutylene polymerization by a polystyrene molecule containing a terminal tertiary bromine (PSt‐Br), in conjunction with diethylaluminum chloride coinitiator. The species PSt‐Br is in turn synthesized by initiating the polymerization of styrene selectively by the tertiary chlorine of the 2‐bromo‐6‐chloro‐2,6‐dimethylheptane/Et3Al initiator system in the absence of chain transfer. The conditions conducive for selective initiation by tertiary chlorine have been worked out. The pure block copolymer, PSt‐b‐PIB, is obtained by selective extraction and some of its properties were determined, e.g., solubility and film behavior, Tg, and intrinsic viscosity versus temperature. The intrinsic viscosity (in toluene) exhibits a maximum and a minimum in the temperature range from 15 to 55°C.
Synthesis and characterization of optically active poly(2‐phenylvinyl alkyl ethers) and corresponding monomers
Authors: Vuković R. , Fleš D.
Published: April 2003

cis‐(S) (+)‐2‐phenylvinyl alkyl ethers having as alkyl groups 1‐methylpropyl (I), 2‐methylbutyl (II), and 3‐methylpentyl (III) were synthesized by condensation of phenylacetylene with the corresponding sodium alcoholates. Polymerization of monomers was performed cationically with BF3 · Et2O or SnCl4 in toluene or CH2Cl2. Specific rotations of polymers were compared with those of low molecular weight model compounds prepared by hydrogenation of monomers, and it was concluded that the difference in the rotation of poly I and model compound ([α]D 19.3° and 5.68°, respectively) and poly II and model compound ([α]D 11.4° and 3.00°, respectively) can be attributed to the asymmetric induction at carbon atoms of the principal polymer chain.
Spontaneous polymerization of the nitroethylene–isobutyl vinyl ether system
Authors: Kushibiki Nobuo , Irie Masahiro , Hayashi Koichiro
Published: April 2003

Initiation and propagation mechanisms of the spontaneous polymerization of the system nitroethylene–isobutyl vinyl ether were studied. An equimolar mixture of these two monomers gives white precipitates below room temperature, though they react explosively to give viscous products at higher temperature. The precipitate was found to be composed of a polynitroethylene and a cycloadduct of these two monomers. The isolated cycloadduct product is so reactive that it not only polymerizes itself spontaneously but also initiates the polymerization of nitroethylene. The polymerization of the cycloadduct was revealed to proceed without termination to produce an alternate copolymer of these two monomers. These results indicate that the explosive spontaneous polymerization of this system consists of three elementary reaction processes; (1) cycloaddition reaction between two monomers, (2) anionic polymerization of nitroethylene induced by the cycloadduct, and (3) the living ring‐opening polymerization of the cyclo‐adduct.
Potential energy calculations of ethylene–butadiene copolymers
Authors: Cernia E. , Conte G. , D'ilario L. , Pavel N. V. , Giglio E.
Published: April 2003

The copolymer ethylene–butadiene (PEBU) was investigated by van der Waals potential energy calculations as a function of four internal rotation angles. The butadiene/ethylene molar ratio was assumed to be very small, no greater than 0.25. The energy values corresponding to the fully extended chain of PEBU and polyethylene (PE) are nearly equal, so that the replacement of a H2CCH2 unit with the trans HCCH group (TDB) in PE crystals can be considered feasible, as found by x‐ray diffraction measurements. The three deepest minima of the van der Wals energy correspond to folded chains, with the double bonds lying in the fold parts. Similar calculations carried out on a PE chain point out that TDB behaves as fold‐supporting. The two energetically more favorable conformations of PEBU reproduce rather well the (110) and (200) folds in PE crystals. The path of the (110) → (200) transition does not appear to be hindered by a large potential barrier. If the HCCH group is in the cis conformation, no stable folded chain can be obtained by means of only four intramolecular degrees of freedom. On the basis of these results it is reasonable to suppose that many TDB's could be located on the surface of PEBU single crystals.
Electroinitiated cationic polymerization of styrene by direct electron transfer
Authors: Akbulut Ural , Fernandez Jack E. , Birke Ronald L.
Published: April 2003

We have studied by cyclic voltammetry the mechanisms of electron transfer and peak potentials of eleven alkenes, propylene oxide, propylene sulfide, and carbon disulfide. We have also studied the cationic polymerization of styrene in acetonitrile solution initiated by controlled potential electrolysis at the anodic peak potential of styrene. The electrolyte used was tetrabutylammonium fluoborate, which was not electroactive at the electrolysis potential, and the reference electrode was a Ag0/Ag+ electrode. The electrochemical studies show that direct electron transfer from styrene is the initiation steps. Plots of reacted monomer concentrations versus time are sigmoidal curves. The propagation rate constant was found from a kinetic relationship based on an autocatalytic reaction. The activation energy is 15.6 kcal/mole at 20°C. The current behavior and effect of stirring on polymerization rate suggest that the growth of polymer takes place partially on the electrode surface.
Photochemistry of nonconjugated bichromophoric systems: Photoreduction and photoreductive polyrecombination kinetics
Authors: De Schryver F. C. , Van Thien Tran , Smets G.
Published: April 2003

The kinetics of the photoreduction of benzophenone and the reductive photopolymerization of diaryl ketones are closely interrelated. The photoreductive polyrecombination presents the characteristics of a polycondensation, namely, an increase in molecular weight with reaction time. In the absence of side reactions, benzophenone and diketone Ia show identical behavior toward hydrogen abstraction, as is reflected in the di‐bis rate constants of hydrogen abstraction.
Preparation and polymerization of difluoramino‐substituted alkyl acrylates and methacrylates
Authors: Reed Samuel F.
Published: April 2003

Several difluoramino‐substituted alkyl acrylic acid esters were conveniently prepared by the debromination of difluoramino‐substituted alkyl‐2,3‐dibromopropionates and 2,3‐dibromoisobutyrates. The polymerization character of difluoramino‐substituted alkyl acrylates and methacrylates was found to be similar to that displayed by other alkyl acrylic esters.
Initiator concentration dependence of the autoacceleration of polymerization rate
Authors: Ito Katsukiyo
Published: April 2003

The dependence of the polymerization rate on initiator concentration over a wide range of conversion is analyzed by an equation derived on the assumption that the primary radical termination is important and another equation derived on the assumption of the chain length dependence of the termination. The analytical result by the former equation, is nearly equivalent to the result by the later when transfer predominates. Fujita‐Doolittle theory is applicable to both results. In the apparent termination, small polymer radicals not exceeding the size of the segment play an important role.
Preparation of new heterocyclic monomers: Vinylisoxazoles, vinylpyrazoles, and vinylpyrazolones
Authors: Ponticello I. S.
Published: April 2003

Vinylisoxazoles, vinylpyrazoles, and vinylpyrazolones have been synthesized by cracking their cyclopentadiene adducts. The latter were derived from the blocked 1,3‐dicarbonyl compounds by treatment with hydroxylamine or hydrazine.
Temperature effects on γ‐initiated polymerization of styrene. III. Conversion in the range 150–200°C
Authors: Taherzadeh M. , Hodgins J. W.
Published: April 2003

Experimental data are presented for the polymerization of commercial styrene in a γ‐radiation flux of 20–51 rad/sec in the temperature range of 150–200°C. At radiation intensities above 20 rad/second, conversion rate is independent of dose rate over the range. Above 165°C, radiation does not enhance the conversion rate but does produce more rapid elimination of residual monomer. Molecular weights of polymer product in this temperature range are too low to be of commercial interest. An optimal temperature range of 110–120°C is suggested for the process.
Cyclic acetal‐photosensitized polymerization. I. Photopolymerization of styrene in the presence of 1,3‐dioxolanes
Authors: Ouchi Tatsuro , Nakamura Sakuro , Hamada Masao , Oiwa Masayoshi
Published: April 2003

Styrene(St) was polymerized in benzene solution in the presence of substituted 1,3‐dioxolane(DO) compounds by means of photoirradiation of the system at 40°C. The subtraction of the square of the polymerization rate in the absence of DO compounds (Rpab) from the square of the rate in the presence of DO compounds (Rppr) was found to follow the equation:

The effect of substituents in the 2‐position on the polymerization rate increased in the order of methyl < hydrogen < ethyl < n‐propyl < phenyl, as shown by the rate constant kd′ of decomposition of DO compounds.
Donor–acceptor complexes in copolymerization. XLIX. Cationic polymerization of donor monomers in presence of polar solvents and acrylic monomers. A revised mechanism for polymerization of comonomer complexes
Authors: Gaylord Norman G. , Deshpande Achyut B. , Dixit Sunit S. , Maiti Sukumar , Patnaik Birendra K.
Published: April 2003

α‐Methylstyrene (MS) and isobutyl vinyl ether (VE) readily polymerize, styrene (S) polymerizes to a small extent, and isobutylene (IB), butadiene (BD), and isoprene (IP) fail to polymerize in the presence of catalytic amounts of AlCl3 when propionitrile, ethyl propionate, and methyl isobutyrate are used as reaction media. MS polymerizes readily and S polymerizes with difficulty in the presence of AlCl3 to yield homopolymers when acrylonitrile (AN) is present and copolymers with ethyl acrylate (EA) and methyl methacrylate (MMA). VE readily homopolymerizes, while IB, BD, and IP fail to polymerize in the presence of AlCl3 and the acrylic monomers. VE readily homopolymerizes, S and MS polymerize to a very small extent, and IB, BD, and IP do not polymerize in the presence of ethylaluminum sesquichloride (EASC) in polar solvents. VE readily homopolymerizes in the presence of EASC and the acrylic monomers. MS polymerizes to a small extent in the presence of EASC and the acrylic monomers to yield equimolar copolymers with EA and MMA and a mixture of cationic homopolymer and equimolar copolymer with AN. S yields equimolar copolymers in low yield in the presence of EASC and the acrylic monomers. IB, BD, and IP in the presence of EASC do not polymerize to any significant extent when EA is present, form AN‐rich copolymers and yield poly(methyl methacrylate) in the presence of MMA. A revised mechanism is presented for the formation of cationic, radical, random, and alternating copolymers as well as alternating copolymer graft copolymers in the copolymerization of donor and acceptor monomers.
Effect of molecular relaxations on the fracture behavior of poly(vinyl chloride)
Authors: Johnson F. A. , Radon J. C.
Published: April 2003

The fracture toughness of PVC has been measured by using three‐point bend specimens tested over a wide range of strain rate and temperature. A method has been described of deriving fracture load indirectly by measurement of stiffness from a preliminary “low blow” test in instrumented impact testing. Some limitations of the method, when used with semi‐ductile material of low stiffness, have been discussed. Fracture toughness results have also been evaluated by an alternative energy method, which is however more suitably applied to the lower speed impact test. The curves of K1c versus temperature for PVC contain a weak maximum at a temperature below Tg, the location of which varies with testing speed. The position of the maximum in the time–temperature field has been compared with the locus of the β damping peak derived from mechanical (flexural vibrations, torsion pendulum) and dielectric loss measurements, with reasonable agreement. Static toughness was higher than dynamic, and this correlated with fracture surface appearance, thereby indicating a real difference in toughness probably associated with crack tip craze development.
Influence of H2O on alternating copolymerization with the EtnAlCl3‐n‐VOCl3 catalyst system
Authors: Akimoto Akira , Ohtsuru Masaaki
Published: April 2003

The effect of the catalytic amount of H2O was investigated with the EtnAlCl3‐n‐VOCl3 catalyst system on the alternating copolymerization of acrylic monomers with diolefins and styrene. The presence of the catalytic amount of H2O produced an improvement in the yield and in the molecular weight as well as the structure of copolymer with the EtnAlCl3‐n‐VOCl3 catalyst system. The efficiency of the aluminum components in the EtnAlCl3‐n‐VOCl3 system appears with AlEt3 and especially with Et1.5AlCl1.5. The catalytic activity was found to depend upon the H2O EtnAlCl3‐n molar ratio and was also affected by the order of mixing of the catalyst components and the monomers. Effective catalyst could be prepared when the catalyst components (except VOCl3) were premixed without presence of monomers. The possible catalytic behavior of H2O was discussed.
Effect of diffusion on rates and molecular weights in graft polymerization
Authors: Odian George , Henry Richard , Koenig Raymond , Mangaraj D. , Trung Le Doan , Chao Bou , Derman Arif
Published: April 2003

A theoretical analysis has been made of the graft polymerization process in terms of the quantitative interrelationship between the initiation rate Ri, the kp/kt1/ ratio of the monomer, the equilibrium solubility M of the monomer in the polymer, the polymer film thickness L, and the diffusivity D of the monomer in the polymer. It is shown how the values of these parameters in any grafting system interact to lead to diffusion‐controlled graft polymerization. Whether graft polymerization is diffusion‐free or diffusion‐controlled depends on the values of Kp, d, kp/kp1/2, and L as gathered in the parameter A = [(Kp/kt1/2)Ri, D,/1/2] L/2. When the values of the various terms are such that A is less than 0.1 (i.e., D is large while Ri, kp, and L are small), the reaction is diffusion‐free. When A is greater than 3 (i.e., D is small while Ri, kp, and L are large), the reaction is diffusion‐controlled. The derived equations showing the relationship between kinetic and diffusional parameters are theoretically applicable to all grafting systems, i.e., for all monomer‐polymer combinations under all conditions of reaction temperature, radiation intensity and polymer film thickness. The theoretical analysis has been verified for the rate and degree of polymerization for the radiation‐induced graft polymerization of styrene to polyethylene.
Effect of triphenyl phosphite on the radical polymerization of styrene and methyl methacrylate
Authors: Taninaka Takumi , Ogawa Takeshi , Minoura Yuji
Published: April 2003

The effects of triphenyl phosphite (TPP) on the radical polymerization of styrene (St) and methyl methacrylate (MMA) initiated with α,α,‐azobisisobutyronitrile (AIBN) was investigated at 50°C. The rate of polymerization of St and MMA at a constant concentration of TPP was found to be proportional to the monomer concentration and the square root of the initiator concentration. The rate of polymerization and the degree of polymerization of both St and MMA increased with increasing TPP concentration. The accelerating effect was shown to be due to the decrease of the termination rate constant kt with an increase in the viscosity of the polymerization systems. The chain transfer constant Ctr of TPP in St and MMA systems was determined from the degree of polymerization system. The Ctr of TPP was almost zero in the St system and 6.5 × 10−5 in the MMA system.
Polymers from 4,4′‐thiodiphenol
Authors: Samyn C. , Marvel C. S.
Published: April 2003

Polyesters were made with aromatic diacid chlorides and 4,4,‐thiodiphenol. Isophthaloyl chloride and/or terephthaloyl chloride were used as acid chlorides alone or together with 5‐cyanoisophthaloyl chloride or [2.2]p‐cyclophane‐3,9‐dicarboxylic acid chloride. The latter components were incorporated in order to make the polymers useful for crosslinking. A polyether could be obtained by polycondensation of 2,4‐dichloro‐benzonitrile and 4,4′‐thiodiphenol. The polycondensations were run in nitrobenzene as solvent.
Polymerization of methacrylates. I. Polymerization reactivity of picryl methacrylate
Authors: Kadoma Yoshinori , Toida Takashi , Takeda Kenji , Uno Keikichi , Iwakura Yoshio
Published: April 2003

The polymerization of picryl (PMA), 2,4‐dinitrophenyl (2,4‐DNMA),2,6‐dinitrophenyl (2,6‐DNMA), 2‐methyl‐4,6‐dinitrophenyl (MDNMA), and 2,6‐dimethylphenyl methacrylates (DMMA) was carried out in benzene at 60°C. PMA, 2,6‐DNMA, and MDNMA did not undergo radical homopolymerization, while 2,4‐DNMA and DMMA did. The results suggest that the growing radical readily attacks the oxygen atom of the nitro group at the 2 position of the terminal phenyl group due to the steric effect of the substituent at the 6 position, resulting in chain termination. PMA formed a charge‐transfer complex with 2‐naphthyl methacrylate (NMA). The stoichiometric composition of this complex was shown to be 1:1 molar complex. PMA was readily copolymerized with NMA. The amount of solvent affected the composition of the copolymer obtained at a given same mole fraction in feed. The results suggest that charge‐transfer interaction between the ester groups affects the copolymerization mechanism.
Singlet oxygen and polymer photooxidations. I. Sensitizers, quenchers, and reactants
Authors: Zweig A. , Henderson W. A.
Published: April 2003

A study designed to ascertain the role of singlet molecular oxygen in the photodegradation of plastics established that most classes of dye chromophores are sensitizers in polymer films, absorbing light and transferring the absorbed energy to ambient triplet ground state molecular oxygen, generating metastable reactive singlet molecular oxygen. Unsaturated polymers containing polybutadiene, polyisoprene, etc. are highly reactive to singlet oxygen produced through photosensitization, generating hydroxylic and carbonyl derivatives and losing their rubbery properties as consequences of such reactions. Many types of transition metal chelates are singlet oxygen quenchers. The relationships of the structures and spectroscopic properties of these chelates to their efficiency in quenching singlet oxygen are examined and discussed.
Studies on reactions of the N‐phosphonium salts of pyridines. XIII. Direct polycondensation reaction of carbon dioxide or disulfide with diamines under mild conditions
Authors: Yamazaki Noboru , Iguchi Tadao , Higashi Fukuji
Published: April 2003

Polyureas of high molecular weight were obtained by the direct polycondensation reaction of carbon dioxide with diamines at 40°C for several hours under a pressure of carbon dioxide (below 30 atm) by use of diphenyl phosphite in pyridine. Optimal temperature and pressure were 40°C and 20 atm of carbon dioxide. The polycondensation reaction was also affected by solvents and type and amounts of tertiary amines. Pyridine was most effective as tertiary amine and solvent as well. Of the phosphorous compounds used, triaryl phosphites and diphenyl phosphite were most effective, but trialkyl phosphites failed to give polymer. The reaction was assumed to proceed via a carbamyl N‐phosphonium salt of pyridine formed by dephenoxylation of phosphites. Similarly, polythioureas were prepared by heating a mixture of carbon disulfide, diamines, and diphenyl phosphite in pyridine at 40°C for 6 hr under nitrogen.
Peculiarities in the copolymerization of trioxane and epichlorohydrin under the influence of EtB⊖F3 A⊕lEt2
Authors: Mateva R. , Pavlova M. , Kabaivanov V.
Published: April 2003

This study deals with the copolymerization of trioxane (TO) and 1‐chloro‐2, 3‐epoxypropane (epichlorohydrin, ECH) catalyzed by EtB⊖F3 A⊕lEt2 in toluene. The rate of exhaustion of monomers during copolymerization was measured by gas chromatography. It was established that no homopolymers were formed. The copolymers obtained show a high alkali resistance, indicating a statistical distribution of the ECH in the polymer chain. During the first stages of the copolymerization the ECH is exhausted almost instantaneously, whereas TO is gradually exhausted, finally reaching a certain equilibrium depending both on the quantity of the initial ECH and on the temperature at which the process was carried out. Copolymerization is inhibited at increased ECH levels, and only homopolymerization occurs at a certain critical concentration of ECH.
Donor‐acceptor complexes in copolymerization. L. Preparation and microstructure of chlorine‐containing alternating conjugated diene–acceptor monomer copolymers
Authors: Gaylord Norman G. , Patnaik Birendra K.
Published: April 2003

Neighboring monomer units cause significant shifts in the infrared absorption peaks attributed to cis‐ and trans‐1,4 units in conjugated diene‐acceptor monomer copolymers. Conjugated diene‐maleic anhydride alternating copolymers apparently have a predominantly cis‐1,4‐structure, while alternating diene‐SO2 copolymers have a predominantly trans‐1,4 structure. Alternating copolymers of butadiene, isoprene, and pentadiene‐1,3 with α‐chloroacrylonitrile and methyl α‐chloroacrylate, prepared in the presence of Et1.5AlCl1.5(EASC), have trans‐1,4 unsaturation. Alternating copolymers of chloroprene with acrylonitrile, methyl acrylate, methyl methacrylate, α‐chloroacrylonitrile, and methyl α‐chloroacrylate prepared in the presence of EASC‐VOCl3 have trans‐1,4 configuration. The reaction between chloroprene and acrylonitrile in the presence of AlCl3 yields the cyclic Diel‐Alder adduct in the dark and the alternating copolymer under ultraviolet irradiation. The equimolar, presumably alternating, copolymers of chloroprene with methyl acrylate and methyl methacrylate undergo cyclization at 205°C to a far lesser extent than theoretically calculated, to yield five and seven‐membered lactones. The polymerization of chloroprene in the presence of EASC and acetonitrile yields a radical homopolymer with trans‐1,4 unsaturation.
Structural irregularities in poly(vinyl alcohol)
Authors: Adelman Robert L. , Ferguson Raymond C.
Published: April 2003

Poly(vinyl alcohols) derived from the product of polymerization of vinyl acetate in methanol have been characterized by various physical and chemical methods before and after NaIO4 cleavage. The 220‐MHz 1H‐NMR spectra confirm the reliability of NaIO4 titrimetry for estimating 1,2‐glycol content and help explain the tendency for viscometry to grossly underestimate the 1,2‐glycol content for low molecular weight polymers. The spectra and related chemical evidence indicate that the major endgroups are HOCH2CH2 and CH3CH(OH)CH(OH)CH2. ß‐Hydroxyethyl groups also occur as short chain branches, mainly attached to α carbon atoms in the normal head‐to‐tail polymer chain sequence. The concentrations of the branch and endgroups depend on polymerization conditions and help explain polymerization “solvent” effects on physical properties.
Alternating structures in copolymers as elucidated by microozonolysis
Authors: Hackathorn Marjorie J. , Brock M. J.
Published: April 2003

The technique of microozonolysis followed by gas chromatography has been used to determine the amount of 1,2‐structures occurring as 1,4–1,2–1,4 sequences in n‐butyl‐lithium‐initiated polybutadienes. The product obtained from the ozonolysis of these sequences, 3‐formly‐1,6‐hexanedial, was directly proportional to the 1,2 (vinyl) content of the polymers as measured by infrared or NMR spectroscopy. An unusual ozonolysis product, 4‐octene‐1,8‐dial, has been found in the ozonolysis products of high‐1,4 poly‐butadienes. Ozonolysis has also been used to determine alternating structures in propylene‐butadiene copolymers. The product obtained from ozonolysis of such structures is 3‐methyl‐1,6‐hexanedial. Ozonolysis of a polyisoprene containing equal amounts of 1,4 and 3,4 structures indicated it to have a nonalternating structure with long blocks of 1,4‐isoprene units. Gas chromatographic separation was accomplished by using sucrose acetate isobutyrate with Carbowax 20M as the liquid phase. Retention times were established by using model compounds where possible.
Singlet oxygen and polymer photooxidations. II. Photodegradation of an olefinically unsaturated polymer
Authors: Zweig A. , Henderson W. A.
Published: April 2003

A method based on infrared spectral changes in thin films was devised and used to evaluate the relative effectiveness of various types of additives on photodegradative processes in an olefinically unsaturated polymer. Nickel chelates of the thiobisphenol‐amine complex type are shown to be quantitatively more effective in retarding the photodegradation of these polymers than other additives having greater singlet oxygen quenching efficiencies, ultraviolet absorption, or radical antioxidant properties. Photosensitization with a singlet oxygen sensitizer (fluoranthene) rapidly produces degradative effects in the polymer which are identical with those of its direct degradation by light. The sensitized effects are also retarded by the nickel chelates. Photosensitization by a hydrogen atom‐abstracting sensitizer (a benzophenone) proved considerably less effective. The effectiveness of the nickel complexes appears to be due to a combination of their ability to quench singlet oxygen and precusor excited states and their relative stability under photoexposure conditions.
Determination of crystallinity of olefin copolymers and polyolefin powders by inverse gas chromatography
Authors: Braun J.‐M. , Guillet J. E.
Published: April 2003

Studies of olefin copolymers by inverse gas chromatography show that the method is suitable for determining the crystallinity of compositions where a linear extrapolation of density determinations is not applicable. Satisfactory estimates of crystallinity were obtained on ethylene copolymers with carbon monoxide and vinyl acetate and on an emulsifiable polyethylene wax. Studies were also made in which the columns were packed with physical mixtures of GC support and polyolefin powders, either obtained direct or ground from film samples. It was shown that good estimates of crystallinity could be obtained if suitable allowance is made for variance in peak retention time with flow rate, due to the relatively slow rate of diffusion of the probe molecule in polymer particles of large diameter (>100 μm). If smaller particles are used it is usually unnecessary to correct for flow rate effects. This extends the usefulness of the “molecular probe” technique to any polyolefin sample which can be ground to a fine particle size and eliminates the need for solution coating of the column packing.
Anionic polymerization of N‐ethyl‐2‐vinylcarbazole and N‐ethyl‐3‐vinylcarbazole
Authors: Limburg W. W. , Yanus J. F. , Williams D. J. , Goedde A. O. , Pearson J. M.
Published: April 2003

The polymerization of N‐ethyl‐2‐vinylcarbazole and N‐ethyl‐3‐vinylcarbazole by an anionic mechanism has been demonstrated. Polymerization reactions were monitored by ultraviolet/visible spectroscopy and λmax and ε values for the propagating carbanions determined. The 2‐vinyl monomer exhibits all the features of a standard “living” polymer; the carbanion is stable at ambient temperatures and high molecular weight, M̄n ≃ 106, narrow distribution polymers and block copolymers with styrene have been prepared. The carbanion from the 3‐vinyl monomer is much less stable and a clean polymerization can only be conducted at temperatures below ‐60°C. A comparison of the anionic polymerization characteristics of the N‐, 2‐, and 3‐vinyl carbazole monomer series is presented.
Polymerization and copolymerization of trioxane: Factors influencing molecular weight and end groups
Authors: Chen Catherine S. Hsia
Published: April 2003

In bulk polymerization and copolymerization of trioxane with ethylene oxide, it has been shown that p‐chlorophenyldiazonium hexafluorophosphate
magnified image
is a superior catalyst as compared to boron trifluoride dibutyl etherate (BF3 · Bu2O). Polymers and copolymers of significantly higher molecular weight have been obtained. The higher molecular weight has been attributed primarily to less inherent chain transfer during propagation, which in turn can be attributed to the superior gegenion PF6−.

The polymerization proceeds via a clear period followed by sudden solidification. Faster polymerization and higher molecular weight polymers have been observed for homopolymerization than for copolymerization. The polymer yield obtained after solidification is determined by both rate of polymerization and rate of crystallization of polymers. These rates, in turn, are dependent on the catalyst concentration. The molecular weight is determined both by polymer yield and extent of inherent chain transfer. In the range of monomer to catalyst mole ration [M]/[C] = (0.5–20) × 104 investigated, it has been found that in the higher range, the polymer yield is independent of the catalyst concentration and the extent of inherent chain transfer is inversely proportional to the half power of catalyst concentration: [M]/[C] = (0.5–8) × 104 for homopolymerization and (0.5–3) × 104 for copolymerization with 4.2 mole % ethylene oxide. In the lower range, the yield decreases with catalyst concentration and the extent of inherent chain transfer is inversely proportional to higher power of catalyst concentration. The dependence of molecular weight of polymers on catalyst concentration has been shown to be a complex one. The molecular weight goes through a maximum as the catalyst concentration is decreased. The maximum molecular weights have been obtained at [M]/[C] ≈ 8 × 104 for homopolymerization and ∼3 × 104 for copolymerization with 4.2 mole % ethylene oxide. Prior to reaching maximum the molecular weight is inversely proportional to the half power of catalyst concentration indicating it is primarily controlled by inherent chain transfer. Upon further decrease of catalyst, molecular weight decreases as a result of both a decrease in polymer yield and an increase in inherent chain transfer.

In copolymerization of trioxane and ethylene oxide, it has been ascertained that methylene chloride exhibits a favorable solvating effect. Although higher inherent chain transfer takes place in copolymerization than in homopolymerization, the extent of chain transfer is independent of ethylene oxide concentration. The difference in polymer yield and molecular weight a t different ethylene oxide concentrations is attributed primarily to the difference in kp/kt ratio. It also has been demonstrated that end capping of polymer chains can be accomplished by the use of a chain transfer agent—methylal.
Autoxidation of poly‐4‐methylpentene‐1. I. The role of diffusion in autoxidation kinetics
Authors: Billingham N. C. , Walker T. J.
Published: April 2003

An apparatus is described for the measurement of oxygen uptake into a polymer sample at constant oxygen pressures in the range 20–1000 mm Hg. Measurements of the rate of oxygen uptake into poly‐4‐methylpentene‐1 show that the rate is accurately first‐order in oxygen pressure over the range 50–800 mm pressure for temperatures ranging from 122 to 154°C and film thickness in the range 0.001–0.025 cm. A theoretical treatment of the kinetics of a reaction in which oxygen diffuses into both faces of a thin film, in which it is consumed by a first‐order reaction shows that the oxidation rate ρ per unit area of film surface is given by ρ = ρ∞ tanh ßL/2 where ρ∞ is the limiting oxidation rate for a thick film, L is the film thickness, and ß = (k/D)1/2, k being the oxidation rate constant and D the diffusion constant. Values of D and the activation energy for diffusion calculated from autoxidation data are in good agreement with values determined directly.
Dependence of structure of dehydrated PVA on the crystallinity of the original PVA
Authors: Nakanishi Yoichiro
Published: April 2003

Poly(vinyl alcohol) (PVA) films having different crystallinities were prepared by elongating PVA films to different degrees and heating the films with and without elongation treatment at several temperatures between 60 and 200°C. Then, they were dehydrated by heating from 80°C to 230 or 330°C in hydrogen chloride gas. Infrared spectral measurements were made on the dehydrated PVA films obtained. Absorbances of the absorption bands due to several groups seen in the infrared spectra depended only on the density of original PVA films, regardless of its degree of elongation. From these dependences, it was found that the dehydration reaction progressed more easily in the crystalline region than in the amorphous region, that the aromatic rings with four or five adjacent hydrogen atoms were formed mainly in the amorphous region and those with two adjacent hydrogen atoms in the crystalline region, and that the aromatic rings with two isolated hydrogen atoms were formed in both the amorphous and crystalline regions. Relative concentrations of the groups of which the dehydrated PVA were composed were estimated. Comparison of the numbers of carbon atoms among the composing groups indicated that the main groups were the methylene group and the aromatic ring.
Determination of rate constants for polymerization of styrene initiated by 2,2′‐azobisisobutyronitrile by utilizing steady‐state population densities
Authors: Scamehorn J. F. , Timm D. C.
Published: April 2003

A theoretical description of chain‐growth polymerization is presented in terms of a distributed parameter model. Analysis of molecular distributions of macromolecular materials results in graphical procedures capable of yielding absolute values for kinetic constants. A steady‐state analysis of styrene polymerizations initiated with 2,2′‐azobisisobutyronitrile in toluene yielded the following rate information, which is in qualitative agreement with previously published results: f = 0.4; Ki = 1.58 × 1015 exp {−30,800/RT} Ktc/K2p = 1.10 × 10−5 exp {13,200/RT}.
Studies of the photooxidation mechanism of polymers. III. Role of tetrahydrofuran in the photooxidative degradation of poly(vinyl chloride)
Authors: Rabek Jan F. , Shur Young J. , Rårnby B.
Published: April 2003

The influence of tetrahydrofuran (THF) on photooxidative degradation of poly(vinyl chloride) in films cast from THF solution was studied. THF is partially retained in the polymer matrix in amounts of 6–8% after casting and drying the film. The last 2–3% is very difficult to remove. By use of thermogravimetric analysis, density measurements, and gas permeability measurements, it was shown that THF residues can be removed by preheating the PVC samples to 80°C. THF forms a charge‐transfer complex with oxygen which is easily photolyzed. During this reaction hydroperoxide radicals are formed. Molecular weight distribution curves by gel‐permeation chromatography (GPC) show that THF in the presence of air promotes the photodegradation of PVC. Attention has been given to the correct interpretation of the infrared absorption spectra of PVC films containing THF residues and ultraviolet‐irradiated in air.
Study on radiation‐induced polymerization of vinyl monomers adsorbed on inorganic substances. II. Radiation‐induced polymerization of methyl methacrylate adsorbed on several inorganic substances
Authors: Fukano Kazuyuki , Kageyama Eiichi
Published: April 2003

The radiation‐induced polymerization of methyl methacrylate (MMA) absorbed on such inorganic substances as silica gel, white carbon, silicic acid anhydride, zeolite, and activated alumina was carried out to compare with the case of styrene. The rate of radiation‐induced polymerization adsorbed on inorganic substances was high compared with that of radiation‐induced bulk state polymerization, as was the case with styrene. Inorganic substrates which contain aluminum as a component element are more likely to be grafted than those which consist of SiO2 alone, as with styrene. The molecular weight distribution of unextractable polymer and extractable polymer differs, depending on the type of inorganic substance. Experiments by a preirradiation method were carried out in case of silica gel, white carbon, and silicic acid anhydride. GPC spectra of the polymer obtained were different from those of polymer formed by the simultaneous irradiation method. It appears that all the unextractable polymer is grafted to the inorganic surface with chemical bond.
Photopolymerization of vinyl fluoride
Authors: Raucher Daniel , Levy Moshe
Published: April 2003

The photopolymerization of vinyl fluoride, in the presence of peroxide, was studied in dimethyl sulfoxide (DMSO) solution and in bulk. It was found that high rates of reaction could be obtained in spite of the fact that the polymer precipitates at an early stage. By continuous supply of monomer the precipitated polymer was converted into a transparent bulk polymer.
Pyrolysis–gas chromatographic analysis of chain branching in polyethylene
Authors: Seeger Michael , Barrall Edward M.
Published: April 2003

A system with flash pyrolysis and gas chromatography (PGC) which includes in‐line hydrogenation and packed columns is described. Under optimal conditions of temperature programming and flow rate, a high degree of resolution was obtained over a broad range of fragment lengths. The system has been applied to the analysis of side groups and long branches in polyethylene. It was found that, for low concentration of branches, yield and distribution of the isoalkanes is very sensitive to the type of polymerization used to form the polyethylene. A great number of the single‐branched isoalkanes have been identified by comparing their retention time with the scale of respective boiling points and by pyrolyzing well characterized ethylene‐propylene copolymers. The pyrograms of the ethylene‐propylene copolymers demonstrated that a CC bond in an α‐ or β‐position to a tertiary carbon cleaves about two times more readily than a CC bond in a linear chain. It was further found that the branch length of the side chain is indicated by the identity of the fragments produced, and the probability of formation of these fragments is directly related to the possibility of a cyclic decomposition mechanism. From the high yields of 3‐ and 5‐methylalkanes it was possible to detect about 20 ethyl and 10 n‐butyl branches per thousand in a low‐density polyethylene. Thus, pyrolysisgas chromatography has to be considered seriously as a method for the determination of branches, even when in present in low concentration (Ziegler‐type polyethylene).
α‐amidoalkylation of polystyrene
Authors: Swiger R. T.
Published: April 2003

Crystal polystyrene was alkylated with N‐methylolacetamide (CH3CONHCH2OH), boron trifluoride being used as the catalyst. A linear relationship between degree of N‐methyleneacetamide substitution and the glass transition temperature Tg of the polystyrene was observed. The Tg values ranged from 104°C for 0% amidization to 125°C for 20% amidization. The critical strain εc of these materials was measured at room temperature in air, hexane, and oil (50–50, a cottonsed oil–oleic acid) and an increase in the εc above which crazing occurs was observed as the degree of alkylation increased. Thermogravimetric analysis (TGA) of the amidized polystyrenes in air at 250°C showed these materials to become more stable as the amount of N‐methylene substitution increased. Tensile data show that the amidized polystyrene, although stronger than the unsubstituted material, exhibits the same elongation at break and tensile modulus.
Monomer‐isomerization polymerization. XI. Monomer‐isomerization copolymerizations of 2‐butene with 2‐pentene and 2‐hexene with Ziegler‐Natta catalyst
Authors: Otsu Takayuki , Shimizu Akihiko , Itakura Keisuke , Endo Kiyoshi
Published: April 2003

2‐Pentene and 2‐hexene were found to undergo monomer‐isomerization copolymerizations with 2‐butene by Al(C2H5)3–VCl3 and Al(C2H5)3–TiCl3 catalysts in the presence of nickel dimethylglyoxime or transition metal acetylacetonates to yield copolymers consisting of the respective 1‐olefin units. For comparison, the copolymerizations of 1‐pentene with 1‐butene and 1‐hexene with 1‐butene by Al(C2H5)3–VCl3 catalyst were also attempted. The compositions of the copolymers obtained from these copolymerizations were determined by using the calibration curves between the compositions of the respective homopolymer mixtures and the values of D766/D1380 in the infrared spectra. The monomer reactivity ratios for the monomer‐isomerization copolymerizations of 2‐butene (M1) with 2‐pentene and 2‐hexene, in which the concentrations of both 1‐olefins calculated from the observed isomer distribution were used as those in the monomer feed mixture, and for the ordinary copolymerizations of 1‐butene (M1) with 1‐pentene and 1‐hexene by Al(C2H5)3‐VCl3 catalyst were determined as follows: 2‐butene (M1)/2‐pentene (M2): r1 = 0.14, r2 = 0.99; 1‐butene (M1)/1‐pentene (M2): r1 = 0.30, r2 = 0.74; 2‐butene (M1)/2‐hexene (M2): r1 = 0.11, r2 = 0.62; 1‐butene (M1)/1‐hexene (M2): r1 = 0.13, r2 = 0.90.
Radiation induced copolymerization of chlorotrifluoro ethylene with butenes
Authors: Tusche R. , Seyhan M. , Schneider Ch.
Published: April 2003

The radiation induced copolymerization of chlorotrifluoro ethylene (CTFE) with various butenes was studied at temperatures between −20°C and +40°C using 60Co‐γ rays.

In the case of isobutene (IB) an almost alternating crystalline copolymer is formed in a heterogeneous reaction. At high IB‐concentrations a cationic homopolymerization of this olefin occurs simultaneously to the radical copolymerization. The copolymerization rate increases with increasing temperature and degree of conversion. The highest rates are obtained for monomer mixtures with about 80 to 90 mole % CTFE. The decrease in rate for monomer mixtures with still higher CTFE concentrations is assumed to be partly due to the low IB‐concentration and partly to degradative chain transfer by the isobutene. In support of this assumption molecular weights and melting points of the copolymer have been determined.

Similar results were obtained for butene‐1 but in this case, no cationic homopolymerization was observed and the reaction proceeded homogeneously.

Cis‐ and trans‐butene‐2 only acted as polymerization inhibitors.
Radical polymerization of methyl methacrylate in the presence of stereoregular poly(methyl methacrylate). V. Kinetics of initial template polymerization
Authors: Gons J. , Vorenkamp E. J. , Challa G.
Published: April 2003

The influence of stereoregular poly(methyl methacrylate) (PMMA) as a polymer matrix on the initial rate of radical polymerization of methyl methacrylate (MMA) has been measured between −11 and +60°C using a dilatometric technique. Under proper conditions an increase in the relative initial rate of template polymerization with respect to a blank polymerization was observed. Viscometric studies showed that the observed effect could be related to the extent of complex formation between the polymer matrix and the growing chain radical. The initial rate was dependent on tacticity and molecular weight of the matrix polymer, solvent type and polymerization temperature. The accelerating effect was most pronounced (a fivefold increase in rate) at the lowest polymerization temperature with the highest molecular weight isotactic PMMA as a matrix in a solvent like dimethylformamide (DMF), which is known to be a good medium for complex formation between isotactic and syndiotactic PMMA. The acceleration of the polymerization below 25°C appeared to be accompanied by a large decrease in the overall energy and entropy of activation. It is suggested that the observed template effects are mainly due to the stereoselection in the propagation step (lower activation entropy Δ Sp†) and the hindrance of segmental diffusion in the termination step (higher activation energy Δ Et†) of complexed growing chain radicals.