bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis and characterization of poly(t‐butyl methacrylate‐b‐isoprene‐b‐t‐butyl methacrylate) block copolymers by anionic techniques
Authors: Long T. E. , Broske A. D. , Bradley D. J. , McGrath J. E. 
Published: April 2003

AbstractPoly(t‐butyl methacrylate‐b‐isoprene‐b‐t‐butyl methacrylate) block copolymers have been synthesized in a controlled manner by anionic techniques. The block copolymers demonstrated predictable chemical composition and stereochemistry, and narrow molecular weight distributions. The addition of a polar solvent was required after complete conversion of the diene block in order to preserve the high 1,4 microstructure of the diene phase and to facilitate the efficient crossover to the poly(t‐butyl methacrylate) lithium enolate. Thermomechanical analysis (TMA) of the triblock copolymers demonstrated a microphase separated morphology. The glass transition temperatures of the diene phase and acrylic phase were approximately −70 and 120°C, respectively. Cast films of the block copolymers from polar and nonpolar solvents were optically clear and elastic.
The interaction of hydrogen and ammonia plasmas with polymethacrylic esters, studied by static secondary ions mass spectrometry
Authors: Lub J. , Van Vroonhoven F. C. B. M. , Benninghoven A. 
Published: April 2003

AbstractThe interactions of H2 and NH3 plasmas with the surfaces of various poly(alkylmethacrylate)s and of poly(phenylmethacrylate) have been studied with XPS and SSIMS. Experiments on poly(methylmethacrylate) reveal that during short treatment times with the NH3 plasma chain, scission takes place and nitrogen is not incorporated into the surface. The chain scission also takes place with the H2 plasma. With the aid of SSIMS results, the nature of the chain scission could be deduced. Comparison of these results with those on poly(n‐butylmethacrylate) and poly(t‐butylmethacrylate) reveals a reaction mechanism in which hydrogen atoms generated in both plasmas play an important role in the chain scission process. After longer treatment time with the NH3 plasma, the poly(methylmethacrylate) surface becomes deoxygenated and nitrogen is incorporated into surface structures of low molecular weight. Experiments on poly(phenylmethacrylate) reveal that already during short treatment times with the NH3 plasma, nitrogen is incorporated into the aromatic ring. Chain scission does not play an important role. One of the processes with the H2 plasma is hydrogenation of the aromatic ring, leading to poly(cyclohexylmethacrylate).
Syntheses and properties of polysulfides containing spiroorthocarbonate moiety
Authors: Tagoshi Hirotaka , Endo Takeshi 
Published: April 2003

AbstractPolysulfides (PI and PII) having spiroorthocarbonate moiety in the main chain were synthesized by the polyaddition of unsaturated spiroorthocarbonate (1 or 2) and dithiols in excellent yields. It is confirmed by DSC and x‐ray measurement that PII is the crystalline polymer. PI and PII were treated with a cationic catalyst such as BF3 · OEt2 and BzS+SbF to afford the crosslinked polymer and to partially undertake the main chain scission. Further, it was also found in the reaction of PI and PII with adipoyl chloride as the crosslinking reagent that PI underwent cleavage of the main chain, but PII mainly gave crosslinked polymers.
A new differential scanning calorimetry based approach for the characterization of peracid resin
Authors: Hsiue Ging‐Ho , Huang Wen‐Kuei , Chu Hsiao‐Lung 
Published: April 2003

AbstractDifferential scanning calorimetry was used to trace the heat of decomposition of the peracid groups (ΔHd) in the oxidized EVA‐g‐AA resin. From the correlation between ΔHd and the oxidation capacity measured by iodometry, it was found that 35 ± 5 cal of energy evolved per miliequivalent of peracid group decomposed. The ΔHd values are also useful in finding the optimum condition for oxidation of acid groups and can be used to investigate the distribution of active peracid groups across the matrix. The stability and the activation energy of decomposition of grafted type peracid resin were also studied, where the activation energy of decomposition was calculated to be 13.4 kcal/mol.
Emulsifier‐free emulsion copolymerization of styrene and butyl acrylate. I. Kinetic studies in the absence of surfactant
Authors: Guillaume J. L. , Pichot C. , Guillot J. 
Published: April 2003

AbstractSoapless emulsion copolymerization of styrene (S) and n‐butyl acrylate (BuA) has been investigated using two types of initiator and different comonomer feed mixtures. When using K2S2O8 as initiator, the particle size and size distribution of the final latexes (500 nm and 1.003, respectively) is not significantly affected by the comonomer feed composition, whereas the molecular weight and surface characteristics were found to sharply change at high butyl acrylate content. Based on the most probable particle nucleation mechanism and type of chain termination in the monomer swollen particles, a tentative explanation of these results has been proposed. Replacing persulfate by a carboxylic initiator (4‐4′‐azobiscyanopentanoic acid) results in the formation of stable particles as α observed with the persulfate, provided the aqueous phase pH is fixed in between 6 and 7. Results on the initiator residue location as a function of the conversion point out that the particle flocculation mechanism is strongly significant in the preparation of such latexes.
Head‐to‐head vinyl chloride–vinyl acetate copolymer
Authors: Tarshiani Y. , Dreyfuss M. P. 
Published: April 2003

AbstractAddition chlorination of cis‐1,4‐polybutadiene in the presence of acetic acid as a cosolvent resulted in the formation of head‐to‐head vinyl chloride–vinyl acetate copolymer. Chlorine analysis, IR, and NMR spectra of the chlorinated polybutadiene indicated that reaction was primarily double bond addition; there was little evidence for substitutive chlorination. Acetate was incorporated by nucleophilic participation of the acetic acid cosolvent. The extent of incorporation of the acetate group in the polymer chain was a function of the acetic acid concentration. Both the glass transition temperatures and the densities of the chloroacetylated polymers decreased as the degree of acetylation increased.
Preparation and properties of aromatic polyamides and aromatic polyesters derived from 4,4′‐sulfonyldibenzoic acid
Authors: Manami Hiroshi , Nakazawa Mikio , Oishi Yoshiyuki , Kakimoto Masa‐Aki , Imai Yoshio 
Published: April 2003

AbstractAromatic polyamides (aramids) having inherent viscosities of 0.3–1.6 dL/g were prepared by the direct polycondensation of 4,4′‐sulfonyldibenzoic acid with various aromatic diamines using triphenyl phosphite and pyridine as condensing agents. Aromatic polyesters (polyarylates) with inherent viscosities of 0.3–1.2 dL/g were prepared by the phase‐transfer catalyzed, two‐phase polycondensation of 4,4′‐sulfonyldibenzoyl chloride with various bisphenols. Most of the aramids and some polyarylates were soluble in a variety of solvents such as dimethylacetamide, N‐methyl‐2‐pyrrolidone, and m‐cresol, and afforded transparent, flexible, and tough films from the polymer solutions. The aramids and the polyarylates had glass transition temperatures in the range of 200–350 and 260–310°C, respectively. These polymers containing sulfonyl group did not lose weight below 350°C, with 10% weight loss being recorded above 430°C in air.
Synthesis of the acetylacetone telechelate of polydimethylsiloxane and its gelation with Cr(III) and Fe(III)
Authors: Liao I‐Wei , Eichinger B. E. 
Published: April 2003

AbstractThe batch synthesis of acetylacetone end‐capped polydimethylsiloxane is described. Efforts to end‐link the telechelic polymer with several simple metal salts yielded poorly gelled systems, except for the cases where FeCl3 and CrCl3 · 3THF were used. With these salts, low but nonetheless appreciable, gel fractions of 45 and 40%, respectively, were obtained. The difficulty experienced in obtaining high gel fractions is traced to incomplete ligand exchange reactions in low polarity media.
Preparation and photochemical properties of poly[2‐(4‐benzoylphenyl)‐2‐(4‐propenoylphenyl)‐propane] and its copolymer with styrene
Authors: Lukáč Ivan , Evans Christopher H. , Scaiano J. C. , Hrdlovič Pavol 
Published: April 2003

Abstract2‐(4‐Benzoylphenyl)‐2‐phenyl propane (4) was prepared by benzoylation of 2,2‐diphenylpropane (2). Acylation of (4) with 3‐chloropropanoic chloride gave 2‐(4‐benzoylphenyl)‐2‐(4‐propenoylphenyl)propane (5). A monomer 2‐(4‐benzoylphenyl)‐2‐(4‐propenoylphenyl)propane (6) was prepared through dehydrochlorination of (5). The homopolymer of 6 (P6) and the copolymer with styrene (P6 / S) were prepared by radical polymerization. Laser flash photolysis was employed to determine the absorption and emission spectra of transients, their lifetimes (τ) and the rate constant (kq) of triplet quenching in benzene at laboratory temperature for 4, P6, and P6 / S. P6 exhibits a transient absorption maximum in a different spectral region than do the model 4 and copolymer P6/S. The products of kq and τ determined by laser flash photolysis for these transients are higher than th Stern–Volmer constants based on inhibition of degradation. Degradation leading to formation of quenchers is the likely cause of this difference although crosslinking may also contribute. Irradiation of polymers (P6 and P6/S) at 366 nm leads to main chain scission with aquantum yield of 0.13 under N2 for P6 and 0.03 for P6/S. In this bichromophoric structural unit, the benzophenone residue absorbs about 80–90% of the incident energy. Its triplet energy is about 5 kJ mol−1 lower than that of the 1‐(4‐alkylphenyl)‐2‐propene‐1‐one chromophore. Different possible pathways of degradation are discussed namely the Norrish Type II reaction of the alkyl aryl ketone and direct reaction of triplet benzophenone with the main chain. In the mechanism favored the benzophenone triplet is proposed to be in equilibrium with the upper acetophenone‐like chromophore from which the Norrish Type II reaction leading to chain fragmentation takes place.
Thermotropic liquid crystalline poly(L‐glutamate) esters with long alkyl chain containing aromatic segment at terminal position
Authors: Hanabusa Kenji , Yanagisawa Kuniko , Higashi Jun‐Ichi , Shirai Hirofusa , Hayakawa Tadao , Hojo Nobumasa 
Published: April 2003

AbstractPoly(L‐glutamate) esters (3a–3d) with long alkyl side chains containing a mesogenic aromatic segment at the terminal position were synthesized. The superstructure of these polypeptides in solution and film were found to hold a α‐helical conformation which was confirmed by CD, IR, and dichroic IR spectroscopy. The thermotropic liquid crystalline behavior was investigated by DSC, x‐ray diffraction, and polarizing microscopy with hot stage. Polymers 3a and 3b, having transesterification over 60%, were assumed at least to have two liquid crystalline states. Polymer 3c‐H‐95 exhibited one crystalline state and two liquid crystalline states; however, 3d‐H‐97 did not show distinct liquid crystalline states.
Preparation and properties of brominated poly(arylcarboxylate)s via interfacial polycondensation
Authors: Yang Chin‐Ping , Hsiao Sheng‐Huei 
Published: April 2003

AbstractThe interfacial polycondensation method has been used for the preparation of brominated poly(arylcarboxylate)s. Brominated poly(arylcarboxylate)s can be prepared easily by mixing a solution of diacid chloride in a water‐immiscible organic solvent with an aqueous alkaline solution of bisphenol in the presence of catalyst such as quaternary ammonium salts. First, in a dichloromethane‐water system using triethylbenzylammonium chloride (TEBAC) as the catalyst a series of 2,2‐bis(4‐hydroxy‐3,5‐dibromophenyl)propane (3,3′,5,5′‐tetrabromobisphenol A, TBBPA) with isophthaloyl (I) and terephthaloyl chlorides (T) has been prepared and some properties as inherent viscosity, solubility, crystallinity, and flammability have been measured. Copolymers prepared from TBBPA and mixed T/I with 33/67–67/33 molar ratios show good solubility and amorphous nature, and can be cast into transparent and tough films with limiting oxygen index of 58–59 (ANSI/ASTM D2683‐77). Second, the effects of some variables as the nature of organic phase and catalysts, concentration of reactants, and basicity of aqueous phase on the interfacial polycondensation of TBBPA with equal parts of T and I [T/I (50/50)] was investigated in some detail. Among the solvents tested dichloromethane was found to be the best solvent and quaternary ammonium salts such as TEBAC and tetra‐n‐butylammonium bromide (TBAB) were highly efficient catalysts. Poly(arylcarboxylate)s with the highest molecular weights were obtained at an acid chloride concentration of 0.2 mol/L in dichloromethane and a concentration of TBBPA of 0.1 mol/L in alkali when TEBAC was used as catalyst. A maximum of inherent viscosity was obtained at two equivalent amounts of alkali corresponding to bisphenol. Polycondensation of several combinations of T/I (50/50) with some other tetrabromobisphenols, such as 3,3′,5,5′‐tetrabromo‐4,4′‐biphenol, 3,3′,5,5′‐tetrabromobisphenol S, 3,3′,5,5′‐tetrabromo‐4,4′‐thiodiphenol, and 3,3′,5,5′‐tetrabromophenolphthalein, were carried out with limited success. Whereas, a more favorable result could be obtained by the mixed copolycondensation of these tetrabromobisphenols and bisphenol A (BPA) with T/I (50/50). Finally, the copoly(arylcarboxylate)s from TBBPA, BPA, T, and I were prepared and characterized. The incorporation of bromine on the polymer backbone caused a decrease of inherent viscosity, glass transition temperature, crystallinity, and thermal stability of copolyarylates, whereas it caused a great enhancement of flame retardancy.
The synthesis and XPS characterization of iodine containing plasma polymers
Authors: Munro Hugh S. , Ward Richard J. , Khor Eugene 
Published: April 2003

AbstractPlasma polymers derived from iodobenzene and four copolymers with benzene of varying monomer ratios have been synthesized. Samples were analyzed for qualitative and quantitative information using x‐ray photoelectron spectroscopy. The optimum conditions whereby a higher iodine content is obtained in the plasma polymer have been achieved. The results indicate that the use of a copolymerization approach is better. These plasma polymers were subsequently exposed to an oxygen plasma and it was found that oxidation and etching of the surfaces of the plasma polymers does occur. The extent of iodine loss via oxygen plasma etching appears dependent on the character of the plasma polymer.
The influence of total monomers concentration and polymerization solvent on the “reactivity” of ω‐(p‐vinylbenzyl ether) macromonomers of poly(2,6‐dimethyl‐1,4‐phenylene oxide)
Authors: Percec Virgil , Wang James H. 
Published: April 2003

AbstractThe influence of the total monomers concentration and of the copolymerization solvent on the reactivity ratio, r1, of methyl methacrylate (MMA) (M1) ω‐(p‐vinylbenzyl ether) macromonomer of poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO–VBE) (M2) monomer pair was investigated. For two different molecular weights of PPO‐VBE macromonomers: Mn = 15,200 and Mn = 5,100, the determined reactivity ratio, r1, decreases with the increase in macromonomer concentration. Therefore the reactivity of the macromonomer, 1/r1, follows the opposite trend. The influence of monomers concentration on r1 is higher for higher molecular weight macromonomers. The nature of polymerization solvent also affects the value of reactivity ratio, r1. Micelle formation was demonstrated by 1H‐NMR spectroscopy performed on the resulting graft copolymers in different solvent mixtures. An attempt to explain the observed concentration and solvent effects based on the partition of comonomer concentrations between the bulk of solvent and around the growing chain is presented. Based on this explanation, the determined r1 represents a product of the partition coefficient, k, and the true reactivity ratio, r10.
Amphiphilic block copolymers of vinyl ethers by living cationic polymerization. II. Synthesis and surface activity of macromolecular amphiphiles with pendant amino groups
Authors: Kanaoka Shokyoku , Minoda Masahiko , Sawamoto Mitsuo , Higashimura Toshinobu 
Published: April 2003

AbstractAmphiphilic block polymers of vinyl ethers (VEs).\documentclass{article}\pagestyle{empty}\begin{document}$\rlap{--} [{\rm CH}_{\rm 2} {\rm CH}\left( {{\rm OCH}_{\rm 2} {\rm CH}_{\rm 2} {\rm NH}_{\rm 2} } \right)\rlap{--} ]_m \rlap{--} [{\rm CH}_{\rm 2} {\rm CH}\left( {{\rm OR}} \right)\rlap{--} ]_n \left( {{\rm R: }n{\rm - C}_{{\rm 16}} {\rm H}_{{\rm 33}} ,{\rm }n{\rm - C}_{\rm 4} {\rm H}_{\rm 9} ;m \simeq 40,{\rm n} = 1 - 10} \right)$\end{document} were prepared, each of which consists of a hydrophilic segment with pendant primary amino groups and a hydrophobic poly(alkyl VE) segment. Their precursors were obtained by the HI/I2‐initiated sequential living cationic polymerization of an alkyl VE and a VE with a phthalimide pendant (CH2 = CHOCH2CH2Im; Im; phthalimide group), where the segment molecular weights and compositions (m/n ratio) could be controlled by regulating the feed ratio of two monomers and the concentration of hydrogen iodide. Hydrazinolysis of the imide functions gave the target polymers which were readily soluble in water under neutral conditions at room temperature. These amphiphilic block polymers lowered the surface tension of their aqueous solutions (0.1 wt%, 25°C) to a minimum ≃ 30 dyn/cm when the hydrophobic pendant R was n‐C4H9 (n = 4–9). The polymers with n‐C4H9 pendants in the hydrophobic segment exhibited a higher surface activity than those with n‐C16 H33 pendants. The surface activity of the polymers also depended on the pH of the polymer solutions; the surface activity increased in more basic solutions where the ionization of the amino group (NH2)2NH3⊕) is suppressed.
Catalytic hydrogenation activity of zerovalent palladium dispersed in functional porous polystyrene matrices
Authors: Bar‐Sela G. , Warshawsky A. 
Published: April 2003

AbstractZerovalent palladium catalysts, dispersed within functional, porous, crosslinked styrene‐divinylbenzene copolymers were prepared by impregnation of lipophylic [(C8H17)2NH+][PdCl4 = ] complexes followed by reduction with hydrazine or formaldehyde. A qualitative survey of the catalytic reactivity in hydrogenation of various alkenes differing in substitution degrees (styrene, +‐methylstyrene, etc.), and competitive reduction of exo/endo bonds (4‐vinylcyclohexene) was performed. The functional groups in the polymer, 2,4‐dinitrophenyl, aminomethyl, methoxybenzyl, dialkylaminomethyl, and pseudocrown were shown to have a major effect on catalyst activity. In the two series of polymeric supports, the polymeric adsorbents (Amberlites XAD‐2, XAD‐4, and XAD‐7) and functionalized Amberlite XE‐305, the general trend indicated preference of Pd0 catalysts dispersed on hydrophobic π‐acceptor type supports over hydrophobic supports, over polar basic or hydrophilic supports. This is generally true for both non‐polar (e.g., styrene) and polar (e.g., allylacrylate) olefins. The most active catalysts, carrying 2,4‐dinitro phenyl groups, also showed higher selectivity in reduction of the exo over endo double bond in 4‐vinylcyclohexene, in comparison to commercial Pd/C catalyst. Electron microscopy (SEM) showed very little change in the inner porous polymer structure and almost homogeneous metal distribution profiles. TEM provided particle sizes. The activity of the catalyst was 8‐fold higher with the smallest crushed particles (0.05–0.12 μm) than with the large (600 μm) noncrushed beads. The catalyst showed exceptional stability on storage (98% activity after 1 year) and marginal loss of activity after 21,000 catalytic cycles per Pd atom.
Triphase catalysis. I. Kinetics and mechanism of alkylation of phenylacetonitrile with alkyl halides catalyzed by aqueous naoh and polymer‐supported benzyltriethylammonium chloride
Authors: Balakrishnan T. , Babu S. Hari , Perumal A. 
Published: April 2003

AbstractThe alkylation and cycloalkylation of phenylacetonitrile (PAN) with excess of 1‐bromobutane and 1,4‐dibromobutane respectively catalyzed by aqueous NaOH and insoluble polystyrene‐bound benzyltriethylammonium chloride were studied and the rates depend upon several experimental parameters. The rate of cycloalkylation of PAN is five times faster than the alkylation and the former proceeds even in the absence of the solid catalyst. Both alkylation and cycloalkylation gave higher rates in reverse addition method than in direct addition. Deprotonation of PAN by hydroxide ion takes place without participation of the polymeric catalyst. The electrostatic force between the positive charge on the nitrogen atom of catalyst and carbanion is responsible for alkylation of active nitrile with polystyrene‐bound phase‐transfer catalyst. The rates of both the reactions increase with increased stirring speed, ring substitution, hydroxide ion concentration and catalyst amount and decrease with increased particle size and the degree of cross‐linking of the polymer. Apparent activation energies for the reactions were calculated. The kinetic results are discussed in terms of mass transfer and a combination of intraparticle diffusion and intrinsic reactivity limitations of the rates.
Thermal decomposition and carbonization mechanism of poly‐para‐phenyleneoxadiazole
Authors: Murakami M. , Yumoto Y. , Mizogami S. , Yasujima H. , Naitoh S. , Yoshimura S. 
Published: April 2003

AbstractThermal decomposition and carbonization mechanism of poly‐para‐phenylene‐1,3,4‐oxadiazole were investigated using FT‐IR, thermogravimetry, gas‐analysis, XPS, 13C‐CP/MASFT‐NMR, and elemental analysis. At temperatures above 500°C, the decomposition reaction proceeds preferentially on the oxadiazole ring, eliminating p‐aminocyanobenzene and p‐dicyanobenzene. Formation of carbodiimide compounds and their coupling followed in residual compounds, whose products are important intermediates leading to a planar and polyconjugated nitrogen‐containing (e.g., graphite‐like) carbon precursor.
Activation energy for urethane‐linkage formation. An improved calculation from the differential scanning calorimetry data
Authors: Hernández‐Sánchez F. , Vázquez‐Torres H. 
Published: April 2003

AbstractDifferential scanning calorimetry (DSC) has been utilized in several studies on polymerization kinetics, at different heating rates. However, there are several factors affecting the precision of kinetic parameters. In this work, the activation energy of urethane‐bond formation between 2,6‐tolylene diisocyanate and diethylene glycol is reported, the latter being in excess in order to minimize problems such as thermal transitions and incomplete reaction in the final step. The DSC technique was applied at different heating rates. Both the equal conversion and equal conversion rate options of the method are discussed. The latter appears to be a more adequate option for the system studied here. The results obtained show a good agreement with the model used.