bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polycarbonate‐poly(methyl methacrylate) block copolymers: Synthesis and characterization
Authors: Gardlund Zack G. , Bator Mary Ann K. 
Published: April 2003

AbstractThe interfacial copolymerization of bisphenol A polycarbonate, bisphenol A‐terminated poly‐(methyl methacrylate), and bisphenol A bischloroformate is described. Monofunctional hydroxy‐terminated poly(methyl methacrylates) were synthesized by the chain transfer polymerization of methyl methacrylate with 2‐mercaptoethanol. Further reaction with bisphenol A bischloroformate yielded monofunctional bisphenol A‐terminated poly(methyl methacrylates). The structure and functionality of these polymers were proven by proton nuclear magnetic resonance (PNMR) spectroscopy. Block copolymers prepared by the interfacial copolymerization were washed with methanol and extracted with acetone to remove unreacted bisphenol A bischloroformate and bisphenol A‐terminated poly(methyl methacrylates). The series of block copolymers, which contained from 0.11 to 0.86 mole fraction polycarbonate, were characterized by infrared, PNMR, and molecular weight analysis.
Synthesis of crosslinked poly(α‐amino acids) with various functional groups
Authors: Kuroyanagi Yoshimitsu , Kim Kea‐Young , Senō Manabu , Kawai Tohru 
Published: April 2003

AbstractThe esterification of the carboxyl group in copoly(γ‐benzyl‐L‐glutamyl‐L‐glutamic acid) was carried out using N‐hydroxysuccinimide and dicyclohexylcarbodimide to yield the activated site for the coupling reaction with amino compounds. The α‐helix stability of the reactive copolymer thus obtained is remarkably affected in the presence of succinimide ring. This copolymer was proved to react nearly completely with amino alcohols such as 2‐aminoethanol, 3‐aminopropanol, and diethanolamine. The copoly(N5‐hydroxyalkyl‐L‐glutamine) thus prepared is insoluble in water, since the benzyl ester remains in this copolymer. The copoly(α‐amino acids) having another functional group were also prepared using aminoalkylsilane. Crosslinked poly(α‐amino acids) were prepared by the reaction of the reactive copolymer with a low‐molecular‐weight polymer of PBLG having one amino group on each end of its main chain which was obtained from the corresponding NCA using p‐diaminobenzene as an initiator. Another crosslinked polymer was prepared using an alkyl diamine such as 1,6‐diaminohexane or 1,12‐diaminododecane as a crosslinking reagent. The crosslinked copoly(α‐amino acids) bearing the activated site are able to further react with various compounds having amino groups.
Mechanism of thermal depolymerization of trimethylsiloxy‐terminated polydimethylsiloxane
Authors: Zeldin Martel , Qian Bo‐Rong , Choi Sung J. 
Published: April 2003

Abstract“Catalyst‐free” trimethylsilyl end‐blocked polydimethylsiloxanes of Mn = 68,300 and 111,000 were isothermally depolymerized above 400°C. The volatilized products were a mixture of cyclic oligomers and trace quantities of Me3Si(OSiMe2)nOSiMe3 (n = 0,1). The relative degree of polymerization was followed as a function of fractional conversion. The data were consistent with the oretical curves for a mechanism involving initiation by random siloxane bond cleavage followed by a rapid and complete unzipping of the kinetically active fragments. It is suggested that catalysis may be responsible for the initiation process, thus accounting for the low activation energy (43 Kcal/mol) relative to the siloxane bond energy (108 kcal/mol).
Kinetics of photopolymerization of acrylamide initiated by copper (II)–bis(amino acid) chelates in aqueous solution. II
Authors: Namasivayam C. , Natarajan P. 
Published: April 2003

AbstractThe kinetics of photopolymerization reactions of acrylamide initiated by copper (II)–bis(amino acid) chelates with amino acids glutamic acid, serine, or valine were studied at 30°C. The extent of monomer conversion increases with increased initiator concentration and falls off after reaching a maximum. Analysis of the results shows that for lower concentrations of the initiator, the rate of monomer disappearance is proportional to light absorption fraction f[monomer] and the square root of the intensity. At higher concentrations of the initiator, the rate of monomer disappearance is proportional to Fε/[initiator]1/2; the monomer exponent is 1.5 and the intensity exponent 0.5. Mutual termination of the radicals is proposed at lower concentrations of the initiator; at higher concentrations of the initiator termination of the initiator radical by the copper (II) complex along with mutual termination occurs. The initiator radical species is identified from flash photolysis studies of these complexes as the Cu(I)‐coordinated radical. The effect of pH on the monomer conversion is explained. The data indicate a free‐radical mechanism of polymerization and a reaction scheme is proposed for the polymerization reactions.
Radiation curing of methacryloyloxyalkyl carbonates
Authors: Barkalov I. M. , Kiryukhin D. P. , Munikhes V. M. 
Published: April 2003

AbstractThe results of studying the radiation curing of methacryloyloxyalkyl carbonates (MC), a new type of oligomer, are presented. These oligomers are notable for their high rates of radiation curing. The radiation yield G(–M) is 2 × 105 for MC and 2 × 104 for triethylene glycol dimethyacrylate. The polymerization rate of MC appeared to be proportional, independent of the conversion degree, to the irradiation dose rate in the power of 0.9–1.0 (for dose rates ranging from 0.4 to 15 rad/s). In regard to the temperature dependence of the polymerization rate of MC for small conversion degrees, two temperature regions with different values of effective activation energy (18–20 kcal/mol and 2 kcal/mol, respectively) were observed. When an irradiated MC sample is being unfrozen, its polymerization occus in the region of devitrification (220–240°K). As distinct from mass polymerization, in the polymerization of MC solutions in acetone and benzol the mobility of growing chains increases so that the bimolecular termination becomes possible and the limiting conversion of double bonds is derived. Rather small irradiation doses necessary for curing MC and the proportionality of the radiation‐induced polymerization rate to the dose rate make these oligomers valuable for various industrial applications.
Determination of in‐cage and out‐of‐cage recombination of initiator radicals in solution polymerization using labeled initiators
Authors: Fink J. K. 
Published: April 2003

AbstractThe amount of in‐cage and out‐of‐cage recombination of initiator radicals has been measured by recovering the recombination products of simultaneous decomposition of an unlabeled and a deuterium‐labeled initiator. The occurrence of recombination products generated from both an unlabeled and a deuterium‐labeled initiator fragment, which can be monitored in a mass spectrometer, indicate out‐of‐cage recombination. It turned out that in the course of decomposition of dibenzoylperoxide in benzene, biphenyl was not produced by direct recombination of the phenyl radicals originally generated, but rather by interaction with benzene. Upon decomposing azoisobutyronitrile in various solvents, however, both in‐cage recombination and out‐of‐cage recombination were observed. When small amounts of styrene were added to such systems, the initiator radicals tended rather to react with styrene than to undergo out‐of‐cage recombination.
Photoinduced electron transfer at the polymer‐solution interface. II. Effects of ionic environment
Authors: Tazuke Shigeo , Takasaki Ryuichiro 
Published: April 2003

AbstractThree types of polymer electron transfer sensitizer were prepared by copolymerization of 1‐pyrenylmethyl methacrylate with styrene (I), vinylbenzyltriethylammonium chloride (II), and sodium p‐styrenesulfonate (III). Irradiation of the pyrenyl group in the presence of leuco crystal violet (LCV), in homogeneous or in heterogeneous systems, induced the formation of crystal violet cation (CV+) in air. The reactivity of I, II, and III was in the order of II > I > III in both systems; this was rationalized in terms of the Coulombic effect. The effect of charge is much greater for the heterogeneous systems. High‐charge density on the polymer surface and enhanced polymer‐solvent affinity account for the high reactivity of II. The high quantum efficiency, coupled with the advantage of facile product separation, warrants the practical application of interfacial sensitization.
Polymerization of acrylamide with ceric ion–malic acid redox pair
Authors: Misra G. S. , Khatib J. I. 
Published: April 2003

AbstractThe polymerization of acrylamide (M) in aqueous sulfuric acid medium initiated with ceric ammonium sulfate–malic acid redox pair was investigated at 35 ± 0.2°C under nitrogen atmosphere. The initiation was caused by the free radical generated by the decomposition of the complex formed between ceric ion and malic acid (MA). The rate of monomer disappearance was proportional to the first power of malic acid, ceric ion, and monomer concentrations at lower ceric ion concentrations. However, at higher ceric ion concentrations the rate was independent of [Ce(IV)]. The rate of ceric ion disappearance was proportional to [MA] and [Ce(IV)] but independent of [M] at lower ceric ion concentrations. The activation energy was found to be 57.74 kJ/mol. Sulfuric acid retarded the reaction. Molecular weights increased with increasing [M] and decreasing [Ce(IV)].
Isomerization polymerization of β‐propiolactones carrying side‐chain ester groups
Authors: Araki Takeo , Hayase Shuzi , Nakamura Akira 
Published: April 2003

AbstractBased on our recent discovery of the isomerization polymerization of β‐(2‐acetoxyethyl)‐β‐propiolactone into poly‐δ‐ester,1,2 we examined the generality of this phenomenon by using two related monomers. The catalysts were (EtAlO)n and Et(ZnO)2ZnEt. The side‐chains in the monomers selected were the (CH3)2CHCOOCH2CH2(2) and (CH3)CICHCOOCH2CH2(3) groups in which steric effects are almost identical but electronic effects are in opposition. The monomers yielded isomerized poly‐δ‐ester units, depending on the terminal substituent groups in the side‐chain. These observations can be interpreted with the bicyclic intermediate proposed in the earlier work. Monomer (2) was reactive and produced a poly‐δ‐ester structure most readily, probably because of the higher electron density at the side‐chain ester group which coordinated with the catalyst. In contrast, monomer (3) was less reactive, and the probability of isomerization was the lowest, i.e., the electron deficient side‐chain ester group apparently interfered with the formation of the intermediate, especially in the Zn‐catalysis. Equibinary random copolymers were prepared from (2) and (3) according to the catalyst and polymerization conditions chosen.
Optically active copolymers from p‐vinyltrifluoroacetophenone
Authors: Altomare A. , Carlini C. , Ciardelli F. , Pearce E. M. 
Published: April 2003

AbstractCopolymers of p‐vinyltrifluoroacetophenone (VTFA) with optically active (−)‐menthyl acrylate (MtA) have been prepared by free radical initiation. The values of reactivity ratios (rVTFA = 4.28 and rMtA = 0.26) indicate that counits are inserted substantially at random into the copolymer macromolecules. CD spectra show a couplet typical of exciton splitting in the absorption region of trifluoromethylphenyl (TFA) chromophore. Dependence of ellipticity on composition and sequence distribution suggests that TFA chromophores are in a chiral environment provided by the dissymmetric conformation of the copolymer macromolecules.
Alternating copolymerization of methyl acrylate with donor monomers having a protected amine group
Authors: Majumdar Ramendra N. , Yang Shih‐Liang , Harwood H. James 
Published: April 2003

AbstractAttempts were made to copolymerize p‐aminostyrene, p‐acetamidostyrene, N‐methyl‐p‐aceta‐midostyrene, N‐(4‐vinylphenyl) phthalimide, N‐vinyl succinimide, and N‐vinyl phthalimide with methyl acrylate complexed with ethyl aluminum sesquichloride. Only reactions involving N‐(4‐vinylphenyl)phthalimide and N‐vinyl phthalimide yielded alternating copolymers. N‐vinyl succinimide gave nonalternating copolymers insoluble in common solvents and the other monomers did not copolymerize. In some cases, the conventional radical copolymers were prepared for comparison purposes. The reactivity ratios of the free‐radical initiated copolymerization of methyl acrylate (I) with N‐(4‐vinylphenyl)phthalimide (II) were r1 = 0.14 and r2 1.56. The alternating copolymers were studied by 1H‐NMR and 13C‐NMR spectroscopy. The alternating copolymer of N‐(4‐vinylphenyl)phthalimide with methyl acrylate was hydrazinolyzed to form the alternating copolymer of methyl acrylate with p‐aminostyrene. Hydrazinolysis of the alternating copolymer of methyl acrylate with N‐vinyl phthalimide removed the phthalimide moiety and generated vinyl amine units which readily cyclized with neighboring methyl acrylate units to form copolymers that contained five‐membered lactam rings. The infrared (IR) spectra of the hydrazinolyzed products contain bands due to amine or amide groups and are devoid of the characteristic bands of the phthalimide ring.
Dehydrochlorination of vinylidene chloride‐vinyl chloride copolymer by aqueous sodium or potassium hydroxide solutions under two‐phase conditions
Authors: He Fei‐Feng , Kise Hideo 
Published: April 2003

AbstractThe reaction of solid copolymer of vinylidene chloride and vinyl chloride with aqueous sodium or potassium hydroxide solutions in the presence of quaternary ammonium or phosphonium salts as phase transfer catalysts gave dehydrochlorinated products with chlorine‐substituted polyene structure. Among the catalysts used tetrapropylammonium bromide was the best and potassium hydroxide was more active than sodium hydroxide. The activity of quaternary ammonium salts was discussed in terms of hydrophile–lipophile balance. The effects of temperature and the concentration of the bases and catalysts were investigated to obtain the optimum reaction condition. Treatment of the polymer films and solutions in tetrahydrofuran with aqueous bases under two‐phase conditions also produced dehydrochlorinated films and powders.
Mutarotation of optically active poly(cis‐5‐ethyl‐D‐proline)
Authors: Yang Wayne W.‐Y. , Overberger C. G. , Venkatachalam C. M. 
Published: April 2003

AbstractThe mutarotation between form I and form II of poly(cis‐5‐ethyl‐D‐proline) has been experimentally realized. A number of hydrogen‐bond‐forming solvents have been found effective in initiating the mutarotational process. The rate of mutarotation seems to be proportional to the acidity of the active solvent. The enthalpy of activation energy for the mutarotation is estimated from the first‐order kinetics at the lower conversion by means of the Arrhenius equation to be approximately 16.7 kcal/mol. The solvent‐polymer interactions are proven to be one of the important driving forces for the mutarotation. The specific site at which hydrogen bonding takes place has been determined to be the carbonyl group of the amide by infrared spectroscopic techniques. The molecular reason for the greater susceptibility of poly(cis‐5‐ethyl‐L‐proline) II to the solvent effect than poly(cis‐5‐ethyl‐L‐proline) I can be satisfactorily explained by the relatively more extended structure of form I than form II. The mechanism for the mutarotation undoubtedly involves a cis‐trans isomerization of the amide bond. The conformation of the transient states during the mutarotational process is still evidently helical in nature, probably consisting of long poly(cis‐5‐ethylproline) I and II segments.
The structure of plasma‐polymerized toluene: A solid‐state 13C‐NMR study of isotopically labeled polymers
Authors: Kaplan S. , Dilks A. 
Published: April 2003

AbstractA detailed magic angle spinning 13C‐NMR investigation of the intractable polymer prepared by plasma polymerization of toluene and isotopically labeled toluene led to a proposed model for the structure of the polymer and suggested some of the likely processes that occur in the gas phase leading to film formation. From the 13C spectra four resolved resonances permitted the determination of the contribution of nonprotonated and protonated unsaturated as well as methyl and other aliphatic carbons to the polymer structure. Specific 13C isotopic labeling of the methyl and phenyl C‐1 toluene carbons in the injected liquid vapor allowed the destination of these carbons in the deposited polymer to be traced. The dominant structure is derived primarily from two precursors: benzyl radical and toluene itself. The 13C data further requires a net saturation of ca. 30% of the toluene double bonds and a net displacement of hydrogen by carbon on ca. 20% of the toluene ring carbons.
Syndiotactic 1,2‐polybutadiene with Co‐CS2 catalyst system. I. Preparation, properties, and application of highly crystalline syndiotactic 1,2‐polybutadiene
Authors: Ashitaka Hidetomo , Ishikawa Hideo , Ueno Haruo , Nagasaka Akira 
Published: April 2003

AbstractHighly crystalline syndiotactic 1,2‐polybutadiene (s‐PB) having melting point (mp) up to 216°C was obtained by using a Co(acac)3‐AIEt3‐CS2 catalyst. The polymer with mp 208°C was found to have 99.7% 1,2 content and 99.6% syndiotacticity by 1H and 13C‐NMR measurements. The s‐PB can be molded by addition of a stabilizer such as 2,6‐di‐t‐butyl‐4‐hydroxymethylphenol into fiber, film, and various shaped articles. The physical properties presented in the present article include stress‐strain and dynamic mechanical behavior. The highly crystalline syndiotactic 1,2‐polybutadiene was applied to a carbon fiber and UBEPOL VCR (cis‐1,4‐polybutadiene reinforced by fibrous syndiotactic 1,2‐polybutadiene).
The reactions of polyacetylene with trimethyloxonium hexachloroantimonate. Covalent doping of (CH)x
Authors: Brant P. , Weber D. 
Published: April 2003

AbstractPolyacetylene, (CH)x, has been doped with trimethyloxonium hexachloroantimonate, (CH3)3O+SbCl(1), in dichloromethane and acetonitrile. The maximally doped (CH)x films have moderate conductivities [σRT(CH2Cl2) = 10, σRT(CH3CN) = 0.7 Ω−1 cm−1]. Reactions between 1 and (CH)x CH2Cl2 or CH3CN were followed in situ by 1H nuclear magnetic resonance spectroscopy and x‐band electron spin resonance spectroscopy. It was found that the reactions in the two solvents are different. In dichloromethane the dopant is SbCl5, which forms from the decomposition of 1, and doping proceeds by electron removal from (CH)x chains. Based on the ESR signal loss, an estimate can be made of the diffusion rate of SbCl5, into the (CH)x fibrils in CH2Cl2; it is found to be ca. 10−17 cm2/s. In acetonitrile the dopant appears to be either CH3CNCH, H+, CH, or a combination of one or more of these dopants. It is postulated that the CH3CNCH, CH, and/or H+ dopant covalently binds to the (CH)x chain. X‐ray photoelectron spectra show that films doped with excess 1 in both solvents have approximately one SbCl per 33 CH units.
Syndiotactic 1,2‐polybutadiene with Co‐CS2 catalyst system. II. Catalysts for stereospecific polymerization of butadiene to syndiotactic 1,2‐polybutadiene
Authors: Ashitaka Hidetomo , Jinda Kazuya , Ueno Haruo 
Published: April 2003

AbstractButadiene is polymerized by cobalt compound–organoaluminum–CS2 catalysts to give highly crystalline syndiotactic 1,2‐polybutadiene (s‐PB) having melting point up to 216°C. An aluminum‐free catalyst, Co(C4H6)(C8H13)‐CS2, is also effective. Syndiotactic polymerization with Co(C4H6)(C8H13)‐CS2 is not interrupted by the addition of protic substances such as water and alcohol, but is influenced by donor or acceptor substances. The donor molecule, e.g., dimethylsulfoxide or dimethylformamide, decreases the stereoregularity, i.e., syndiotacticity and 1,2 content. An acceptor molecule of organoaluminum with appropriate acidity such as AlEt3‐AlEt2Cl or tetraethylaluminoxane increases the molecular weight, stereoregularity, and yield of the polymer. In the presence of CS2 a mixture of cis‐PB and s‐PB was obtained by using Co(octoate)2‐AlEt2Cl‐H2O, with molar ratio H2O/Co less than unity. In the case of H2O/Co > 1, only cis‐PB was obtained. By the addition of donor substances such as ester, ether, nitrile, and AlEt3, s‐PB was obtained even when H2O/Co > 1. The amount and ratio of cis‐PB and s‐PB are dependent upon the nature and amount of the additives.
Syndiotactic 1,2‐polybutadiene with Co‐CS2 catalyst system. III.1H‐ and 13C‐NMR study of highly syndiotactic 1,2‐polybutadiene
Authors: Ashitaka Hidetomo , Inaishi Kazutoshi , Ueno Haruo 
Published: April 2003

AbstractThe 1H and 13C‐NMR spectra of highly crystalline syndiotactic 1,2‐polybutadiene (s‐PB) are discussed in order to clarify the mechanism of butadiene polymerization with cobalt compound–organoaluminum–CS2 catalysts. Cis opening of the double bonds in the syndiotactic polymerization is affirmed by the study of the copolymer from perdeuteriobutadiene and cis,cis‐1,4‐dideuteriobutadiene. S‐PB (mp 210°C) has 99.7% 1,2 units, 0.3% isolated cis‐1,4 units, and 99.6% syndiotacticity. Polymer ends (2‐methyl‐3‐butenyl group and conjugated diene structure) are also determined. The differences in free energy of activation between 1,2 and cis‐1,4 propagation and between syndiotactic and isotactic propagation are 14.0 and 9.6 kcal/mol, respectively, for Co(acac)3‐AlEt3‐AlEt2Cl‐CS2, and 6.7 and 5.7 kcal/mol, respectively, for the aluminum‐free Co(C4H6)(C8H13)CS2 system. The conformation of s‐PB in o‐dichlorobenzene at 150°C is described by the sequence (tt)1.6(gg)(tt).
Surface ozonation and photooxidation of polyethylene film
Authors: Peeling James , Clark David T. 
Published: April 2003

AbstractHigh‐density polyethylene (HDPE) and low‐density polyethylene (LDPE) films were oxidized by treatment with ozone and by photooxidation with a low‐pressure mercury lamp. The changes that resulted in the surfaces of the films were followed by ESCA. On ozonation, the surface of LDPE initially is oxidized more rapidly than that of HDPE; however, extended ozonation produces a surface composition that corresponds to C8O for HDPE and to C18O for LDPE. The surface oxidation products are mainly carboxyl groups, with lower levels of carbonyl and CO groups. For both polymers photooxidation provides more extensively oxidized surfaces than ozonation, although the surface of HDPE oxidizes slightly faster than that of LDPE treated under identical conditions. In both cases the surface stoichiometry after extensive photoxidation is C6O. The functional groups formed are mainly carboxyl and CO. The effects of ozonation and photooxidation on the polyethylene surfaces are compared with those produced by several other means of surface oxidation.
New polymer‐supported catalysts. (Polyvinylchloride‐containing redox) catalyst cyclopentadienyl iron moiety: [η5C5H5Feη6C6(CH3)5CH2]+
Authors: Román E. , Valenzuela G. , Gargallo L. , Radic D. 
Published: April 2003

AbstractNew polymer‐supported catalysts that contain the redox cyclopentadienyl iron moiety [η5C5H5Feη6C6(CH3)5CH2]+ were prepared with polyvinylchloride (PVC) as support. The active center is attached as a pendant organometallic moiety in the side groups of the PVC chain. Metallocenic groups and the supported polymers with various Fe content were analyzed by spectroscopic techniques and by polarographic and cyclic voltammetry. The absorption spectra show a similar profile to that of the nonsupported cation, which indicates that the supported polymer contains side groups in the chain with metallocenic structures. The new polymer‐supported catalysts were characterized by viscometric measurements and by differential calorimetry (DSC). A linear relationship between intrinsic viscosity/[η] and the Fe content was observed. The glass transition temperature (Tg) values are higher than those of PVC without modification.