bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinetics and steric limitation of quaternization of poly(4‐vinylpyridine) with mesogenic ω‐(4′‐methoxy‐4‐biphenylyloxy)alkyl bromides
Authors: Navarro‐Rodriguez Damaso , Frere Yves , Gramain Philippe 
Published: April 2003

AbstractThe kinetics and characteristics of the quaternization of poly(4‐vinylpyridine) with very large alkylating agents are studied with the main aim to demonstrate the occurrence of a limitation of the reaction due to steric effect. Kinetics are carried out in sulfolane at different temperatures with two ω‐(4'‐methoxy‐4‐biphenylyloxy)alkyl bromides. An important limitation of the reaction is demonstrated: 30% of the pyridine groups are inaccessible at 333 K, 23% at 355.5 K, and 4% at 363 K. Post‐quaternization experiments with butyl bromide of already partially quaternized P4VP also demonstrate this limitation. The occurrence of global steric hindrance and hydrophobic effects affecting the conformation of the chain in solution is proposed to explain the limited accessibility of the pyridine groups. The results question the classical neighboring group model generally used to describe the slowing down of the quaternization reaction with increasing quaternization ratio. The thermal stability of the quaternized polymers and the colors of the reaction medium are also discussed. © 1992 John Wiley & Sons, Inc.
Metallocene catalysts for olefin polymerizations. XXIV. Stereoblock propylene polymerization catalyzed by rac‐[anti‐ethylidene(1‐η5‐tetramethylcyclopentadienyl)(1‐η5‐indenyl)dimethyltitanium: A two‐state propagation
Authors: Chien James C. W. , Llinas Geraldo Hidalgo , Rausch Marvin D. , Lin Ye‐Gang , Winter H. Henning , Atwood Jerry L. , Bott Simon G. 
Published: April 2003

AbstractRacemic‐anti‐[ethylidene(1‐η5‐tetramethylcyclopentadienyl) (1‐η5‐indenyl)dimethyltitanium (6) has been synthesized and its molecular structure determined by x‐ray diffraction methods. The two TiMe(1) and TiMe(2) units have bond distances differing by 0.08 Å and their proton NMR resonances are separated by over 1 ppm. Using this compound and methylaluminoxane (MAO) as the activator, at 25°C the 6/MAO catalyst produced polypropylene having crystalline domain with physical crosslinks. The polymers obtained at lower polymerization temperatures are rheologically liquids. The behaviors of this catalyst system resembles closely the previously reported rac‐[anti‐ethylidene(1‐η5‐tetramethylcyclopentadienyl) (1‐η5‐indenyl)dichlorotitanium (4)/MAO system. The structure of 6 determined here furnishes tangible support for the proposed two‐state (isomeric)‐switching propagation mechanism. Addition of MAO to 6 causes broadening of the Me(1) resonance in the 1H‐NMR spectra, and 6 is decomposed by Ph3C+B(C6F5)‐4. © 1992 John Wiley & Sons, Inc.
Emulsion polymerization of vinyl acetate using a polymerizable surfactant. I. Kinetic studies
Authors: Urquiola M. B. , Dimonie V. L. , Sudol E. D. , El‐Aasser M. S. 
Published: April 2003

AbstractA polymerizable surfactant, sodium dodecyl allyl sulfosuccinate (TREM LF‐40; Henkel) and its nonpolymerizable counterpart were used in comparative studies of the emulsion polymerization of vinyl acetate. The conversion‐time behavior differed for the two surfactants; the TREM LF‐40 showed a decrease in the polymerization rate with increasing concentration while its hydrogenated derivative showed the opposite behavior, the rate increasing with increasing surfactant. Particle size analysis revealed a decreasing particle size with increasing surfactant concentration for both series of reactions. An explanation for the seemingly ambiguous results obtained for the polymerizable surfactant was sought by examining the reactivity of its vinyl group in copolymerization with vinyl acetate and its allylic group in a chain transfer reaction. The results suggest that both the copolymerization and chain transfer reactions can lead to the observed reduction in polymerization rate with increasing TREM LF‐40 concentration. © 1992 John Wiley & Sons, Inc.
Polymerization of propargylamine and 1,1‐diethylpropargylamine by transition metal catalysts
Authors: Gal Yeong‐Soon , Jung Bal , Lee Won‐Chul , Choi Sam‐kwon 
Published: April 2003

AbstractSome polyacetylene derivatives containing an amine functional group were prepared by the polymerization of propargylamine (PA) and 1,1‐diethylpropargylamine (DEPA) with various transition metal catalysts. In the polymerization of PA, Mo‐based catalysts were more effective than that of W‐based catalysts, and organoaluminum compounds, especially EtAlCl2, were found to be very effective cocatalysts. In the polymerization of DEPA, Mo‐and W‐based catalyst systems showed a similar catalytic activity. The polymerization easily proceeded in polar solvents such as nitrobenzene and DMF as well as nonpolar aromatic solvents such as chlorobenzene, toluene, etc. The resulting poly(PA) and poly(DEPA) were insoluble in organic solvents regardless of polymerization catalysts but the polymers were found to be stable to air oxidation. Thermogravimetric analyses and thermal transitions of poly(PA) and poly(DEPA) were also studied. © 1992 John Wiley & Sons, Inc.
Palladium catalyzed ethylene‐carbon monoxide alternating copolymerization
Authors: Zhao Allen X. , Chien James C. W. 
Published: April 2003

AbstractA new [(PPh2CH2CH2CH2PPh2)Pd(CH3CN)2](BF4)2/CH3OH catalyst for olefin/carbon monoxide alternating copolymerization has been found which is far more active and more stable than previous monodente phosphine Pd catalysts. Methanol is a coinitiator as well as a chain transfer agent. Protonic acid is not a coinitiator but causes chain transfers. In the absence of methanol, the copolymerization was characterized by long induction period and slow rate © 1992 John Wiley & Sons, Inc.
The synthesis and characterization of a poly(maleimide‐ether) containing pendent thiophene rings
Authors: Edge Stephen , Charlton Adam , Varma Karikath S. , Underhill Allan E. , Hansen Thomas K. , Becher Jan , Kathirgamanathan Poopathy , Khosravi Ezat 
Published: April 2003

AbstractThe preparation of a poly(maleimide‐ether) containing pendent thiophene rings via the reaction of 2‐(3‐thienylmethyl)‐1,3‐N,N'‐bis(3,4‐dichloromaleimido) propane with 1,4‐dihydroxybenzene is described. The novel 2‐substituted‐1,3‐N,N'‐bis(3,4‐dichloromaleimido) propanes were obtained by allowing their corresponding diamine hydrochlorides to react with 3,4‐dichloromaleic anhydride in acetic acid in the presence of sodium methoxide. The diamine hydrochlorides were prepared by the reduction of their respective diamides. The poly(maleimide‐ether)s were fully characterized and 13C‐NMR spectroscopy was used to confirm the microstructure of the materials. The properties of the thiophene substituted polymer are compared with model poly(maleimide‐ether)s. Electrochemical studies indicated that the thiophene rings in the thiophene‐substituted poly(maleimide‐ether) were not electroactive. © 1992 John Wiley & Sons, Inc.
Metalloporphyrins catalyze polyene‐polymers to polyepoxides
Authors: Tornaritis M. J. , Coutsolelos A. G. 
Published: April 2003

AbstractPolyene polymers [natural rubber (cis‐polyisoprene), trans‐polyisoprene, and cis‐polybutadiene] were transformed to the corresponding polyepoxides which are a polyalcohol and soap precursor. The catalysts used were chloro‐ or acetato‐manganese(III) tetraphenylporphyrin [MnIII(TPP)Cl or MnIII(TPP)OAc] in association with two different oxygen donors, sodium hypochloride and iodosylbenzene (Por, unspecified porphyrinato ligand; TPP, 5,10,15,20‐tetraphenylporphyrinato ligand). This transformation in either biphasic system, H2O(aqua)‐CH2Cl2 or PhIO(solid)‐CH2Cl2, was monitored by 1H‐NMR and IR spectroscopy. In both cases the transformation to the polyepoxide was completed within a few hours. © 1992 John Wiley & Sons, Inc.
Resist system based on the cationic photocrosslinking of poly(4‐hydroxystyrene) and polyfunctional electrophiles
Authors: Fahey J. T. , Shimizu K. , Fréchet J. M. J. , Clecak N. , Willson C. G. 
Published: April 2003

AbstractNew resist systems based on acid‐catalyzed, electrophilic aromatic substitution are described. These new resists show high sensitivity to deep UV and E‐beam radiation with values approaching 2 mJ/cm2and 2 μC/cm2, respectively. The resists are based on a three component system consisting of poly(4‐hydroxystyrene), a polyfunctional, low molecular weight, latent electrophile, and a photoactive onium salt used as an acid generator. Irradiation of the resist film produces a latent image of acid dispersed in the matrix. During the postbaking step the photo‐generated acid reacts with the latent polyfunctional electrophile and releases a reactive carbocationic intermediate with concomitant liberation of acetic acid. The carbocationic intermediate then reacts with neighboring phenolic moieties in a crosslinking reaction. The substitution reaction liberates a proton, making the process catalytic in nature, thus incorporating the concept of chemical amplification. These highly sensitive materials can be used as nonswelling negative multipurpose resists that function in deep‐UV, x‐ray or E‐beam modes. © 1993 John Wiley & Sons, Inc.
Studies on the thermotropic liquid crystalline polymer. VII. Synthesis and properties of photocrosslinkable poly(ether‐ester) containing cinnamic group
Authors: Li Chen‐Hui , Lai Wen‐Wei , Hsu Keh Ying , Chang Teh‐Chou 
Published: April 2003

AbstractA series of semi‐aromatic poly(ether‐ester)s containing cinnamic group was prepared from 4,4′‐diacrylic acid‐α,ω‐phenoxyalkanes with diols in the presence of diphenylchlorophosphate (DPCP) and pyridine as a catalyst and solvent. The phase behavior of these polymers was studied by differential scanning calorimetry (DSC), optical polarizing microscopy equipped with a heating stage, and wide‐angle x‐ray diffraction (WAXD). All of the poly(ether‐ester)s, except P3, show nematic or smectic thermotropic liquid crystalline behaviour under optical polarizing microscopic observation. These polymers can undergo photocrosslinking reaction upon heating, as examined by IR, solubility, and DSC analysis. © 1993 John Wiley & Sons, Inc.
Synthesis of triphenylsilyl‐ and triphenylmethyl‐telechelic polyisobutylene: An approach to the synthesis of multi‐ion telechelic ionomers
Authors: Storey Robson F. , Lee Youngkwan 
Published: April 2003

AbstractTriphenylsilyl‐ and triphenylmethyl‐telechelic polyisobutylene (PIB) were prepared by lithiation of three‐arm star PIBs carrying either olefinic or tert‐alkyl chloride end groups, followed by reaction with triphenylsilyl chloride or triphenylcarbenium ion, respectively. Since the lithiated intermediate is a substituted allylic carbanion, the chain end also possesses a double bond which is located β‐γ relative to the silyl or triphenylmethyl group. The phenyl groups were incorporated into the polymers to provide extra sites for sulfonation, in addition to the double bond, to enable the synthesis of multi‐ion telechelic ionomers. 1H‐ and 13C‐NMR spectroscopy showed that triphenylsilylation and triphenylmethylation were essentially quantitative when applied under the prescribed conditions to either the model compound, 2,4,4‐trimethyl‐1‐pentene, or to the telechelic PIBs. It was observed that exhaustive sulfonation of these materials using acetyl sulfate or chlorosulfonic acid yielded only about 50% sulfonation of the available sites. This suggests that sulfonation of closely adjacent, multiple sites within the same molecule fails due to deactivation of the remaining sites after one or perhaps two sulfonations. However, the triphenylsilyl‐ and triphenylmethyl‐telechelic PIBs represent novel prepolymers which can perhaps be derivatized by some method other than sulfonation, and the general concept for producing telechelic ionomer precursors with multiple sulfonation sites may prove successful with other moieties containing spacer groups between sites. © 1993 John Wiley & Sons, Inc.
Kinetics of radical polymerization of dimethylphenyl methacrylates
Authors: Vrhovac Ljubica , Djurasović Nebojs̃a , veličković Jovan 
Published: April 2003

AbstractThe kinetics of free radical polymerization of all six existing isomeric dimethylphenyl methacrylates were studied in bulk at 60°C, initiated by dilauroyl peroxide, using dilatometry. The different polymerization rates observed, resulting from the different monomer structures, are discussed in terms of steric and other effects, considering also the previous results for tolyl methacrylates. © 1993 John Wiley & Sons, Inc.
Functional polymers for colloidal applications. V. Novel behavior of polymeric emulsifiers in emulsion polymerization
Authors: Kuo Ping‐Lin , Chen Chaur‐Jinn 
Published: April 2003

AbstractThe polymeric emulsifier poly(dodecyl acrylate‐co‐acrylic acid) [i.e., the sodium salt (PDA)] and monomeric emulsifier sodium dodecyl glutarate (SDG) have been synthesized. PDA and SDG are used as emulsifiers in the emulsion polymerization of styrene with both the water‐soluble initiator potassium persulfate (K2S2O8) and the oil‐soluble initiator 2,2′‐azobisisobutyronitrile (AIBN). The PDA/K2S2O8 system showed a bimodel distribution of particle sizes (2 and 0.05 μm). A bimodel particle distribution was also found for the PDA/AIBN system, but the distribution for the large particles was wide (0.1–10 and 0.07 μm). The SDG/K2S2O8 system displayed only one kind of particle size (0.05 μm), but the SDG/AIBN system also showed a bimodel distribution of particle sizes (0.05 and 5 μm). These bimodel distribution results for the PDA/K2S2O8, PDA/AIBN, and SDG/AIBN systems indicate that the polymerization sites are both in oil droplets and in micelles (polymer aggregates). This mechanism is interpreted in terms of the formation of polymer aggregates, which is supported by the results of pyrene solubilization, pyrene fluorescence, surface tension, and pyrene excimer experiments. © 1993 John Wiley & Sons, Inc.
Synthesis and emulsion copolymerization of amphiphilic poly(2‐oxazoline) macromonomer possessing a vinyl ester group
Authors: Uyama Hiroshi , Honda Yoichiro , Kobayashi Shiro 
Published: April 2003

AbstractThe present article describes the synthesis and emulsion copolymerization of a block‐type amphiphilic poly(2‐oxazoline) macromonomer possessing a polymerizable vinyl ester group. The macromonomer was synthesized by one‐pot two‐stage block copolymerization of 2‐oxazolines using vinyl iodoacetate as initiator. 2‐Methyl‐ and 2‐n‐butyl‐2‐oxazolines were employed for the construction of hydrophilic and hydrophobic segments, respectively. The surface activities evaluated by the surface tension of the macromonomer in water were fairly good. Emulsion copolymerization of vinyl acetate with the macromonomer was carried out. The macromonomer acted as a polymeric surfactant, as well as a comonomer. The resulting copolymer latex particles were spherical and their diameter was in the sub‐micron range. The effects of the composition of the macromonomer on the emulsion copolymerization and the resulting latex particles were examined. © 1993 John Wiley & Sons, Inc.
Anionic copolymerization of 2,3,4,5,6‐pentafluorostyrene and divinylbenzene
Authors: Nishimura Shin , Nagai Akira , Takahashi Akio , Narita Tadashi 
Published: April 2003

AbstractAnionic copolymerizations of 2,3,4,5,6‐pentafluorostyrene (PFS) with 1,3‐divinylbenzene (m‐DVB) and 1,4‐divinylbenzene (p‐DVB) were performed by using lithium diisopropylamide as an initiator in order to synthesize the fluorine‐containing linear polymer with pendant vinyl groups. The products were soluble copolymers possessing both PFS and DVB monomeric units, and the DVB monomeric unit in copolymer had pendant vinyl group. This copolymerization reaction took a much longer time than that of styrene with DVB. The copolymerization parameter of this system was examined from copolymer composition curves. In this system, m‐DVB was found to be more reactive than p‐DVB. The reactivity of copolymerization was largely influenced by the reactivity of active species. © 1993 John Wiley & Sons, Inc.
Water penetration in nylon 6,6: Absorption, desorption, and exchange studied by NMR microscopy
Authors: Fyfe Colin A. , Randall Leslie H. , Burlinson Nick E. 
Published: April 2003

AbstractThe uptake of water by nylon 6,6 [42DB Adipure (trade name of Dupont Canada Inc.)] at 100°C has been monitored by a combination of one‐dimensional proton NMR spectroscopy, relaxation time (T1 and T2) measurements and proton microscopic NMR imaging techniques. The relaxation times of the water absorbed into the nylon matrix are very short at room temperature, (T2 < 1 ms and T1 ≈ 1 s) indicating that the water is located in a highly restricted environment and suggesting that strong interactions exist between the absorbed water and the polymer. The diffusion profiles measured at room temperature indicate that the diffusion of water into nylon 6,6 at 100°C is Case I Fickian diffusion. The spatial dependence of the T2 relaxation time constant and its variation with the water content was also examined. The results reveal that both T2 and T2* decrease toward the center of the sample in samples that have a concentration gradient of sorbed water. In fully saturated samples, no spatial dependence was observed. The overall values of T2 and T2* are also observed to increase as a function of exposure time. An evaluation of the desorption process at room temperature and at 100°C was performed. A continuous, exponentially decreasing solvent profile was observed for the desorption process which again indicates Case I Fickian kinetics. The exchange process of external bulk and atmospheric water with deuterium oxide (D2O) saturated nylon rods has also been studied using the microscopic imaging technique. © 1993 John Wiley & Sons, Inc.
Cyclopolymerization. XIX. Effect of N‐substituents on cyclopolymerizability of N‐allylmethacrylamides
Authors: Kodaira Toshiyuki , Okumura Miyuki , Urushisaki Michio , Isa Kimio 
Published: April 2003

AbstractThe effect of bulky N‐substitutents of N‐t‐butyl‐ and N‐phenyl‐N‐allylmethacrylamides (BAMA and PAMA, respectively) on their cyclopolymerizability was investigated. BAMA yielded an almost completely cyclized polymer while the degree of cyclization of poly (PAMA) was about 95%. The latter value indicates that the effect of phenyl group is comparable with that of methyl group, since N‐methyl‐N‐allylmethacrylamide was reported to give a polymer with a degree of cyclization of 93%. Structural investigation on telomerization products of BAMA and PAMA permitted the assignment of the repeating cyclic units of these polymers to that of a five‐membered ring. This structural characteristic was also supported by the observation of five‐membered cyclized radicals on ESR measurements of these monomers. Rotation around amide CN bonds of these monomers and related compounds studied by 13C‐NMR was found to be strongly dependent on N‐substitutents. The mechanism of the cyclization was discussed in terms of the structure of the ring formed and rotation around amide CN bonds of these monomers. The reactivity of the methacryloyl and allyl groups involved in these monomers were compared based on the information obtained by structural investigation of polymers and telomerization products and by ESR studies. © 1993 John Wiley & Sons, Inc.
Crosslinked liquid crystal polymers from liquid crystal monomers: Synthesis and mechanical properties
Authors: Litt Morton H. , Whang Wha‐Tzong , Yen Kung‐Ti , Qian Xue‐Jun 
Published: April 2003

AbstractDifunctional acrylates and methacrylate monomers have been made which are high order smectic liquid crystal (or crystalline) at room temperature. This report discusses materials with the following structure: F–S–M–S–F, where F is a functional group, acrylate or methacrylate (A or M); S is a spacer (CH2)n(n), and M is a mesogen—in this case 4,4′‐dioxybiphenyl (B). They are codified as BnA or BnM where n is the number of methylenes in the spacer. High conversion with high Tg can be obtained when polymerizing in the smectic state because the reactive end groups are concentrated in a small volume and can react well with little or no diffusion. B2A, B3A, B6A, B11A, and B3M were polymerized in the smectic state and compared to polymers made at temperatures where the monomers were isotropic. High conversion was obtained below final Tg—even then, probably because the polymers were ordered. All the polymers were studied by WAXD and dynamic mechanical spectroscopy. Solid‐state NMR on B3A showed that there was very high conversion of the double bonds at all temperatures. B3A photopolymerized in the smectic state (60–76°C) produced a crystalline polymer with Tg = 185°C (1 Hz). When photopolymerized at 85°C, above the isotropization temperature (Ti), a poorly organized polymer was obtained with a Tg of 155°C (1 Hz). Monomers with an odd number of methylene groups as spacers were crystalline after polymerization. With an even number of methylene groups, they lost most of their crystallinity on polymerization below Ti, but retained a low order smectic structure. Similar structures were obtained with all the monomers when they were polymerized above Ti. There was little effect of polymerization temperature on Tg when the spacers had an even number of methylene groups. © 1993 John Wiley & Sons, Inc.
Preparation of poly(4‐vinyl‐2‐hydroxypyridine) and its catalytic activity on mutarotation of 2,3,4,6‐tetramethyl‐α‐D‐glucose
Authors: Arai Kenichiro 
Published: April 2003

AbstractPoly(4‐vinyl‐2‐hydroxypyridine), PVHP, was prepared by the reaction of poly(4‐vinylpyridine) with hydrogen peroxide in acetic acid, and subsequent refluxing in acetic anhydride at 150°C. Conversion of pyridine units to 2‐hydroxypyridine units was about 75% and the obtained product was a deep‐brown powder. Mutarotation rates of 2,3,4,6‐tetramethyl‐α‐D‐glucose, TMG, in chloroform and in ethanol in the presence of the PVHP were measured and compared with those in the presence of 2‐hydroxypyridine. The PVHP was found to show higher catalytic activities on the mutarotation than 2‐hydroxypyridine in both solvents, which was deduced to be due to more efficient formation of the complex between TMG and the catalyst molecules. The mutarotation rates were higher in chloroform than in ethanol for both catalysts, which suggests that the mutarotation in the presence of the catalyst is more favorable in the strongly hydrogen bonding solvent because of higher interaction between the substrate and the catalyst molecules. The mutarotation rates increased proportionally with increasing concentration of the substrate in both solvents and in the presence of both catalyst, while they increased but not proportionally with increasing concentration of the catalyst; the increase began to level‐off with increasing concentration of the catalyst. The latter tendency was assumed to result from the association of the catalyst units themselves, which makes efficiency of the complex formation between TMG and the catalyst molecules lower. © 1993 John Wiley & Sons, Inc.
Polymerization of ethylene using a high‐activity Ziegler–Natta catalyst. II. Molecular weight regulation
Authors: Marques Maria M. V. , Nunes Clemente Pedro , Tait Peter J. T. , Dias Alberto Romão 
Published: April 2003

AbstractThis article describes studies on the variables that regulate the molecular weight in ethylene polymerization using a highly active Ziegler–Natta catalyst with hydrogen for molecular weight control. The dependence of the degree of polymerization on the concentration of catalyst, cocatalyst, monomer, partial pressure of hydrogen, and temperature has been established. The rate constant for chain transfer with cocatalyst has been evaluated. © 1993 John Wiley & Sons, Inc.