bluuebunny/crossref_metadata_2025_split huggingface dataset:
Aqueous photopolymerization with visible‐light photoinitiators: Acrylamide polymerization photoinitiated with a phenoxazine dye/amine system
Authors: Villegas L. , Encinas M. V. , Rufs A. M. , Bueno C. , Bertolotti S. , Previtali C. M. 
Published: August 2002

AbstractWe studied the photoinduced electron‐transfer polymerization of acrylamide with, as a visible‐light initiator, the heterocycle‐N‐oxide resazurin in the presence of triethanolamine. The irradiation of resazurin produces resorufin, which also absorbs in the visible region. Both phenoxazine dyes in the presence of the amine are efficient photoinitiators of acrylamide polymerization in an aqueous medium. The polymerization rates were measured at several amine concentrations. These values increase with the amine concentration, reaching a maximum value; further amine addition slightly decreases the polymerization rate. Time‐resolved photolysis studies of the dyes were carried out under the polymerization conditions. The quenching of the dye excited states by the amine was analyzed with static‐fluorescence and laser‐flash photolysis. These data were used for fitting curves of the polymerization rate versus the amine concentration, and it was concluded that the interaction of triplet excited dyes with the amine leads to acrylamide polymerization. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 4074–4082, 2001
Synthesis of linear and starlike polymers from poly(propylene glycol) methacrylate using controlled radical polymerization
Authors: Shemper Bianca S. , Acar A. Ersin , Mathias Lon J. 
Published: August 2002

AbstractThe copper‐catalyzed atom transfer radical polymerization (ATRP) of poly(propylene glycol) methacrylate (PPGM) in solution to produce linear and starlike polymers is reported, using methylethyl ketone as the solvent and a temperature of 80 °C. The ATRP system used was efficient for polymerization of the functionalized monomer without protecting hydroxyl end groups of monomer. The polymerizations were consistent with “living” or controlled processes, as revealed by the linear evolution of molecular weight with conversion. Increasing the [M]0:[I]0 ratio resulted in increasing molecular weights, whereas the polydispersity indices remained low (Mw/Mn < 1.4) even at high conversion. Decreasing the [CuBr]0:[I]0 ratio resulted in lower conversions, slightly larger polydispersities, and decreased molecular weights, likely resulting from a lower initiation efficiency. Polymers were characterized by 1H and 13C NMR; molecular weights of polymers with low degrees of polymerization were estimated by end‐group analysis from 13C NMR spectra obtained using distortionless enhancement by polarization transfer and the gated decoupling techniques. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 334–343, 2002
Synthesis and biodegradation of poly(ester amide)s containing amino acid residues: The effect of the stereoisomeric composition of L‐ and D‐phenylalanines on the enzymatic degradation of the polymers
Authors: Fan Yujiang , Kobayashi Masami , Kise Hideo 
Published: August 2002

AbstractBiodegradable poly(ester amide)s that contained phenylalanine residues in the main chains were synthesized by the polycondensation of di‐p‐nitrophenyl sebacate and phenylalanine 2‐aminoethyl ester. The stereoisomeric composition (L/D ratio) of the phenylalanine residue in the monomer did not affect the yield and molecular weight of the polymer much. From the optical rotations of the polymers, it was found that the L/D ratio of the phenylalanine residue in the polymer was almost equal to the L/D ratio of the phenylalanine residue in the monomer. The biodegradability of the poly(ester amide)s was studied in aqueous solutions with proteases as catalysts. The polymer with 100% L‐phenylalanine residue was effectively degraded by α‐chymotrypsin or subtilisins. However, the replacement of 10% L‐phenylalanine with D‐isomer resulted in a dramatic decrease in degradability. The polymers with less than 30% L‐isomer were hardly degraded by the enzymes. Gel permeation chromatography studies suggested that the solubility of the degradation products in water greatly affected the rate and extent of biodegradation. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 385–392, 2002
Novel tricontinuous hydrophilic–lipophilic–oxyphilic membranes: Synthesis and characterization
Authors: Kurian Pious , Kennedy Joseph P. 
Published: August 2002

AbstractNovel tricontinuous membranes consisting of well‐defined hydrophilic poly(ethylene glycol) (PEG) and lipophilic polyisobutylene (PIB) segments crosslinked by oxyphilic poly(pentamethylcyclopentasiloxane) (PD5) domains have been synthesized and characterized. Tricontinuity arises because the three membrane constituents—PEG, PIB, and PD5—are mutually incompatible and give rise to three independent cocontinuous phases (channels). The continuous PEG segments impart swelling in water (hydrogel character), the rubbery PIB moieties provide strength, and the PD5 domains provide crosslinking and enhanced O2 permeability. The synthesis involves the random cohydrosilation of various lengths (number‐average molecular weights) of α,ω‐diallyl‐PEG and α,ω‐diallyl‐PIB segments by pentamethylcyclopentasiloxane (D5H) followed by water‐mediated oxidation of the SiH groups of the D5H to SiOH groups, which immediately polycondense to PD5 domains. Membranes containing about equal amounts of PEG, PIB, and PD5 give rise to tricontinuous morphologies that allow the simultaneous permeation of water, heptane, and oxygen via three cocontinuous channels. The number‐average molecular weight of the PEG segment, that is, the number‐average molecular weight of the hydrophilic segment between two PD5 crosslink sites, determines the dimensions (pore sizes) of the channels through which water can permeate. A method has been developed for studying the oxygen permeability of membranes. The microarchitecture of the membranes has been investigated with selective swelling experiments and Fourier transform infrared spectroscopy, their mechanical properties have been examined in the water‐swollen state with Instron measurements, and their bulk morphologies and thermal degradation have been determined with differential scanning calorimetry and thermogravimetric analysis, respectively. The findings have been interpreted in terms of phase‐separated PEG, PIB, and PD5 microdomains. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1209–1217, 2002
Synthesis and properties of poly(ether imide)s based on a benzonorbornane bis(ether anhydride)
Authors: Hsiao Sheng‐Huei , Huang Tai‐Lin 
Published: August 2002

AbstractA novel bis(ether anhydride) monomer, 3,6‐bis(3,4‐dicarboxyphenoxy)benzonorbornane dianhydride, was synthesized from the nitro displacement of 4‐nitrophthalonitrile with 3,6‐dihydroxybenzonorbornane in the presence of potassium carbonate, followed by the alkaline hydrolysis of the intermediate bis(ether dinitrile) and the cyclodehydration of the resulting bis(ether diacid). A series of poly(ether imide)s bearing pendant norbornane groups were prepared from the bis(ether anhydride) with various aromatic diamines via a conventional two‐stage process that included ring‐opening polyaddition to form the poly(amic acid)s followed by thermal imidization to the poly(ether imide)s. The inherent viscosities of the poly(amic acid) precursors were 0.81–1.81 dL/g. The poly(ether imide) with m‐phenylenediamine as a diamine showed good organosolubility. Most of the cast poly(ether imide) films have had high tensile strengths and moduli. The glass‐transition temperatures of these poly(ether imide)s, except for those from rigid p‐phenylenediamine and benzidine, were recorded between 211 and 246 °C by differential scanning calorimetry. The softening temperatures of all the poly(ether imide) films stayed within 210–330 °C according to thermomechanical analysis. No polymers showed significant decomposition before 500 °C in a nitrogen or air atmosphere. A comparative study of the properties with the corresponding poly(ether imide)s without pendant substituents was also made. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1712–1725, 2002
Synthesis, characterization, and in vitro degradation of liquid‐crystalline terpolyesters of 4‐hydroxyphenylacetic acid/3‐(4‐hydroxyphenyl)propionic acid with terephthalic acid and 2,6‐naphthalene diol
Authors: Prasad V. S. , Pillai C. K. S. 
Published: August 2002

AbstractMelt‐processable liquid‐crystalline terpolyesters of 4‐hydroxyphenylacetic acid (HPAA) and 3‐(4‐hydroxyphenyl)propionic acid (HPPA) with terephthalic acid and 2,6‐naphthalene diol were synthesized by one‐step acidolysis melt polycondensation followed by postpolymerization and were characterized with viscosity studies, Fourier transform infrared (FTIR) and NMR spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), polarized light microscopy, and wide‐angle X‐ray diffraction. The melting behaviors and liquid‐crystalline transition temperatures of the terpolyesters were dependent on the composition of the HPAA/HPPA content. The transition temperatures of the polyesters could be effectively reduced by the introduction of an even number of built‐in short methylene spacers in combination with the 2,6‐naphthalene offset structure. A terpolyester with an HPPA content of 33% (NTP33) showed optimum properties for the glass‐transition temperature, around 71 °C, and the melting temperature, near 240 °C, with a Schlieren nematic texture. The polymer showed excellent flow behavior in a Brabender plasticorder. It was also thermally stable up to 400 °C. NTP33 showed 2.5% in vitro hydrolytic degradation in buffer solutions of pH 10 at 60 °C after 540 h. Considerable enzymatic degradation was also observed with porcine pancreas lipase/buffer solutions in comparison with Candida rugosa lipase after 60 days. The degradation was also followed with FTIR, DSC, and TGA. Apart from the temperature and pH of the buffer solution, several structural parameters, such as the aromatic content, crystallinity percentage, and composition of the polymer, affected the degradation behavior. FTIR studies indicated the involvement of chain scission during degradation. Scanning electron microscopy studies further showed that surface erosion also played a major role in the degradation. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1845–1857, 2002
MALDI‐TOF‐MS analysis of living cationic polymerization of vinyl ethers. II. Living nature of growing end and side reactions
Authors: Katayama Hiroshi , Kamigaito Masami , Sawamoto Mitsuo 
Published: August 2002

AbstractMatrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry analysis revealed that the HCl–vinyl ether adduct/SnCl4/n‐Bu4NCl initiating system induced living cationic polymerization of isobutyl vinyl ether in CH2Cl2 at −78 °C, that is, the well‐resolved spectra demonstrated that the produced polymers consist of only one series of polymers carrying one initiator fragment at the α end and one methoxy group originated from quenching with methanol at the ω end. The polymer molecular weight as well as the terminal structure were unchanged even when the reaction mixtures were kept unquenched at −78 °C for an interval of more than five times longer than the reaction period after complete consumption of monomer, which indicates the long lifetime of the living end even under such starved conditions. In contrast, the polymers obtained at a higher temperature, −15 °C, showed an additional minor series of polymers formed via proton initiation, originating from adventitious water. Under the starved conditions, other side reactions occurred to generate minor series of polymers with an aldehyde ω end or a diisobutyl acetal ω end. Rather surprisingly, however, unsaturated CC end groups were not detected, which means the absence of β‐proton elimination under these conditions. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1249–1257, 2001
Hydrazone initiators for vinyl polymerizations
Authors: Wolf Richard A. , Warakomski John M. , Staples Thomas L. , Fazio Michael J. 
Published: August 2002

AbstractA series of hydrazones were prepared and tested for their ability to act as free‐radical initiators for vinyl monomers. The most active initiators were the tertiary butyl hydrazones of aromatic, aliphatic ketones. The most reactive vinyl monomers were acrylate‐type monomers, with methacrylate‐type monomers being somewhat less reactive. When the most reactive hydrazone initiators, such as compound 1, were added to ambient‐temperature solutions of acrylate monomers, such as aqueous sodium acrylate or aqueous acrylamide, polymerizations to hard gels occured within 1 min. In some cases of vinyl polymerizations, these hydrazone initiators can act as low‐temperature alternatives to redox initiators. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1391–1402, 2001
Synthesis, characterization, and crosslinking of novel stars comprising eight poly(isobutylene‐azeotropic‐styrene) copolymer arms with allyl or hydroxyl termini. II. Stars of eight isobutylene/styrene azeotropic copolymer arms emanating from a calix[8]arene core
Authors: Hull Diana L. , Kennedy Joseph P. 
Published: August 2002

AbstractOur objective was the precision synthesis of novel stars consisting of a well‐defined calix[8]arene core out of which radiate eight poly(isobutylene‐aze‐styrene) [P(IB‐aze‐St)] arms fitted with crosslinkable end groups. We reached our objective by preparing the octafunctional calixarene derivative C[8]OCH3, inducing the living azeotropic copolymerization of IB/St charges with the C[8]OCH3/BCl3·TiCl4 initiating system, and end‐quenching living IB/St copolymerizations with allyltrimethylsilane. With this strategy, we obtained stars C[8][P(IB‐aze‐St)CH2CHCH2]8 of various molecular weights. The number of CH2CHCH2 termini of the arms was 8.0 ± 0.2 by quantitative 1H NMR analysis. The eight allyl termini were quantitatively converted to CH2CH2CH2OH termini by hydroboration/oxidation. To confirm that the latter second‐generation stars possessed eight primary alcohol end groups, we quantitatively converted the CH2OH termini to OSi(CH3)3 termini, the concentration of which was quantitated by 1H NMR spectroscopy. According to this analysis, the stars contained 8.0 ± 0.3 hydroxyl termini. The glass‐transition temperatures of the P(IB‐aze‐St) arms increased from 59 to 65 °C as the weight‐average molecular weights of the arms increased from about 2500 to about 4300 g/mol, respectively. The α and K constants of the Mark–Houwink–Sakurada relationship and the intrinsic viscosity of a representative allyl‐telechelic star were determined and compared with a linear azeotropic IB/St copolymer of similar molecular weight. The crosslinking of C[8][P(IB‐aze‐St)CH2CH2CH2OH]8 stars with 4,4′‐methylene bis(phenyl) diisocyanate and 2,4‐tolylene diisocyanate in various solvents afforded tightly crosslinked films of potential interest for scratch‐resistant coatings, mar‐resistant coatings, or both. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1525–1532, 2001
Using polymers to control substrate, ligand, or catalyst solubility
Authors: Bergbreiter David E. 
Published: August 2002

AbstractThe attributes and design of soluble polymer supports for catalysis and synthesis are discussed. By manipulating polymer structure, polymer supports can be prepared so that the solubility of an attached reagent, substrate, or ligand is affected by heating, cooling, pH, or solvent identity. Supports with such engineered solubility are useful both in organic synthesis and catalysis. They can be used as purification handles in organic synthesis as a way to recover catalysts, as a way to turn reactions on or off, and more generally, as a handle for separations. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2351–2363, 2001
Photoinitiated polymerization of methacrylic monomers in a polybutadiene matrix (PB): Kinetic, mechanistic, and structural aspects
Authors: Mateo J. L. , Calvo M. , Bosch P. 
Published: August 2002

AbstractThe kinetics and mechanism of the photoinitiated polymerization of tetrafunctional and difunctional methacrylic monomers [1,6‐hexanediol dimethacylate (HDDMA) and 2‐ethylhexyl methacrylate (EHMA)] in a polybutadiene matrix (PB) have been studied. The maximum double‐bond conversion, the maximum polymerization rate, the intrinsic reactivity, and the kinetic constants for propagation and termination have been calculated. Unlike the behavior followed by the SBS‐HDDMA and PS‐HDDMA systems, where a reaction‐diffusion mechanism occurs from the start of the polymerization at low monomer concentrations (<30–40%), in the PB‐HDDMA system the reaction diffusion controls the termination process only after approximately 10% conversion is reached, as for the bulk polymerization of polyfunctional methacrylic monomers. Before reaching 10% conversion the behavior observed can be better explained by a combination of segmental diffusion‐controlled (autoaccelerated) and reaction‐diffusion mechanisms. This is probably a consequence of the lower force of attraction between the monomer and the matrix and between the growing macroradical and the matrix than those corresponding to the other systems mentioned. For the PB‐EHMA system, the termination mechanism is principally diffusion‐controlled from the beginning of the polymerization for monomer concentrations below 30–40%, and for higher monomer concentrations, a standard termination mechanism takes place (kt ≈ 106) at low double‐bond conversions, which is diffusion‐controlled for high conversions (>40%). For PB‐HDDMA and PB‐EHMA systems, crosslinked polymerized products are obtained as a result of the participation of the double bonds of the matrix in the polymerization process. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2444–2453, 2001
Emulsion polymerization of methyl methacrylate in the presence of novel addition–fragmentation chain‐transfer reactive surfactant (transurf)
Authors: Monteiro Michael J. , Bussels Raf , Wilkinson Terence S. 
Published: August 2002

AbstractReactive surfactants allow the surfactant molecules to become covalently bound to the particles and thus provide added stability to the colloid particles, longer shelf life, better shear resistance, and polymer particles that can be redispersed. This article reports for the first time the use of a novel addition–fragmentation chain‐transfer reactive surfactant (transurf) in ab initio emulsion polymerizations of methyl methacrylate at 70 °C. It was found that the rate was lowered and average particle diameter nearly doubled when the transurf was used as compared with the SDS experiments (control). In addition the molecular weight distribution was very broad but had a lower Mn than observed in the sodium dodecyl sulfate experiment. Unfortunately because of the formation of many water‐soluble oligomers, the amount of transurf incorporated could not be obtained accurately. However, it was estimated theoretically that only a very small amount of transurf would be consumed, but for an alternative method to increase the incorporation of transurf into the particles, the ratio of monomer to transurf must be kept as low as possible. The best way to achieve this would be to carry the experiments out under starved‐feed conditions. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2813–2820, 2001
Synthesis and characterization of soluble polyimides derived from [1,1′;4′,1″]terphenyl‐2′,5′‐diol and biphenyl‐2,5‐diol
Authors: Xu Jianwei , He Chaobin , Chung T.‐S. 
Published: August 2002

AbstractTwo series of polyimides based on laterally attached p‐terphenyl and biphenyl groups were synthesized. The solubility and thermal properties were studied using DSC, thermogravimetric analysis, and the solubility test. These polymers exhibited good thermal stability and excellent solubility. The high solubility for both polymer series was attributed to the non‐coplanarity of diamine monomers and the use of fluorinated dianhydride, whereas the slightly better solubility for polymers based on p‐terphenyl was attributed to further weakening of interchain interaction of the polymers. Both polymer series exhibited glass‐transition temperatures (Tg's) in the range of 244–272 °C. The Tg's of polymers containing laterally attached p‐terphenyls were higher than those of their counterparts containing biphenyls by 5–17 °C. This was attributed to the formation of an interdigitated structure that hinders the segmental movement of polymer chains. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2998–3007, 2001
Synthesis, characterization, and in vitro degradation of thermotropic polyesters and copolyesters based on terephthalic acid, 3‐(4‐hydroxyphenyl)propionic acid, and glycols
Authors: Nagata Minoru , Nakae Masayuki 
Published: August 2002

AbstractA new series of thermotropic liquid‐crystalline (LC) polyesters were prepared from a diacyl chloride derivative of 4,4′‐(terephthaloyldioxy)‐di‐4‐phenylpropionic acid (PTP) and glycols with a different number of methylene groups (n) [HO(CH2)n OH, n = 6–10, 12] by high‐temperature solution polycondensation in diphenyl oxide. PTP6/10 and PTP6/hydroquinone (H) LC copolyesters were also prepared according to a similar procedure. The chemical structure, LC, phase‐transition behaviors, thermal stability, and solubility were characterized by elemental analysis, Fourier transform infrared spectroscopy, 1H and 13C NMR spectra, differential scanning calorimetry (DSC), thermogravimetric analysis, and a polarizing light microscope. The melting and isotropization temperatures decreased in a zigzag manner as the number of n increased. All of the polyesters formed a nematic phase with the exception of PTP8. The temperature ranges of the mesophase (ΔT) were much wider for the polyesters with an odd number of n's than those with an even number. ΔT increased markedly for the PTP6/10 and PTP6/H copolyesters. The in vitro degradations of the polymers were ascertained by enzymatic hydrolysis and alkaline hydrolysis. The model compound, PTP dihexylester, was synthesized and found to be degraded into terephthalic acid, 3‐(4‐hydroxyphenyl)propionic acid, and 1‐hexanol by Rhizopus delemar lipase, but PTPn homopolyesters and PTP6/10 and PTP6/H copolyesters were resistant to Rhizopus delemar hydrolysis. They were degradable in a sodium hydroxide buffer solution of pH 12 at 60 °C, depending on the number of n's and the copolymer composition. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3043–3051, 2001