bluuebunny/crossref_metadata_2025_split huggingface dataset:
Probing organic‐inorganic interactions and curing processes in coatings by photoacoustic fourier transform infrared spectroscopy
Authors: Urban Marek W. , Salazar‐Rojas Evelisse M. 
Published: April 2003

AbstractPhotoacoustic Fourier transform infrared spectroscopy (PA FT‐IR) was utilized to follow the curing processes in pigmented linseed oil based coatings deposited on a substrate. This nondestructive technique allows us to monitor both chemical reactions and processes such as solvent evaporation and pigment stratification during auto‐oxidative curing. Spectroscopically detected solvent evaporation is correlated with the weight loss measurements. Apparently, only a small portion of the solvent molecules evaporates during the curing process and the remaining fraction participates in the crosslinking process.The interactions between organic (binder) and inorganic (pigment) phases of the coatings are also detected. It is found that in order to obtain a uniform distribution of the inorganic phase across the coating, it is necessary to consider both the hydrogen bonding between the two phases and the gravitational forces imposed on the pigment particles. Essentially, a lack of hydrogen bonding leads to stratification of the pigment phase and pigment volume gradient (PVC) across the coating. These processes are monitored spectroscopically and indicate that the hydrogen bonding is equally significant with other processes such as crosslinking and degradation.
Electrical properties of poly‐trans‐2,5‐dimethylpiperazine‐fumaramide. II. Conduction and relaxation processes
Authors: Sandrolini Franco , Motori Antonio , Saccani Andrea 
Published: April 2003

AbstractDc and ac electrical properties of poly‐trans‐2,5‐dimethylpiperazine‐fumaramide samples with different inherent viscosities were investigated as a function of temperature, applied electrical field (dc properties), and frequency (ac properties). Dc electrical conductivity of such a polymer is chiefly electronic below 180°C and ionic above 200°C. Protons coming from unavoidable moisture absorption due to hydrophilic nature of the polymer should be the main source of ionic charge carriers. No usual polymer chains relaxation processes were found, due to the high polymer crystallinity, which does not allow to detect any glass transition. Only slight polarization processes of the interfacial Maxwell‐Wagner‐Sillars type seem therefore to occur in the polymer. No effect of polymer average molecular weight on the dc as well as ac electrical properties was found.
Chemical structure of networks resulting from curing of N,N‐diglycidylaniline‐type resins with aromatic amines. II. Detection and characterization of intermolecular etherification on model compounds
Authors: Attias A. J. , Ancelle J. , Bloch B. , Laupretre F. 
Published: April 2003

AbstractThe reactivity of model compounds representative of the structures resulting from the first steps of curing in uncatalyzed (or LiClO4‐catalyzed) N,N‐diglycidylaniline/aromatic amine systems was studied. The results indicate that the intermolecular etherification either does not occur or is very slow under these conditions. Moreover, the latter situation is observed only in the very specific configuration when two hydroxyl groups are very close to each other. From these experiments, it can be inferred that the most likely reactions occurring after the epoxy‐primary amine addition in uncatalyzed N,N‐diglycidylaniline/aromatic amine systems are the are the epoxy‐secondary‐amine addition and the cyclization reactions discussed in a previous paper.
Poly(Alkylene phosphate)s bearing tetrahydrofuran rings (1,4‐anhydroerythritol) in the main chain
Authors: Lapienis Grzegorz , Penczek Stanislaw 
Published: April 2003

AbstractPoly(alkylene phosphate)s, bearing anhydroerythritol units in the chain, have been prepared by both polycondensation and polymerization methods. The highest molecular weight product (1.3 × 104) has been obtained by polycondensation of trans‐3,4‐dihydroxytetrahydrofuran (1) with bis(diethylamino)methoxyphosphine (2) with further oxidation and dealkylation. Polymerization (anionic) of the corresponding cyclic phosphite of cis‐diol gave lower molecular weight polyphosphite (˜ 3.0 × 103), whereas cyclic phosphoramidite of cis‐diol did not polymerize at all. Microstructure of the polymers has been analyzed on the basis of 1H‐, 13C‐, and 31P‐NMR spectra.
Trimethylsilyl trifluoromethanesulfonate as “initiator” of the cationic polymerization of styrenes
Authors: Lin Chih‐Hwa , Matyjaszewski Krzysztof 
Published: April 2003

AbstractThe cationic polymerization of styrene and p‐methylstyrene has been initiated in the presence of trimethylsilyl trifluoromethanesulfonate. In a dry system, no polymerization was observed. In wet systems, polymers were formed in agreement with earlier reports. In the presence of hindered pyridines, used as proton traps, polymerization has started after complete protonation of the hindered pyridines; at the same time hexamethyldisiloxane was formed. These results indicate that silyl triflates cannot react directly with styrenes, and that initiation proceeds via triflic acid which is formed by hydrolysis of silyl triflate.
A study of XPS O1s spectrum of poly(ethylene terephthalate)
Authors: Nakayama Youichi , Takahagi Takayuki , Soeda Fusami , Ishitani Akira , Kosugi Nobuhiro , Kuroda Haruo 
Published: April 2003

AbstractThe XPS (x–ray photoelectron spectroscopy) O1s spectrum of PET [poly(ethylene terephthalate)] was examined in detail. Spectra of related compounds were also studied for comparison. The O1s peak profile of asymmetric doublet with π–π* satellites characteristic of PET was successfully explained both from comparison with the observed O1s spectra of the related compounds and from ab initio δSCF calculation.
Microemulsion polymerization of styrene: A study using pulsed laser initiation
Authors: Holdcroft S. , Guillet J. E. 
Published: April 2003

AbstractMicroemulsions of styrene were polymerized using pulsed UV lasers. Molecular weights of the polystyrene produced were linearly dependent on the time interval between pulses when the number of photons absorbed per mL of microemulsion was ca. 5 × 1015. In contrast, laser pulses with much higher intensity produced polymers with molecular weights which were nonlinear with laser repetition rate.
Studies of poly(ortho‐acylstyrene)s. II. Photoreactions of poly(o‐acetylstyrene)
Authors: Weir N. A. , Whiting K. , Arct J. 
Published: April 2003

AbstractPoly(o‐acetylstyrene) (POAS) films were exposed under vacuum conditions to long wave ultraviolet radiation (λ ≥ 300 nm). Gaseous products, determined quantitatively by mass spectrometry, were methane, ethane and CO (trace), their formation indicating that POAS was undergoing Norrish Type I photodecompositions. Quantum yields for CH4 and C2H6 formation were more than an order of magnitude lower than the corresponding values for the isomeric poly(vinylacetophenone) (PVAP). Transient spectral measurements at 390 nm indicate the presence of enols (syn and anti), which result from the photoenolization of the ketone. Lifetimes are 161 and 4500 ns, respectively. The polymer undergoes crosslinking, the rate being much lower than that of PVAP. The mechanisms of the reactions are discussed, and it is proposed that the photostability of POAS (relative to PVAP) is the result of photoenolization, which competes favourably with degradation. POAS has considerable potential in sunlight storage applications.
Control of Y1Ba2Cu3Ox microstructures by polymer‐metal‐complex precursor synthesis
Authors: Chien James C. W. , Gong Ben Ming , Mu Xiangi , Yang Yingsong 
Published: April 2003

AbstractSingle phase Y1Ba2Cu3Ox material (1,2,3‐compound) have been synthesized from polymer‐metal‐complex (PMC) precursor between 860 and 950°C using a reaction time as short as 0.5 h. The morphology of the films and of fibers prepared by this process have been investigated. At low calcination temperatures the material is comprised of submicron grains, which are extensively interconnected forming a natural percolation network. Nodules with outgrowths are formed at intermediate temperatures; oblong shaped discs are obtained at high temperatures. The size and shape of grains are remarkably uniform in a given preparation; the former increases monotonically with the increase of calcination temperature. The 1,2,3‐compounds produced are pure according to x‐ray; they possess good superconducting properties (Tc (midpoint) = 90.6 K; ΔTc (90%‐10% resistivity) < 1 K) as prepared. Similar control of grain size and microstructure has been achieved for fibers of the 1,2,3‐compound, the mechanical strength of which is inversely related to grain size. Pure Y2Ba1Cu2O5 has also been prepared by the precursor method. X‐ray diffraction gave unit cell dimension of a = 12.18 Å, b = 5.66 Å and c = 7.13 Å belong to Pnma or P space group.
Analytical and kinetic approaches for the basic type of MgCl2‐supported high yield catalysts
Authors: Terano Minoru , Kataoka Takuo , Keii Tominaga 
Published: April 2003

AbstractThermal analysis in combination with infrared spectroscopy was applied to investigate the states of ethylbenzoate (EB) and TiCl4 in the simple type of the MgCl2‐supported high‐yield catalysts. A further attempt was made to evaluate kinetic parameters in the initial stage of propylene polymerization (< 1s) by a stopped flow method. The catalysts employed in the present study were prepared by co‐grinding MgCl2 and TiCl4 · EB complex. Thermal analysis and infrared spectroscopy showed that TiCl4 · EB complex decomposes during co‐grinding process. It was also indicated that EB, thus produced, has strong interaction with MgCl2. This was consistent with observations made by infrared spectroscopy. It was deduced that EB and TiCl4 are supported at separate sites of MgCl2 in the co‐ground catalyst. Kinetic parameters including rate constants of propagation (kp) and transfer (ktr), and concentration of polymerization centers ([C*]) were determined. The values of kp and ktr remained almost constant throughout the range of co‐grinding time, but [C*] increased with time of co‐grinding. No significant changes in the value of ktr were observed. Accordingly, the improvement of catalyst activity was attributed to an increase in [C*] rather than kp. These results lead to the conclusion that the complex decomposes during the co‐grinding to yield EB and TiCl4 which interact only with MgCl2.
Attachment of fluorescent dyes to polyacrylamides in aqueous media
Authors: Borg Robert , Winnik Mitchell A. 
Published: April 2003

AbstractFluorescent derivatives of polyacrylamide can be prepared by reacting an acidic aqueous solution of the polymer with xanthenol and dibenzosuberenol. These reactions take advantage of the carbocation stability of these dyes when they are treated with acid (i.e., pKR+ values near zero). In this way the O‐alkylated amide that one expects to be formed is too unstable to persist, and, eventually, the stable N‐alkylated derivative is formed. UV absorption and fluorescence spectra for the labelled polymers are reported. The presence of the dye affects the hydrophobic–hydrophilic balance of the polymer.
A new method for the production of large spherical monosized polymer particles for biomedical and chromatographic applications
Authors: Colvin M. , Chung S. K. , Hyson M. T. , Chang M. , Rhim W. K. 
Published: April 2003

AbstractMonosized droplets of 2‐hydroxyethyl methacrylate (HEMA) and glycerol monomethacrylate (GMA) were made by passing the monomers under pressure through a nozzle coupled to an energized piezoelectric crystal. The droplets were allowed to fall into liquid nitrogen where they vitrified. The radiation post‐polymerization of the monomer spheres was investigated. Uniform monosized poly‐HEMA particles in the 100–300 μm diameter range were prepared with a coefficient of variation of 1.57% for particles of 155 μm in diameter. Monosized poly‐GMA was also prepared. The post‐polymerization conversion of pre‐irradiated GMA vitrified monomer droplets as a function of thawing rate and radiation dosage was investigated.
Copolymerization kinetics of 4‐methoxystyrene with methyl methacrylate and 4‐methoxystyrene with styrene: A test of the penultimate model
Authors: Piton Mark C. , Winnik Mitchell A. , Davis Thomas P. , O'driscoll Kenneth F. 
Published: April 2003

AbstractThe propagation kinetics for the copolymerization of 4‐methoxystyrene with methyl methacrylate and 4‐methoxystyrene with styrene have been investigated using a pulsed laser technique. The dependence of the copolymerization propagation rate constant on the monomer feed ratio shows a diviation from classic Mayo–Lewis model kinetics for 4‐methoxystyrene with methyl methacrylate but not for 4‐methoxystyrene with styrene. These results have been interpreted to indicate that a penultimate effect is apparent in the first monomer pair but not in the second. With r1r2 = 0.092 for the copolymerization of 4‐methoxystyrene with methyl methacrylate and r1r2 = 0.95 for 4‐methoxystyrene with styrene, it is suggested that a deviation of the product of the coplymerization reactivity ratios from unity may be an indication of the presence of a penultimate effect.
Aqueous polymerization on clay surfaces. V. Role of lattice substituted iron in montmorillonite in polymerizing methyl methacrylate in the presence of thiourea
Authors: Bhattacharyya J. , Saha S. K. , Guhaniyogi S. C. 
Published: April 2003

AbstractThe aqueous polymerization of methyl metacrylate in the presence of thiourea and hydrogen montmorillonite was initiated by radicals generated in situ. A part of the polymer was bound to the clay. Electrochemical analysis by cyclic voltammetry on this system and FeCl3/thiourea indicated that a slow one‐electron transfer process was responsible for the formation of the amidosulfenyl radical. The oxidant in the clay was lattice substituted Fe3+.
Imide–aryl ether benzoxazole block copolymers
Authors: Hedrick J. L. , Hilborn J. , Palmer T. D. , Labadie J. W. , Volksen W. 
Published: April 2003

AbstractImide–aryl ether benzoxazole multiblock copolymers were investigated. A key feature of these copolymers is the preparation of bis(amino) aryl ether benzoxazole (PBO) oligomers via nucleophilic aromatic substitution. The molecular weights of the oligomers were 10,500 and 26,000 g/mol with T'gs of 210 and 227°C, respectively. The oligomers were co‐reacted with 4,4′‐oxydianaline (ODA) and pyromellitic dianhydride (PMDA) diethyl ester diacyl chloride in a N‐methyl‐2‐pyrrolidone/cyclohexanone solvent mixture in the presence of N‐methylmorpholine. The resulting amic ethyl ester‐aryl ether benzoxazoles were isolated and washed to remove homopolymer contamination. Copolymer compositions, determined by 1H‐NMR, ranged from 7 to 54 wt% PBO and the measured compositions were close to those charged. Solutions of the copolymers were cast and cured (350°C) to effect imidization producing clear films. The films showed tough ductile mechanical properties (∼50% elongations) with moduli comparable to PMDA/ODA polyimide. The copolymers displayed good thermal stability with decompositions temperatures in excess of 450°C. Multiphase morphologies were observed irrespective of PBO block lengths or compositions. Good auto‐adhension was achieved in the copolymers containing the high PBO compositions.
Liquid crystalline properties of the copolyesters prepared from n‐octylhydroquinone, resorcinol, and 1,4‐bis(4‐carboxyphenoxy) butane
Authors: Rami Reddy C. , Kameswara Rao K. , Jin Jung‐Il , Lenz Robert W. 
Published: April 2003

AbstractA series of copolyesters was prepared by the melt reaction of a mixture of n‐octylhydroquinone and resorcinol in varying ratios with 1,4‐bis(4‐chloroformylphenoxy)butane. Resorcinol was used as a comonomer to study the effect of a nonmesogenic structural unit on the thermotropic properties of a main chain liquid crystalline polyester with a flexible spacer. The effect of a tetramethylene spacer was compared with that of a longer, decamethylene spacer, which was included in similar copolyesters reported earlier by us. The inclusion of resorcinol units in increasing amounts destroyed the ability of the copolyesters to crystallize, as expected, and the copolymer containing as low as 20 mol % resorcinol showed no melting transition on analysis by differential thermal analysis (DSC). In contrast, the ability to form a liquid crystalline phase persisted until at least 40 mol % resorcinol was present. As expected, the isotropization temperature and the enthalpy and entropy changes for isotropization decreased with increasing non‐mesogenic comonomer content.
Effect of the way of addition of the reactants in the graft copolymerization of a vinyl acetate–methyl acrylate mixture onto cellulose
Authors: Fernandez M. J. , Casinos I. , Guzman G. M. 
Published: April 2003

AbstractIn order to graft a vinyl acetate–methyl acrylate mixture onto cellulose, an exploration of the way of addition of the reactants has been made. The influence of several factors on the grafting parameters was studied, i.e., the order of addition of the ceric ion initiator and the monomer mixture, the removal of the ceric ion solution after a cellulose‐ceric ion contact time, and the delayed addition along the polymerization period of the more reactive monomer (methyl acrylate) towards the cellulosic radicals. Some grafting parameters were determined: grafting yield, grafting efficiency, cellulose conversion, molecular weight, ceric ion consumption, grafting frequency, number of grafted chains, and synthetic copolymer composition. After a short period (ca. 15 min) for the ceric adsorption on cellulose, a fast formation of cellulosic radicals arises in the initial stages of the polymerization. These initial cellulosic radicals should be trapped by a sufficiently reactive monomer if high grafting yield and high number of grafted chains are to be reached. A portion of the synthetic polymer chains anchored to cellulose that are formed in the first stages of the polymerization, which are generated from cellulosic hemiacetal groups, should constitute block copolymer.
A method for the extraction of the unreacted cellulose from its graft copolymers
Authors: Fernandez M. J. , Casinos I. , Guzman G. M. 
Published: April 2003

AbstractThe extraction of the ungrafted cellulose allows us to know some grafting parameters as the cellulose conversion and the true frequency of grafting. The extraction of the unreacted cellulose from cellulose‐g‐poly(vinyl acetate‐co‐methyl acrylate) was tried by several approaches but only one of them has been successful. The other attempts have failed because an undesired chemical modification of the synthetic grafted polymer occurs while the unreacted cellulose was extracted. The method proposed here is particularly suggested for the cellulose extraction from its graft copolymers whose grafted chains arise from acrylic and vinylic esters. The effect of the reaction time on the graft polymerization of the vinyl acetate‐methyl acrylate mixture onto cellulose was also studied. The very similar average composition of grafted polymer and homo‐copolymer suggests that the polymerization site is the same for both types of growing chains.
Polymerization of epoxides in the presence of tertiary amino alcohols
Authors: Vazquez A. , Matĕjka L. , S̆pac̆ek P. , Dus̆ek K. 
Published: April 2003

AbstractPolymerizations of phenyl glycidyl ether (PGE) and the diglycidyl ether of Bisphenol A (DGEBA) were initiated with tertiary amino alcohols. The reaction was followed by means of HPLC and IR spectroscopy. The main products isolated from the reaction mixture were identified by using mass spectrometry. The sol fraction and the critical conversion at the gel point were determined for the crosslinking polymerization of DGEBA.Three series of oligomers arise from three initiating centers during the polymerization of PGE. In addition to the amino alcohol—a product of the secondary amine addition to the epoxy group—the phenol arising in the reaction mixture also acts as an initiator. The third oligomer series propagates by an anionic mechanism from a quaternary ammonium base originating from the reaction of PGE with the amino alcohol. Formation of the new initiating centers during the reaction results in a decrease in the molecular weight of the polymer relative to the value predicted from the amount of initiator initially added. The relative content of products of the particular oligomeric series in the reaction mixture depends on temperature and on the concentration of the initiator.
Phthalocyanine polymers. I. Synthesis and characterization of fused copper phthalocyanine polymers
Authors: Liao Ming Sy , Kuo Kung‐Tu 
Published: April 2003

AbstractFused copper phthalocyanine polymers have been prepared by reacting an equimolar mixture of pyromellitic dianhydride and phthalic anhydride with urea, ammonium chloride, ammonium molybdate, and copper sulfate via a baking method. The products have been characterized by elemental analyses, infrared, near‐infrared, UV/VIS spectroscopies and conductivity measurement. It has been found that: (1) the reaction temperature must exceed 350°C during this synthesis to obtain product of good yield and higher molecular weight; (2) a high reaction temperature favored the reaction of PA with PMDA to form polymer; (3) the peripheral end groups of the crude products, untreated with acid or base, were imide structures; (4) additional vacuum and heat treatment increased the purity and structural uniformity and, therefore, increased the conductivity of polymers.
Kinetics of emulsifier‐free emulsion polymerization of styrene
Authors: Song Zhiqiang , Poehlein Gary W. 
Published: April 2003

AbstractThe influence of initiator concentration, monomer/water ratio, reaction temperature, and agitator speed on the kinetic behavior of emulsifier‐free emulsion polymerization of styrene with potassium persulfate initiator has been investigated. Polymerization rate and the particle number increased with increasing initiator concentration and reaction temperature. The particle size distribution became broader as the initiator concentration decreased. Monomer conversion, at a common time, was smaller when the initial monomer/water ratio was increased. Particle size, at the same conversion, increased with an increasing initial monomer charge. High agitator speed caused significant particle coagulation. As a result, a smaller number of larger particles with broad size distribution were produced when the agitation was intense. Reaction rate decreased with increasing agitator speed. The two‐stage model developed in this paper can describe the kinetics of emulsifier‐free emulsion polymerization of styrene when potassium persulfate is used as initiator. Values of the termination rate constant, ktp, obtained from fitting the model to the experimental data are in agreement with ktp data reported in the literature for emulsion polymerization. ktp increases with increasing agitator speed because of a reduced gel effect. The rate coefficient for particle coagulation, Kf, increases with decreasing initiator concentration, with decreasing reaction temperature and with increasing agitator speed. The rate coefficient for radical capture by particles, kc, increases with increasing reaction temperature and with increasing agitator speed.