bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis of macromolecular antioxidants by reaction of aromatic amines with epoxidized polyisoprene, 3. Reaction of 4‐anilinoaniline with epoxidized 1,4‐polyisoprene
Authors: Jayawardena Shanthilal , Reyx Danièle , Durand Dominique , Pinazzi Christian Pierre 
Published: April 2003

Abstract4‐Anilinoaniline (6) reacts with expoxidized 1,4‐polyisoprene in toluene under phenol catalysis. Secondary cyclization reactions are detected at longer reaction times (≧ 18 h). However, the kinetic results, obtained at the beginning of the reaction and for limited phenol concentrations, agree with a mechanism involving a trimolecular transition state and a concerted transfer.
Polymer‐supported bases, 2. Polystyrene‐supported 1,8‐diazabicyclo[5.4.0]undec‐7‐ene as reagent in organic syntheses
Authors: Tomoi Masao , Kato Youichi , Kakiuchi Hiroshi 
Published: April 2003

AbstractPolystyrene‐supported 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (PDBU) was prepared by the reaction of lithiated 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU) with chloromethylated or ω‐bromoalkylated polystyrene resins. PDBU is effective as reagent for dehydrobromination and esterification. The reactivity of PDBU in dehydrobromination is lower than that of DBU. In the case of esterification, PDBU with 19% ring substitution exhibits almost the same reactivity as DBU. PDBU, regenerated from the hydrobromide salt, can be re‐used without decrease in reactivity.
Sequence distribution and glass transition of vinyl alcohol/n‐alkyl vinyl carbonate copolymers
Authors: Arranz Félix , Sánchez‐Chaves Manuel , Molinero Ana 
Published: April 2003

Abstract13C NMR spectroscopy was used for the determination of the sequence distribution in vinyl alcohol‐ethyl vinyl carbonate copolymers prepared by reaction of poly(vinyl alcohol) with ethyl chloroformate. The 13C NMR spectra of the methylene carbons in the main chain show three split peaks whose intensities change with copolymer composition. These peaks can be assigned to the three dyad sequences. The obtained results show that ethyl vinyl carbonate units have an alternating tendency in the copolymer chain. The Tg values of the vinyl alcohol‐ethyl vinyl carbonate and vinyl alcohol‐butyl vinyl carbonate copolymers are influenced by both the overall copolymer composition and the monomer sequence distribution.
Concentration dependence of the Flory‐Huggins parameter at different thermodynamic conditions
Authors: Schotsch Kurt , Wolf B. A. , Jeberien Hans‐Edwin , Klein Joachim 
Published: April 2003

AbstractBy means of data from critical demixing and vapour pressure measurements and by inverse gas chromatography, including the results of published light scattering measurments, a consistent picture is obtained for the entire dependence of the Flory‐Huggins parameter χ on the weight fraction w2 of the polymer and on the temperature T for the system tert‐butyl acetate/polystyrene. Within the entire T‐range (ca. 0°C – 140°C), χ increases stronger than exponentially with w2, the rise being the larger the larger χH (the enthalpy contribution to χ) becomes in the limit of infinite dilution. At sufficiently high temperatures (≳ 50°C), χH changes its sign from negative to positive as w2 is raised. This behaviour, as well as the general shape of χ(w2) is in qualitative accord with the results of the corresponding‐states theory as developed by Flory et al.
Elastic and quasielastic light scattering studies on the branching characteristics of dextrans
Authors: Fahner Eva M. , Großmann Georg H. , Ebert Klaus H. 
Published: April 2003

AbstractThe influence of branching on the radius of gyration and the hydrodynamic radius of dextran macromolecules was studied by elastic and quasielastic light scattering (ELS and QELS). The hydrodynamic radius is more sensitive to low levels of branching than the radius of gyration. At higher branching levels a saturation of the hydrodynamic radius rh is observed, while the radius of gyration rG still changes distinctly. The ratio rG/rh proves to be a measure of the flexibility of the macromolecules; the latter is increasing with molecular weight for short linear chains and is decreasing with increasing degree of branching. Measurements were carried out in water (thermodynamically good solvent) and in ethylene glycol (under theta conditions) on four series of dextran fractions having rather narrow molecular weight distributions.
Kinetics of polymerization of styrene with butoxy titanium trichloride and diethylaluminium chloride
Authors: Sehra Jagdish C. , Gundiah Subbaraya 
Published: April 2003

AbstractThe kinetics of the polymerization of styrene, using H3C(CH2)3OTiCl3/Al(C2H5)2Cl as catalyst, was examined in a vacuum dilatometer. The polymerization rate was found to decrease continuously with time and the initial and overall rates vary linearly with the catalyst concentration, exhibiting a nearly second‐order and first‐order dependence, respectively, with regard to the monomer. The decrease of the rate with time is attributed to the chemical deactivation of the sites.
The stereoregularity of poly(methyl methacrylate)s formed in the presence of highly syndiotactic poly(methyl methacrylate)s
Authors: Matsuzaki Kei , Kanai Taiichi , Ichijo Chikara , Yuzawa Makoto 
Published: April 2003

AbstractMethyl methacrylate (MMA) was radically polymerized in the presence of highly syndiotactic deuterated or undeuterated poly(methyl methacrylate)s. In contrast to observations found in the literature no increase in isotacticity was observed. The stereoregularity of the polymers formed in the presence of an undeuterated PMMA as matrix was found by 1H NMR spectroscopy to be about the same as that in polymers prepared without any matrix, except the polymers formed in the early stage of polymerization which show a little lower syndiotacticity. Determinations of triad tacticities of polymers formed in the presence of deuterated PMMA, gave values of syndiotacticity a little higher than in the case of undeuterated matrixes. The polymer formed in the graft copolymerization of MMA onto pre‐irradiated syndiotactic PMMA was fractionated by GPC. The high molecular weight fraction showed a lower syndiotacticity than that of lower molecular weight.
Anionic polymerization of exo‐3,4,5‐trithiatetracyclo[5.5.1.O2,6.O8,12]tridec‐10‐ene (dicyclopentadiene trisulfide)
Authors: Baran Teresa , Duda Andrzej , Penczek Stanistaw 
Published: April 2003

AbstractThe anionic polymerization of exo‐3,4,5‐trithiatetracyclo[5.5.1.O2,6.O8,12]tridec‐10‐ene (1) in bulk and/or in aromatic solvents (benzene, toluene) was studied. The polymerization was initiated with sodium benzenethiolate (sodium cation complexed with dibenzo‐18‐crown‐6). Polymers with high‐molecular weights were obtained (Mn ≈ 105, osmometrically). The polymerization was found to be living and reversible; the equilibrium monomer concentration increases with the temperature. The ceilling temperature was estimated as 167°C. The thermodynamic data of the polymerization in toluene was determined and compared with those of the polymerization of exo‐3,4,5‐trithiatricyclo[5.2.O2,6]decane. The standard enthalpy ΔH = −(6,6 ± 0,6)kJ · mol 1 and entropy ΔS = −(29,3 ± 2,1)J · mol 1 · K 1 of the polymerization of 1 were evaluated from the temperature dependence of the equilibrium monomer concentration, determined dilatometrically.
Rapid succinoylation of cellulose in methanesulfonic acid
Authors: Hirabayashi Yasuhiko , Allan G. Graham 
Published: April 2003

AbstractThe reaction of cellulose with succinic anhydride in nonaqueous methanesulfonic acid under hetero‐or homo‐geneous conditions at 25°C was studied. Homogeneous reaction conditions minimized the formation of crosslinking diester linkages, but during the initial period of heterogeneous succinoylation, topochemically restricted reactions generated crosslinked cellulose derivatives which were not soluble in dilute alkali.
Ethylene‐propene copolymerization in the presence of a 13C enriched catalyst: End group analysis and monomer reactivities in the first insertion steps
Authors: Ammendola Paolo , Vitagliano Aldo , Oliva Leone , Zambelli Adolfo 
Published: April 2003

AbstractEthylene and propene were copolymerized in the presence of an isotactic specific 13C enriched catalyst. The 13C enriched end groups in the copolymers were detected by 13C NMR analysis. The resonances of the enriched carbons of the end groups could be assigned and the relative reactivities of the monomers in the insertion steps occurring at the beginning of the copolymerization were determined.
Ziegler‐Natta polymerization of 1‐alkenes: relative reactivities of some monomers toward insertion into metal‐methyl bonds
Authors: Ammendola Paolo , Zambelli Adolfo 
Published: April 2003

AbstractThe relative reactivities of ethylene, 1‐butene and 3‐methyl‐1‐butene in the insertion reaction into the metal‐methyl bond of the active site of the catalytic system δ‐TiCl3/Al(13CH3)3/Zn(13CH3)2 are determined by 13C NMR end groups analysis. The relative reactivities of propene, 3‐methyl‐1‐pentene and 3‐ethyl‐1‐pentene are also calculated from previous data. Some correlations between relative reactivities and reaction mechanism are proposed.
The sedimentation behaviour of polystyrene in various solvents in semidilute solutions
Authors: Huang Tianbao , Meyerhoff Günther 
Published: April 2003

AbstractSedimentation coefficients of S of polystyrene covering a broad range of molecular weights M, are measured in toluene and 2‐butanone in the semidilute regime. The results are compared with literature data using a plot of S · NA · η/(1 − νρ) = M · η/f versus concentration c, allowing experiments in different solvents of different density ρ and viscosity η to be compared (ν: partial specific volume of polymer; f: friction coefficient; NA: Avogadro number). According to scaling theory for concentrations higher than a critical concentration c, linear plots are to be expected. This is true for the theta‐solvent cyclohexane, but for the theta‐solvent cyclopentane as well as for the thermodynamically semi‐good and good solvents bent curves are obtained, the slopes of which turn toward a limiting value for high M and low c. The theoretical values of the slope for theta‐solvents (−1) is well represented by both theta‐solvents. For the semi‐good and good solvents the experimental limiting slopes are (slightly) lower than the predicted ones. With samples of still higher M becoming available this difference might become more pronounced.
Crystallinity of methylene‐oxyethylene‐methylene triblock oligomers. A study of the C21, C26 and C30 di‐n‐alkyl ethers of pentadecaethylene glycol
Authors: Yeates Stephen G. , Teo Hoon Hong , Booth Colin 
Published: April 2003

AbstractBlock oligomers of general formula H(CH2)nO(CH2CH2O)15(CH2)nH, where n = 21, 26 and 30, were prepared. Both the oxyethylene and the alkyl blocks are homogeneous. Examination of their crystalline structure (by X‐ray scattering, Raman and IR spectroscopy and differential scanning calorimetry) reveals two characteristic forms: type II formed on slow crystallisation of oligomers with n = 21 or 26, and type III b formed on rapid crystallisation of oligomers with n = 26 or 30. Structure II has unfolded chains in a completely crystalline layer structure, with helical oxyethylene blocks and planar zig‐zag alkyl blocks. Structure III b has once‐folded chains in a partly crystalline layer structure, with non‐crystalline planar zig‐zag oxyethylene blocks and crystalline planar zig‐zag alkyl blocks.
13C NMR characterization of branched structures in polyesters resulting from the reaction of maleic and phthalic anhydride with 1,2‐propanediol
Authors: Judas Didier , Fradet Alain , Maréchal Ernest 
Published: April 2003

AbstractSeveral model compounds were synthesized in order to study the side reactions taking place during the synthesis of polyesters, especially chain branching due to the addition of hydroxyl groups to maleate or fumarate double bonds. Diesters or polyesters from 1,2‐propanediol with fumaric acid and various dialkyl alkoxysuccinates were used as models. Their synthesis and characterization are described. The interpretation of their 13C NMR spectra is reported. These spectra are compared with those of the diesters and polyesters of phthalic acid previously described and with the spectrum of a commercial unsaturated polyester. It was possible to identify and to assign the various end groups and the structures resulting from chain branching.
The effects of various catalysts in the in‐situ precipitation of reinforcing silica in polydimethylsiloxane networks
Authors: Jiang C.‐Y. , Mark J. E. 
Published: April 2003

AbstractA variety of inorganic and organic acids, bases, and salts were studied as catalysts for the hydrolysis of tetraethyl orthosilicate, the reaction previously employed for the precipitation of silica within already‐cured elastomeric networks of polydimethylsiloxane. These substances were compared with regard to the amount of silica precipitated at room temperature, and the extent of reinforcement as judged by the upturns in the stress‐strain isotherms at high elongations. On this basis, the acids were the least effective and the salts the most effective.
Dimethylsiloxane‐ethylene oxide block copolymers, 1. Microphase separation of low segment mass copolymers and their compatibility with water and oil
Authors: Haesslin Hans W. , Eicke Hans F. , Riess Gerard 
Published: April 2003

AbstractTernary phase diagrams of linear tri‐block and multi‐block copolymers consisting of poly(dimethylsiloxane) with a constant segment mass of M̄n = 103 and varying poly(oxyethylene) segment masses in the range 100 ≤ M̄n ≤ 2000 with water and oil (cyclohexane) are reported. Also binary mixtures of the same copolymers with water and oil are investigated by differential scanning calorimetry (DSC). Microphase separation of the copolymers and different states of water are detected as a function of composition and structure of the copolymers as well as oil and water content, respectively. The results are discussed in terms of a model having an interphasial zone where intermixing of the dissimilar segments occurs.
Structures of liquid crystalline side group polymers oriented by drawing
Authors: Zentel Rudolf , Strobl Gert R. 
Published: April 2003

AbstractThe fiber patterns of a series of liquid crystalline polymers were analysed. For polymers with smectic phases and for polymers with long spacers and nematic phases, the mesogenic groups orient perpendicularly to the polymer main chains which are parallel to the fiber axis. The fiber pattern indicate a short range order of the mesogenic groups analogous to that in low‐molecular weight liquid crystals. For polymers with short spacer groups and nematic phases qualitatively different fiber patterns are found. These fiber patterns are indicative for a special nematic phase formed by ribbon‐like molecules.
Interaction of poly(diallyldimethylammonium chloride) with ferro‐ and ferricyanide anions
Authors: Bekturov Esen A. , Kudaibergenov Sarkyt E. , Ushanov Valeri Zh. , Saltybaeva Saule S. 
Published: April 2003

AbstractThe interaction of poly(1,1‐dimethylpyrrolidinium‐3,4‐diylethylene chloride) [poly(diallyldimethylammonium chloride)] (1) with ferro‐ and ferricyanide anions was investigated by conductometric titration, viscometry, IR and Raman spectroscopy. It could be shown that the binding of ferro‐ and ferricyanide anions with 1 proceeds by means of an ionic mechanism and is accompanied by a spectral shift of the cyanide bands.
Kinetic investigation of the free radical crosslinking copolymerization in the pre‐gel state, 1. Styrene/m‐ and p‐divinylbenzene systems
Authors: Hild Gérard , Okasha Rouzi 
Published: April 2003

AbstractThe kinetic investigation of the free radical crosslinking copolymerization of styrene with m‐or p‐divinylbenzene was performed at 60°C in benzene solution with 2,&2prime;‐azoisobutyronitrile as initiator. The mole ratio of divinylbenzene to styrene was steadily kept small. At various stages of the process the concentrations of the remaining monomers were measured by vapor phase chromatography which allowed to calculate both the conversion degrees and the instantaneous composition of the copolymers formed. The radical reactivity ratio of styrene, determined kinetically, was found to be in good agreement with the value obtained by the Kelen‐Tüdös linearization method. The branched polymers formed prior to gelation were studied by light scattering and by size exclusion chromatography. The number of pendant double bonds was determined by analytical titration. From all these results, conclusions were drawn concerning the mechanism of network formation, and more specifically on the reactivity of the pendant double bonds that are formed whenever a divinylbenzene unit is incorporated. This latter factor determines the rate of the formation of the branch points and crosslinks.
Conformational transition in poly(methacrylic acid)
Authors: Chidambaram Subbarao , Gundiah Subbaraya 
Published: April 2003

AbstractThe potentiometric behaviour of poly(methacrylic acid) was examined in water/1,4‐dioxane mixtures at 25°C. Conformational transitions were observed in about the same range of apparent ionization in the 1,4‐dioxane concentration range 0 to 15 vol.‐%. Transitions were not observed in the 1,4‐dioxane concentration range 20 to 35% and the corresponding Henderson‐Hasselbalch plots were found to be linear. Phase separations were observed to occur beyond 40 vol.‐% 1,4‐dioxane. The free energy of the conformational transition decreased very rapidly with the initial incorporation of 1,4‐dioxane but slowly at higher concentrations. Van der Waals methyl‐methyl interactions as the cause of the compact form has been inferred. The large increase in intrinsic viscosity observed for the unneutralized poly(methacrylic acid) in a relatively narrow range of composition of the 1,4‐dioxane/water mixtures has been ascribed to a solvent induced conformational transition.
Copolymerization of styrene with Zn(II), Co(II), Ni(II) and Cu(II) acrylates
Authors: Wojtczak Zbigniew , Gronowski Adam 
Published: April 2003

AbstractThe radical copolymerization of styrene with Zn(II), Co(II), Ni(II) and Cu(II) acrylates in methanol at 60°C was studied and that of styrene with Cu(II) acrylate also in acetonitrile at 80°C. In a given period of time an increase of conversion was observed with increasing concentration of the first three metal acrylates in mixtures with styrene. With Cu(II) acrylate, however, a decrease of conversion was found. The monomer reactivity ratios were determined as follows: rSt = 1,10, r = 0,90; rSt = 1,74, r = 0,56; rSt = 1,83, r = 0,53; rSt = 5,94, r = 0,12 (in acetonitrile). The products of the reactivity ratios, almost equal to one, reflect an “ideal” copolymerization and therefore a very little alternating tendency in propagation reactions. The Alfrey‐Price Q‐e parameters for the metal acrylates were calculated and discussed.
The thermodynamics of polyether sulfone‐poly(ethylene oxide) mixtures
Authors: Walsh David J. , Rostami Shamsedin , Singh Vir Bhanu 
Published: April 2003

AbstractMixtures of poly(ethylene oxide) and polyether sulfone have previously been shown to be miscible and undergo phase separation on heating, the minimum in the cloud point occurring at about 80°C and at 10:90 w/w PES:PEO composition. This paper describes an attempt to understand the thermodynamics of this system and to simulate the spinodal curves of the phase diagram using a modified form of the equation‐of‐state theory of Flory et al. Two methods were used to gain information about the interactional energy of the polymers. Heat of mixing measurements at 90°C on low molecular weight analogues were used to obtain a value of X12 of −40 J. cm−3. A modified form of the equations for the melting point depression of PEO in the blend was used to obtain values of X̄12 in the range of −35 to −50 J. cm−3 at 52°C, the melting point of PEO. In order to adjust the location of the simulated spinodal, using a value of X12 = −40 J. cm−3, it was necessary to assume an unfavourable non‐combinatorial entropy contribution of Q12 = −0,048 J. cm−3 · K−1. If the spinodals were simulated assuming Q12 = 0 and hence X12 ≡ X̄12 then a value of X12 = −18 J · cm−3 must be used. This is not inconsistent with the melting point depression result considering the large uncertainties in this method and the fact that the results are obtained at a lower temperature. The simulated spinodals are not very molar mass dependent which corresponds to the similar findings of the cloud point. The shape of the spinodal is dominated by the value of the surface area to unit volume ratio S2/S1 through its effect on the interactional terms in the spinodal equation.
α,ω‐dichloropoly(2‐methylpropene) as an inifer: A modification to the Kennedy‐Smith mechanism
Authors: Nuyken Oskar , Pask Stephen D. , Vischer Axel , Walter Michael 
Published: April 2003

AbstractExperimental details are given of attempts to enumerate the binary ionogenic equilibria (B.I.E.) of 1‐chloro‐1‐methylethylbenzene (1)/BCl3, 1,4‐bis(1‐chloro‐1‐methylethyl)benzene (2)/BCl3 and 1,3,5‐tris(1‐chloro‐1‐methylethyl)benzene (3)/BCl3 in CH2Cl2. Due to chemical reaction (dimerisation or polymerisation) no experimental values for the B.I.E. constants could be obtained. A Born‐Haber cycle is constructed to estimate the relative sequence of the overall B.I.E. constants. A similar treatment for 2‐chloro‐2methylpropane as a thermodynamic model for α,ω‐dichloropoly(2‐methylpropene) (4) suggests that the overall B.I.E. constant for these polymers is somewhat smaller than those for 1 and 2 but greater than that for 3. Using 2/BCl3 as initiator for the polymerisation of 2‐methylpropene (IB) it is shown, that the degree of polymerisation of 4 can be controlled within the limits 10 < DP < 100. It is shown that 4 can also act as an initiator for the polymerisation of IB, that these polymerisations involve only free ion propagation and, from a kinetic analysis of these polymerisations, that: (k)2/k = 12 1 · mol−1 · s−1, k = 1,2 · 10−3 l · mol−1 · s−1, k [P] = 1,7 · 10−3 s−1, and k/(k K) = 102. The same analysis demonstrates that the self‐ionisation of BCl3 can be neglected in terms of any influence on the molar mass of the products. Experiments are also described which show that 2‐chloro‐2‐methylpropane is not suitable as a substitute initiator for IB, but that 2‐chloro‐2,4,4‐trimethylpentane is a useful model for 4 as an initiator for the polymerisation of IB.
Synthèse et copolymérisation avec l'acrylamide de macromonomères d'acrylate de dodécyle
Authors: Bonardi Christian , Boutevin Bernard , Piétrasanta Yves , Taha Mohammed 
Published: April 2003

AbstractGraft copolymers of well‐defined structure and composition were prepared by radical copolymerization of acrylamide and poly(dodecyl acrylate) macromonomers. The macromonomers were prepared by telomerization of dodecyl acrylate in the presence of 2‐mercaptoethanol as a transfer agent, followed by reaction with acryloyl chloride. Poly(dodecyl acrylate) macromonomers with Mn = 1100, 1100, 2200 and 4600 were synthesized. The kinetics of the radical telomerization of dodecyl acrylate with 2‐mercaptoethanol and AIBN was studied at 66°C in THF. Under these conditions we obtained the transfer constant CT = 0,9. The graft copolymerization of acrylamide with the poly(dodecyl acrylate) macromonomer was carried out in the presence of the transfer agent C6F13C2H4SH. If C0 = [AIBN]/[Acrylamide] = 0,01 and R0 = [C6F13C2H4SH]/[Acrylamide] = 0,01, for acrylamide a DPn = 160 was obtained in all cases, for the macromonomer of Mn = 1100 a DPn = 2,5, and for the macromonomer of Mn > 1100 a DPn = 1.