bluuebunny/crossref_metadata_2025 huggingface dataset:
Block copolymers of ethylene. I. Butadiene
Authors: Hay J. N. , McCabe J. F.
Published: April 2003

Block copolymers of ethylene and butadiene have been prepared to study their properties. The method of preparation of polybutadiene, polyethylene, and block copolymers of ethylene and butadiene with n‐butyl lithium‐tetramethyl ethylene diamine complex is outlined. Kinetic studies have been reported elsewhere and these are assessed to determine that suitability of the system to produce monodispersed “living” chains so that simple correlations between physical properties and molecular weight can be made. The properties were somewhat restricted by the 1,2‐microstructure of the butadiene block.
Copolymerization of vinyl monomers with irradiated acrylamide crystals
Authors: Kücükyavuz Savas , Baysal Bahattin M.
Published: April 2003

Liquid vinyl monomers (styrene and methyl methacrylate) were copolymerized with γ‐irradiated acrylamide in a two‐phase system. The products obtained were mainly diblock copolymers of acrylamide and the vinyl monomer used, but small amounts of homopolymers were also formed. The effects of radiation dose, copolymerization temperature, initial molar ratio of monomers, crystal size of acrylamide, mode of irradiation, and the existence of a solvent were investigated. In addition to the conventional methods, the reaction was studied by electron spin resonance spectroscopy. A mechanism was proposed and a kinetic rate equation was established for this copolymerization. Characterization of the copolymers was made by physical and mechanical testing.
Study of associated reaction variables in the synthesis of titanium (IV) polyamines and a comparison of synthesis by different techniques
Authors: Carraher Charles E. , Jorgensen Steven
Published: April 2003

Synthesis of titanium polyamines was accomplished with “inverse” and “normal” interfacial and aqueous solution systems. Yield was independent of the usual reaction parameters for substituents
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on p‐phenylenediamine for the interfacial systems but might be dependent on the particular diffusion rates of the diamines. Yield decreases as the nucleophilicity of the diamine decreases for the aqueous solution systems. Yield is independent of pH, decreases with reduction in reactant concentration and increases with increases in the amine: Cp2TiCl2 ratio for both normal interfacial and aqueous solution systems.
Studies on diphenylguanidine–accelerated sulfur vulcanization of styrene butadiene rubber in the presence and absence of dicumylperoxide
Authors: Das C. K. , Banerjee S.
Published: April 2003

Diphenylguanidine (DPG) raises the rate of decomposition of dicumylperoxide (DCP) and the crosslinking maxima due to DCP is lowered to some extent by DPG. When the molar proportion of DPG–S is approximately 1:1, no additive results of crosslink formation (as reported for NR) are observed. Zinc oxide and stearic acid increase the rate of crosslinking as well as the crosslinking maxima. In the present study it appears most probable that DPG‐accelerated sulfuration of SBR is an ionic process. At a constant level of DCP and sulfur crosslink density increases when the amount of DPG is increased; a constant level of DCP and DPG crosslinking increases with rising sulfur concentration.

An increase in the concentration of DPG or sulfur leads to greater formation of the complex as well as a change in its composition. The effect of DPG is more pronounced, for by reducing the number of sulfur atoms more sulfur is available for crosslinking. Sulfur absorbs little SO2 or H2S; if it is already saturated, there is no perceptible effect. DPG does absorb H2S or SO2 and the rate and maxima of crosslinks is increased. The effect of SO2 is higher because of the higher Ka values of H2SO3 and consequently higher concentration of HSO3−. Reversion is a free‐radical process inhibited by free DPG present in the system. In the presence of zinc oxide and stearic acid the reaction follows a polar mechanism as well as a radical mechanism.
The cationic dimerization of 1,1‐diphenylethylene. II. Cation formation with titanium tetrachloride in dichloromethane solution
Authors: Sauvet G. , Vairon J. P. , Sigwalt P.
Published: April 2003

The initiation reaction of 1,1‐diphenylethylene (DPE) dimerization by TiCl4 in dichloromethane has been studied at −30 and −70°C in the presence and absence of added cocatalyst. When water was added to the medium, the concentration of active centers was proportional to cocatalyst concentration. When carbocations R+ are formed without a cocatalyst, their usually low concentration depends on initial concentrations of reagents; thus |R+| ∝ |C|0/|M|0, which indicates that the olefin has an inhibiting effect. The simplest hypothesis applicable to these two observations is the existence of a secondary reaction parallel to initiation which traps the initiator in an inactive form; for example, as a complex with the monomer. The two kinetic schemes, which are proposed according to the stoichiometry of the inactive complex (bimolecular C,M or trimolecular C,M2), support mechanisms that would involve solvent cocatalysis, electronic transfer, or direct addition of TiCl4 on the monomer double bond. Consideration of these rival theories reveals that the most likely is the direct addition of TiCl4 on monomer, but unfortunately the known instability of the corresponding organotitanium intermediates does not allow their characterization.
Radical block polymerization of vinyl chloride. I. Ozonized polypropylene oligomers as heterofunctional initiator
Authors: Smets G. , Weinand G. , Deguchi S.
Published: April 2003

Isotactic polyproplyene has been peroxidized in the solid state by treatment with ozone at room temperature, eventually followed by treatment with oxygen at 100°C. The total active oxygen content—peroxides and hydroperoxides—was determined iodometrically, and the hydroperoxide content with triethyl arsine, following the method of Horner and Jürgens. Post‐treatment with oxygen causes a very strong increase in total active oxygen content; the relative amount of hydroperoxides compared with that without oxygen treatment is, however, markedly decreased. The stability and rate of decomposition of PPO2 have been considered in relation to the solubility parameter of the different monomers and solvents. It was used at 30–40°C for initiating the emulsion polymerization of styrene, methyl‐, and butyl methacrylate and methyl, ethyl, n‐butyl, and 2‐ethyl‐hexyl acrylate. These polymers contain an average number of peroxide links per macromolecule, ranging between 7 and 23; they can be used for the block polymerization of a second vinyl monomer, e.g., vinyl chloride.
Direct pyrolysis in the mass spectrometer of aromatic polysulfonates and polythiosulfonates
Authors: Bottino F. , Foti S. , Montaudo G. , Pappalardo S. , Lüderwald I. , Przybylski M.
Published: April 2003

The thermal degradation mechanism of three aromatic polysulfonates and polythiosulfonates was investigated by direct pyrolysis in the ion source of a mass spectrometer. Thermal degradation reactions were followed directly by this method by detecting the thermal and electron impact induced fragments. The results obtained have provided evidence that sulfur dioxide extrusion from the polymer backbone takes place in these polymers above 300°C. The synthesis and molecular characterization of the polymers studied are reported in the text.
Synthesis and study of block copolycondensates containing polysiloxane and unsaturated polyester blocks in the chain. I. Poly(unsaturated esters‐b‐siloxanes) with blocks linked by SiOC bonds
Authors: Madec Pierre‐Jean , Marechal Ernest
Published: April 2003

Block copolycondensates containing both unsaturated polyester and polysiloxane blocks have been prepared by copolycondensation of reactive oligomers; the bonds between the blocks are either SiOC or SiC. This article is devoted to poly(ethylene adipate‐co‐maleate‐b‐siloxane) with SiOC bonds. The reactive oligomers are studied, before or after modification, by tonometry, end‐group titration, GPC, and NMR. Contrary to the block copolycondensates of the same kind described in the literature, those reported in this work have high molecular weights (five block of each kind). These high‐molecular‐weight block polycondensates have been obtained by a careful study of the parameters of the polycondensation.
Synthesis and study of block copolycondensates containing polysiloxane and unsaturated polyester blocks in the chain. II. Poly(unsaturated esters‐b‐siloxanes) with blocks linked by SiC bonds and poly(butadienes‐b‐siloxanes)
Authors: Madec Pierre‐Jean , Marechal Ernest
Published: April 2003

Poly(unsaturated esters‐b‐siloxanes) whose blocks are linked by SiC bonds and poly(butadienes‐b‐siloxanes) have been obtained by polycondensation of ω,ω′‐diepoxy polydimethylsiloxanes and ω,ω′‐dicarboxylic poly(unsaturated esters). The reaction between polysiloxanes with SiH end groups and allylepoxy has been studied; the resulting ω,ω‐diepoxy polysiloxanes have the expected structure. The polycondensation of oligomers with, respectively, epoxy and carboxylic end groups has been studied and the optimal conditions established. The samples with SiC bonds are not affected by hydrolysis in pure water. The poly(siloxanes‐b‐unsaturated esters) can be cured by UV light.
A theoretical investigation of molecular core binding and relaxation energies in a series of oxygen‐containing organic molecules of interest in the study of surface oxidation of polymers
Authors: Clark D. T. , Cromarty B. J. , Dilks A.
Published: April 2003

Nonempirical LCAO MO SCF computations (in the ΔSCF formalism) have been carried out of binding energies and relaxation energies for an extensive series of oxygen‐containing organic systems encompassing most of the common functionalities. The molecules for which experimental data are available for comparison demonstrate the adequacy of the treatment for describing the relative binding energies for both the Cls and Ols core levels. A sound basis is therefore provided for the discussion of relative core binding energies (Cls and Ols) for functionalities for which experimental data are not available, that is, hydroperoxides, peroxides, peroxyacids, and peroxyesters, a knowledge of which is essential for investigations of the surface oxidation of polymers by means of ESCA. Cls shifts are discussed in terms of primary and secondary substituent effects of oxygen, which greatly simplify the analysis of complex unresolved spectra, whereas for the Ols levels a similar but less straightforward situation exists. The relaxation energies associated with both Cls and Ols core ionization follow a dependence on the binding energy for a given structural type.
Preparation and degradation of salts of poly(methacrylic acid). I. Lithium, sodium, potassium, and caesium salts
Authors: McNeill I. C. , Zulfiqar M.
Published: April 2003

The polymers of lithium, sodium, potassium, and caesium salts of methacrylic acid have been prepared by free radical polymerization of the respective monomers in methanol solution. The degradation behavior of the polymers has been investigated by thermal volatilization analysis, thermogravimetry, and product analysis. These materials are stable to about 350°C under programmed heating at 10°C/min in vacuo. The principal degradation products are monomer, the corresponding isobutyrate, carbonate, oxide, carbon dioxide, and a fraction of liquid volatiles that is complex and contains a variety of aldehydes and ketones. The mechanism of degradation is discussed in detail.
Gas permeation in freeze‐dried cellulose acetate membrane
Authors: Kakuta A. , Ozaki O. , Ohno M.
Published: April 2003

Gas permeation rates for helium, nitrogen, argon, and oxygen have been studied by using freezedried cellulose acetate membrane. When the gas permeation rate in freeze‐dried cellulose acetate membrane is high, the gas permeation rate through the pores is predominant. On the other hand, when this rate is small, it is predominant at the dense part, except for the pores. Therefore the gas permeation rate in freeze‐dried cellulose acetate membrane can be explained by the sum of two gas permeation rates.
Radiation degradation susceptibility of vinyl polymers: Nitriles and anhydrides
Authors: Helbert John N. , Poindexter Edward H. , Stahl Glenn A. , Chen Chi‐Yu , Pittman Charles U.
Published: April 2003

The effect of γ irradiation on a series of vinyl polymers, which included polymethacrylonitrile, poly(α‐chloroacrylonitrile), poly(dimethyl itaconate), poly(acrylic anhydride), and poly(methacrylic anhydride), was studied as part of a program to develop improved positive lithographic resists. Radiation‐induced degradation was observed for polymethacrylonitrile, poly(α‐chloroacrylonitrile), and poly(methacrylic anhydride). Molecular weight degradation as a function of dose was monitored by membrane osmometry or GPC techniques. For γ‐irradiated poly(dimethyl itaconate) and poly(acrylic anhydride) crosslinking was found to predominate over chain scission. [G(s)–G(x)] values, calculated from molecular weight inverse versus dose curves, indicate that both nitrile polymers degraded more efficiently than a poly(methyl methacrylate) reference standard on the basis of Mn changes. The radiation behavior of the first three polymers confirms earlier findings than vinyl polymers with quaternary carbons predominantly degrade when subjected to ionizing radiation.
Kinetics and mechanism of the cationic polymerization of tetrahydrofuran in solution: THF‐CH3NO2 system
Authors: Matyjaszewski Krzysztof , Słomkowski Stanisław , Penczek Stanisław
Published: April 2003

Polymerization of tetrahydrofuran (THF) in CH3NO2 solvent was initiated with 1,3‐dioxolan‐2‐ylium cations with AsF and SbF anions, as well as with esters of FSO3H and CF3SO3H acids. Polymerization shows in this solvent a living feature: values of kp (determined directly from the semilogarithmic kinetic plots) were the same for all of the listed above initiators; thus kp is the same for AsF, CF3SO, FSO, and SbF anions. The identity of the kp values for complex and noncomplex (ester‐forming) anions comes from the fact that in CH3NO2 solvent equilibrium between macroesters and macroion pairs is shifted almost completely (Ke = 33.0 at 25°C and |THF|0 = 7.0M) to the macroions side. Dissociation constants of the polytetrahydrofuranium ion pairs (CF3SO and SbF anions) were measured (e.g., KD = 2 × 10−3 M at 25°C and |THF|0 = 7.0M; i.e., at D = 22.8, ΔHD = −3.8 ± 6 kcal mole; ΔSD = −25 ± 2 eu). On the basis of the known values of KD, and therefore dissociation degrees α, rate constants of propagation on the free and paired THF cations (k and k) were determined for a large range of degrees of dissociation (α from 0.15 to 0.52). The rate constants k and k were found to be the same within an experimental error of measurements (± 15% of the value of kp). Apparently, the polytetrahydrofuranium cations are highly solvated or even separated from their anions by molecules of THF itself. At these conditions the reactivities of the solvated “free” and solvated (or separated) paired cations became undistinguishable.
Polymerization of N‐(fluoro phenyl) maleimides
Authors: Barrales‐Rienda J. M. , Ramos J. González , Chaves M. Sánchez
Published: April 2003

Poly(N‐aryl maleimide)s of characteristic structures have been synthesized and some of their physical properties studied. These include N‐(2‐fluoro phenyl), N‐(3‐fluoro phenyl), N‐(4‐fluoro phenyl), N‐(2,4‐difluoro phenyl), N‐(2,5‐difluoro phenyl), N‐(2,3,5,6‐tetrafluoro phenyl), and N‐(pentafluoro phenyl). The polymerization of N‐(fluoro phenyl) maleimides by free‐radical initiation in bulk or in solution and by anionic catalyst have been studied to compare the characteristics of polymerization by γ‐ray irradiation with that by free‐radical initiation. The polymers were characterized by elemental analysis, intrinsic viscosity, spectroscopy (IR and NMR), programmed thermogravimetric analysis, and x‐ray diffraction. Spectra of polymers prepared by radiation and anionic polymerization were nearly identical with those of polymers prepared by free‐radical polymerization initiated by AIBN in bulk or in solution and by the self‐initiated thermal polymerization. A variety of reaction conditions were tried, but all attempts to change the molecular structure of the polymers were unsuccessful. Rates of thermal degradation for poly[N‐(fluoro phenyl) maleimide]s have been analyzed by using a multiple‐heating‐rate procedure. Overall activation energy, order of reaction, and frequency factor have been evaluated. On the basis of the comparison between the overall activation energy of the thermal degradation of poly[N‐(fluoro phenyl) maleimide]s and NMR spectra of their corresponding monomers, it can be concluded that the 1H shifts due to ethylenic protons are so characteristic in sign and magnitude as to be useful in thermal stability elucidation. Some qualitative explanations were given on the stability of these polymers as affected by the type and size of the substituent. The x‐ray diffractograms of all samples show two rather broad peaks indicative of noncrystalline structures. The location of the peaks does not depend upon preparation conditions and temperature. Poly(N‐maleimide)s of fluoroanilines have not been hitherto described.
Emulsifier‐free emulsion polymerization of tetrafluoroethylene by radiation. III. Simultaneous formation of hydrofluoric acid
Authors: Suwa Takeshi , Watanabe Terutaka , Okamoto Jiro , Machi Sueo
Published: April 2003

Simultaneous formation of hydrofluoric acid (HF) in the radiation‐induced polymerization of tetrafluoroethylene (TFE) was investigated. HF concentration in PTFE latex was determined mainly by conductometric titration with 0.01 and 0.001N NaOH. The amount of HF formed is almost independent of agitation speed and the amount of n‐hexadecane added and is maximal at ca. 70°C corresponding to the rate of polymerization.

The rate of HF formation increases with the initial pressure of TFE monomer and dose rate and decreases with polymerization or TFE consumption. This fact suggests that HF is formed mainly by TFE reactions and not by the degradation of PTFE.

The mechanism of HF formation in this reaction system in the absence of oxygen is shown in the following two schemes: scheme I is the reaction of TFE with primary radicals (OH·, H·, e) from the radiolysis of water; scheme II is the reaction of water with the species from the radiolysis of TFE. On the assumption that HF is formed only according to scheme I, the G value of HF formation G(HF)calc can be calculated as 11.25. All observed G values G(HF)obs are larger than G(HF)calc. When the polymerization is carried out at 20 kg/cm2 under various dose rates, G(HF)obs increases with the dose rate. When the polymerization is carried out at 3.0 × 104 rad/hr under various pressures, G(HF)obs decreases with the decrease in pressure from 20 to 2 kg/cm2 and is fairly close to G(HG)calc at 2 kg/cm2. This indicates that HF formation is due mainly to scheme II at high pressure (in the presence of enough TFE) and to scheme I as the pressure is lowered.
High‐molecular‐weight hydrolyzed polyacrylamides. II. Potentiometric titrations
Authors: Fenyo J. C. , Laine J. P. , Muller G.
Published: April 2003

Potentiometric titrations in water of high‐molecular‐weight partly hydrolyzed polyacrylamides were analyzed by the Lifson—Katchalsky rodlike model. A fair concordance was found between theory and experimental curves with pK0 of acid functions of about 4.75 when 0 < τ < 0.49. Two methods were derived to calculate the parameter n of the extended Henderson‐Hasselbach equation by using a series expansion of pKa vs. α, not yet reported in the literature. A new equation for n was established and comparison between two sets of values of n, obtained by using the theoretical ΔpK curves and series expansion is discussed.
Prediction of the directional effect of pressure on the reactivity ratios in free‐radical copolymerizations
Authors: Jenner Gérard
Published: April 2003

The Q–e concept of the Alfrey and Price1 has been applied successfully to the prediction of the pressure effect on the individual reactivity ratios in free‐radical copolymerizations. Although the Q value of a given monomer is generally little affected by an increase in pressure, the e value is pressure dependent. The knowledge of the Q and e values at high pressures permits the prediction of variations in reactivity ratios with pressure. Some important consequences have been drawn from this concept.
Cationic copolymerization of isobutene and conjugated small‐ring dienes
Authors: Tsao Jung‐Hsien , Lenz Robert W.
Published: April 2003

1‐Methyl‐3‐methylenecyclobutene (MMCB) and 1,2‐dimethylenecyclobutane (DMCB) copolymerized readily with isobutene with aluminum chloride as initiator in methyl chloride solution at temperatures from −95 to −78°C. No polymers were obtained with methylenecyclobutene (MCB) under similar conditions. The copolymerization of MMCB with isobutene took place through a 1,5‐addition reaction while that of DMCB through both 1,2‐ and 1,4‐addition reactions. Large amounts of gel were present in the copolymers obtained from DMCB if the reaction was carried to high conversion. The commonly observed effects of dienes (i.e., rate retardation and molecular weight depression) on cationic copolymerization reactions were observed but to a much higher degree with these small ring dienes. The thermal crosslinking behavior of the resulting copolymers was investigated. In conjunction with the copolymerization studies, homopolymers of MMCB, DMCB, and 3,3‐dimethyl‐1‐isopropylidene‐2‐methylenecyclobutane (IMCB) were prepared and their chemical structures examined.
Effect of dose rate on radiation‐induced polymerization of styrene adsorbed on silica gel
Authors: Kusama Yasuo , Udagawa Akira , Takehisa Masaaki
Published: April 2003

The effect of dose rate on the rate of polymerization and molecular weight distribution of radiation‐induced polymerization of styrene adsorbed on silica gel was studied in a wide dose rate range of 4.4 × 104 to 3 × 108 rad/hr by γ rays of 60Co and electron beams with a Cockcroft‐Walton‐type accelerator. Dose rate dependence on the initial rate of polymerization was about 1 below 3 × 107 rad/hr, and it decreased gradually at high dose rates. Throughout the dose rate range, graft polymerizations and homopolymerizations by cationic and radical mechanisms proceeded simultaneously. Dose rate dependence of the cationic polymerization was 1 below 3 × 107 rad/hr, while dose rate dependence of the radical polymerization was 0.65 below 3 × 107 rad/hr. At high dose rates, molecular weight and fraction of graft polymer decreased, and fraction of cationic polymerization increased. A very high‐molecular‐weight graft polymer was formed above 4.4 × 105 rad/hr at the initial stage of the polymerization. The dose rate dependence of this polymerization was larger than 1 and decreased with increase in dose rate. The polymerization seems to be related to an excitation of monomer or growing chain.
Stabilization of high nitrile polymers. I. Effect of dienophilic compounds
Authors: Marien Bruce A.
Published: April 2003

The effect of certain stabilizers on the discoloration of high nitrile polymers is discussed in terms of an in situ Diels‐Alder reaction. Dienophiles react with cis azadienes formed during thermal degradation of the nitrile polymer to interrupt conjugated sequences prior to oxidative chromophore formation. Several nondienophilic additives decompose upon heating to release a strong dienophile that stabilizes the polymer.
The kinetics of unterminated polymerization reactions
Authors: Baer S. , Kremer M. L.
Published: April 2003

The kinetics of the intermediates in unterminated polymerization reactions were studied. It was found that in a first‐order initiation (A) all intermediates accumulate monotonically. In a second‐order initiation (B) the first intermediates pass through a maximum, whereas the later ones strictly accumulate. An initiator‐started polymerization can follow course A or course B, depending on the initial ratio of the concentrations of the initiator and monomer.
Radical copolymerization of optically active l‐menthyl vinyl ether with maleic anhydride, dimethyl maleate, and dimethyl fumarate
Authors: Kurokawa Masahiro , Minoura Yuji
Published: April 2003

The copolymerizations of l‐menthyl vinyl ether (l‐MVE) with the monomers, that is, maleic anhydride (MAn), dimethyl maleate (DMM), and dimethyl fumarate (DMFu), were undertaken to obtain optically active copolymers. The optically active l‐menthyl group in the side chain of copolymers was removed by the ether cleavage reaction with dry‐hydrogen bromide gas. The ethercloven copolymers were still optically active. Hence it was concluded that asymmetric carbon atoms were introduced into the copolymer main chain, the reason given being that l‐MVE and comonomers (MAn, DMM, and DMFu) made the stereoselective charge‐transfer complex one another and copolymerized stereospecifically. From the results of the measurements of optical rotatory dispersion (ORD) and circular dichroism (CD) for copolymers before and after the ether cleavage reaction, the mode of bond opening for α,β‐substituted monomers (MAn, DMM, and DMFu) was discussed and the microstructures of copolymers were prepared.
Monomer chain‐transfer constants from emulsion copolymerization data: Styrene and α‐methylstyrene
Authors: Rudin Alfred , Samanta M. C. , Van Der Hoff B. M. E.
Published: April 2003

Radical chain‐transfer constants can be deduced from corresponding measurements of rates and degrees of polymerization in copolymerization experiments. It is particularly useful to carry out such copolymerization in emulsion systems where the normal termination reactions are relatively less important and chain‐transfer processes are significant in determining the number‐average degree of polymerization. The method is illustrated for copolymerization of styrene and α‐methylstyrene at three temperatures. Rate constants for transfer of styryl and α‐methylstyryl radicals to either monomer were measured. All the rate constants are consistent with the relative stabilities of the product radicals which could be formed by the various transfer reactions. The procedure described here can be extended for measurements of rate constants for reactions of other potential transfer agents.
A new synthetic route to polycarbonate
Authors: Soga K. , Hosoda S. , Ikeda S.
Published: April 2003

A detailed study has been carried out on the new synthetic reaction of poly(p‐xylylene carbonate) from potassium carbonate and p‐xylylene dibromide by using a variety of crown ethers as a catalyst, which was recently found by the present authors. Crown ethers having 18‐member ring showed the best catalytic property of the various crown ethers, and the reaction was conducted in various solvents at 50–160°C by using 18‐crown‐6‐ether. Both the polymer yield and the molecular weight of the polymer increased in proportion to the amount of potassium carbonate, and they increased rapidly and reached constant values with increasing the concentration of 18‐crown‐6‐ether. They also depended significantly upon the reaction temperature as well as the solvent used. A maximum yield with the highest molecular weight was obtained from the reaction at 100–120°C in diglyme solvent. The spectroscopic analysis of the polymer indicated that all the end groups of the resulting polymer had the structure of benzyl bromide. From these results, a plausible mechanism was proposed for the reaction. Similar reactions were also conducted by using several aliphatic dibromides, Br(CH2)xBr, in place of p‐xylylene dibromide. The products were strongly dependent of the value of x: polycarbonate was obtained from dibromides with ≧4, and cyclic carbonates from dibromides with ≦3.
Aqueous polymerization of acrylamide
Authors: Shukla J. S. , Singh Khajan
Published: April 2003

The polymerization of acrylamide (I) initiated by a potassium bromate—thioglycollic acid (TGA) redox pair has been studied in aqueous media at 30°C in a nitrogen atmosphere. The reaction order related to the catalyst concentration (KBrO3) was 0.501, which indicated a bimolecular mechanism for the termination reaction in the range of 1.0−3.0 × 10−3 mole/liter. The polymerization rate varied linearly with monomer (I) concentration over the range of 1.0−5.0 × 10−2 mole/liter. A typical behavior is observed, however, by changing the thioglycollic acid concentration. The initial rate of polymerization (Ri), as well as the maximum conversion, increases by increasing the temperature to 30°C, but the initial rate and the maximum conversion falls as the temperature rises above 30°C. The overall energy of activation is 6.218 kcal in the temperature range of 20–40°C. Water‐miscible organic solvents, namely, CH3OH and C2H5OH, depress the rate of polymerization.
Effect of pressure on free radical copolymerization kinetics. II. Novel methods of measuring monomer reactivity ratios under high‐pressure conditions
Authors: Van Der Meer R. , German A. L.
Published: April 2003

Two new techniques for the determination of monomer reactivity ratios in copolymerization under high‐pressure conditions have been developed, viz., the “sandwich” and the “quenching” method. Both methods are based on repeated quantitative gas chromatographic analysis of the reaction mixture during the low‐pressure stages preceding and succeeding the high‐pressure stage, of which the kinetics is under investigation. Application of the “sandwich” method implies the occurrence of reaction during both low‐pressure stages and consequently the low‐pressure kinetic data are required to obtain the transition points of low to high pressure and vice versa. These points constitute the initial and final conditions of the relevant high‐pressure reaction. On the contrary, in the “quenching” method no reaction occurs during the low‐pressure stages, owing to the lower temperature and the high activation energy of the initiator decomposition. As a consequence, the initial and final conditions of the high‐pressure stage can be determined by a simple averaging procedure. Both methods have been tested for the ethylene—vinyl acetate copolymerization at 62°C and 600 kg/cm2 with tert‐butyl alcohol as solvent, and appear to lead to almost identical monomer reactivity ratios, although the “quenching” method is slightly preferred in case of copolymerization reactions. Both methods are particularly valuable when one of the reactants is gaseous or the reaction produces a gas. Further merits and drawbacks of both methods are discussed.
Pseudoheterogeneous polymerization of methyl methacrylate initiated by sodium bisulfite in presence of glassy powder of PbOSiO2
Authors: Moustafa A. B. , Badran A. S.
Published: April 2003

The aqueous polymerization of methyl methacrylate with sodium bisulfite as initiator was catalyzed by PbOSiO2, PbO (70 mole %)SiO2 (30 mole %) with a particle size < 200 mesh had the highest catalytic effect. The average molecular weight obtained in the presence of amorphous PbOSiO2 glass was higher than that obtained in the presence of crystalline PbO—SiO2 glass powder. In this system mild shaking increased the rate of polymerization. Silicon dioxide catalyzed the rate of polymerization to a higher extent than PbO, which had a slightly higher catalytic effect than lead silicate powder. The average molecular weight formed in the presence of PbO was higher than that formed in the presence of lead silicate, which in turn was higher than that formed in the presence of silicon dioxide. Increasing the initiator concentration decreased the average molecular weight. Mild shaking decreased the average molecular weight obtained when polymerization was carried out in air but increased it in a nitrogen atmosphere. Methanol decreased the conversion percentage of monomer to polymer and the average molecular weight due to its transfer reaction.
Thermal oligomerization of isophthalonitrile catalyzed by o‐carborane
Authors: Klingen T. J. , Johnson B. M.
Published: April 2003

The thermal reaction of equimolar quantities of isophthalonitrile and o‐carborane has been shown to produce an adduct oligomer of isophthalonitrile. The structure was determined to involve condensation of three to five isophthalonitrile molecules to form a triazine‐type system. This type of bonding gave rise to a trimer and pentamer. Further, the reaction was a homogeneous liquid phase reaction in which o‐carborane is involved in a catalytic manner in the oligomerization. The overall reaction has first‐order kinetics with an activation energy of 32.2 kcal/mole.
High‐molecular‐weight hydrolyzed polyacrylamides. I. Characterization. Effect of salts on the conformational properties
Authors: Muller G. , Laine J. P. , Fenyo J. C.
Published: April 2003

The effect of ionization (α) and added salts (NaCl, CaCl2, MgCl2) on the dimensions of commercially available high‐molecular‐weight polyacrylamides (Mw ≃ 4 × 106), hydrolyzed at various extents (0.04 < τ < 0.49) and which have been characterized, was investigated by viscosity and light‐scattering measurements performed at 25°C. The data point with evidence to the strong dependence of the chain dimensions on the charge density (ατ) and the effect of the nature and concentration of added salts. From a practical point of view it is shown that there is no advantage to using too highly hydrolyzed samples (τ > 0.45) in media containing large amounts of salts that lead to precipitation of polymers, especially in the presence of divalent ions.
Peroxide‐initiated crosslinking of maleic anhydride‐modified low‐molecular‐weight polybutadiene. I. Mechanism and kinetics of the reaction
Authors: Gancarz I. , Łaskawski W.
Published: April 2003

The crosslinking mechanism and kinetics of low‐molecular‐weight polybutadiene, its mixtures with maleic anhydride, and the products of its grafting with maleic anhydride and styrene, using dicumyl peroxide (DCP) as an initiator, were studied. It was shown that for all systems crosslinking is a radical polymerization of the double bonds. Modification of polybutadiene changes only the kinetic parameters of the crosslinking reaction and causes mainly a decrease of the termination step velocity. From DSC data the crosslinking reaction order, activation energy, and reaction heats were calculated.
Effect of structure on the thermal stability of polyimides
Authors: Varma I. K. , Goel R. N. , Varma D. S.
Published: April 2003

Polyimides with different proportions of m‐phenylene and p‐phenylene (or p,p′‐biphenylene) were prepared by polymerizing different molar ratios of m‐phenylene diamine and p‐phenylene diamine (or p,p′‐diaminobiphenyl) with pyromellitic dianhydride in dimethylformamide at 0°C. Chemical cyclodehydration of polyamic acids resulted in the corresponding polyimides. Polymers were characterized by infrared (IR), viscosity, and density measurements. Viscosity and density of polymers decreased with an increase on m‐phenylene groups in the backbone. The thermal and thermooxidative stabilities were investigated by dynamic thermogravimetry. Stability decreased when m‐phenylene groups were introduced in the backbone.
Chemical modification of polymers. XI. Photoreactive polymers from poly(vinylbenzyl chloride)
Authors: Gibson Harry W. , Bailey F. C. , Chu Joseph Y. C.
Published: April 2003

Photocrosslinking has been observed in a number of polymers derived by chemical modification of poly(vinylbenzyl chloride). Included are polymers bearing pendant benzophenone, stilbazolium, fluorenone, carbazole, and sulfonylazido moieties. The synthesis and properties of these polymers are described.
Functional monomers and polymers. XXXXVII. Complex formation of stereoregular methacryloyl‐type polymers containing nucleic acid bases
Authors: Akashi M. , Okimoto T. , Inaki Y. , Takemoto K.
Published: April 2003

The complex formation between a poly(N‐β‐methacryloyloxyethyl) derivative of adenine with one of thymine or uracil was studied in dimethyl sulfoxide and ethylene glycol mixture by ultraviolet (UV) spectroscopy. For the polymer pairs containing complementary nucleic acid bases both hypochromicity and hyperchromicity were found. Stereoregularity of the polymers, as well as the conditions for measurement of, for example, solvent, temperature, and time, affected the complex formation. Both inter‐ and intramolecular interaction of polymers in solution were discussed in some detail.
Photoinitiated cationic polymerization with triarylsulfonium salts
Authors: Crivello J. V. , Lam J. H. W.
Published: April 2003

Triarylsulfonium salts Ar3S+MX with complex metal halide anions such as BF, AsF, PF, and SbF are a new class of highly efficient photoinitiators for cationic polymerization. In this article we describe several synthetic routes to the preparation of these compounds along with their physical and spectroscopic properties. Mechanistic studies have shown that when these compounds are irradiated at wavelengths of 190–365 nm carbon–sulfur bond cleavage occurs to form radical fragments. At the same time the strong Br∅︁nsted acid HMXn, which is the active initiator of cationic polymerization that takes place in subsequent “dark” steps, is also produced. A study of the parameters that affect the photolysis of triarylsulfonium salts is reported with a measurement of the absolute quantum yields. The cationic polymerizations of four typical monomers—styrene oxide, cyclohexene oxide, tetrahydrofuran, and 2‐chloroethyl vinyl ether—with triarylsulfonium salt photoinitiators are described.
Problems associated with the surface characterization of polystyrene latices
Authors: Goodall A. R. , Hearn J. , Wilkinson M. C.
Published: April 2003

It has been shown that polystyrene latices prepared by the surfactant free emulsion polymerization process often contain sufficient residual monomer and possibly low‐molecular‐weight material and reaction by‐products, such as benzaldehyde, which are not efficiently removed by dialysis, to affect their bulk and surface characteristics. These materials have been identified by gel permeation chromatography (GPC) and infrared (IR) spectroscopy studies and their effective removal by steam stripping has been investigated. Steam stripping has proved to be efficient in this process but it led to rapid hydrolysis of the surface sulfate groups and a consequent change in the surface characteristics. The problem of hydrolysis of sulfate groups under various environments has been studied. The problems associated with the identification of weak acid end groups are discussed and several alternative explanations for their occurrence are advanced.
Molecular weight standards from sulfonation of polystyrene
Authors: Brown D. W. , Lowry R. E.
Published: April 2003

Polystyrene was sulfonated with sulfur trioxide–triethyl phosphate complexes in dichloroethane, the object being to prepare polystyrene sulfonates substantially free of sulfone links between polymer chains. Variations in the sulfone content with reaction conditions were conveniently followed by exclusion chromatography, the sulfone peak appearing at about twice the molecular weight of the main peak. The desired products were obtained from polystyrenes with molecular weights between 1.1 × 105 and 8.7 × 105 by using (at −20 to +25°C) a 5:1 excess of a 1.5:1 complex, the last at a concentration of 0.5M. Completely soluble polystyrene sulfonate was also obtained from polystyrene of molecular weight 2.05 × 106. Requirements for the successful use of the 1.5:1 complex include careful purification of the dichloroethane and, if 2 g or more polystyrene is to be sulfonated, formation of the complex at −20°C. A method is given for measuring the sulfonating capability of the reagent before adding the polymer.
Effect of interfacial chemical bonding on the strength of adhesion of glass–polybutadiene joints
Authors: Runge M. L. , Dreyfuss P.
Published: April 2003

A new example of a positive effect of interfacial chemical bonding on the strength of adhesive bonds is reported. The chemical bond was formed between a p‐bromomethylphenylpolysiloxane‐coated glass slide and a liquid dicarboxy‐terminated polybutadiene that was subsequently bonded to an elastomeric polybutadiene by crosslinking with dicumylperoxide. Peel tests at 180° led to cohesive failure in the elastomer layer for two different proportions of p‐bromomethylphenyl groups on the glass slides, whereas uncoated slides and slides coated with an inert polysiloxane layer, p‐tolyl‐polysiloxane, showed interfacial failure. Further confirmation of interfacial bonding was obtained from SEM studies. When peel tests resulted in cohesive failure, it was found possible to distinguish between different degrees of interfacial by the different times required for failure at the interface on swelling the elastomer layer with pentane.
Heat‐curable polyaromatic keto‐ether‐sulfones. XIV. More polymers with 2,2′‐diphenylethynyl‐4,4′‐diphenyl units and their rearrangement products
Authors: Frentzel Richard L. , Marvel C. S.
Published: April 2003

Polymers were prepared from 4,4′‐diphenoxydiphenylsulfone, isophthaloyl dichloride, and bis‐p‐phenoxyphenyl‐4,4′‐(2,2′‐dibromodiphenyl)ketone, 2,2′‐dibromodiphenyl‐4,4′‐dicarbonyl dichloride, or bis‐p‐phenoxyphenyl‐4,4′‐(2,2′‐diphenylethynyldiphenyl)ketone in Friedel‐Crafts type of polymerization. Bromine groups were subsequently replaced with phenylacetylene residues, and the polymers were cured at high temperatures, with the apparent formation of benzanthracene linkages. Cured polymers exhibited higher softening points, decreased solubilities, and, in some instances, higher melting points than their uncured precursors. Significant weight losses occurred during isothermal aging tests.
The charge‐transfer polymerization of nitroethylene in electron‐donating solvents
Authors: Kushibiki Nobuo , Ogasawara Masaaki , Yoshida Hiroshi
Published: April 2003

The anionic polymerization of nitroethylene was studied in N,N‐dimethylformamide (DMF) and in dimethyl sulfoxide (DMSO) at 0–40°C. The polymerization proceeds spontaneously when monomer is mixed with solvent in the absence of light. From the observed results of the rate of polymerization, the molecular weight of polymer, the effects of additives and solvents, the copolymerization with acrylonitrile, and the optical absorption spectra it is concluded that the polymerization is initiated by the nitroethylene radical anion generated by the slow dissociation of the electron donor–acceptor (EDA) complexes between the solvent molecule and the monomer. The activation energy for the rate of polymerization was 50 and 29 kJ/mole in DMF and DMSO, respectively, which seems to be determined primarily by the dissociation of the EDA complexes. The significant features of this polymerization are that the initiation proceeds slowly and there is essentially no termination.
Polyimidines: A new class of polymers. III. A comparison of isomers of polypyromellitimidines
Authors: Cassidy Patrick E. , Lin J‐C. , Fawcett Newton C.
Published: April 2003

The cis (3,3,5,5‐), trans (3,3,7,7‐), oxo, and thio analogs of tetraphenylpyromellitide were polymerized with 1, 6‐hexane diamine, p‐phenylene diamine, and p,p'‐diaminodiphenyl ether under various conditions. A comparison was then made of reactivity of the isomers and of the properties of the polymers. In general the thio monomers were more soluble and reactive than the oxo. They also gave more thermally stable polymers. The cis isomers of the monomers were more soluble than the trans, but the trans were more reactive. The least stable of the 12 polymers prepared was that from the cis–oxo monomer and 1,6‐hexane diamine. It gave a 10% weight loss at 300°C in air and 340°C in nitrogen by TGA. The most stable polymer was from the reaction of the cis–thio pyromellitide with p,p'‐diaminodiphenyl ether, which showed 10% weight losses by TGA at 560 and 650°C in air and nitrogen, respectively. The polymers were stable in hot dilute hydrochloric acid and sodium hydroxide. They were all soluble in chloroform, dimethylformamide, and sulfuric acid. Polymers that contained sulfur were also soluble in carbon tetrachloride, benzene, xylene, and toluene. Brittle films could be cast from solution or melt‐pressed.
Electroinitiated polymerization of arylvinyl monomers
Authors: Smith J. D. B. , Phillips D. Colin , Davies D. H.
Published: April 2003

The electroinitiated polymerizations of styrene, 2‐vinylnaphthalene, and 9‐vinylanthracene were compared in sulfolane and acetone solvents in the presence of ZnCl2. The relative orders of polymerization rates and polymerization efficiencies, in both solvents, were 9‐vinylanthracene > 2‐vinylnaphthalene > styrene, with faster rates and higher efficiencies occurring in sulfolane. Data obtained from viscosity and gel permeation chromatography (GPC) studies indicate that the molecular weights of the polymers produced in these systems are extremely low, <5000. Chemical composition and infrared (IR) spectral data suggest that abnormal transfer reactions (possibly from solvent) may be occurring in the electroinitiated 9‐vinylanthracene polymerizations. The polymerization mechanism appears to be cationic in these monomer–solvent systems with ZnCl2.
Monomer‐isomerization polymerization. XVIII. Monomer‐isomerization copolymerizations of 4‐phenyl‐2‐butene with 4‐methyl‐2‐pentene and 3‐heptene with Ziegler‐Natta catalyst
Authors: Endo Kiyoshi , Otsu Takayuki
Published: April 2003

4‐Phenyl‐2‐butene (4Ph2B) undergoes monomer‐isomerization copolymerization with 4‐methyl‐2‐pentene (4M2P) and 2‐and 3‐heptene (2H and 3H) with TiCl3–(C2H5)3Al catalyst at 80°C to produce copolymer consisting exclusively of 1‐olefin units. For comparison the copolymerization of 4‐phenyl‐1‐butene (4Ph1B) with 4‐methyl‐1‐pentene (4M1P) and 1‐heptene (1H) was carried out under similar conditions. The composition of the copolymers obtained from these copolymerizations was determined from the ratios of optical densities D1380 and D1600 of infrared (IR) spectra of their thin films. The apparent monomer reactivity ratios for the monomer‐isomerization copolymerization of 4Ph2B with 4M2P, 2H, and 3H in which the concentration of olefin monomer in the feed was used as internal olefin and those for the copolymerization of 4Ph1B with 4M1P and 1H were determined as follows: 4Ph2B(M1)‐4M2P(M2); r1 = 0.90, r2 = 0.20, 4Ph1B(M1)‐4M1P (M2); r1 = 0.40, r2 = 0.70, 4Ph2B(M1)‐2H(M2); r1, = 0.45, r2 = 1.85, 4Ph2B(M1)‐3H(M2); r1 = 0.50, r2 = 1.20, 4Ph1B(M1)‐1H(M2); r1 = 0.55, r2 = 0.75. The difference in monomer reactivity ratios seemed to originate from the rate of isomerization from 2‐ or 3‐olefins to 1‐oletins in these monomer‐isomerization copolymerizations.