bluuebunny/crossref_metadata_2025 huggingface dataset:
Branching kinetics in copolymerization of styrene with a chain‐transfer monomer
Authors: Tung L. H.
Published: April 2003

In an earlier work it was shown that a random long‐chain branching structure can be incorporated in polystyrene by copolymerizing styrene with a small amount of monomer that contains a chain transfer group. The use of vinylbenzylthiol as the chain transfer monomer produced a polystyrene with low number‐average molecular weight and a degree of branching lower than expected. In this study polymerization kinetics were used to compute the theoretical molecular weight and degree of branching. The results show that if the chain‐transfer constant of the chain transfer monomer is as high as that for vinylbenzylthiol the expected molecular weight and degree of branching will indeed be as low as those found experimentally. The theory also predicts that if the chain transfer constant is near one a highly branched bushy structure will result.
Polymerization of coordinated monomers. XVIII. Sequence distribution in methyl acrylate–styrene copolymers prepared in the presence of zinc chloride
Authors: Tanabe Tsuneaki , Koinuma Hideomi , Hirai Hidefumi
Published: April 2003

Methyl acrylate and styrene have been copolymerized in the presence of zinc chloride either by photoinitiation or spontaneously. The copolymerization mechanism is investigated by analyses of copolymers composition and monomer sequence distribution. The resulting copolymers are not always alternating, their composition being dependent especially on the monomer feed ratio. Appreciable deviation to higher methyl acrylate unit content from an equimolar composition occurs at monomer feed fractions of methyl acrylate over 0.7. The larger deviation is induced by higher temperature, by photoirradiation, and by greater dilution of the reaction mixture with toluene. The 13C‐NMR spectrum of the alternating copolymer shows a sharp singlet at the carbonyl region, whereas the spectra of random copolymers prepared by benzoyl peroxide initiation at 60°C show a triplet splitting at the carbonyl carbon region, irrespective of copolymer composition. The relative intensities of the triplet peaks for the random copolymers are in good correspondence to the contents of triad sequences calculated by means of conventional radical copolymerization theory. These results clearly indicate that the carbonyl splitting is caused predominantly by variation of the monomer sequence and not by variation of the stereosequence. The monomer sequence distribution in the copolymers is thus directly and quantitatively measured from the split carbonyl resonance. Although the same triplet splitting appears in the spectra of methyl acrylate–rich copolymers prepared in the presence of zinc chloride at high feed ratios (>0.7) of methyl acrylate, the relative intensities of the split peaks do not fit the sequence distributions of random copolymers calculated by means of the Lewis–Mayo equation. The copolymerization yielding these peculiar sequences and the alternating sequence in the presence of zinc chloride is fully comprehended by a copolymerization mechanism proceeding between two active coordinated monomers, i.e., the ternary molecular complex composed of zinc chloride, methyl methacrylate, and styrene, and the binary molecular complex composed of zinc chloride and methyl methacrylate.
Functional monomers and polymers. XCIV. Photochemical reactions on the synthetic polymers containing thymine bases in the presence of adenine derivatives
Authors: Kita Yasuo , Uno Taizo , Inaki Yoshiaki , Takemoto Kiichi
Published: April 2003

Photodimerization reactions of polyacrylate and polymethacrylate derivatives and the dimer model compound containing thymine bases were studied in the presence of adenine derivatives in dimethyl sulfoxide; N,N‐dimethylformamide; and dimethyl sulfoxide–ethylene glycol solutions. The photodimerization of thymine bases both in the polymers and in the dimer model compound was found to be quenched by the addition of adenine derivatives. Base‐base interaction in the ground state was also studied by ultraviolet (UV) spectroscopy in the three solvents. The quenching of the photodimerizationof thymine bases in the presence of adenine derivatives was discussed in terms of the specific interaction between adenine and thymine bases both in ground and excited states.
Studies of some bioactive N‐p‐methacrylamidobenzoic esters
Authors: Lu (C. X. Lu) Chengxun , Yang Jijin , Leng Liecheng , Feng (S. T. Voong) Xinde , Li Dechang
Published: April 2003

Preparations of four typical bioactive esters of N‐p‐methacrylamidobenzoic monomers and their reactive polymers as immobilized trypsin carriers are described. N‐p‐methacrylamidobenzoic active ester monomers containing COONB, COOSu, COOObt, or COOBT group can react with an aliphatic amine such as benzylamine at room temperature to give an identical product, N‐benzyl‐p‐methacrylamidobenzamide. However, only monomers with COOObt or COOBT group can also react with an aromatic amine such as aniline to give N‐phenyl‐p‐methacrylamidobenzamide. These monmoers polymerized readily in solution with azobisisobutyronitrile as free‐radical initiator; the polymers were used to immobilize trypsin. Among the four different active esters for the immobilization of trypsin, thE HONB and HOSu active ester showed rather higher bioactivities than the HOObt or HOBT active ester under the same conditions. Both P(MABONB)‐trypsin and P(MABOSu)‐trypsin matrices possess higher biological activities by about four or three times that of P(MABOObt)‐trypsin or P(MABOBT)‐trypsin matrices, respectively. It is proposed that these rather high bioactivities may be attributed to the “specific” aminolysis of reactive polymer with COONB or COOSu active ester group by aliphatic amino substituents.
Time dependence of crack healing
Authors: Wool R. P. , O'Connor K. M.
Published: April 2003

We propose that crack healing in polymers occurs by the stages of surface rearrangement, surface approach, wetting, diffusion, and randomization. The stages of wetting and diffusion are responsible for the majority of the mechanical property recovery or healing, and control the intrinsic healing function Rh(t). However, the observed macroscopic recovery R is a convolution product of Rh(t) and a wetting distribution function Φ(t). Each Rh(t) function contains a wetting and diffusion component. Experiments were designed to investigate intrinsic healing functions for fracture stress, strain, and energy; the results were found to be in excellent agreement with theory.
Synthesis of carbonate‐containing high temperature poly(arylene‐siloxanylenes)
Authors: Rosenberg Harold , Tsai Tsu‐Tzu , Ngo Ngoc Kim
Published: April 2003

A method for the first synthesis of high molecular weight carbonate‐containing siloxanylene polymers was successfully developed. The procedure covered the preparation and polymerization of pure carbonate‐containing bis‐silanols which included bis(4‐hydroxydimethylsilylphenyl)‐carbonate, bis[4‐(1‐hydroxy‐1,1,3,3‐tetramethyldisiloxanyl)‐phenyl] carbonate, and their meta analogs. Because conventional siloxane polymerization methods, such as the heterocondensation of bis‐silanols with diaminosilanes or homocondensation reactions catalyzed by alkali reagents, decomposed carbonate linkages, a new polymerization technique that involved the use of phosgene was used. The procedure was both facile and effective in the polymerization of other arylene bis‐silanols.
Kinetic approach to radiation‐induced grafting in the polyethylene‐styrene system. V. The behavior of initiator radicals
Authors: Imai Masahiko
Published: April 2003

With high‐density polyethylene (HDPE) and low‐density polyethylene (LDPE) films the grafting reactions were performed by the preirradiation method. By holding the total absorption dose constant irradiation time was varied. The initial rate of grafting decreased with irradiation time. The relative concentration of alkyl radical in the polyethylene film also decreased with irradiation time, but the relative concentration of allyl increased. The differences in the ESR spectrum before and after the introduction of styrene indicate that the allyl‐type radical reacted with styrene. To elucidate these results the allyl radical in the amorphous region was considered.
Kinetics of isothermal degradation of poly vinyl bromide (PVBr). A typical case of “autocatalytic” thermal degradation
Authors: Mazón‐Arechederra J. M. , Quíntero M. P. Delgado , Barrales‐Rienda J. M.
Published: April 2003

The kinetics of thermal degradation of a sample of 46.0% isotactic polyvinyl bromide (PVBr) was studied in a static procedure. An integrated analytical method is presented for the estimation of rate constants. Reaction curves for the formation of hydrogen bromide (HBr) can be interpreted in terms of two concurrent first‐order reactions; namely,
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with activation energies of 29.7 and 40.6 kcal/mol, respectively. The mathematical derivation does not involve an approximation; thus the accuracy of the procedure depends only on the experimentation. Good agreement between calculated and experimentally determined values of a series of characteristic kinetical parameters was obtained. The formation of HBr from PVBr was studied kinetically by a thermogravimetric programmed procedure at room temperature to 700°C. By this method it is possible to determine the activation energy of the stripping process of the main chain without knowing the form of the kinetic equation. The activation energy of 40.1 kcal/mol for the overall process was evaluated by the MacCallum and Tanner method. This dynamic heating developed two distinct temperature regions in which maximum rate loss occurred at characteristic temperatures. The first temperature region was associated with the quantitative evolution of 100% HBr molecules.
New telechelic polymers and sequential copolymers by polyfunctional initiator‐transfer agents (inifers). XIII. Influence of lewis acid strength and counteranion stability on the synthesis of telechelic polyisobutylenes
Authors: Wondraczek Reinhard H. , Kennedy Joseph P. , Storey Robson F.
Published: April 2003

Efforts have been made to prepare perfect terminally functional linear telechelic polyisobutylenes with various Lewis acid coinitiators, BCl3, AlCl3, TiCl4, SnCl4, VCl4, and SbCl5. However, the expected desirable results (F̄n = 2.0, M̄w/M̄n = 1.5) were obtained only with BCl3. Moreover, the concentration of BCl3 affects the molecular weight of telechelic polyisobutylenes prepared by the inifer technique. The Kennedy–Smith inifer mechanism is insufficient to explain these observations. Extending this model by the concept of counteranion stability, of Heublein et al.,5 and assuming the participation of free ions and ion pairs in propagation and termination, led to a satisfactory mechanistic model. The exceptional utility of the BCl3/BCl⊖ system is due to the high Lewis acid strength of BCl3 and low counteranion stability of BCl⊖.
Polymerization photoinitiated by carbonyl compounds. IV. α‐diketones and α‐substituted alkanones
Authors: Encina M. V. , Lissi E. A. , Koch V. , Elorza E.
Published: April 2003

The photoinitiation efficiency of the free‐radical polymerization of methyl methacrylate and styrene by several carbonly compounds has been determined. The compounds considered were α‐substituted ketones and α‐dicarbonyl compounds. For the ketones, the initiation efficiency employing methyl methacrylate depends on the α substitution; the values obtained change from less than 10−3 (acetone) to 0.65 (3‐hydroxy‐3‐methyl‐2‐butanone). All ketones are more efficient towards methyl methacrylate than styrene. This result can be explained in terms of triplet quenching by the last monomer. The results obtained employing α‐dicarbonyl compounds do not conform to a simple pattern. In particular, benzil shows a considerably larger efficiency towards styrene than for methyl methacrylate. Since benzil is efficiently quenched by styrene, the initiation must involve the interaction of an excited benzil molecule and the monomer.
Preparation of polyamides via the phosphorylation reaction. Poly‐4,4′‐benzanilides
Authors: Asrar J. , Preston J. , Krigbaum W. R.
Published: April 2003

4,4′‐Diaminobenzanilide (DAB) was reacted with diacids via the Yamazaki phosphorylation reaction to yield simple polyamides and random copolyamides. The use of DAB was found to promote polycondensation because DAB contains a preformed amide linkage which minimizes the amounts of by‐products formed. It also maximizes polymer solubility since the monomer is unsymmetrical. The order of the inherent viscosity values of the polymers obtained from DAB by reaction with different diacids, isophthalic > aliphatic > terephthalic, was found to parallel polymer solubility in the reaction medium. The inherent viscosity of the polyamide based on terephthalic acid, DAB‐T, was increased greatly by copolymerization, isophthalic acid being more effective than an aliphatic diacid in this regard. None of the polymers formed a thermotropic nematic phase, but the copolymer having an equimolar ratio of terephthalic and adipic acid formed anisotropic solutions in 100% sulfuric acid at polymer concentrations exceeding 40%. Strong films were cast from such solutions.
Polymerization of acrylamide initiated by the Ce4+/thiourea redox system
Authors: Misra G. S. , Bhattacharya S. N.
Published: April 2003

The polymerization of acrylamide (M) initiated by the Ce4+/thiourea (TU) redox system has been studied in an aqueous sulfuric acid medium at 35 ± 0.2°C under nitrogen atmosphere. The rate of polymerization is governed by the expression

The activation energy is 5.9 kcal deg−1 mol−1 in the investigated temperature range 30–50°C. The molecular weight is directly proportional to the concentration of monomer and inversely proportional to the catalyst concentration. With increasing concentration of DMF molecular weight decreases. The range of concentrations for which these observations hold at sulfuric acid concentration of 2.5 × 10−2 mol/L are [monomer] = 5.0 × 10−2–3.0 × 10−1, [catalyst] = (5.0–15.0) × 10−4, and [activator] = (1.0–6.0) × 10−3 mol/L.
Initiation of the stereospecific polymerization of p‐chlorophenylglycidyl and phenylglycidyl ethers by the Al(OiPr)3 + ZnEt2 (1:1) initiator system
Authors: Bero M.
Published: April 2003

The Al(OiPr)3 + ZnEt2 (1:1) system has been found to be an efficient initiator of the polymerization of phenylglycidyl ethers. About 40–60% of the polymer obtained was an isotactic polymer fraction (ca. 80% of iso diads). By using aluminum isopropoxide containing C14, the amount of linear polymer molecules terminated by isopropoxide groups was shown not to exceed 50%. IR spectrophotometric studies of the structure of the initiator system showed that its components form a complex compound by an exchange of substituents between the aluminum and zinc atoms.
Comments on “(A) critical examination of the dissociation‐association phenomena in the hexane solution of lithium polyisoprenyl” by M. Szwarc
Authors: Fetters L. J. , Morton M.
Published: April 2003

A note has appeared which seeks to question work from these laboratories (which appeared in 1964). The author of this recent paper attempts to demonstrate that the ΔH and ΔS values, based on our results, for the dissociation of the polyisoprenyllithium dimer “have no meaning.” This assessment ignores information in the literature. For similar reasons, other claims by the author of this recent paper are shown to be subject to scrutiny.
The synthesis of bisitaconamic acids and isomeric bisimide monomers
Authors: Galanti Anthony V. , Liotta Franic , Keen Brian T. , Scole Daniel A.
Published: April 2003

Members of a series of N,N′‐alkylene bisitaconamic acids were synthesized from the reaction between itaconic anhydride and a homologous group of aliphatic diamines with the general formula H2N (CH2)n NH2, where n = 4–12. Cyclodehydration of the acids in toluene gave the isomeric imides: bisitaconimide, biscitraconimide, and citra‐itaconimide. The isomeric imides were isolated, purified, and characterized for each diaminoalkane studied.
A simplified data treatment for dead‐end and high conversion polymerization kinetics
Authors: Hill D. J. T. , O'Donnell J. H.
Published: April 2003

A simplified approximation method for the treatment of dead‐end and high conversion polymerization kinetics is presented. The method is based on the treatment of dead‐end polymerization first described by Tobolsky. In appropriate circumstances, by contrast with Tobolsky's method, this method provides measurements of kd and kp/kt1/2 without recourse to the measurement of the monomer conversion at infinite time.

Kinetic studies of free radical polymerizations are normally confined to measurements of initial rates. At low conversions the predictions of the general mechanism for chain‐growth polymerization involving initiation, propagation, and termination steps are generally obeyed. Thus the polymerization rate should be first order in the vinyl monomer and half‐order in the initiator concentrations.

At high conversions, however, large deviations which can be ascribed to various effects can occur; for example, (1) the effect of the increasing viscosity of the polymerization medium on the termination rate constant kt, and possibly also on the propagation rate constant kp, which have been considered by North1 and Cardenas and O'Driscoll,2 or (2) depletion of the initiator as the polymerization progresses. This depletion will occur in all polymerizations but its significance will depend on the magnitude of the rate constant for initiator decomposition (kd) and the period of polymerization. Appropriate conditions will lead to limiting monomer conversion even after infinite polymerization time; this phenomenon has been called dead‐end polymerization by Tobolsky.3

Free radical polymerizations to high conversion are particularly important in the industrial context when initial kinetics are obviously inadequate. Suitable treatment of the conversion/time relationship is highly desirable.

Senogles and Woolf4 have examined the polymerization of n‐lauryl methacrylate at 60°C with 2‐azobisisobutyronitrile as initiator under dead‐end conditions.

Here we propose a modification of Tobolsky's treatment of such polymerizations by using an approximation for the exponential decay in the initiator concentration. This method permits easy manipulation of the experimental data and the estimation of values for the kinetic parameters in favorable circumstances without recourse to the measurement of the conversion at infinite time or the evaluation of complicated functions of the monomer conversion. The method thus allows the duration of the laboratory experimentation to be significantly shortened and the complexity of the subsequent data analysis to be considerably reduced.
Syntheses of amphiphilic block copolymers. Block copolymers of methacrylic acid and p‐N,N‐dimethylaminostyrene
Authors: Morishima Yotaro , Hashimoto Toshihiko , Itoh Yoshihiro , Kamachi Mikiharu , Nozakura Shun‐Ichi
Published: April 2003

Amphiphilic block copolymers consisting of methacrylic acid (MA) sequences and p‐N,N‐dimethylaminostyrene (DMS) sequences were prepared by living anionic polymerization. DMS was polymerized by lithium naphthalene in tetrahydrofuran to yield a living polymer solution, to which trimethylsilyl methacrylate (TMSM) was added to allow the block copolymerization. The conversion of TMSM was dependent on the countercation, i.e., with Na+ as counterion, no quantitative conversion was reached owing to premature termination, whereas with Li+ the conversion was quantitative. The role of the counterion was discussed in some detail in connection with self‐termination by the backbiting mechanism. The trimethylsilyl ester groups in the block copolymer were quantitatively hydrolyzed by treatment with aqueous methanol at room temperature, yielding MA sequences. The block copolymer of MA and DMS exhibited micellar properties in an aqueous solution.
Some aspects of curing novolac with hexamethylenetetramine
Authors: Aranguren M. I. , Borrajo J. , Williams R. J. J.
Published: April 2003

Curing novolac with hexamethylenetetramine in closed molds at T = 190°C was studied. Cured products were examined with the following experimental techniques: sol fraction determination, % N fixed in sol and gel fractions, and IR spectra. The fraction of fixed N decreased from 1 to 0.5 when the hexa mass fraction was increased from 0 to 0.3 in the mixture with novolacs. A segregation of the fixed N in the sol fraction was observed. Azomethine derivatives were present, their amounts increasing with the hexa mass fraction. Curing was described by a reaction scheme similar to the one derived from studies with model phenols. A simplified scheme was adequate for the prediction of the minimum hexa amount necessary to gel the system at full conversion.
Studies of particle size distribution and adsorption of stabilizers in dispersion polymerization
Authors: Almog Yaacov , Levy Moshe
Published: April 2003

The conditions for obtaining stable dispersions of 10‐μ droplets of monomer in an aqueous phase using steric and electrostatic stabilizers, were studied. The nature and concentration of the surfactant in the aqueous phase has an important effect on the size of the droplets and the stability of the dispersion during the polymerization reaction. The amount of polyvinylalcohol adsorbed on the interface was measured and the rate of desorption was shown to be very slow. It was also shown that sodium dodecyl sulfate, on the other hand, is more readily desorbed. These findings have an effect on the amount of the submicron emulsion particles formed during the polymerization process.
Polymer‐supported phosphines: Reactivity of pendant and crosslink groups
Authors: McKenzie W. M. , Sherrington D. C.
Published: April 2003

Two groups of phosphine‐containing resins were prepared by bead copolymerization. In one the phosphine residues were introduced as pendant groups with p‐styryldiphenylphosphine, whereas in the other the phosphine residues were located specifically at crosslinked points with bis(p‐styryl)phenylphosphine. Both groups of resins were used to convert alcohols to alkyl chlorides in the presence of carbon tetrachloride and benzaldyhyde to benzal chloride and β,β‐dichlorostyrene. In the first reaction an increase in the crosslink ratio of the support reduced the reactivity of the resins, although both octanol and octadecanol substrates behaved similarly. No clear difference emerged between resins with pendant phosphine groups and those located on crosslinks and the absence of a strong substrate size effect or substrate selectivity with both series of resins was apparent. The production of benzal chloride and β,β‐dichlorostyrene requires interaction of two phosphine residues to generate the reactive intermediate, and inhibition of phosphine–phosphine interactions in these highly crosslinked networks does indeed inhibit this reaction. Again both series of resins behaved similarly. Among the possible routes by which PPh3/CCl4 converts alcohols to chlorides one involving phosphine‐phosphine interactions must also be inhibited in these supported systems.
The solubility of cellulose in liquid ammonia/ammonium thiocyanate solutions: Thermoreversible gelation and a preliminary report on fiber formation
Authors: Hudson Samuel M. , Cuculo John A.
Published: April 2003

The melting temperatures of thermoreversible gels formed from solutions of cellulose in liquid ammonia/ammonium thiocyanate mixtures were measured over a volume fraction range of .01–.004. Three samples of cellulose with Mw ranging from 1 × 105 to 1.64 × 105 were used. The findings show that the structural makeup of the gels is strongly reflected in their time‐dependent behavior. The reciprocal of their melting temperature is a nearly linear function of the logarithm of the cellulose concentration. The relation between the logarithm of Mw and the reciprocal temperature of gel melting was also nearly linear. Exothermic heats of reaction ranging from 150 to 460 kcal/mol were calculated from the Ferry‐Eldridge relationship (∂ ln C/∂) = ΔHx/R for the formation of cross‐links, assuming that they result from a binary association of chains. It is inferred that the cross‐linking loci in the gel were crystallites that consisted of glucose units. In addition, an initial study is reported of the fiber‐forming potential of the liquid ammonia/ammonium thiocyanate system. Rudimentary fiber extrusion from a modified syringe was readily demonstrated. Operable coagulation systems involved proton‐donating agents as well as methanol. Tenacities of these unstretched, as spun fibers, ranged as high as 0.89 g/d.
Interaction between dyes and polyelectrolytes. XIII. Effect of dye aggregation on the excitation energy transfer between bound dyes
Authors: Shirai Masamitsu , Ohyabu Motoshi , Ono Yoshiki , Tanaka Makoto
Published: April 2003

Effect of polyanions on the aggregation of methylene blue (MB) was investigated spectrophotometrically. The following polyanions were used: potassium poly(vinyl sulfate), potassium poly(styrenesulfonate), sodium poly(methacrylate), and sodium poly(acrylate). The state of aggregation was largely dependent on the kind of polyanion and polyanion‐MB ratio. MB‐photo‐sensitized isomerization of cis‐p‐(phenylazo)phenyltrimethylammonium iodide(cis‐PTA) to the transisomer was used advantageously to investigate the effect of dye aggregation on the triplet excitation energy transfer between cationic dyes bound to polyanions. Although the efficiency of the excitation energy transfer between MB and cis‐PTA was enhanced by the addition of polyanions, the formation of highly aggregated MB reduced the efficiency of the excitation energy transfer. Correlation with the dye aggregation induced by polyanions and the efficiency of excitation energy transfer between dyes was discussed.
Studies on polyyne polymers containing transition metals in the main chain. VII. Synthesis and characterization of palladium‐polyyne polymers
Authors: Takahashi S. , Morimoto H. , Murata E. , Kataoka S. , Sonogashira K. , Hagihara N.
Published: April 2003

Metal‐polyyne polymers consisting of palladium and conjugated acetylenic systems,
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where PD and R represent the —Pd(PBu3)2—moiety and alkyl groups, respectively, were prepared by polycondensation between palladium chlorides and α,ω‐diethynyl compounds in amines using a catalytic amount of cuprous iodide. The molecular weights of the polymers formed were greatly affected by the basicity of the amines and the addition of free phosphines to the polymerization system. Under the optimum conditions, i.e., in the presence of CuI and PBu3 (in molar ratio 1/4) in piperidine at room temperature, polymer Ia (R1 = R2 = H) having M̄w = 29,000 was obtained.
Vinyl polymerization initiated by peroxydiphosphate. V. Polymerization of acrylonitrile initiated by peroxydiphosphate‐cyclohexanol redox system in the presence of silver ion
Authors: Lenka Subasini , Dhal Akshaya K.
Published: April 2003

The polymerization of acrylonitrile was carried out using peroxydiphosphate‐cyclohexanol redox system in the presence of silver ion. The rate of polymerization increases with increasing peroxydiphosphate concentration and the initiator exponent was computed to be 0.5. The rate of polymerization increases with increasing monomer concentration and the monomer exponent was computed to be unity. The plot of Rp vs [Ag+]1/2 was linear, indicating 0.5 order with respect to [Ag+]. The reaction was carried out at three different temperatures and the overall activation energy was calculated to be 7.60 kcal/mol. The effect of certain surfactants on the rate of polymerization has been investigated and a suitable kinetic scheme has been pictured.
Intramolecular charge transfer complexes. VIII. Poly[N‐(2‐hydroxyethyl) carbazolyl acrylate‐co‐2,4‐dinitrophenyl methacrylate]
Authors: Simionescu C. I. , Percec V. , Natansohn A.
Published: April 2003

Radical copolymerization of N‐(2‐hydroxyethyl) carbazolyl acrylate (HECA, M1) with 2,4‐dinitrophenyl methacrylate (DNPM, M2) can be described by a simple terminal mechanism having the relative reactivities r1 = 0.14, r2 = 1.10 (at 60°C); 0.28, 0.96 (80°C); and 0.41, 0.79 (100°C), respectively. The dependence of the reactivity ratio values on copolymerization temperature, analyzed by Arrhenius equation, takes place mainly through the frequency factor. The copolymers obtained are intramolecular charge transfer complexes. The intramolecular interaction is evidenced by the shift of the aromatic protons from the DNPM structural unit in the copolymers' 1H‐NMR (nuclear magnetic resonance) spectra. This shift depends on sequence distribution and chain conformation, but is not affected by the copolymerization temperature.
Polybenzimidazoles containing anthracene photodimer
Authors: Niume K. , Toyofuku K. , Toda F. , Uno K. , Hasegawa M. , Iwakura Y.
Published: April 2003

Polybenzimidazoles that contained anthracene photodimer were prepared. The molecular weights of the polymers prepared by the photopolymerization of bis‐anthrylbenzimidazoles were limited by the precipitation of the resulting polymers from the reaction organic solvents. Higher molecular weight polymers were obtained by the photopolymerization of bis‐anthryl‐Schiff's bases, followed by the oxidation of the resulting polymers. These polymers were soluble in acidic solvents such as formic and sulfuric acids but were insoluble in organic solvents.
Mixed ligand complexes in vinyl polymerization. I. [N,N′‐ethylenebis (salicylideneiminato)](acetylacetonato)cobalt(III) as an initiator
Authors: Thiagarajan R. , Kalpagam V. , Nandi U. S.
Published: April 2003

Polymerization of methyl methacrylate in the presence of a mixed ligand complex, [N,N′‐ethylenebis(salicylideneiminato)](acetylacetonato)cobalt(III) in benzene was studied. The rate of polymerization was proportional to the square root of the concentration of the chelate and the monomer exponent was 1.67 and 1.69 at 60 and 70°C, respectively. The activation energy and the kinetic and transfer constants were evaluated. A free‐radical mechanism has been proposed.
Preparation and properties of ordered and random polyamide‐esters from 4‐(4‐amino‐α,α‐dimethylbenzyl)phenol and aromatic diacyl chlorides
Authors: Imai Yoshio , Abe Shigemitsu , Takahashi Takeyoshi , Ueda Mitsuru
Published: April 2003

Random polyamide‐esters were prepared directly by the interfacial and solution polycondensation of 4‐(4‐amino‐α,α‐dimethylbenzyl)phenol (I) with iso‐ and terephthaloyl chlorides. Authentic samples of ordered polyamide–esters with an amide‐amide–ester‐ester structure were synthesized by the two‐step procedure; that is, the preparation of amide–bisphenol monomers from I and subsequent polycondensation with aromatic diacyl chlorides. The random and ordered polyamide–esters differed from one another with respect to solubility in organic solvents and glass transition temperature, whereas all the random and ordered polymers were of equal low crystallinity. All of these polymers began to decompose around 350°C in both air and nitrogen atmospheres.
The chemistry and kinetic behavior of Cu‐Cr‐As/B wood preservatives. III. Fixation of a Cr/As system on wood
Authors: Pizzi A.
Published: April 2003

The kinetic behavior of a Cr/As system in its reaction with wood is described, as are its reactions with lignin and carbohydrates of wood for CrVI alone. ChromiumIII arsenate complexes with the guaiacyl units of lignin, as well as the usual chromic acid/guaiacyl unit complexes already characterized, was formed. The interference of As concentration on the various zones of fixation of chromium are identified. Complexes between guaiacol and chromium arsenates indicate that in this Cr/As system CrIII can also be linked to the guaiacyl units of lignin when in the form of CrAsO4·6H2O contrary to what obtained with systems not containing As. An initial increase in the rate of reduction CrVI → CrIII by the carbohydrates fraction in wood is ascribed to the catalytic effect of the arsenic. The percentages of chromium fixed onto lignin and cellulose of wood compare well with experimental values.
Some of the dielectric properties of cotton cellulose and viscose
Authors: Moteleb M. M. Abdel , Naoum M. M. , Shinouda H. G. , Rizk H. A.
Published: April 2003

Complex dielectric constants were measured at frequencies of 0.1–10,000 kc/s over the temperature range of 0–60°C in medicated cotton cellulose and viscose. In these fibers evidence is found for a new secondary relaxation process within the frequency region of 0.1–1 kc/s. The significance of the results is discussed.
Some 1‐substituted quaternary imidazolium compounds and related polymers: Qualitative and quantitative infrared analysis
Authors: Petrak K. , Degen I. , Beynon P.
Published: April 2003

It was found that 1‐substituted quaternary imidazolium compounds show some characteristic infrared (IR) activity. On quarternization of 1‐substituted imidazoles strong absorption bands appeared at about 1150 and 1550 cm−1 in the IR spectra of these compounds. The band at 1150 cm−1 was assigned to the position 2 C−H bending mode and the 1550 cm−1 band was attributed to a ring vibration mode of the quaternary imidazolium compounds. The concentration of the quaternary imidazolium units in a polymer can be determined by measuring the intensity of the absorption bands at 1150 or 1550 cm−1 in relation to another suitable absorption band of the spectrum.
A free‐volume model for photopolymerizable/cross‐linkable dry‐film systems
Authors: Molaire Michel F.
Published: April 2003

A photopolymerizable/cross‐linkable dry‐film system is generally a compatible mixture of three main ingredients: a preformed polymeric binder, a multifunctional polymerizable monomer, and a photoinitiating system. The photographic speed of systems sensitized with certain free‐radical sensitizers which undergo intermolecular hydrogen‐abstraction (e.g., benzophenone/Michler's ketone) is proportional to the excess fractional free volume (Vf − Vfg), of the dry coating. Free‐volume dependence appears to be determined by the molecular size or configuration of the actual initiating species. We used as a working model the copolymer system poly[4,4′‐isopropylidenediphenylene‐1,1,3‐trimethyl‐3‐phenylindan‐5,4′‐dicarboxylate:azelate] and tri(6‐acryloyloxyhexyl)‐1,3,5‐benzenetricarboxylate as the polymerizable/cross‐linkable monomer. A mathematical model based on experimental data and the free‐volume theory was developed. The photographic speed of a photopolymerizable/cross‐linkable dry‐film system suffering from free‐volume dependence can be correlated with the glass transition temperatures of the polymeric binder and the monomer, the volume fraction of the monomer, and the temperature of exposure.
Kinetics and mechanism of the anionic polymerization of cyclohexadienes initiated by naphthalene radical anions and dianions
Authors: Sharaby Z. , Jagur‐Grodzinski J. , Martan M. , Vofsi D.
Published: April 2003

The anionic polymerization of 1.3‐cyclohexadiene (1.3‐CHD) was investigated in temperatures that ranged from 25 to −77°C. Initiation by lithium naphthalene (N−·,Li+) in tetrahydrofuran at −20°C yields polymers with fairly narrow molecular weight distribution. The M̄w of these polymers so prepared is ca. 20,000. Polymerization of 1.3‐CHD conducted at room temperature is accompanied by the dehydrogenation and disproportionation of the monomer, especially when N−·,K+ acts as initiator. Oligomers are formed when hexamethylphosphoramide is used as a solvent. The mechanism of the initiation of the polymerization of 1.3‐CHD by N−·,Li+ was elucidated and the rate constants at −20°C in tetrahydrofuran of the elementary reactions were determined. It was established that the dianions formed by disproportionation of N−·,Li+ act as effective initiators for 1.3‐CHD. The adducts formed constitute the cyclohexanyl and naphthyl carbanionic groups. The former carbanions (λmax ∼ 275 nm) propagate the polymerization. The initially formed dimeric adducts are stabilized by the separation of the carbanionic end groups by the additional monomer units. Chain transfer to the monomer limits the growth of the polymers. The isomerization of the cyclohexadienyl anions, formed as result of chain transfer, may be followed by the elimination of lithium hydride. The latter reaction represents a termination step. Addition of 1.4‐CHD to the reaction mixture enhances the chain transfer and the termination.
Amylose–polyester block copolymers
Authors: Lee K. S. , Stannett V. T. , Gilbert R. D.
Published: April 2003

The synthesis of amylose–polyester block copolymers is described. 2,3,6‐Tri‐0‐allyl amylose was synthesized by amylose alkoxide and allyl bromide and hydrolyzed by hydronium ions to give an hydroxyl‐terminated allyl amylose oligomer (HTAA). The allyl groups were isomerized with t‐BuoK to yield the prop‐1‐enyl isomer (HTPA). The HTPA was capped with a diisocyanate. The HTPA prepolymer was reacted with hydroxy‐terminated poly(ethylene‐co‐propylene adipate) and poly‐(ethylene terephthalate) to form block terpolymers. Block terpolymer formation was demonstrated by intrinsic viscosity increases, gel permeation chromatographic results, and infrared (IR) and PMR spectroscopy. The products were depropenylated by HgCl2 to yield amylose block terpolymers. These polymers were readily degraded by α‐amylase.
Thermal degradation study of isotactic polypropylene using factor‐jump thermogravimetry
Authors: Dickens Brian
Published: April 2003

The degradation of isotactic polypropylene in the range 390–465°C was studied using factor‐jump thermogravimetry. The degradations were carried out in vacuum and at pressures of 5 and 800 mm Hg of N2, flowing at 100–400 standard mL/s. At 800 mm Hg this corresponds to linear rates of 1–4 mm/s. In vacuum bubbling in the sample caused problems in measuring the rate of weight loss. The apparent activation energy was estimated as 61.5 ± 0.8 kcal/mol (257 ± 3 kJ/mol). In slowly flowing N2 at 800 mm Hg pressure the activation energy was 55.1 ± 0.2 kcal/mol (230 ± 0.8 kJ/mol) for isotactic polypropylene and 51.1 ± 0.5 kcal/mol (214 ± 2 kJ/mol) for a naturally aged sample of atactic polypropylene. For isotactic polypropylene degrading at an external N2 pressure of 5 mm Hg the apparent activation energy was 55.9 ± 0.3 kcal/mol (234 ± 1 kJ/mol). A simplified degradation mechanism was used with estimates of the activation energies of initiation and termination to give an estimate of 29.6 kcal/mol for the ß‐scission of tertiary radicals on the polypropylene backbone. Initiation was considered to be backbone scission ß to allyl groups formed in the termination reaction. For initiation by random scission of the polymer backbone, as in the early stages of thermal degradation, an overall activation energy of 72 kcal/mol is proposed. The difference between vacuum and in‐N2 activation energies is ascribed to the latent heat contributions of molecules which do not evaporate as soon as they are formed. At these imposed rates of weight loss the average molecular weights of the volatiles in vacuum and in 8 and 800 mm Hg N2 are in the ratios 1–1/2–1/9.
Studies on syntheses and permeabilities of special polymer membranes. 48. Transport of organic ions through crosslinked poly(isobutylene‐alternative co‐maleic anhydride) membranes
Authors: Uragami Tadashi , Watanabe Shizuharu , Sugihara Mizuho
Published: April 2003

Ion exchange membranes with carboxyl groups, which were insoluble in acidic and alkaline aqueous solutions, were prepared from poly(isobutylene‐alternative co‐maleic anhydride) and poly(vinyl alcohol). When a membrane, one side of which was alkaline, the other, acidic, was fixed in a diaphragm cell, it transported organic ions, such as amino acids and aniline, from the acidic to the alkaline side or vice versa. The passage of organic ions through the membrane was governed by an electrochemical interaction between carboxyl groups in the membrance and transporting ions. The direction of the organic ions depended on a pH difference between the two sides of the membrane.
The role of chain transfer agents in the emulsion polymerization of styrene
Authors: Nomura Mamoru , Minamino Yasunobu , Fujita Kazumi , Harada Makoto
Published: April 2003

The effect of chain transfer agents on the nucleation and growth of polymer particles in the emulsion polymerization of styrene were examined extensively. The chain transfer agents used are carbon tetrachloride, carbon tetrabromide, and four primary mercaptans (C2, n‐C4, n‐C7, and n‐C12). It is shown that with an increase in the amount of chain transfer agents charged the rate of polymerization per particle decreases progressively. The number of polymer particles formed, on the other hand, increases initially then decreases. These effects can be enhanced by using a chain transfer agent with higher values of chain transfer constant and solubility in water. It is also demonstrated that with increasing radical desorption from the particles, aided by chain transfer agents, the emulsifier dependence exponent for the number of polymer particles formed increases from 0.6 to 1.0 and the initiator dependence exponent decreases from 0.4 to 0. The effect of chain transfer agents on the nucleation and growth of polymer particles in the emulsion polymerization of styrene can be explained in terms of desorption of chain‐transfered radicals from the polymer particles.
Copolymerization of β‐pinene with styrene oxide and N‐vinylpyrrolidone
Authors: Martínez Francisco , Florsheim René , Martínez Héctor
Published: April 2003

The copolymerization of β‐pinene with styrene oxide (SO) and β‐pinene with N‐vinylpyrrolidone (VP) was investigated by using SnCl4 in dichloromethane diluent at low temperature. Monomer reactivity ratios were evaluated for both copolymers at −80°C; these are r1(SO) = 2.979 and r2(β‐pinene) = 0.002 and r1(VP) = 0.096 and r2(β‐pinene) = 0.294.
Diffusion‐controlled vinyl polymerization. III. Free volume parameters and diffusion‐controlled propagation
Authors: Soh S. K. , Sundberg D. C.
Published: April 2003

The values of the parameters that are necessary to compute the free volume changes accompanying polymerization were determined from viscosity data of concentrated polymer solutions. Relationships applicable above and below the glass transition temperature of the polymer were quantified. A general treatment of the variation of the propagation rate constant with free volume was postulated, based on the variation of the monomeric diffusivity with free volume. This, in turn, was related to the friction coefficient of a polymer chain segment, the values of which are readily available. A discussion of the reaction behavior in the last stage of polymerization and the occurrence of limiting conversion is also presented.
Modification of the wettability of a poly(ethylene terephthalate) film treated by corona discharge in air
Authors: Amouroux J. , Goldman M. , Revoil M. F.
Published: April 2003

The wettability of poly(ethylene terephthalate) films is an important criterion for their industrial use. The attainment of that property is realized by treatment of the material under corona discharge. The purpose of this article is to describe the influence of the principal parameters of the discharge on the modification of the surface properties; the influence was measured by physicochemical methods (ESCA, contact angle). The results prove that the most important physical parameters of the discharge are the wire‐cylinder distance, the current intensity, and the time of treatment. The analysis shows that the fixed species are oxygen and nitrogen in the form of carboxylic functions and amines or nitrogen oxides. In any case, the correlation between free surface energy and concentration of fixed chemical species shows that the surface properties depend on the chemical functions introduced into the material by the discharge.
Model hard segments from diphenyl methane diisocyanate and different chain extenders, and corresponding linear block polyurethanes
Authors: Camberlin Y. , Pascault J. P. , Letoffé J. M. , Claudy P.
Published: April 2003

Model hard segments from MDI and different chain extenders have been studied by DSC. Among the studied α‐ω alkane diol‐type chain extenders, all giving crystalline hard segments, butane diol shows the highest melting temperature, while other types such as 1,4‐diaminobutane, 1,4‐benzene dimethanol, and 4,4′‐methylene‐bis(2‐chloroaniline), so‐called MOCA, have no melting endotherm in the range 30–260°C. In addition to DSC, dynamic mechanical properties were measured on linear block polyurethanes having both hard segments and soft ones of hydrogenated 1,2‐polybutadiene. The hard segments in the polyurethane chains are of amorphous structure or low crystallinity, and their high‐temperature behavior depends only on their strength of interaction in the amorphous state. Accordingly, MOCA shows the highest hard‐block softening temperature.
Solvent effect on radical polymerization of butyl acrylate
Authors: Kamachi Mikiharu , Fujii Masakazu , Ninomiya Shin‐Ichiro , Katsuki Shuhei , Nozakura Shun‐Ichi
Published: April 2003

The propagation and termination rate constants kp and kt for the radical polymerization of butyl acrylate initiated by biacetyl have been measured by using the rotating‐sector method, in various solvents at 30°C. The value of kp and initiation rate Ri varied with solvents, while the value of kt did not change with solvents except for benzonitrile. The variation of kp with aromatic solvents has a trend against Hammett σp of the solvent substituents similar to that for methyl methacrylate or phenyl methacrylate except for the value in benzonitrile, when it is larger than the variation for methyl methacrylate or phenyl methacrylate. The larger variation of kp for butyl acrylate is compatible with the view that the origin of the solvent effect lies in complex formation between the propagating radical and aromatic solvent molecules. The exceptional decrease in kp and kt in benzonitrile is explained by a contraction of the poly(butyl acrylate) chain in the poor solvent.
Interaction of Tb(III) and hydrolyzed polyacrylamides in solution as a gel and in the solid state
Authors: Rodrigues Judith Feitosa , Galembeck Fernando
Published: April 2003

Formation of the HPAM‐Tb3 complex in solution was observed in the intensification of Tb(III) fluorescence, viscosity, and light scattering. The interaction is dependent on the degree of hydrolysis of the copolymer and the pH of the solution. As the pH value increases, an intensification of the interaction and formation of a gel is observed. The latter was associated with the appearance of crosslinks in which terbium, or one of its hydrolysis products, works as a binding agent between chains. After drying, the characterization of the residues of the gels was effected by analytical determination (C, H, N, Cl, Tb), fluorescence, and infrared spectrophotometry. The analysis and fluorescence revealed the existence of particles of terbium hydroxide; the infrared spectrophotometry showed the binding of terbium (III) to carboxylate of the copolymer.
Acrylonitrile–4‐vinylpyridine copolymers effect of comonomer sequence distribution on properties
Authors: Harris Stephen H. , Gilbert Richard D.
Published: April 2003

Acrylonitrile–,4‐vinylpyridine copolymers were prepared in chloroform solution at 60°C with AIBN as initiator. Copolymer compositions were determined from their 15.01‐MHz 13C‐NMR spectra. Reactivity ratios of rAN = 0.093 and r4VP = 0.32 were calculated by the Kelen and Tudos method. The run number, number‐average sequence lengths, and monomer sequence distributions were also calculated. The Tg values of the copolymers, their dye uptake, and degree of alkaline hydrolysis were influenced by the overall copolymer composition but particularly by the monomer sequence distribution in the copolymers.