bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sulfonation of tert‐alkyl chlorides: Application to the tert‐chloride‐terminated polyisobutylene system
Authors: Storey Robson F. , Lee Youngkwan 
Published: April 2003

AbstractThe direct sulfonation of tert‐chloride‐terminated polyisobutylene was carried out using acetyl sulfate in methylene chloride/hexanes diluent to produce low molecular weight model ionomer systems with narrow molecular weight distribution. The room temperature sulfonation of 2‐chloro‐2,4,4‐trimethylpentane, which serves as a model for the polyisobutylene chain end obtained in the controlled cationic polymerization of isobutylene, was found to be quantitative after 3 h reaction. The two major products, isomeric β,γ‐unsaturated sulfonic acids differing only in the location of the double bond, were the same products obtained from the sulfonation of 2,4,4‐trimethyl‐1‐pentene, which serves as a model for the polyisobutylene chain end after quantitative dehydrochlorination. Near‐monodisperse, tert‐chloride‐terminated, three‐arm star polyisobutylene was synthesized under living cationic polymerization conditions using the tricumychloride/TiCl4/pyridine initiation system in hexanes/methyl chloride consolvents. Sulfonation was carried out directly upon the obtained polymer, and the sulfonated product was purified using ion‐exchange chromatography. Structural elucidation was performed using NMR. Titration and molecular weight characterization revealed that sulfonation produced exactly one sulfonic acid group per polyisobutylene chain end.
Selective vinyl cationic polymerization of monomers with two cationically polymerizable groups. IV. New initiating systems for selective and living polymerization of p‐isopropenylphenyl glycidyl ether
Authors: Hashimoto Tamotsu , Sano Yoshiyuki , Sawamoto Mitsuo , Higashimura Toshinobu , Saito Noriaki , Kanagawa Shuichi 
Published: April 2003

AbstractA variety of cationic initiators were employed for p‐isopropenylphenyl glycidyl ether (IPGE), an α‐methylstyrene derivative with an epoxy pendant, and optimum initiators and reaction conditions were evaluated in terms of its selective vinyl polymerization and living polymerization. Despite the coexistence of two cationically polymerizable groups in IPGE, binary initiating systems (HI, CF3COOH, or CH3CH(OiBu)‐OCOCH3, each coupled with ZnI2) and sulfonic acids (CF3SO3H and CH3SO3H) selectively polymerized the vinyl group of IPGE in CH2Cl2 at −78°C to produce soluble polymers with epoxy pendant groups in high yield. Metal halides (BF3OEt2 and AlEtCl2) polymerized both the vinyl and epoxy groups of IPGE to give crosslinked insoluble polymers. In contrast, under these conditions, the HI/ZnI2 system also led to a long‐lived polymer, the molecular weight of which increased upon addition of a fresh feed of monomer to a completely polymerized reaction mixture, whereas the use of other initiators resulted in nonliving polymers. At higher temperatures (−40 and −15°C), soluble poly(IPGE) was also obtained with HI/ZnI2, but the polymer yield decreased with raising temperature, because of the occurrence of termination reaction.
Copolymerization behavior of 2‐vinylbenzofuran: Copolymers of ethyl acrylate, n‐butyl acrylate, and methyl methacrylate
Authors: Trumbo D. L. 
Published: April 2003

AbstractThe reactivity of 2‐vinylbenzofuran in copolymerization reactions with n‐butyl acrylate, ethyl acrylate, and methyl methacrylate was investigated. The vinylbenzofuran was found to be a very reactive monomer with the growing chain preferring to react with this monomer no matter what its terminus. Reactivity ratios were calculated using a nonlinear least squares error‐in‐variables method, which gives more reliable values of r1 and r2.
Preparation and properties of polyesters and copolyesters based on 4‐methyl‐2,4‐bis (p‐hydroxyphenyl)‐1‐pentene
Authors: Yang Chin‐Ping , Huang Ching‐Jung 
Published: April 2003

Abstract4‐Methyl‐2,4‐bis (p‐hydroxyphenyl)‐1‐pentene (MBHPP) was prepared from thermal cracking of bisphenol A (BPA). Unsaturated polyesters were synthesized from the polycondensation of MBHPP with diacid chlorides. Three synthetic routes—solution, interfacial, and melt polycondensation—were employed. MBHPP‐polyesters with higher molecular weights were obtained by the interfacial polycondensation reaction. During the preparation of MBHPP‐polysters, the products usually contain some insoluble gel, which is probably caused by the crosslinking reaction of the vinyl groups of MBHPP in the aqueous NaOH. Thus, a modified interfacial polycondensation method was proposed, in which both of the bisphenol MBHPP and diacid chloride were dissolved in organic phase and then the solution was stirred with an aqueous NaOH solution to promote the polycondensation. This method reduced the time of MBHPP present in the alkali and produced polymers with higher inherent viscosity and lower gel fraction. The effects of some variables, such as the nature of porganic solvents and phase transfer agents and the concentration of reactants, on the modified interfacial polycondensation of MBHPP with the mixture of equal parts of isophthaloyl and terephthaloyl chloride [IPC/TPC (50/50)] were investigated in some detail. Copolyesters of mixed bisphenols of BPA/MBHPP with IPC/TPC (50/50) were also prepared and characterized.
Conformational analysis of poly(2‐hydroxyethyl methacrylate)
Authors: Yoon Jeong Hyeok , Shin Jae Min , Kang Young Kee , Jhon Mu Shik 
Published: April 2003

AbstractThe poly(2‐hydroxyethyl methacrylate) (PHEMA) is a disubstituted vinyl chain in which the substituents CO2CH2CH2OH and CH3 differ in size and shape. In order to verify the various characteristics of the PHEMA chain, the conformational energy calculations for meso and racemic diads, which are the segments consisting of the stereoregular isotactic and syndiotactic chains, respectively, were carried out using ECEPP/2 potential. From these calculations, the averaged geometry and the statistical weights were obtained in a local minima. The characteristic ratio, C∞ = (〈r2〉o/nl2)∞, was determined from the statistical weights and geometries. The calculated C∞ for the isotactic and syndiotactic chain are 10.2 and 2.3, respectively. The characteristic ratio for isotactic chain is larger than that for syndiotactic chain. This shows that the syndiotactic chain is more folded than the isotactic chain is, and that the calculated tendency is in reasonably agreement with the experimental tendency of acrylate polymers.
Preparation and properties of Si‐containing copolymer for near‐UV resist. I. Poly(N‐(4‐hydroxyphenyl) maleimidealt‐p‐trimethylisilylstyrene)
Authors: Chiang Wen‐Yen , Lu Jin‐Yuh 
Published: April 2003

AbstractA new negative near‐UV photoresist consisting of poly(N‐(4‐hydroxyphenyl) maleimidealt‐p‐trimethylisilylstyrene) (PHMS) and a naphthoquinonediazide ester was developed. PHMS was synthesized by solution free‐radical polymerization of the comonomers with azobisisobutyronitrile (AIBN) in 1,4‐dioxane at 60°C. The preparation of PHMS in terms of reaction time, thermal initiator, and solvent was evaluated; and a series of different molecular weight copolymers were prepared. PHMS was 1: 1 in composition and was predominantly alternating. These copolymers dissolved in a wide range of solvents (including 5% tetramethylammonium hydroxide). The thermal properties of these copolymers were investigated by DSC and TGA. The chain‐stiffening effect of the maleimide group played an important role in effecting high thermal resistance. Near‐UV exposure was carried out using a Canon PLA‐501F contact printer. High resolution negative images were obtained which had resistance to thermal deformation at 330°C and above. The developed patterns exhibited good adhesion to the silicon substrates without the use of an adhesion promoter. The lithographic applications of a bilayer photoresist system in which the prepared resist was used as the top imaging layer were examined. It is supposed that if PHMS was used as a binder for a diazonaphthoquions sulfonate (NDS) photochemically, positive images would be obtained; however, on the contrary, negative images were observed. It is proposed that photocrosslinking occurred in the PHMS main chain.
Laminating resins obtained from 2,2′‐(1,4‐phenylenedivinylene)bispyridine bismaleimides and maleimide‐terminated styrylpyridine prepolymers
Authors: Mikroyannidis John A. 
Published: April 2003

AbstractA new bismaleimide (2a), biscitraconimide (2b), and bisnadimide (4) were synthesized by reacting 2‐amino‐6‐methylpyridine with an equimolar amount of maleic, citraconic, or nadic anhydride, respectively, and then with a half molar amount of 1,4‐benzenedicarbaldehyde in the presence of acetic anhydride. They, as well as the intermediate amic acids (1a, 1b, and 3) were characterized by IR and 1H‐NMR spectroscopy. The DTA thermograms showed that crosslinking of polymer precursors started at 180–212°C. The crosslinked resins obtained from 2a and 2b were stable up to 300–313°C and afforded anaerobic char yield of 53–60% at 800°C. The cured resin of 4 was less thermostable. In addition, end‐capping of styrylpyridine prepolymers was accomplished by reacting 2,6‐dimethylpyridine (n mol) with 1,4‐benzenedicarbaldehyde (n + 1 mol) in acetic anhydride to yield a formyl‐terminated styrylopyridine prepolymer. The latter reacted with the maleamic acid 1a (2 mol) to afford a series of maleimide‐terminated styrylpyridine prepolymers MTSOs. They showed lower curing temperatures than did the ordinary poly(styrylpyridine). Their cured resins did not lose weight up to 310–344°C both in N2 or air and afforded anaerobic char yield of 66‐72% at 800°C.
Polyisobutylene‐containing block polymers by sequential monomer addition. I. The living carbocationic polymerization of styrene
Authors: Kaszas G. , Puskas J. E. , Kennedy J. P. , Hager W. G. 
Published: April 2003

AbstractThe living carbocationic polymerisation of styrene (St) has been investigated by the 2‐chloro‐2,4,4‐trimethylpentane (TMPCI)/TiCl4 initiating system in the presence of various additives such as electron pair donors (EDs) and the proton trap 2,6‐di‐tert‐butylpyridine (DtBP) by the use of the mixed solvent CH3Cl/methyl‐cyclohexane (MCHx) (40/60 v/v) at −80°C under conventional laboratory conditions. The TMPCl/TiCl4 system in the absence of additives produces ill‐defined bimodal molecular weight distribution (MWD) polymers. Much better defined polystyrenes (PSt) can be obtained in the presence of EDs, such as N,N‐dimethylacetamide (DMA) and hexamethylphosphoramide (HMPA). Monomer depletion should be avoided to prevent intra‐ or intermolecular alkylation yielding indanyl end groups or branched polymers, respectively. In the combined presence of an ED and the proton trap, i.e., DMA + DtBP, the living polymerization of St has been achieved and thus the foundations for the carbocationic synthesis of PSt block polymers by sequential monomer addition have been laid.
Synthesis and double ring‐opening polymerization of cyclic ketals of γ‐methylenelactones
Authors: Bailey William J. , Zheng Zhi‐Feng 
Published: April 2003

AbstractSeveral cyclic ketals of γ‐methylenelactones such as 7‐methylene‐1,4,6‐trioxaspiro‐[4,4] nonane (3a), 2‐methyl‐7‐methylene‐1,4,6‐trioxaspiro [4.4] nonane (3b), and 2,7‐dimethylene‐1,4,6‐trioxaspiro [4.4] nonance (3c) were prepared, and polymerized. The results indicated that the former two monomers polymerized with a quantitative double ringopening to form high polymers via a catonic mechanism, but the latter monomer under the same conditions generated a polymer with a network structure.
Kinetics and stereochemical control of propylene polymerization initiated by ethylene bis(4,5,6,7‐tetrahydro‐1‐indenyl) zirconium dichloride/methyl aluminoxane catalyst
Authors: Chien James C. W. , Sugimoto Rynichi 
Published: April 2003

AbstractThe kinetics and sterochemical control of propylene polymerization initiated by rac‐ethylene bis (4,5,6,7‐tetrahydro‐1‐indenyl) zirconium dichloride/methyl aluminoxane (1/MAO) and by rac‐ethylene bis (1‐indenyl) zirconium dichloride/MAO (2/MAO) were investigated. The polymerization activities increase monotonically with temperature corresponding to an overall activation energy of 10.6 kcal mol−1. This is accompanied, however, by reduction of stereochemical control as reflected in the amount of the polypropylene (PP) soluble in low boiling solvent. At a temperature of 30°C and higher, polymerization initiated by 1/MAO produced no PP insoluble in refluxing n‐heptane. Tritium radiolabeling showed that at [Al]/[Zr] ≥ 3500 and 30°C, two‐thirds of 1 becomes catalytically active. There are at least two kinds of active species formed in about equal amounts; one has more stereoselectivity, 10–20 times greater rate constant of propagation, and a factor of 5–15 faster chain transfer to MAO than the second kind of Active species. This is also true at low [Al]/[Zr] of 350, except that the total amount of the two active species corresponds to only 13% of the [1]. Replacement of MAO with trimethyl aluminum resulted in the decrease of stereoselectivity and loss of catalytic activity proportional to the amount of replacement. A comparison was made with the polymers obtained with 2/MAO.
Effects of ultraviolet irradiation on substituted polyacetylenes
Authors: Tsuchihara Kenji , Masuda Toshio , Higashimura Toshinobu 
Published: April 2003

AbstractEffects of UV irradiation on various substituted polyacetylenes were examined. Upon irradiation in air, main‐chain scission and crosslinking occurred with a wide range of probabilities dependent on the nature of substituents. For example, poly(2‐alkyne)s rapidly degraded to low molecular weights, whereas polymers from aromatic monosubstituted acetylenes [e.g., poly(o‐CF3‐phenylacetylene)] were quite stable. Several other polyacetylenes [e.g., poly(1‐Me3Si‐1‐propyne)] showed intermediate degradability. Polymer degradation was minimal in vaccum. The polymers irradiated in air contained CO and OH groups, and dissolved in polar solvents which are nonsolvents for the initial polymers. These results indicate that oxidation causes degradation. Only poly(1‐chloro‐1‐alkyne)s of the polyacetylenes studied, formed gels upon UV irradiation. The amount of the gel was larger, when the polymer was irradiated in vacuum than in air. Further, the longer the alkyl pendant in the polymer, the higher the gel fraction. Differences between photo‐and thermal degradations are discussed.
13C‐NMR studies of compositional and configurational sequence distribution in acrylonitrile–ethyl methacrylate copolymers
Authors: Kapur G. S. , Brar A. S. 
Published: April 2003

AbstractAcrylonitrile–ethyl methacrylate (A/E) copolymers of different monomer concentrations were prepared in bulk by free radical initiation. Copolymer composition was determined by nitrogen analysis and the comonomer reactivity ratios were determined by the method of Kelen‐Tüdos. 13C‐NMR spectra of several acrylonitrile/ethyl methacrylate copolymers are discussed in terms of their triad monomer sequence and cotacticity. Terminal and penultimate reactivity ratios have been calculated using the observed monomer triad sequence distribution determined from 13C‐NMR spectroscopy for individual samples. Triad sequence distribution was used to calculate dyad concentrations, probability parameters, number average sequence lengths, and the comonomer mole fractions in the copolymers. The configurational sequence distributions in terms of all the 10 A‐centered and 10 E‐centered triad cotactic sequences have been determined and found to be in excellent agreement with those obtained using various cotactic probability parameters.
Studies of particle formation in styrene emulsion polymerizations using 9‐vinyl anthracene as a probe molecule
Authors: Pearson L. T. , Louis Pierre E. J. , Gilbert Robert G. , Napper Donald H. 
Published: April 2003

AbstractThe effects of 9‐vinyl anthracene (VAn) on solution and emulsion polymerization of styrene are examined, to gain information about the mechanism of particle formation in emulsion polymerizations. Styrene solution polymerization in ethyl benzene is found to be inhibited by small amounts of VAn. In an emulsion system, the effects of VAn are found to depend on surfactant concentration [S]. With [S] = 0, addition of VAn engenders some inhibition and very little change in the steady‐state polymerization rate. As [S] is increased from zero to above the critical micelle concentration (cmc), a slight increases in the induction period and an increasing retardation (reduction in the steady‐state rate) are observed. Below the cmc, VAn has no significant effect on the particle number, but above the cmc it considerably increases the latter with concomitant appearance of very small (5–15 nm radius) particles. The data strongly support the supposition that the coagulative/homogeneous nucleation mechanism dominates particle formation for [S] below the cmc. Above the cmc, the data are compatible with both the micellar entry and coagulative/homogeneous mechanisms.
Investigations of the chemical structure of sulfonated amino‐formaldehyde resins. V. 13C‐NMR analysis of sulfonated urea–melamine–formaldehyde resins
Authors: Pasch Harald , Hovakeemian George , Lahalih Shawqui 
Published: April 2003

Abstract13C‐NMR spectroscopy was used to characterize the chemical structure of sulfonated urea–melamine–formaldehyde resins, prepared by a three‐step procedure (addition, sulfonation, condensation). Each of the three reaction steps was investigated separately and the average number of functional groups, obtained after each step, was determined quantitatively. The effect of the reactant ratios on the chemical structure was studied.
Polyanhydrides. IV. Unsaturated and crosslinked polyanhydrides
Authors: Domb Abraham J. , Mathiowitz Edith , Ron Eyal , Giannos Steven , Langer Robert 
Published: April 2003

AbstractUnsaturated polyanhydrides of the structure [(COCHCHCOO)x(CORCOO)y]n, were synthesized. The polymers were prepared by either melt or solution polycondensation. Weight average molecular weights of up to 30,000 were obtained. The double bonds remain intact throughout the polymerization process and were available for a secondary reaction to form a crosslinked matrix. Poly(fumaric acid) is crystalline and insoluble in common organic solvents. Copolymers of fumaric acid with aliphatic diacids are less crystalline and soluble in chlorinated hydrocarbons. These copolymers displayed nearly constant degradation rates and drug release rates under physiological conditions. The time for complete degradation of 14 × 1.5 mm discs of poly(fumaric anhydride) and poly(sebacic anhydride) occurred in 2 and 15 days, respectively, while their copolymers degraded within this range. Further crosslinking of the polyanhydrids is demonstrated.
Spin trapping of propagating radicals derived from dialkyl fumarates
Authors: Yamada Bunichiro , Yoshikawa Eilchiro , Otsu Takayuki 
Published: April 2003

AbstractPropagating radicals of dialkyl fumarates (DRFs) and deuterated fumarate were trapped by admitting a 2‐methyl‐2‐introsopropane (BNO) solution to the polymerization mixture containing the active radicals or by the polymerizations initiated with di‐t‐butyl hyponitrite in the presence of BNO. Although ESR spectra of the propagating radicals were appreciably changed with the size of the ester alkyl groups, all the nitroxyl radicals resulting from the spin trapping exhibited similar six‐line spectra. The hyperfine splitting constant for the α‐hydrogen of the radical moiety showed a slight dependence on the chain length, and the bulkiness of the ester alkyl group did not affect splitting of the spectra. These findings indicate that a substituted methylene radical is produced by addition of the primary radical to DRF followed by propagation throughout the polymerization and that poly(DRF) radical does not encounter severe hindrance in the reaction with BNO.
Monomer‐isomerization polymerization. XXVI. Formation of polyallylcyclohexane from propenylcyclohexane through monomer‐isomerization polymerization with Ziegler–Natta catalysts
Authors: Endo Kiyoshi , Otsu Takayuki 
Published: April 2003

AbstractMonomer‐isomerization polymerization of propenycyclohexane (PCH) with TiCl3 and R3‐xAICIx (R = C2H5 or i‐C4H9, x = 1–3) catalysts was studied. It was found that PCH underwent monomer‐isomerization polymerization to give a high molecular weight polymer consisting of an allylcyclohexane (ACH) repeat unit. Among the alkyaluminum cocatalysts examined, (C2H5)3Al was the most effective cocatalyst for the monomer‐isomerization polymerization of PCH, and a maximum for the polymerization was observed at a molar ratio of Al/Ti of about 2.0. The addition of isomerization catalysts such as nickel acetylacetonate [Ni(acac)2] to the TiCl3–(C2H5)3Al catalyst accelerated the monomer‐isomerization polymerization of PCH and gave a maximum for the polymerization at a Ni/Ti molar ratio of 0.5. PCH also undergoes monomer‐isomerization copolymerization with 2‐butene (2B).
Interfacial electrostatic potential of polyions as probed by acid‐base indicator dyes covalently attached to the main chain
Authors: Morishima Yotaro , Higuchi Yuji , Kamachi Mikiharu 
Published: April 2003

AbstractPolyanions with various charge densities with a solvatochromic acid‐base indicator dye attached to the main chain were prepared by the terpolymerization of acrylic acid, acrylamide, and a small mole fraction of 1‐(2‐methacryloyloxyethyl)‐4‐(2‐(4‐hydroxyphenyl)ethenyl)pyridinium bromide. The apparent pK value for the polymer‐bound indicator dye (pKabs) was determined by the spectroscopic pH titration. The interfacial electrostatic potential (ψ) was calculated from pKobs. Dielectric contribution to the acid‐base equilibrium was taken into account for the calculation. The electrostatic potentials thus obtained were compared with those calculated from the nonlinearized Poisson‐Boltzmann equation for a cylinder model. The indicator dye moieties are suggested to be reporting the mean field potential at a distance of about 10 Å from the axis of the polyion cylinder. The observed values as a function of the charge density were also discussed in connection with Manning's theory.
The effect of sodium methacrylate on the soapless emulsion copolymerization of methyl methacrylate and n‐butyl acrylate
Authors: Pan Ting‐Chung , Kuo Jen‐Feng , Chen Chuh‐Yung 
Published: April 2003

AbstractThe soapless emulsion polymerization of methyl methacrylate (MMA) and n‐butyl acrylate (BA) containing various concentrations of sodium methacrylate (NaMA) or methacrylic acid (MMA) is studied. The hydrosoluble yields in final latexes are not larger than 1.3–5%, depending on the concentration of NaMA used. Below 25% conversion, the change of conversion with reaction time follows the square rule and the particle size is proportional to the 2/3 power of time. Above 25% conversion, serious gel effect occurs, and the conversion follows the seventh power on time and the growth of particle diameter obeys the 2.5 power on time. The multiple glass transition (Tg) occur below 20% conversion, where monomer droplets exist. NaMA added induces more Tgs. The effect of molecular weight of the copolymers obtained on Tg (even the molecular weight distributions were shown to be shouldertype bimodal) is estimated to be insignificant. Thus, the heterogeneity of copolymer compositions for multiple Tgs is ascribed to be caused from neither the molecular weight heterogeneity nor the shifts in compositions due to the difference of the monomer reactivity ratios. Referring to the results mentioned, we assume the sublayer surrounding the particle, rich with SO4− and COO− groups, and the concentration gradients of monomers in particles to illustrate particle morphology. In addition, the relatively hydrophilic sublayer is proposed to be closely relative with the occurrence of the composition heterogeneity in particles.