bluuebunny/crossref_metadata_2025 huggingface dataset:
Theoretical aspects of the radiation effects of polymers
Authors: Tsuda Minoru , Oikawa Setsuko
Published: April 2003

The Millar–Wall–Charlesby empirical rule of radiation effects on polymers was theoretically examined. The theoretically calculated adiabatic potential curves of the main chain scission and side chain cleavage revealed that the effects of radiation on polymers are clearly interpreted as chemical reactions in the excited states; namely, that degradation occurs when little or no activation energy is required in the main chain cleavage reaction in the excited states, or, in other words, stabilization of the excited polymer molecule leads to the main chain cleavage. Crosslinking occurs when moderate or large activation energy is required in the main chain cleavage reaction in any electronic state and little or no activation energy is needed in the CH bond cleavage reaction in the excited states. Therefore stabilization of the excited polymer molecule leads to the formation of a polymer radical that crosslinks. It was concluded that Millar–Wall–Charlesby's rule is exact only when the shape of the adiabatic potential curve in the ground state reflects those in the excited states.
Photosensitive polymers containing diaryliodonium salt groups in the main chain
Authors: Crivello J. V. , Lam J. H. W.
Published: April 2003

Photosensitive polyimidothioethers were prepared by the base‐catalyzed condensation of bisthiols with 4,4′‐(N‐maleimido)diphenyliodonium chloride. Copolymers with other bismaleimide monomers were also prepared. The ultraviolet‐induced degradation of two of the copolymers was studied and the effects of light intensity on the rate of photolysis determined. It was also demonstrated that the range of spectral sensitivity of these polymers can be extended into the visible region through the use of dye sensitizers.
Synthesis and polymerizations of methyl 3,3‐difluorocyclobutene‐1‐carboxylate and methyl 3,3,4,4‐tetrafluorocyclobutene‐1‐carboxylate
Authors: Hall H. K. , Okamoto Y. , Padias A. Buyle , Deutschman A. , Berry J. W.
Published: April 2003

Two new monomers, methyl 3,3‐difluorocyclobutene‐1‐carboxylate (MDFC) and methyl 3,3,4,4‐tetrafluorocyclobutene‐1‐carboxylate (MTFC), were synthesized. Under free radical conditions, MDFC gave homopolymer; MTFC did not. Copolymerizations of these monomers showed them to behave as very electron‐deficient monomers, MTFC more so than MDFC. MDFC copolymerized with various vinyl ethers and styrenes to give high yields of almost 1:1 copolymers. Acrylonitrile copolymerized in lower yield with less incorporation of MDFC; trimethylethylenetricarboxylate did not copolymerize. Bicyclobutane‐1‐carbonitrile copolymerized well. MTFC copolymerized with the very electron‐rich monomers t‐butyl vinyl ether and p‐methoxystyrene, leading to alternating and nearly alternating copolymers, respectively, and even styrene tended to give almost 1:1 copolymers. Acrylonitrile gave only polyacrylonitrile, and trimethylethylenetricarboxylate did not react with MTFC under free radical conditions. The reaction of MTFC with the electron‐rich monomers t‐butyl vinyl ether and p‐methoxystyrene occurred spontaneously via charge transfer complexes. Thermally, the copolymers were rather stable, those of MTFC more so than those of MDFC.
The termination reaction in free radical copolymerization. I. Methyl methacrylate and butyl‐ or dodecyl methacrylate
Authors: Ito K. , O'driscoll K. F.
Published: April 2003

Using a spatially intermittent reactor, the absolute rate constant for the termination reaction in free radical copolymerization has been measured for the monomer pair methyl methacrylate (MMA)–butyl methacrylate (BMA). For the pair MMA–dodecyl methacrylate (DMA) the relative rate constant for termination has been measured. In both cases the termination rate constant was a monotonically changing function of the monomer feed composition. This function can be well approximated by a simple calculation of the enchained monomer units' contributions to the average segmental friction coefficient of the copolymer chain. An attempt to apply a previously derived theoretical treatment based on penultimate unit effects produced physically unrealistic results.
Stereochemistry in cationic polymerization of alkenyl ethers. III. Effect of the alkoxy group on the steric structure of polymers
Authors: Hirokawa Yoshitsugu , Higashimura Toshinobu , Matsuzaki Kei , Kawamura Tokiji , Uryu Toshiyuki
Published: April 2003

Propagation mechanism in the cationic polymerization of alkenyl ethers was investigated through the effect of the bulkiness of alkoxy groups on the steric structure of a polymer. In polymerization with BF3O(C2H5)2 in toluene at −78°C, trans‐propenyl ethers having less bulky alkoxy groups–methyl, ethyl, and benzyl propenyl ethers–produced a stereoregular polymer having a threo‐meso structure, and the cis isomer a nonstereoregular one having threo‐meso and racemic structures. On the other hand, in the polymerization of propenyl ethers having bulky alkoxy groups–isopropyl and 1‐methylpropyl propenyl ethers–the trans isomer yielded a nonstereoregular polymer with threo‐meso and racemic structures, and the cis isomer a stereoregular one with a erythro‐meso structure. This result suggests that a bulky alkoxy group plays an important role in determining the steric structure of the polymer by repulsion between the alkoxy groups of a growing chain end and of a monomer. The effect of solvent polarity on the steric structure of a polymer was also studied.
Allylation of phenoxides by crown ethers and their polymers
Authors: Akabori Sadatoshi , Miyamoto Shigeo , Tanabe Hideo
Published: April 2003

Allylation of sodium phenoxide in the presence of crown ethers produces a high ratio of O/O + C allylation when conducted in water, phenol, benzene, or diethyl ether. The striking increase in the product ratios is attributed to specific complexation of the crown ethers that facilitate the dissociation of the ion pair aggregate of the sodioderivative in benzene or diethyl ether. The crown ethers may act as a phase transfer catalyst when the reaction is run in water. Furthermore, the O/O + C ratios of the allylation strongly depend on the kind of crown ethers used. To examine their effect the allylation of sodium phenoxide was studied with various crown ethers, such as 18‐crown‐6, benzo‐18‐crown‐6, benzo‐15‐crown‐5, poly(vinylmonobenzo‐15‐crown‐5), and poly(vinylmono‐benzo‐18‐crown‐6), as catalysts. It was found that among these crown ethers poly(vinylmono‐benzo‐15‐crown‐5) was the most effective catalyst.
Stereoselectivity of the cyclooctene ring‐opening polymerization
Authors: Syatkowsky A. I. , Denisova T. T. , Ikonitsky I. V. , Babitsky B. D.
Published: April 2003

The stereoselectivity of the cyclooctene ring‐opening polymerization in the presence of the tungsten hexachloride–tetraisobutylalumoxane (TBAO) catalyst system has been studied. The reaction conditions have been established in which the polymer chain isomerization is reduced to a minimum. Under these conditions the stereoselectivity is determined by an individual act of the monomer molecule insertion. The dependence of stereoselectivity on monomer concentration, number of active sites, and temperature has been investigated. The results obtained suggest that the cyclooctene polymerization is selective in favor of the geometrical configuration of the starting cycloolefin (the “retention” effect) by analogy with the previously reported metathesis of acyclic olefins. Considerations which support the idea that cis and trans units are reproduced by the same type of active sites are discussed. The experimental evidence indicates that in this case the stereoselectivity is determined by the difference in kinetics of two reaction paths of the monomer molecule insertion that lead to the formation of cis and trans units.
Pyrolysis/Gas chromatography/mass spectrometry of polymers: Polyisopropenylcyclohexane and copolymers with its aromatic counterpart, α‐methylstyrene
Authors: Gritter Roy J. , Gipstein E. , Adams Gary E.
Published: April 2003

Flash pyrolyses at 400, 650, and 900°C of polyisopropenylcyclohexane (PIC) and copolymers, produced by partial hydrogenation of poly‐α‐methylstyrene (PAMS), have shown that the decomposition of the PIC or IC sequences is complex. In comparison, PAMS and AMS sequences give only depolymerization to monomer at the two lower temperatures but a more complex degradation at 900°C, based on the products identified. It is interesting to note that traces of decalin solvent initiated the depolymerization of PAMS and the AMS sequences in the copolymers at 400°C. The products identified by copolymer pyrolyses indicated that no reaction occurred between S and IC units during decomposition. Average sequence data on the copolymers could not be determined because of the facile unzipping of the AMS sequences and the greater thermal stability of the IC sequences. The fragmentation pattern did indicate that partial hydrogenation of PAMS had produced random copolymer and not a blend of two homopolymers.
X‐Ray diffraction technique to assess radiation damage in semicrystalline polymers. I. Isotactic poly(methyl methacrylate)
Authors: Kusy R. P. , Greenberg A. R.
Published: April 2003

By using x‐ray diffraction the total damage to a semicrystalline polymer is determined after exposure to high‐energy ionizing radiation. By rearrangement of the first‐order dependence of the fractional change in crystallinity on the dose the number of chemical and/or physical changes per 100 eV of energy absorbed [i.e., G(–units)] is computed. In the present effort on isotactic poly‐(methyl methacrylate) (PMMA) the value of G(–units) ≈ 15 confirms previous results obtained by cryoscopy, and thereby yields a ratio of ca. 8:1 for chemical plus physical (i.e., total damage) versus chemical damage alone. From nuclear magnetic resonance (NMR) results, a partition of the physical damage into configurational and conformational changes yields G values of 6 and 7, respectively.
Influence of antimony catalysts with hydroxyethoxy ligands on polyester polymerization
Authors: Maerov S. B.
Published: April 2003

The effectiveness of antimony polymerization catalysts for polyester, with varying numbers of hydroxyethoxy ligands on antimony, was studied. The ligand number, ranked in decreasing effectiveness was 5 = 3 > 2 > 1 ≫ 0. Results for this series of compounds are consistent with a mechanism in which antimony bonds with polyester chain ends to catalyze intermolecular condensation.
Amorphous polyacrylonitrile: Synthesis and characterization
Authors: Joh Yasushi
Published: April 2003

Amorphous polyacrylonitrile was successfully synthesized with bis(pentamethyleneimino)magnesium in heptane at 70°C. The amorphousness of the polymer increased with rising polymerization temperature and was favored by the nonpolar solvent. The polymer showed regular head‐to‐tail sequences which were confirmed by converting the polymer into polyacrylic acid and polymethylacrylate. The amorphous PAN produced a broad x‐ray diagram with a maximum at 2θ = 16.1° and a less intense halo at 2θ = 27.5°. This pattern did not change after heat treatment. The synthesis of amorphous PAN strongly supports Imai's hypothesis that polyacrylonitrile consists of paracrystalline and amorphous phases. The amorphous PAN also tends to support Minami's assignment of the two absorptions in the temperature dependence of the dynamic loss tangent; the absorption at the lower temperature (110°C) is due to molecular motions in the paracrystalline phase and the absorption at the higher temperature (160°C) is attributed to the molecular motions in the amorphous region.
Polyelectrolytes conformational probes: Auramine O and ethidium bromide interactions with hypercoiling maleic acid–olefin copolymers
Authors: Fenyo J. C. , Mognol L. , Delben F. , Paoletti S. , Crescenzi V.
Published: April 2003

Two cationic dyes—auramine O (AuO) and ethidium bromide (EBr)—have been tested for their ability to respond to conformational states of maleic acid–olefin copolymers in aqueous solution. The fraction of bound dye and the intensity of fluorescence of AuO are extremely sensitive to the presence of polyelectrolyte compact coils and to changes in ionic strength and counterion species. A related behavior is shown by the shift in the absorption visible spectrum of EBr, whereas its fluorescence seems to depend somewhat on the “structure” of the compact coils. These properties of the two dyes, which find a convincing correlation with viscosity and equilibrium thermodynamic data for the copolymers considered, are thus proved to be useful in probing the degree of compactness of polyelectrolyte coiled conformations in dilute aqueous solutions.
Investigations on the kinetics of copolymerization of vinyl acetate with acrylonitrile by Co(acac)3–Al(C2H5)3 catalyst system
Authors: Sharma Y. N. , Gandhi V. G. , Bhardwaj I. S.
Published: April 2003

Vinyl acetate and acrylonitrile were copolymerized with Co(acac)3‐Al(C2H5)3 catalyst system in benzene at 40°C. The rate of copolymerization is linearly proportional to monomer concentration and catalyst concentrations up to a certain value. The overall activation energy was found to be 11.3 kcal/mole. The effect of hydroquinone on the rate of copolymerization indicates the presence of free radicals in this system. The possibility of simultaneous formation of coordinate anionic and free radical active sites has been proposed.
Synthesis of poly(ester carbonate) copolymers
Authors: Prevorsek D. C. , Debona B. T. , Kesten Y.
Published: April 2003

The synthesis of poly(ester carbonate) copolymers based on bisphenol A, terephthalic acid, and phosgene is reviewed, and a new synthetic route is described leading to polymers which are different from those obtained by methods described in the literature. The most important features of the new method are quantitative incorporation of the dicarboxylic acid into the polymer and absence of undersirable side reactions. Synthesis of the random copolymer in which the dicarboxylic acid and carbonic acid groups are present in about equal molar amounts is discussed. Solution properties, effects of M̄n and copolymer composition on Tg, sequence length distribution, the effect of ester interchange reactions on molecular weight distribution, and effects of monofunctional chain termination on molecular weight of the final product are also discussed.
Functional monomers and polymers. LIX. Properties and function of Cu(II) complexes of the copolymers having pendant sulfide and imidazolyl groups
Authors: Sato M. , Shindo H. , Kondo K. , Takemoto K.
Published: April 2003

The Cu(II) complexes of copolymers having pendant sulfide and imidazolyl groups were prepared by a free radical copolymerization of ethylvinylsulfide with vinylimidazole, and their properties and function were studied spectrophotometrically in comparison with those of poly[4(5)‐vinylimidazole]. The complexes were found to be effective as catalysts for the oxidation of hydroquinone. Visible and ESR spectra of the Cu(II)‐copolymer complexes were similar to those of the Cu(II)‐homopolymer complexes, while the catalytic activity for the oxidation was different between these complex systems. A rapid reaction followed by a slow reaction, particularly at high ethylvinylsulfide content in the copolymers, was observed in the Cu(II)‐copolymer complex systems, but a continuous reaction proportional to the reaction time was observed in the Cu(II)‐homopolymer complex systems. The reoxidation rate of Cu(I) to Cu(II) complex, which was little affected by the concentration of imidazolyl group, decreased with a rise of the ethylvinylsulfide content in the copolymer. It was suggested that the sulfur atom of the sulfide group was weakly coordinated to Cu(II) but strongly to Cu(I), and an electron transfer reaction from substrate to the Cu(II) complex was increased, while reoxidation reaction of the Cu(I) complex was decreased in the copolymer complex systems.
Poly‐α‐ester degradation studies. VI. Thermal degradation of poly(3‐pentylidene carboxylate)
Authors: Cooper D. R. , Molloy R. , Sutton G. J. , Tighe B. J.
Published: April 2003

The thermal degradation of poly(3‐pentylidene carboxylate) has been studied kinetically over the temperature range 200–300°C using thermogravimetry, gas evolution analysis, and rheogoniometry together with isolation and analysis of the reaction products. The observed behavior is completely different from that previously reported for poly(isopropylidene carboxylate) and poly(methylene carboxylate). Whereas in the latter cases the decomposition occurs by a first‐order intramolecular ester interchange process characterized by an activation energy in the region of 27 kcal mole−1, poly(3‐pentylidene carboxylate) decomposition occurs by random chain scission superimposed on a first‐order hydrogen abstraction process. The activation energy associated with this decomposition reaction is in the region of 47 kcal mole−1, and the major degradation products are cis‐ and trans‐2‐ethyl crotonic acid.
Thermal cis–trans isomerization of cis–transoidal polyphenylacetylene
Authors: Simionescu C. I. , Percec V.
Published: April 2003

Solution and solid‐state thermal cis‐trans isomerization of cis–transoidal polyphenylacetylene was investigated. At temperatures higher than 120°C, cis‐trans thermal isomerization in solution is accompanied by cyclization, aromatization, and scission of the polymer chain. Both spectral and kinetics data showed that at temperatures lower than 120°C, not only cis‐trans thermal isomerization takes place but also intramolecular cyclization.
Radiation‐induced polymerization at high dose rate. I. Isobutyl vinyl ether in bulk
Authors: Hayashi Kanae
Published: April 2003

Bulk polymerization of isobutyl vinyl ether was studied at 25°C in a wide dose rate range, 8.2‐277 rad/sec by γ rays and 8.8 × 103‐2.2 × 105 rad/sec by electron beams. At low dose rate, 8.2‐277 rad/sec, only the radical polymerization took place. At high dose rate exceeding 8.8 × 103 rad/sec, cationic polymerization was found to occur in addition to the radical polymerization. DPn of the product at high dose rate was 9‐10. Further drying of the monomer increased Rp, and molecular weight of the product formed by cationic mechanism also increased.
Thermal degradation of a series of polyester polyurethanes
Authors: Grassie N. , Zulfiqar M. , Guy M. I.
Published: April 2003

A series of polyester polyurethanes with a range of polyester contents was prepared from an ethylene glycol/propylene glycol/adipic acid polyster, butane diol, and methylene bis (4‐phenyl isocyanate) (MBPI). They were thermally degraded under vacuum and the products of degradation were identified. The urethane linkages decompose first as the temperature is increased and the stability increases with polyester content. Reaction mechanisms were proposed which account for the principal features of the reaction and the products of degradation.
Polyacrylamide. I. Polymer content and hydrolysis level determination by potentiometric titration
Authors: St. Kenyeres J. , Ursu V.
Published: April 2003

A method of determining the degree of hydrolysis by potentiometric titration of polyacrylamide (PAA) with HCl and NaOH was developed. From the titration curves and the control of the degree of purity it is possible to calculate the level of hydrolysis and the quantity of pure acid contained in the PAA of a commercial product.
Block copolymers of polystyrene and poly(dimethyl siloxane). I. Synthesis and characterization
Authors: Bajaj P. , Varshney S. K. , Misra A.
Published: April 2003

The block copolymers of the ABA type, poly(dimethyl siloxane‐b‐styrene‐b‐dimethyl siloxane), were synthesized by the anionic polymerization of styrene and cyclic siloxane monomer, hexamethyl cyclotrisiloxane (D3) or octamethylcyclotetrasiloxane (D4), with lithium or sodium biphenyl as initiator. The effect of initiator concentration, gegenion, and the polymerization temperature for styrene on molecular weight distribution (MWD) was investigated. Gel permeation chromatography (GPC) data show broader MWD of polystyrene prepared by sodium biphenyl in comparison to that produced by lithium biphenyl. The block copolymers have been characterized by infrared (IR) and nuclear magnetic resonance (NMR) spectra. The influence of dimethylsiloxy units on thermal stability of the copolymers has also been discussed.
Copolymerization of liquid sulfur with certain olefinic systems and structure‐property studies on the polymeric materials
Authors: Bordoloi Binoy K. , Pearce Eli M. , Blight L. , Currell B. R. , Merrall R. , Scott R. A. M. , Stillo C.
Published: April 2003

Liquid sulfur–olefinic reactions at 140°C forming crosslinked polysulfide polymers have been investigated. A systematic approach to the characterization and some structure–property studies on these new polymeric materials has been presented. The olefinic systems of interest are endo‐and exo‐dicyclopentadiene and an oligomeric alkenyl polysulfide. Equimolar S8–olefinic system copolymers are amorphous and they show no tendency for sulfur crystallization. A correlation has been drawn between chemical structure and glass transition temperature of the copolymers and terpolymers. Mechanical properties and, in particular, chemical stress relaxation of the crosslinked polysulfide polymers have been investigated.
2‐methyl‐3‐methylenecyclobutene‐1‐carbonitrile: A corrected structure and a new methylenecyclobutene monomer
Authors: Hall H. K. , Snider S. C.
Published: April 2003

The correct structure of the compound originally reported as 3‐methylene[2.1.0]bicyclopentane‐1‐carbonitrile is 3‐methylene‐2‐methylcyclobutene‐1‐carbonitrile. This new monomer undergoes free radical polymerization in the expected 1,5 manner.
New processable polyaromatic amides curable by intramolecular cyclization. XVI
Authors: Sankaran V. , Lin Shiow‐Ching , Marvel C. S.
Published: April 2003

New Processable Polyaromatic amides were prepared from 2,2′‐diiododiphenyl‐4,4′‐dicarbonyl dichloride (I) and several aromatic diamines. Phenylethynyl groups were introduced in these polymides by replacing the iodine groups with copper phenyl acetylide. On thermal curing, 2,2′‐di(phenylethynyl)biphenyl group undergoes intramolecular cyclization to form 9‐phenyl dibenzanthracene derivative. The cured polymers showed increased heat and chemical stabilities. No melting points were observed for all the polymers below 500°C. The viscosity of the polymers was decreased on substitution of the iodine by phenylethynyl groups.
Influence of the tacticity on thermal degradation of PVC. IV. Degradation in solution in comparison with degradation at solid state
Authors: Millan J. , Martinez G. , Mijangos C.
Published: April 2003

Four fractions of PVC were obtained by successive extractions with appropriate solvents from PVC samples prepared in bulk at 60, 40, 0, and −50°C. Then they were carefully characterized, especially as far as stereoregularity is concerned. The samples were submitted to thermal degradation both at solid state and as solutions in dioctyl phthalate. The type of the polyene sequence distribution in degraded samples was determined by both the UV‐visible spectroscopy and the number of chain scissions resulting from the ozonization reaction. The degradation rate was proved to rise together with the syndiotactic sequence content in agreement with results in Parts I–III, obtained only with degradation at solid state. On the other hand, The content of the long polyenes relative to that of the short polyenes in the degraded polymers was found to be higher, and the number of chain scissions through ozonization reaction lower, when the syndiotactic sequence content is high. These results enable us to conclude that the actual mechanism of the PVC thermal degradation depends markedly on the tacticity distribution regardless of whether the degradation occurs either at solid state or in solution.
Reactions of stabilizer compounds. IV. ESR studies of the formation of stable nitroxyl radicals in the photooxidation of polypropylene containing hindered amine light stabilizers
Authors: Hodgeman Daryl K. C.
Published: April 2003

ESR studies of the formation of stable nitroxyl radicals in the photooxidation of polypropylene containing 2,2,6,6‐tetramethyl‐4‐hydroxypiperidine (II) and the commercial light stabilizer bis(2,2,6,6‐tetramethyl‐4‐piperidinyl)sebacate (III) are described. Spectra of the stable nitroxyl radicals in solid polymer and in solution after extraction from the polymer were obtained. The extract from photooxidized polypropylene containing the bifunctional stabilizer (III) showed only the mononitroxyl radical. The possible formation of polymer‐bonded nitroxyl radicals from (III) is discussed.
Sequence distribution in polyethylene/tetramethylene terephthalate copolyesters by 13C‐NMR
Authors: Newmark Richard A.
Published: April 2003

13C‐NMR gives sequence information in copolyesters synthesized from ethylene glycol (EG), 1,4‐butane diol (BD), and methyl terephthalate (TP). The EG‐TP‐EG and BD‐TP‐BD blocks are distinguishable from the unsymmetrical diester sequence EG‐TP‐BD. The carbonyl and aromatic quaternary carbons of terephthalate have different chemical shifts but identical relaxation times and nuclear Overhauser enhancements in the three different triad sequences. Peak areas indicate random copolymerization of the three copolyesters studied.
Cationic oligomerization of styrene by solid acids. I. Catalysis by poly(styrenesulfonic acid) resin
Authors: Hasegawa Hiroshi , Higashimura Toshinobu
Published: April 2003

Cationic oligomerizations of styrene by a solid acid [poly(styrenesulfonic acid) resin, Amberlyst 15] and by the corresponding soluble catalyst (p‐toluenesulfonic acid) were compared with respect to their reactivity and the molecular weight distribution of products. The feature of Amberlyst 15 as oligomerization catalyst, in addition to its easy separation from products, was found to be was follows: The activity of Amberlyst 15 was 10 times larger than that of p‐toluenesulfonic acid in benzene, although catalyst deactivation at high conversions was observed for Amberlyst 15 at high monomer concentrations. Styrene trimer and tetramer were dominantly produced by Amberlyst 15 at low monomer concentrations, whereas a linear dimer was obtained in 85% yield with p‐toluenesulfonic acid. Characteristically, solvent polarity had almost no effect on the reaction rate and product composition in the Amberlyst 15‐catalyzed oligomerization. These facts were discussed in relation to differences between the heterogeneous and homogeneous catalyses.
Further studies on the postpolymerization of methyl methacrylate
Authors: Sarkar Arun K. , Palit Santi R.
Published: April 2003

A search has been made for electroinitiators of postpolymerization. A number of hydroxycarboxylic acids and some of their sodium salts have been found to be quite efficient. Factors controlling the rate of polymerization and yield have been described. Surprisingly, citric acid, though not an electroinitiator of polymerization, is a good initiator of postpolymerization. Other active species that deserve mention are tartaric acid and its salts. A free radical mechanism involving formation of oligomeric initiator fragments, growth by attachment of imbibed monomer, and termination by chain transfer has been proposed to explain the observed facts.
Statistical mechanical estimation of the entropy of fusion of linear vinyl polymers
Authors: Gupta Mool C. , Nath Jaya D.
Published: April 2003

The entropy of fusion of linear vinyl polymers [polypropylene, polystyrene, and poly(vinyl chloride)] having asymmetric carbon atoms was calculated on the basis of the rotational isomeric state model. The results are found to be in good agreement with the experimental entropies of fusion per bond for these polymers.
Chemical modification of poly(N‐vinylcarbazole) by chloromethylation reaction
Authors: Pielichowski J. , Morawiec E.
Published: April 2003

Chloromethylation reaction of poly(N‐vinylcarbazole) was studied. The effect of the chloromethylating agent, catalyst, temperature, and reaction time on the course of chloromethylation reaction was investigated. The optimum conditions for introducing one chloromethyl group per one monomer unit were found. Thermal studies of chloromethylated poly(N‐vinylcarbazole) were carried out.
Diffusion‐controlled reaction. VI. Radiation graft polymerization of 4‐vinylpyridine to polyethylene
Authors: Odian George , Derman Arif , Imre Kaya
Published: April 2003

The radiation‐initiated graft polymerization of 4‐vinylpyridine to high‐density polyethylene was studied over a wide range of reaction conditions of radiation intensity I, monomer concentration M1, and polymer film thickness L. The conditions included both diffusion‐free and diffusion‐controlled graft polymerizations. The results corroborate our previous theoretical predictions on the effect of I, M1, and L on the experimental grafting rate. The grafting rate is inverse first order in L for diffusion‐controlled reaction and independent of L for diffusion‐free reaction. The dependence of grafting rate on radiation intensity decreases from 1/2 to 1/4 order for diffusion‐controlled reaction. Diffusion control results in a decrease in the dependence of rate on monomer concentration. The observed decrease is somewhat greater than theoretically predicted.
Photocrosslinking of elastomer systems. II. Ultraviolet light‐induced reactions in an EPDM modified by grafting of benzoin derivatives
Authors: Bousquet Jean‐Alain , Donnet Jean Baptiste , Faure Jean , Fouassier Jean‐Pierre , Haidar Bassel , Vidal Alain
Published: April 2003

Photocrosslinking experiments were performed on elastomeric polymer films (EPDM) previously modified by grafting a photosensitive initiator (benzoin derivative) onto the macromolecular backbone. This modification was performed by a series of Friedel–Crafts reactions and the resulting materials were characterized by infrared (IR) spectroscopy in conjunction with model reactions. After ultraviolet (UV) irradiation the photocrosslinked samples were studied by IR spectroscopy in conjunction with the measurement of physical properties. It apperared that grafting the photosensitizer onto the elastomer considerably enhances the crosslinking reaction even with a limited quantity of grafted benzoin derivative. Moreover, the results obtained suggest that the structure of the resulting networks is strongly dependent on the crosslinking process used; that is, curing the elastomer with peroxide or UV irradiation either of a blend of elastomer and photosensitizer or of the same elastomer modified by grafting the chromophore.
Synthesis and properties of polydiene and polypentenamer having formyl or hydroxymethyl groups and their photosensitive derivatives
Authors: Azuma Chiaki , Mitsuboshi Takao , Sanui Kohei , Ogata Naoya
Published: April 2003

cis‐1,4‐Polybutadiene and polypentenamer having pendant functional groups such as formyl, aldoxime, hydroxymethyl, or cinnamoyloxymethyl groups have been prepared, and some of their properties were investigated in terms of structural effect on physical properties of these polymers. cis‐1, 4‐Polybutadiene and polypentenamer having a different content of formyl group were prepared by the hydroformylation reaction with rhodium catalyst under mild conditions. The pendant formyl group was reduced to a hydroxymethyl group by using various reducing agents such as sodium borohydride or sodium trimethoxyborohydride which were effective to avoid a crosslinking reaction among the formyl groups. Glass transition temperature of polypentenamer having hydroxymethyl groups increased with increasing the content of the hydroxymethyl groups in the polymer. Cinnamoyl group was introduced into the polypentenamer having hydroxymethyl groups by reacting with cinnamoyl chloride so as to prepare a photosensitive rubber. The relationships between the photosensitivity of the cinnamoylated polypentenamer and the mobility of polymer main chains have been elucidated. A linear relationship between the photodimerization rate constant and the difference between ultraviolet (UV) irradiation temperature and the glass transition temperature of the polymer was found. It has become apparent that the photosensitivity of cinnamoylated polypentenamer can be estimated by the glass transition temperature of the original polymer, UV irradiation temperature, activation energy of the dimerization, and γ, which is a coefficient of the relationship between the photosensitive group concentration and the glass transition temperature of the polymer.
Metal complexes with ligands–organic phosphites as polyolefin antioxidants. I. Kinetics and mechanism of polyolefin and model hydrocarbon stabilization by organic phosphites
Authors: Pobedimskii D. G. , Kirpichnikov P. A.
Published: April 2003

The most effective mechanism of protective action of organic phosphites–linear termination of kinetic chains on the inhibitor—has been established and the relative contribution of the other phosphite reactions (with hydroperoxides, their chain “self‐oxidation”) to the summary mechanism has been determined. The quantitative kinetic characteristics of efficiency and length of inhibitive action of different structure phosphites in the wide range of the phase state of the oxidized substrate (solid polymer, its melt, liquid phase) have been given. On this basis the regularities which allow the prediction of the structures of phosphites scavenging peroxy substrate radicals more effectively (effective inhibitors) have been formulated.
Vinyl polymerization in the presence of copper salts
Authors: Billingham Norman C. , Chapman Angela J. , Jenkins Aubrey D.
Published: April 2003

The radical polymerization of several vinyl monomers has been studied in the presence of cupric chloride. A termination reaction with CuII species leads to the formation of CuI species which can also participate significantly in termination with some, but not all, of the monomers studied. A theoretical treatment of the kinetics of such systems is presented which takes full account of initiator depletion during extended inhibition during extended inhibition periods. Specific velocity constants for reactions of polymer radicals with both CuII and CuI moieties are derived from observations on the nonstationary phase at the end of the inhibition period and from the subsequent steady state of polymerization. On the basis of the results presented here, together with the work of other authors, the patterns‐of‐reactivity approach gives α = −5.4, β = 9.0 as the parameters for copper (II) chloride. The implications of the results in relation to the mechanisms of the reactions between polymer radicals and both copper(II) chloride and copper(I) chloride are discussed. The kinetic treatment also provides an improved method for the determination of the rate of initiator decomposition and the rate of initiation form studies of the inhibition period.
Immobilization of enzymes with use of photosensitive polymers having the stilbazolium group
Authors: Ichimura Kunihiro , Watanabe Shoji
Published: April 2003

Reaction of the homopolymer of 2‐chloroethyl vinyl ether and the copolymer of N‐vinylpyrrolidone with stilbazole produced photosensitive polymers. The photocrosslinking mechanism is discussed. Irradiation of a film of the water‐soluble photosensitive polymer yielded insolubilized material in which the enzymes were entrapped. The activity of entrapped invertase, glucoamylase, and catalase was 30, 60, and 35%, respectively.
An experimental study of ideal and nonideal behavior in styrene emulsion polymerization
Authors: James D. R. , Sundberg D. C.
Published: April 2003

An experimental investigation was conducted to relate the average number of radicals per particle, n̄ to the dimensionless parameter α, as suggested by Stockmayer. Seed emulsion polymerizations of polystyrene were run over a wide range of particle sizes and initiator levels in the 50−70°C temperature range. The seed polymerization technique removed the question of particle formation behavior and allowed a straightforward determination of n̄. Alpha was varied more than three orders of magnitude and resulted in measured values of n̄ in the range 0.5−1.3. These data are in good agreement with Stockmayer's relationship as long as the value of the termination rate constant is taken at the monomer/polymer ratios found in emulsion polymerization. For polystyrene at a monomer/polymer ratio of 60/40 this value is an order of magnitude lower than that found for infinitely dilute polystyrene solutions.
Polymerization of diethylene glycol bis(allyl carbonate) by means of di‐sec‐butyl peroxydicarbonate
Authors: Schnarr Elizabeth , Russell Kenneth E.
Published: April 2003

The initial stages of the free radical polymerization of diethylene glycol bis(allyl carbonate) at temperatures of 35–65°C have been studied. The polymer is unsaturated and cyclization to give a 16‐membered ring occurs only to a small extent. The kinetic order with respect to the initiator, di‐sec‐butyl peroxydicarbonate, has an average value of 0.79; the order increases slightly with peroxydicarbonate concentration over the range 0.018–0.22M. The molecular weight of the polymer isolated after 3% polymerization is close to 19,000. It shows no significant dependence on initiator concentration or on temperature. The dominant feature of the bulk polymerization, as in free radical polymerization of the other allyl and diallyl monomers, is degradative chain transfer in which the growing polymer radical abstracts a hydrogen atom from a monomer unit to give a relatively unreactive allylic radical. The dependence of rate on initiator concentration is rationalized if some of these allylic radicals are able to reinitiate polymerization. The transfer constant to monomer is 0.014 at 50°C, assuming that the main termination step involves mutual termination of allylic radicals. Carbon tetrachloride is an active transfer agent with a transfer constant of 0.20 ± 0.04 at 50°C. Toluene, which is less active, has a transfer constant of 0.0064 at 50°C and also retards the polymerization. Some kinetic studies have been made with other initiators, including di‐2‐methyl‐pentanoyl peroxide which initiates polymerization at temperatures as low as 13°C.
Polymer flammability. I
Authors: Stuetz D. E. , Diedwardo A. H. , Zitomer F. , Barnes B. P.
Published: April 2003

The transport of oxygen by diffusion from the environment into a gas stream was investigated as a model for the analogous process in a diffusion flame. The amount transported at steady‐state conditions depended on the flow rate, diameter, and spatial orientation of the gas stream. A change of the same extrinsic parameters in a diffusion flame caused changes of burner surface temperature, maximum flame temperature, and flame height. These responses were correlated and yielded an overall activation energy of the rate‐controlling reaction step in the combustion process equal to 49 kcal/mole. This value was the same for several types of diffusion flames examined and appeared to be associated with the CO/CO2 conversion process at the high‐temperature flame boundary. Flame quenching was demonstrated to occur at a minimum fuel flow rate and minimum environmental oxygen concentration which were characteristic for a given fuel. Quenching conditions were related to the diffusion rate of oxygen into the product effluent stream. Quenching of a polymer flame by depletion of environmental oxygen was governed by the same processes. The effect of extrinsic parameters on polymer flames is discussed in Part II.
Polymer flammability. II
Authors: Stuetz D. E. , Diedwardo A. H. , Zitomer F. , Barnes B. P.
Published: April 2003

The responses of a polymer flame to changes of specimen diameter, ignition position, and stability of the burning surface were determined. These extrinsic flame parameters restricted the transport of oxygen from the environment to the burning surface. With increasing restriction the oxygen demand from the environment for self‐sustained combustion increased from a minimum oxygen demand at maximum access of environmental oxygen to the burning surface. This increase in oxygen demand was measured and correlated with surface oxygen concentrations estimated from the diffusion data of Part I. The minimum oxygen demand was demonstrated as characteristic for a given polymer and intrinsic in its chemical structure. This minimum oxygen demand, termed intrinsic combustibility, has been correlated with a polymer's thermooxidative stability, measured by thermogravimetric analysis at specific conditions. An intrinsic combustibility scale for polymers is given. In contrast, polymer flammability, as commonly measured in air, is interpreted as a variable property that depends on the extent of the interaction between extrinsic parameters, which are set by the testing configuration, with intrinsic combustibility.
NMR relaxation study of crosslinked cis‐1,4‐polybutadiene
Authors: Munie G. C. , Jonas Jiri , Rowland T. J.
Published: April 2003

Proton relaxation measurements have been used to investigate the effects of crosslinking on the segmental motion in cis‐1,4‐polybutadiene samples. The temperature dependence of proton spin–lattice relaxation time T1 and spin–spin relaxation time T2 at 60 and 24.3 MHz are reported in cis‐1,4‐polybutadiene (PB) samples with different crosslink density including uncrosslinked PB and samples with 140, 40, and 14 repeat units between crosslinks. In addition, spin‐lattice relaxation times in rotating coordinate frame, T1p, have also been determined. The relaxation data are interpreted in terms of the effects of crosslinks on segmental chain motions. Because of their sensitivity to low‐frequency motion, T2 data are of major interest. At temperatures well above the T1 minimum the small T2 temperature dependence resembles solidlike behavior reflecting the nonzero averaging of dipolar interactions due to anisotropic motion of the chain segments between crosslinks. The magnitude of T2 at 60°C is found to be proportional to the average mass between crosslinks.
Kinetics of step polymerization with reactants of unequal functional group reactivity
Authors: Ozizmir Ercument , Odian George
Published: April 2003

A general solution is presented for the kinetics of an A–A plus B–C step polymerization. B and C are the same type of functional group but with different reactivities (k1 and k2, respectively) toward A groups. The decay of the concentrations of B, C, and A groups and the increase in the degree of polymerization with time are described for various values of the ratio k2/k1.
Utilisation du dicyclohéxyl‐18 couronne‐6 en polymérisation anionique. II. Polymérisation du methacrylate de methyle amorcee par les metaux alcalins
Authors: Alev Samson , Collet André , Viguier Michel , Schué François
Published: April 2003

The purpose of the present work, relative to anionic polymerization, is to describe the use of DCHE in order to prepare stable alkali metal solutions in low‐dielectric‐constant solvents. All these new species initiate the polymerization of methyl methacrylate avoiding the inconvenience of heterogeneous reactions. The presence of complexed ion pairs increases the syndiotactic structure. The polymerization seems to obey the Bernoullian statistics.
Grafting onto wool. IV. Effect of amines upon ceric ion‐initiated grafting of poly(methyl acrylate)
Authors: Misra B. N. , Chandel P. S.
Published: April 2003

Grafting of poly(methyl acrylate) onto wool has been carried out in an aqueous medium at 45 ± 1°C by using ceric ammonium nitrate (CAN) in the presence of triethylamine, diethylamine, n‐butylamine, triethanolamine, and N,N‐dimethylaniline. The percentage of grafting varied with the nature and concentrations of the amines. Reactivity of the different amines toward grafting reactions followed the order: triethylamine > diethylamine > n‐butylamine > triethanolamine ≥ N,N‐dimethylaniline. In the presence of N,N‐dimethylaniline grafting did not occur. An attempt has been made to explain the observed reactivity of Ce4+ in various amine systems in graft copolymerization reactions.
Thermal‐induced conversion of maleic and fumaric acid anion radicals in poly(methyl methacrylate)
Authors: Torikai Ayako , Fukumoto Mikiya
Published: April 2003

Thermal‐induced conversion of maleic and fumaric acid anion radicals produced by γ irradiation at 77 K in poly(methyl methacrylate) (PMMA) was studied by electron spin resonance (ESR) and optical absorption spectroscopic measurements. The ESR spectra of these acid anion radicals change into two‐line spectra with a line separation of ca. 10 G by thermal annealing. This spectrum is assigned to a protonated radical of each acid anion radical. Anion radicals of the solutes are relatively stable below the γ transition point of PMMA and the conversion reaction takes place near this point. This means that the molecular motion of matrix molecule affects the radical conversion reaction.
An investigation of the vacuum UV spectra of inductivity coupled RF plasmas excited in inert gases as a function of some of the operating parameters
Authors: Clark D. T. , Dilks A.
Published: April 2003

The vacuum ultraviolet (UV) emission from inductively coupled radio‐frequency (RF) plasmas excited in a series of inert gases has been studied as a function of the pressure and applied power of the system. The effects of discharge tube size and pulsing of the applied RF power are also considered and a comparison is made between RF and microwave excitation.
Circular dichroism of polyethylenimine containing optically active thymine derivatives as grafted pendants
Authors: Overberger C. G. , Morishima Y.
Published: April 2003

Optical properties of linear polyethylenimine containing optically active (+)‐ or (−)‐2‐(thymin‐1‐yl)propionyl group as grafted pendant were investigated by circular dichroism (CD) and compared with those of the related monomer and dimer model compounds. CD spectra of the polymer in neutral aqueous solution were different from those of related model compounds, which suggest that the polymer exists in some ordered conformation (at least locally) to allow exciton coupling of π–π* (B2u) transition in the base chromophores along the polymer chain. This ordered conformation tends to be randomized on heating. The effects of complementary base pairing on the CD spectra have also been studied by using a linear polyethylenimine containing (±)‐2‐(adenin‐9‐yl) propionyl grafts and its related monomer and dimer models.
A new method of estimating monomer reactivity ratios in copolymerization by linear regression methods
Authors: Watts D. G. , Linssen H. N. , Schrijver J.
Published: April 2003

Sequential gas‐liquid chromotographic analysis of the reaction mixture throughout a copolymerization reaction in conjuction with the improved curve‐fitting I (integrated form) method, which accounts for measurements errors in both variables, allows accurate estimation of the monomer reactivity ratios. In this article an alternative method is presented for estimating r values in copolymerization with linear regression only, which is especially suited to cases in which one or two of the r values is close to 1. In these cases the improved curve‐fitting I method tends to converge slowly because of the numerical instability of the integrated copolymerization equation. The use of the new method is illustrated for the estimation of the r values for ethylene and vinyl acatate in benzene at 35 kg/cm2 and 62°C. The linear regression method was also tried on other copolymerizations and the results are compared with those obtained from the improved curve‐fitting I method. The limits of the applicability of the linear regression method were determined by simulated sequential sampling experiments. It appears that the new method is applicable when the product of the r values is between 0.001 and 2, provided both monomer conversions are large enough compared with the measurements error.