bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preparation of sulfonyl aromatic polyamides and copolyamides by means of di‐ or triphenyl phosphite
Authors: Yang Chin‐Ping , Hsiao Sheng‐Huei , Huang Ching‐Jung 
Published: April 2003

AbstractHigh molecular‐weight aromatic polyamides were obtained by the direct polycondensation reaction of 4,4′‐sulfonyldibenzoic acid (SDA) with various aromatic diamines, by means of di‐ (DPP) or triphenyl phosphite (TPP) in N‐methyl‐2‐pyrrolidone (NMP)‐pyridine solution containing metal salts such as LiCl and CaCl2. The factors affecting the phosphorylation reaction were investigated, in particular for the reaction of SDA and 4,4′‐oxydianiline (ODA). For the polymerization by means of TPP, the optimum conditions are: molar ratio of TPP to diacid, higher than 2.3; concentration of metal salts, 8 wt % LiCl or 6 wt % CaCl2; reaction temperature, 100°C; and monomer concentration, 0.4 mol/L. For the polymerization by means of DPP, the optimum conditions are: molar ratio of DPP to diacid, higher than 3.8; concentration of metal salts of 8 wt % LiCl or 10 wt % CaCl2; reaction temperature, 110°C; and monomer concentration, 0.4 mol/L. Copolyamides were also prepared from the reaction of ODA with the mixed diacids of SDA and other dicarboxylic acids such as terephthalic acid, isophthalic acid, and 2,6‐naphthalene dicarboxylic acid by using TPP and DPP as the condensing agents.
Accessibility of the gel phase in macroporous network polymers: A comparison of the fluorescence probe and inverse steric exclusion chromatography techniques
Authors: Jerábek K. , Shea K. J. , Sasaki D. Y. , Stoddard G. J. 
Published: April 2003

AbstractTwo independent methods of analysis were employed to evaluate accessibility of the gel phase in macroporous network polymers. Fluorescence probes, covalented incorporated into the gel during polymerization, can provide a qualitative assessment of accessible surface area from an analysis of the solvatochromic shift of fluorescence emission. These findings are corroborated by inverse steric exclusion chromatography (ISEC). The data permits quantification of the polymers surface character in the solvated state. The results call attention to the inadequacy of dry surface area technique (e.g., BET analysis) in providing information of this type.
Catalytic aminolysis of acrylic copolymers in solution and in the melt. I. Mechanism and kinetics
Authors: Hu G. H. , Holl Y. , Lambla M. 
Published: April 2003

AbstractThe aminolysis of poly(styrene‐co‐methyl acrylate) (SMA) by octadecylamine was studied in solution and in the melt at temperatures around 200°C. This reaction is rather slow, so several types of catalysts were tested to accelerate it. The most efficient is 2‐pyridone, a compound in tautomeric equilibrium with 2‐hydroxypyridine. A mechanism of the catalytic reaction is proposed whereby the tautomeric nature of the catalyst plays a key role in a very important step of the reaction, namely the proton transfer. This mechanism is confirmed by the kinetic data determined in a 1,2,4‐trichlorobenzene solution and in the melt. In addition, it was found that the kinetic data obtained in both media are very close, indicating no significant difference of local polarity in the two reaction media. Data also show only a minor effect due to difference in viscosity. Finally, the question of the homogeneity of the molten medium is discussed.
Catalytic aminolysis of acrylic copolymers in solution and in the melt. II. Comparison between styrenic and ethylenic copolymers
Authors: Hu G. H. , Lorek S. , Holl Y. , Lambla M. 
Published: April 2003

AbstractThe aminolysis of poly(styrene‐co‐methyl acrylate) (SMA) by octadecylamine in solution and in the melt has been reported in Part I. We now have studied the aminolysis of poly(ethylene‐co‐methyl acrylate) (EMA) with the same amine in the melt and compared the two sets of data in this paper. With EMA, the data confirmed and precised the catalytic mechanism proposed in Part I. The best tautomeric catalysts are the ones which form an eight‐atom ring structure with the ester and amine groups. With EMA aminolysis is faster than with SMA because of the steric hindrance of phenyl groups in SMA. But EMA aminolysis remains a rather slow reaction. In a corotating twin‐screw extruder the conversion was only around 4% at 220°C with a mean residence time of 150 s. It was also shown that the EMA/octadecylamine/catalyst system, like the SMA system, is homogeneous in the molten state at temperatures around 200°C.
Poly(N‐acylethylenimine) copolymers containing pendant pentamethyldisiloxanyl groups. I. Synthesis
Authors: Cai Gangfeng , Litt Morton H. 
Published: April 2003

Abstract10‐(Pentamethyl disiloxanyl) decyl oxazoline (Si) was synthesized. It was copolymerized with either undecyl (U) or nonyl (N) oxazolines using methyl 4‐nitrobenzenesulfonate as initiator. Two series of random poly(N‐acylethylenimine) copolymers, U/Si and N/Si, were synthesized over the whole composition range of Si monomer with a total degree of polymerization of about 100. Narrow molecular weight distributions were obtained. At a monomer to initator ratio of about 1060, the final degree of polymerization was 374 with a polydispersity index of 1.93. This shows the effect of chain transfer in this system.
Poly(N‐acylethylenimine) copolymers containing pendant pentamethyldisiloxanyl groups. II. Thermal behavior and x‐ray diffraction study
Authors: Cai Gangfeng , Litt Morton H. 
Published: April 2003

AbstractTwo series of random copolymers of 10‐(pentamethyl disiloxanyl) decyl oxazoline (Si) with undecyl (U) (four copolymer compositions) and nonyl (N) (eight copolymer compositions) oxazolines over the whole composition range, with a total degree of polymerization of about 100, were studied by DSC and wide angle X‐ray diffraction. All the polymers are crystalline. For the N/Si copolymers, the melting points, normalized ΔH and ΔS of fusion are almost constant in a broad range of copolymer composition from 10 to 65 mol % of Si. The rationale for this behavior is that the copolymers crystallize two dimensionally, with the crystalline polymethylene plates separated by the bulky flexible pentamethyl disiloxanyl (P) groups. In this range, increasing Si only increases the distance between the plates. With more than 65 mol % Si, the bulky P groups interfere with the packing of the alkyl chains and change the crystallization behavior; the polymers show disordered packing as demonstrated by their X‐ray patterns and extremely low ΔH. In the U/Si copolymers, since the undecyl side chain has one more carbon than the decyl group to which the P group is attached, the P groups interfere much more strongly with the packing of the side chains than in the N/Si polymers. The copolymer melting points uniformly decrease as the concentration of Si increases. The plateau on the plot of normalized ΔH versus polymer composition is only from 10 to 50 mol % of Si. The average long spacings of the annealed polymers increase linearly from 24 Å (N/Si polymers) or 28 Å (U/Si polymers) to 34.1 Å with the increase of Si up to 50%. With more than 50% Si, the polymers have an identical lamellar thicknesses of 34 Å, within the experimental error. Copolymers with less than 75 mol % of Si can crystallize from hexadecane solutions forming gels down to polymer concentrations of 2‐3 wt %. The long spacings of the gels are almost identical with those of the pure crystalline polymers and independent of the polymer/solvent ratios. When hexamethyl disiloxane is added to the solutions, it can intercalate and the resulting crystalline gels have long spacings larger than those found in the absence of siloxane.
Polymerization of vinylcyclohexane with ziegler–natta catalyst
Authors: Endo Kiyoshi , Otsu Takayuki 
Published: April 2003

AbstractPolymerization of vinylcyclohexane (VCHA) with TiCl3–aluminum alkyl catalysts was investigated. The polymerization rate of VCHA was low due to the branch at the position adjacent to the reacting double bond. The effects of aluminum alkyl on the polymerization and monomer‐isomerization were observed; the polymer yield decreased in the following order: (CH3)3Al > (i–C4H9)3Al > (C2H5)3Al. Isomerization of VCHA was observed with the TiCl3–(i–C4H9)3Al and the TiCl3–(C2H5)3Al catalysts during the polymerization, while with the TiCl3–(CH3)3Al catalyst such isomerization was not observed. Monomer‐isomerization copolymerization of VCHA and trans‐2‐butene took place to give copolymers consisting of VCHA and 1‐butene units.
Particle nucleation and monomer partitioning in styrene O/W microemulsion polymerization
Authors: Guo J. S. , Sudol E. D. , Vanderhoff J. W. , El‐Aasser M. S. 
Published: April 2003

AbstractParticle nucleation in the polymerization of styrene microemulsions was found to take place throughout the polymerization as indicated by measurements of the particle number as a function of conversion. A mechanism based on the nucleation in the microemulsion droplets was proposed to explain the experimental findings although homogeneous nucleation and coagulation during polymerization were not completely ruled out. A thermodynamic model was developed to simulate the partitioning of monomer in the different phases during polymerization. The model predicts that the oil cores of the microemulsion droplets were depleted early in the polymerization (4% conversion). Due to the high monomer/polymer swelling ratio of the polymer particles, most of the monomer resides in the polymer particles during polymerization. The termination of chain growth inside the polymer particles was attributed to the chain transfer reaction to monomer. The low n̄ (less than 0.5) of the microemulsion system was attributed to the fast exit of monomeric radicals.
Synthesis and characterization of bismaleimides from epoxy resins
Authors: Park Jung O. , Jang Sung H. 
Published: April 2003

AbstractNovel bismaleimides (BMIs) were prepared from functional monomaleimides and diglycidyl ether of bisphenol A (DGEBA) and some of them were shown to have good processibility and improved water resistance while retaining characteristic thermal stability of polyimide. Functional monomaleimides were synthesized via the condensation reaction of maleic anhydride with either aminobenzoic acid or aminophenol. Crosslinking reaction of thus obtained BMIs was carried out with or without catalyst at the temperature range of 100–250°C. The type of the functional group species and their position in monomaleimides significantly affected the crosslinking behavior of the resulting BMIs and the thermal property of their crosslinked products. BMIs with meta linkage, obtained from meta monomaleimides, exhibited much faster thermal crosslinking behavior than corresponding para BMIs. When the molecular weight of BMI was larger, the crosslinking density became smaller and Tg was lower as expected, while the viscosity started to increase at a higher temperature. Glass transition temperatures of the crosslinked resins were in the range of 160–250°C and these resins showed excellent thermal stability up to 370°C.
Molecular weight distribution in emulsion polymerization. II. The copolymer case
Authors: Storti Giuseppe , Polotti Gianmarco , Canu Paolo , Morbidelli Massimo 
Published: April 2003

AbstractA model for evaluating instantaneous degree of polymerization distribution and the chain composition distribution of copolymers produced in emulsion is developed. The approach adopted is based on the mathematics of Markov processes and represents an extension of the one developed for homopolymers in Part I. As in the homopolymer case, the main aspect of the theoretical treatment is the definition of the proper one step transition probability matrix through the so called subprocess‐main process procedure. The model accounts for monomolecular and bimolecular termination (both by combination and disproportionation) and, in principle, it can be applied to any number of reacting monomer species as well as to any number of active chains per particle. However, only the 0–1–2 and 0–1–2–3 emulsion copolymerization systems are discussed in detail. In the case of the chain composition distribution, the model allows the calculation of its moments only, through the method of the Generating Function associated with the probability density function. The expression obtained for the instantaneous probability density functions, as well as for the corresponding cumulative distributions, are all in explicit form and involve only algebraic operations among matrices. Efficient numerical procedure for their application are reported in the Appendix. Illustrative calculations are reported for a 0–1–2–3 copolymerization system, simulating the copolymer styrene–methylmethacrylate. The effect of the various termination mechanisms on the distribution of degrees of polymerization and on the first two moments of the chain composition distribution is discussed in detail. Finally, the three dimensional overall distribution function of both chain length and composition is shown under the assumption of Gaussian type chain composition distribution.
Template polymerization of N‐vinylimidazole along poly(methacrylic acid) in water. VI. Crosslinked PMAA as template
Authors: Van De Grampel H. T. , Santing A. G. M. , Tan Y. Y. , Challa G. 
Published: April 2003

AbstractThe effect of crosslinked poly(methacrylic acid) (c‐PMAA) on the polymerization of N‐vinylimidazole in aqueous solution was studied using UV, calorimetry, SEM, and TEM. It was established that synthetic lightly crosslinked PMAA samples behaved intermediate between rigid crosslinked PMAA particles functioning as microreactors, and linear conventional PMAA, where template and conventional polymerization in the surrounding solution are integrated. A modified calorimetric technique was used to measure monomer conversion, and to correct for the rapid adsorption process. Rate enhancements up to a factor of 4 were obtained for the c‐PMAA's, which were lower than those obtained for linear conventional PMAA, and which slightly decreased with increasing crosslink density of the samples. Template complexes possessed a platelet‐like morphology similar to template complexes obtained for linear PMAA.
Selective vinyl polymerization of 4‐vinyl‐1‐cyclohexene with ziegler–natta catalyst
Authors: Endo Kiyoshi , Fujii Kazuyoshi , Otsu Takayuki 
Published: April 2003

AbstractThe polymerization of 4‐vinyl‐1‐cyclohexene (4VCHE) with Ziegler–Natta catalysts was studied. The polymerization of 4VCHE by the vinyl group took place with TiCl3–aluminum alkyls catalysts, while vinylene group of 4VCHE did not participate in the reaction, but it affected the polymerization rate of 4VCHE. The effects of aluminum alkyl and type of TiCl3 on the polymerization were examined. The overall activation energy for the polymerization was estimated to be 41.9kJ/mol. Monomer‐isomerization copolymerization of 4VCHE and trans‐2‐butene occurred with the TiCl3‐(i‐C4H9)3Al catalyst to give copolymers consisting of 4VCHE and 1‐butene units.
Flame‐retardant modification of UV‐curable resins with monomers containing bromine and phosphorus
Authors: Guo Wenjeng 
Published: April 2003

AbstractUV‐curable urethane acrylate resin and oligoester acrylate resin have been effectively flame retarded with vinyl‐type flame‐retardant monomers containing both bromine and phosphorus atoms. Thermogravimetric analysis indicates that the decomposition temperature of flame‐retardant monomer is more closely matched to the decomposition temperature of cured oligoester acrylate resin than to that of cured urethane acrylate resin. The efficiency of each flame‐retardant monomer in oligoester acrylate resin is higher than in urethane acrylate resin by a factor of ∼ 2.2. The individual and the combined effects of tribromophenyl acrylate and triphenyl phosphate on the oxygen index of UV curable urethane acrylate resin have been studied. The bromine phosphorus synergistic action of the two flame‐retardant components is evaluated quantitatively, and a maximum intermolecular bromine phosphorus synergism was observed in a flame‐retarded formulation containing a Br/P atom ratio of 2. In the three acrylic monomers containing both bromine and phosphorus atoms, the optimum intramolecular bromine phosphorus synergism was observed at a monomer also containing a Br/P atom ratio of 2.
Interpenetrating polymer networks of poly(carbonate‐urethane) and polyvinyl pyridine
Authors: Zhou Peiguang , Frisch Harry L. , Ghiradella H. 
Published: April 2003

AbstractSimultaneous interpenetrating polymer networks (IPN's), pseudo IPN's, and liner blends of aliphatic poly(carbonate‐urethane) (PCU) and polyvinyl pyridine (PVP) have been prepared and characterized by DSC, DMA, and TEM. The full IPN's of PCU and PVP had a single phase morphology only above 50 wt % PCU, as determined by both DSC and DMA and confirmed by transmission electron microscopy (TEM). However, in both pseudo IPN's of PCU and PVP and in their linear blends there exist multiple glass transitions and melting points seen by DSC and DMA indicating phase incompatibility. The full IPN's exhibited superior ultimate mechanical properties and solvent resistance as compared to the pseudo IPN's, liner blends, and the pure crosslinked PCU and PVP networks.
Consistent values of rate parameters in free radical polymerization systems. II. Outstanding dilemmas and recommendations
Authors: Buback M. , Gilbert R. G. , Russell G. T. , Hill D. J. T. , Moad G. , O'Driscoll K. F. , Shen J. , Winnik M. A. 
Published: April 2003

AbstractThe problems of determining reliable, well‐characterized values of kinetic parameters in free‐radical polymerizations are discussed. The origins of the fact that experimental determinations of rate coefficients of ostensibly identical systems often result in quite different values being reported can be ascribed to subtle mechanistic assumptions made in data interpretation, which are considered in detail. A series of recommendations to assist in overcoming these problems, and to highlight their origins, are presented, with emphasis placed on new techniques including those employing laser photolysis and EPR.
The mechanism of core–shell inversion in two‐stage latexes
Authors: Lee Sharon , Rudin Alfred 
Published: April 2003

AbstractIn two‐stage latexes where the first polymer is more hydrophilic than the second, inversion of the core and shell can occur. The mechanism of core–shell inversion during the initial and final intervals of the second‐stage polymerization was investigated using model PMMA/PS systems. The phase behavior of polymer solutions intended to model the two‐stage system during the initial interval of the second stage polymerization has yielded some insight into the thermodynamics of phase inversion. If the second stage monomer dissolves first stage polymer, the latter will tend to precipitate at the water/monomer interface, particularly in the presence of surfactant. The energy of the oil/water interface is thereby reduced. In the final interval, when much of the second monomer has polymerized, phase mobility is crucial to the inversion process.
Effect of degradation on thermotropic cholesteric optical properties of (2‐hydroxypropyl) cellulose (HPC) esters
Authors: Rusig I. , Dedier J. , Filliatre C. , Godhino M. H. , Varichon L. , Sixou P. 
Published: April 2003

AbstractSome esters of (2‐hydroxypropyl) cellulose have been prepared and studied. Their cholesteric properties change with ageing and may disappear. Accelerated aging has been performed in order to analyze degradation processes which are relevant to the scission of the polymeric main chain and to the hydrolysis of the ester bonds which are mainly due to traces of water. The necessity of carefully elaborate purification is highlighted.
Mechanistic studies of the oxidative coupling polymerization of phenols. VI. Comparison of reactivities of DMP, PPO‐dimer, and ‐trimer in the copper‐catalyzed oxidative coupling polymerization
Authors: Viersen F. J. , Renkema J. , Challa G. , Reedijk J. 
Published: April 2003

AbstractIn the oxidative coupling polymerization, catalyzed by copper‐amine complexes, the oxidation rates of 2,6‐dimethylphenol (DMP) and its CO‐coupled dimer [4‐(2′,6′‐dimethylphenoxy)‐2,6‐dimethylphenol] and trimer [4‐(‐4′‐(2″,6″‐dimethylphenoxy)‐2′,6′‐dimethylphenoxy))‐2,6‐dimethylphenol] have been determined. The DMP concentration dependence shows a Michaelis–Menten‐type behavior. On the other hand, the dimer and trimer showed a first‐order rate‐dependence in the respective phenol concentrations. This indicates that the slow reaction step, following an equilibrium complex formation between DMP and copper complex, is relatively fast for both the dimer and the trimer. Therefore, coordination of dimer or trimer to the copper complex appears to be rate‐determining. Furthermore, the dimer and trimer gave overall reaction rates approximately eight times higher than found for DMP. Following the Flory principle of equal reactivity for functional groups of oligomers in polycondensations, all PPO oligomers can be assumed to have equally high oxidation rates as the dimer and trimer. The yield of undesired DPQ side product is strongly reduced when starting with the dimer (0.18%), or trimer (0.17%), compared to 3.3% for DMP. This is not unexpected, since DPQ can only be formed from two monomeric DMP residues. In fact, using a 1/10 molar mixture of dimer/DMP already results in a DPQ yield of only 1.7%. Furthermore, when starting from DMP, it has been observed that DPQ was predominantly formed during the first 30% conversion. Starting from dimer (or trimer) DPQ was formed at an almost constant very low rate during the whole course of the reaction. From these experiments it can be concluded that the most important polymerization reaction involves oxidation of copper‐coordinated DMP anion to its corresponding cations, followed by coupling with a copper coordinated PPO chain.
Poly(1,3‐cyclohexadiene‐alt‐α‐fluoroacrylonitrile): Synthesis and structural analysis of a new alternating copolymer
Authors: Panchalingam V. , Reynolds John R. 
Published: April 2003

AbstractPoly(1,3‐cyclohexadiene‐alt‐α‐fluoroacrylonitrile) [poly(1,3‐CHD/α‐FAN)], an alternating copolymer of α‐fluoroacrylonitrile and 1,3‐cyclohexadiene has been prepared in bulk using varied monomer feed ratios and AIBN as initiator at 65°C. Elemental and 1H‐NMR analyses indicate that the copolymer contains an equimolar composition of α‐FAN and 1,3‐CHD as observed for alternating copolymers with donor‐acceptor polymerizations. A 2‐D 1H‐COSY NMR experiment indicates that the copolymer contains 1,4‐linkages across the cyclohexene unit while more reliable 13C‐NMR spectra suggests the copolymer to contain both 1,2‐ and 1,4‐linkages. Poly(1,3‐CHD/α‐FAN) exhibits improved thermal stability relative to the alternating copolymer of 1,3‐CHD and α‐chloroacrylonitrile due to a higher resistance to HF elimination relative to HCl elimination.
Effect of the reaction state on the polymerization of p‐xylenesulfonium salts
Authors: Garay R. O. , Lenz R. W. 
Published: April 2003

Abstract1,4‐Phenylenebis(methylene) sulfonium salts were polymerized under different conditions to yield p‐xylylene sulfonium salt polyelectrolytes in a broad range of molecular weights. The aqueous reaction mixture formed a reversible gel at initial monomer concentrations higher than 1.0M, but at lower concentrations it remained as an emulsion until reaction completion. The effect of reaction time on intrinsic viscosities and polymer yields for both the emulsion and the gel state is discussed. The higher yields obtained when the reaction was carried out in the presence of a water‐immiscible organic solvent were apparently due to the effect of this solvent on increasing the concentration of the reactive intermediate that led to the polyelectrolyte. Both the addition of an organic solvent and the variation of the initial monomer concentrations allowed some control over the molecular weight of the polyelectrolyte formed.