bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dipole–dipole interaction directed liquid crystalline polymers. I. Aliphatic poly(carbonate‐sulfone)s based on 1,3‐bis(3‐hydroxypropylsulfonyl)propane
Authors: Zhang Tianhong , Litt Morton H. , Rogers Charles E. 
Published: April 2003

AbstractAliphatic poly(carbonate‐sulfone) homo‐ and copolymers were prepared from 1,3‐bis(3‐hydroxypropylsulfonyl)propane (Diol‐333) and various alkanediols. The copolymers are random in nature since they were prepared by melt copolymerization. Both the homopolymer and the copolymers exhibited multiple reproducible first‐order transitions during differential scanning calorimetry (DSC) heating scans, but most of them exhibited only single exotherm during cooling scans. Typical schlieren textures were observed when these polymers were cooled from their isotropic melts. The copolymers have wide‐angle x‐ray diffraction (WAXD) patterns almost identical to that of the homopolymer except in the low‐angle spacing, indicating their packing in the crystalline domain in similar. DSC, cross‐polarized optical microscopy, and WAXD revealed that these polymers were smectic liquid crystalline at room temperature. Since aliphatic poly(carbonate‐sulfone)s are flexible linear polymers with no rigid rod components, the liquid crystalline phase formation is probably directed by the dipole–dipole interactions between sulfone groups in adjacent chains. © 1994 John Wiley & Sons, Inc.
Hydrolyzable poly(ester‐urethane) networks from L‐lysine diisocyanate and D,L‐lactide/ϵ‐caprolactone homo‐ and copolyester triols
Authors: Storey R. F. , Wiggins J. S. , Puckett A. D. 
Published: April 2003

AbstractBioabsorbable poly(ester‐urethane) networks were synthesized from ethyl 2,6‐diisocyanatohexanoate (L‐lysine diisocyanate) (LDI) and a series of polyester triols. LDI was synthesized by refluxing L‐lysine monohydrochloride with ethanol to form the ester, which was subsequently refluxed with 1,1,1,3,3,3‐hexamethyldisilazane to yield a silazane‐protected intermediate. This product was then phosgenated using triphosgene. Polyester triols were synthesized from D,L‐lactide, ϵ‐caprolactone, or comonomer mixtures thereof, using glycerol as initiator and stannous octoate as catalyst. Polyurethane networks were cured using [NCO]/[OH] = 1.05 and stannous octoate (0.05 wt %) for 24 h at room temperature and pressure and 24 h at 50°C and 0.1 mm Hg. LDI‐based polyurethane networks were totally amorphous and possessed very low sol contents. Networks based on poly (D,L‐lactide) triols were rigid (Tg ∽ 60°C) with ultimate tensile strengths of ∼ 40–70 MPa, tensile moduli of ∼ 1.2–2.0 GPa, and ultimate elongations of ∼ 4–10%. Networks based on ϵ‐caprolactone triols were low‐modulus elastomers with tensile strengths and moduli of ∼ 1–4 MPa and ∼ 3–6 GPa, respectively, and ultimate elongations of ∼ 50–300%. Networks based on copolymers displayed physical properties consistent with monomer composition and were tougher than the networks based on the homopolymers. Tensile strengths for the copolymers were ∼ 3–25 MPa with ultimate elongations up to 600%. Hydrolytic degradation under simulated physiological conditions showed that D,L‐lactide homopolymer networks were the most resistant to degradation, undergoing virtually no change in mass or physical properties for 60 days. ϵ‐Caprolactone‐based networks were resistant to degradation for 40 days, and high‐lactide copolymer‐based networks suffered substantial losses in physical properties after only 3 days. © 1994 John Wiley & Sons, Inc.
Polymerization of propylene by zirconocenium catalysts with different counter‐ions
Authors: Chien James C. W. , Song Wei , Rausch Marvin D. 
Published: April 2003

AbstractPropylene was polymerized by binary zirconocenium catalysts derived from rac‐ethylenebis(1‐η5‐indenyl)dimethylzirconium and cation forming agents (C6H5)3C+(C6F5)4B− and (C6F5)3B. Polymerizations were also performed with the ternary systems of Et[Ind]2ZrCl2, Et3Al, and the cation forming agents. The catalyst systems, with the inert noncoordinating counter‐ion, (C6F5)4B−, have much higher activity and stereoselectivity than the ones with the CH3B−(C6F5)3 counter‐ion. Much less active still are catalysts having BF4− or (C6H5)4B− counter‐ions. Similar but smaller effects of counter‐ion structure on ethylene polymerization were observed. © 1994 John Wiley & Sons, Inc.
Hindered lithium dialkylamide initiators for the living anionic polymerization of methacrylic esters
Authors: Long T. E. , Guistina R. A. , Schell B. A. , Mcgrath J. E. 
Published: April 2003

AbstractLithium diisopropylamide is an efficient initiator for the anionic polymerization of methyl methacrylate in polar solvents at –78°C. Predictable molecular weights based on the initiator concentration were obtained, yields were quantitative, and molecular weight distributions were relatively narrow (<1.30). The presence of an amino end group and confirmation of the initiation mechanism were confirmed by potentiometric titration using HClO4. Number‐average molecular weights determined by titration agreed well with values determined by SEC. Other lithium dialkylamides that contain larger alkyl groups such as lithium diisobutylamide were less efficient initiators. This was attributed to the more nucleophilic anion due to less steric hindrance near the nitrogen atom. Molecular weight distributions were significantly broadened (>2.0), and molecular weight control was not achieved. However, polymer yields were quantitative. In all cases, PMMA stereochemistry was indicative of a solvent‐separated lithium counterion, and triad compositions were identical to organolithium initiated homopolymers, i.e., 78% syndiotactic, 20% heterotactic, and 2% isotactic. © 1994 John Wiley & Sons, Inc.
Synthesis and properties of poly (diphenylacetylenes) having aliphatic para‐substituents
Authors: Kouzai Hiroaki , Masuda Toshio , Higashimura Toshinobu 
Published: April 2003

Abstract1‐(p‐t‐Butylphenyl)‐2‐phenylacetylene and 1‐(p‐n‐butylphenyl)‐2‐phenylacetylene were polymerized in catalytic systems based on TaCl5 to give new polymers in high yields. These monomers were more reactive than diphenylacetylene (DPA) in copolymerization. Unlike poly (DPA), the present polymers were soluble in toluene, CHCl3, etc. owing to the high configurational entropy induced by the para‐substituents. Their relative weight‐average molecular weights determined by GPC were in the range of 6 × 105–36 × 105, and films could be obtained by solution casting. These polymers were fairly thermally stable, as seen from their high onset temperatures (320–380°C) of weight loss in TGA in air. The oxygen permeability coefficient of the polymer with t‐Bu group was 1100 barrers, the highest among those of all the hydrocarbon polymers. © 1994 John Wiley & Sons, Inc.
Cationic ring‐opening polymerization of oxetane derivatives initiated by superacids: Studies on their propagating mechanism and species by means of 19F‐NMR
Authors: Liu Ying‐Ling , Hsiue Ging‐Ho , Chiu Yie‐Shun 
Published: April 2003

AbstractThe nature of ring‐opening polymerization of oxetane derivatives initiated by triflic acid and triflic anhydride was investigated via 19F‐NMR spectroscopy. Two types of propagating species, which were directly observed from the 19F‐NMR spectra, were found to be oxonium macroions and triflic macroesters. These two propagating species established and equilibrium relationship during the polymerization process. The forming of oxonium macroion active species was highly dependent upon the substituents of the oxetane ring, and were enhanced when a more polar solvent was employed. The initiator effect, which occurred primarily in the initiating stage of the polymerization, is also discussed. © 1994 John Wiley & Sons, Inc.
Dual‐Phase structure of polymer electrolytes comprised of NBR/SBR latex films swollen with lithium salt solution
Authors: Matsumoto Morihiko , Ichino Toshihiro , Rutt J. Steven , Nishi Shiro 
Published: April 2003

AbstractDual‐phase polymer electrolytes (DPE) that have high ionic conductivity (> 10−3 S/cm) and good mechanical strength were prepared by mixing NBR and SBR latices and casting films. The latex films absorbed large quantities of lithium salt solution (e.g., 1M lithium perchlorate in γ‐butyrolactone) to obtain DPE films but did not dissolve with swelling. The NBR phase is polar and was impregnated selectively with the polar lithium salt solution, whereas the SBR phase is nonpolar and formed a mechanically‐supportive matrix. Transmission electron microscopic (TEM), electron energy loss spectral (EELS), and energy‐dispersive x‐ray (EDX) analyses showed microscopically the dual‐phase structure. Evidence for swelling by lithium salt solution was found only in the NBR phase and not in the SBR phase by EDX microanalysis. Ionic conductivity as a function of NBR content or swelling degree showed clearly that a percolation threshold for ionic conductivity exists. © 1994 John Wiley & Sons, Inc.
Solution viscosity behavior of polystyrene‐based cationic ionomers. Effects of ion content and solvent
Authors: Ohtani Noritaka , Inoue Yukihiko , Mizuoka Hiroshi , Itoh Kenya 
Published: April 2003

AbstractDilute‐solution viscosities of polystyrene‐based cationic ionomers containing ammonio or phosphonio groups were measured in several solvents. In polar solvents with dielectric constant (εr) beyond 10, the ionomers showed a typical polyelectrolyte behavior, indicating that a large part of ionic groups were dissociated into ions. In nonpolar solvents with low εr, the reduced viscosity of the ionomers linearly decreased with a decreasing ionomer concentration. At low polymer concentrations, every ionomer gave a reduced viscosity lower than that of the corresponding chloromethylated polystyrene. With an increasing ion content, the intrinsic viscosity progressively decreased if the nonpolar solvents had a low acceptor number (AN), such as toluene or tetrahydrofran (THF). In the halogenated solvents with high AN value, such as chloroform, however, the intrinsic viscosity was hardly dependent on the ion content. This indicates that the intramolecular aggregation among the ionic groups is inhibited in the halogenated solvents due to a strong anion solvation. An addition of a protic solvent to a nonpolar solvent eliminates the aggregation between ionic groups and leads to polyelectrolyte behavior. © 1994 John Wiley & Sons, Inc.
Miscibility study in the blends of novel poly (styrene‐co‐4‐vinylphenyldimethylsilanol) and poly (n‐butyl methacrylate)
Authors: Lu Shaoxiang , Pearce Eli M. , Kwei T. K. 
Published: April 2003

AbstractThe miscibility of poly (styrene‐co‐4‐vinylphenyldimethylsilanol) (ST‐VPDMS) and poly (n‐butyl methacrylate) (PBMA) blends has been investigated by means of DSC and FT‐IR spectroscopy. It was found that miscible blends were formed only for the copolymers containing 9–34 mol % 4‐vinylphenyldimethylsilanol (VPDMS). The glass transition behavior of the miscible blends was analyzed by recently proposed equations in terms of the physical meaning of the fitting parameters. The results of FT‐IR study were found to be fully consistent with the observation of the miscibility window obtained from glass transition temperature measurements. Quantitative information concerning intermolecular hydrogen bond interaction in the carbonyl stretching vibration region of the miscible blends was obtained by curve‐fitting method. © 1994 John Wiley & Sons, Inc.
New poly(amide‐imide) syntheses. XII. Preparation and properties of poly(amide‐imide)s based on the diimide‐diacid condensed from 9,9‐bis[4‐(4‐aminophenoxy)phenyl] fluorene and trimellitic anhydride
Authors: Yang Chin‐Ping , Lin Jiun‐Hung 
Published: April 2003

AbstractA dicarboxylic acid (I) was prepared from the condensation of 9,9‐bis[4‐(4‐aminophenoxy) phenyl] fluorene and trimellitic anhydride. A new family of poly(amide‐imide)s having inherent viscosities of 0.75‐1.04 dL/g was prepared by the triphenyl phosphite activated polycondensation from the diimide‐diacid I with various aromatic diamines in a medium consisting of N‐methyl‐2‐pyrrolidone (NMP), pyridine, and calcium chloride. Most of the resulting polymers showed an amorphous nature and were readily soluble in polar solvents such as NMP and N,N‐dimethylacetamide. All the soluble poly(amide‐imide)s afforded transparent, flexible, and tough films. The glass transition temperatures of these polymers were in the range of 262–325°C and the 10% weight loss temperatures were above 525°C in air. © 1994 John Wiley & Sons, Inc.
Multifunctional coupling agents for living cationic polymerization. IV. Synthesis of end‐functionalized multiarmed poly(vinyl ethers) with multifunctional silyl enol ethers
Authors: Fukui Hiroji , Sawamoto Mitsuo , Higashimura Toshinobu 
Published: April 2003

AbstractTelechelic (8) and end‐functionalized four‐arm star polymers (9) were synthesized through the coupling reactions of end‐functionalized living poly(isobutyl vinyl ether) (5; DPn ∼ 10) with the bi‐and tetrafunctional silyl enol ethers, H4‐nC[CH2OC6H4C(OSiMe3) = CH2]n (3: n = 2; 4: n = 4). The precursor polymers 5 were prepared by living cationic polymerization with functionalized initiators, CH3CH(Cl)OCH2CH2X(6), in conjunction with zinc chloride in methylene chloride at −15°C. The initiators 6 were obtained by the addition of hydrogen chloride gas to vinyl ethers bearing pendant functional groups X, including acetoxy [OC(O)CH3], styryl (OCH2C6H4‐p‐CH = CH2), and methacryloyl [OC(O)C(CH3) = CH2]. The coupling reactions with 3 and 4 in methylene chloride at −15°C for 24 h afforded the end‐functionalized multiarmed polymers (8 and 9) in high yield (>91%), where those with styryl or methacryloyl groups are new multifunctional macromonomers. © 1994 John Wiley & Sons, Inc.
A novel palladium catalyst for the polymerization of propargyl alcohol
Authors: Yang Mujie , Zheng Min , Furlani Anita , Russo Maria Vittoria 
Published: April 2003

AbstractHomogeneous polymerization of propargyl alcohol (OHP) with Pd (CCCH2OH)2(PPh3)2 [PdC] catalyst in CHCl3‐CH3OH mixed solvent system has been investigated. [PdC] was found to be a novel effective catalyst for the OHP polymerization. Some features, kinetic behavior, and effect of solvent for the OHP polymerization are described and discussed. The overall polymerization activation energy was found to be 75.6kJ/mol and the rate equation can be expressed as Rp = kp[OHP] [PdC]0.7, where kp = 3.14 × 10‐4 L0.7/ mol0.7 S (60°C). Polypropargyl alcohol (POHP) obtained is a brown powder with a number‐average molecular weight (M̄n) of 103‐2 × 103, and soluble in MeOH, DMF, and DMSO. Conducting properties of the resulting POHP were investigated. © 1994 John Wiley & Sons, Inc.
Phase‐mixed poly(ethylene glycol)/poly(trimethylolpropane triacrylate) semi‐interpenetrating polymer networks obtained by rapid network formation
Authors: Drumheller Paul D. , Hubbell Jeffrey A. 
Published: April 2003

AbstractSemi‐interpenetrating polymer networks (semi‐IPNs) of poly(ethylene glycol) (PEG) in poly(trimethylolpropane triacrylate) (TMPTA) were synthesized from PEG melts in neat TMPTA monomer, using PEG of molecular weights from 4000 to 100,000 g/mol. Differential scanning calorimetry and transmission electron microscopy were used to examine phase separation occurring during network formation. The degree of phase separation was observed to depend upon the rate of PEG aggregation relative to the rate of network formation during TMPTA polymerization. Higher molecular weight PEG and acrylate‐functionalized PEG formed more phase‐mixed networks compared to lower molecular weight PEG; acetatefunctionalized PEG showed no difference from unmodified PEG in the extent of phase mixing. For networks that demonstrated phase separation, the PEG was observed to be in two states: some being phase mixed and solvent inextractable, and some being phase separated and solvent extractable. Phase‐mixed networks could be obtained from this thermodynamically incompatible polymer pair utilizing rapid photopolymerization systems to overcome PEG phase aggregation and kinetically entrap the PEG in a nonequilibrium phase‐mixed state. These mixed‐phase semi‐IPNs of PEG and TMPTA may be useful in biological applications where the presence of PEG is desired throughout the bulk matrix rather than as a surface graft to reduce biological interactions. © 1994 John Wiley & Sons, Inc.
Radical polymerization of methyl acrylate by use of benzyl N, N‐diethyldithiocarbamate in combination with tetraethylthiuram disulfide as a two‐component iniferter
Authors: Doi Toru , Matsumoto Akikazu , Otsu Takayuki 
Published: April 2003

AbstractPolymerization of methyl acrylate (MA) with benzyl N, N‐diethyldithiocarbamate (BDC) was carried out in bulk or in benzene under UV irradiation. The polymerization proceeded to give a high yield of polymer, however it was found that BDC did not function as an iniferter in the MA polymerization. Bimolecular termination leading to deactivation of the iniferter site was observed during the polymerization in preference to chain transfer and primary radical termination which reproduce the iniferter site. The deactivation was successfully prevented by combining BDC and tetraethylthiuram disulfide (TD) as a two‐component iniferter. This two‐component iniferter system was also applied to synthesis of a star polymer with 1,2,4,5‐tetrakis (N,N‐diethyldithocarbamylmethyl) benzene (DDC) as a tetrafunctional photoiniferter. © 1994 John Wiley & Sons, Inc.
Selective extraction of Fe3+ by a polymeric calix[4]arene
Authors: Deligöz Hasalettin , Tavasli Mustafa , Yilmaz Mustafa 
Published: April 2003

AbstractA polymeric compound containing more than one calixarene molecule was synthesized by reacting the oligomer (2) with 25,26,27‐tribenzoyloxy‐28‐hydroxy calix[4]arene. After basic hydrolysis of 3a, the polymeric calixarene (3b) was utilized for selective extraction of some metal cations from aqueous phase to organic phase. It was found that the compound (3b) was selective toward Fe3+ from an aqueous solution containing Cu2+, Ni2+, Co2+ and Fe3+ cations. The mechanism of the extraction process was discussed. © 1994 John Wiley & Sons, Inc.
Mechanism of lactide polymerization in the presence of stannous octoate: The effect of hydroxy and carboxylic acid substances
Authors: Zhang Xichen , MacDonald David A. , Goosen Mattheus F. A. , McAuley Kim B. 
Published: April 2003

AbstractThe effect of hydroxy and carboxylic acid substances on lactide polymerization in the presence of stannous octoate was investigated. A polymerization mechanism was postulated to attempt to explain the controversies existing in the literature and also to explain our experimental observations. Stannous alkoxide, a reaction product between stannous octoate and alcohol, is proposed as the substance initiating the polymerization through coordinative insertion of lactide. Alcohol can affect the polymerization through the reactions of initiator formation, chain transfer, and transesterfication. Carboxylic acid affects the polymerization through a deactivation reaction. Experiments showed that alcohol increased PLLA production rate while carboxylic acid decreased it. Both alcohol and carboxylic acid reduced PLLA final molecular weight. The higher the alcohol concentration, the lower the polymer molecular weight. However, the final molecular weight of PLLA was not sensitive to the carboxylic acid concentration. A polymerization induction period was observed at high carboxylic acid concentration, due to the deactivation reaction caused by carboxylic acid. © 1994 John Wiley & Sons, Inc.
A comparison of thermoreactive water‐soluble poly‐N,N‐diethylacrylamide prepared by anionic and by group transfer polymerization
Authors: Freitag Ruth , Baltes Thomas , Eggert Martin 
Published: April 2003

AbstractSeveral batches of poly‐N,N‐diethylacrylamide were synthesized by anionic and by group transfer polymerization (GTP). A radical poly‐N,N‐diethylacrylamide prepared from the same monomer was also included in the comparison. According to matrix‐assisted laser desorption/ionization mass spectrometry (MALDI‐MS) both types of living polymerization resulted in narrow molecular weight distributions with Mw/Mn values below 1.5. Average molecular weights (Mn) between 888 and 4678 g/mol were calculated in these cases. The radical polymer had an average molecular weight (Mn) of approximately 130,000 g/mol. The dry anionic and GTP polymers were investigated by differential scanning calorimetry (DSC) and x‐ray diffraction spectrometry. Evidence for partial crystallinity in the solid state was found. The conformation of all polymers was examined by high resolution (600 MHz) NMR. According to these measurements, 75% of the CHR groups of the anionic poly‐N,N‐diethylacrylamide were located in an isotactic triade. The remaining 25% had heterotactic structure, while no indication for the presence of syndiotactic protons was found. Poly‐N,N‐diethylacrylamide prepared by GTP, on the other hand, had mainly syndiotactic structure. The aqueous solutions of the polymers showed phase separation upon heating. Whereas the lower critical solution temperature (LCST) was approximately 30°C in the case of the poly‐N,N‐diethylacrylamide prepared by GTP and by radical polymerization, uncommonly high LCSTs of more than 40°C were observed for the anionic poly‐N,N‐diethylacrylamide. © 1994 John Wiley & Sons, Inc.
Synthesis and characterization of 3‐aryl‐2‐(polystyryl)cyclopropenones via cyclopropenium ion substitution on polystyrene
Authors: Weidner C. H. , Long T. E. 
Published: April 2003

AbstractElectrophilic substitution of cyclopropenium ions on aromatic polymers offers a unique opportunity to introduce polar functionality in a controlled manner to conventional, nonpolar polymers. Phenylcyclopropenone substituted polystyrene with predictable chemical composition and narrow molecular weight distribution were prepared. Size exclusion chromatography (SEC) analysis demonstrated the absence of branching or crosslinking in these functionalized polystyrenes during electrophilic substitution of the parent homopolymer. 13C‐NMR confirmed that the degree of phenylcyclopropenone substitution was both highly efficient and predictable over a broad compositional range. The glass transition temperature (Tg) of the polymers was found to vary linearly with mole % phenylcyclopropenone substitution of the polystyrene. Thermal gravimetric analysis (TGA) indicated that thermal decarbonylation of the appended cyclopropenones occurred at approximately 180°C. Weight loss vs. temperature profiles correlated reasonably well with levels of substitution based on 13C‐NMR analysis, confirming that decarbonylation of the calculated cyclopropenone substituents was the predominant thermal decomposition pathway. © 1995 John Wiley & Sons, Inc.
Complex‐radical terpolymerization of phenanthrene, maleic anhydride, and trans‐stilbene
Authors: Bastürkmen Meray , Rzaev Zakir M. O. , Akovali Güneri , Kisakürek Duygu 
Published: April 2003

AbstractThe radical terpolymerization of the donor‐acceptor‐donor monomer system, phenanthrene (P)—maleic anhydride (M)—trans‐stilbene (S), was studied. These monomers are known to be nonhomopolymerizable. The terpolymerization was carried out in p‐dioxane and/or toluene at 70°C in the presence of benzoyl peroxide used as the initiator. P and S were found to form charge transfer complexes (CTC) with M in p‐dioxane at 35°C. The results obtained are discussed in terms of the free monomer and complex propagation models. It is shown that terpolymerization is carried out at a stage close to binary copolymerization of two complexomers. The reactivity ratio of P … M and S … M complexes was estimated by the Kelen‐Tüdös method. Absorbance ratios at 1770 cm−1 (vC=0 of anhydride group), 764 cm−1 (δCH in monosubstituted benzene of S), and 820 cm−1 (δCH in disubstituted benzene of P) as a function of terpolymer composition were established. P—M—S terpolymers are shown to have high thermal stabilities. © 1995 John Wiley & Sons, Inc.