bluuebunny/crossref_metadata_2025_split huggingface dataset:
Microdomain control in graft copolymer and polymer blends by means of epitaxial growth
Authors: Ishizu Koji , Mitsutani Kenji 
Published: April 2003

AbstractPoly(vinyl acetate) (PVAc) and poly(tert‐butyl methacrylate) (PBMA) macromonomers with vinyl end‐groups were synthesized by radical or anionic polymerizations. 4‐Vinylpyridine (4VP)/vinyl acetate (VAc) and 4VP/tert‐butyl methacrylate (BMA) graft copolymers were prepared by radical copolymerization of these macromonomers with 4VP as a comonomer. The 4VP/vinyl alcohol (VA) graft copolymer was derived from alkaline hydrolysis of 4VP/VAc graft copolymer. After having fixed the microdomains of 4VP/VA graft copolymer film, the solution of graft copolymer (or polymer blends) was cast on a support film of 4VP/VA graft copolymer. It was shown that the domain structure of the upper layer is governed by epitaxial growth of the microdomain pattern of the support film surface.
Synthesis of star‐shaped poly(ethylene oxide)
Authors: Gnanou Yves , Lutz Pierre , Rempp Paul 
Published: April 2003

AbstractThree different methods to synthesize star‐shaped poly(ethylene oxide) are discussed in the present article. In all three cases, the branches are grown from a plurifunctional initiator. It is established that even though the early stages of the polymerization occur in heterogeneous phase, the consequences on the polymers formed are of minor importance. The most significant method is a core‐first process, involving multifunctional poly‐DVB cores as the initiating species, made anionically in dilute solution. Although strong association phenomena are occurring during the growth of the branches, star‐shaped poly(ethylene oxide)s with a high number of functionalized branches are obtained. The polymers arising from all three methods were characterized accurately.
Heterogene polymeranaloge Reaktionen zwischen Polybutadienepoxiden und anorganischen Feststoffoberflächen
Authors: Heublein Günther , Heublein Brigitte , Hortschansky Peter , Schütz Heidrun , Flammersheim Hans‐Jürgen 
Published: April 2003

AbstractHeterogeneous, polymeranalogous reactions between polybutadieneepoxides (PBDE) and inorganic surfaces (SiO2, Al2O3, hydroxyapatite) were investigated. The composition of the resulting composites was determined by gravimetric methods and expressed as “degree of reaction” (RG). Interface reactions could be followed by spectroscopic methods and by differential scanning calorimetry. The results of the reaction mechanisms are discussed. Infrared and 13C solid state NMR studies suggest that the PBDE macromolecules are linked by bonds to the SiO2 surface and by and bonds to the Al2O3 surface.
In situ photopolymerization of an oriented liquid‐crystalline acrylate, 2
Authors: Broer Dirk J. , Mol Grietje N. , Challa Ger 
Published: April 2003

AbstractDuring the photo‐initiated free‐radical bulk polymerization of 4‐biphenylyl 4‐(6‐acryloyloxy‐hexyloxy)benzoate (1) in the liquid‐crystalline state, the ordering is maintained, leading to an oriented liquid‐crystalline side‐chain polymer. The course of the photopolymerization depends on the phase of monomer1. In the monotropic smetic‐A and in the monotropic nematic phase the polymerization rate and conversion are affected by crystallization during polymerization. In the stable nematic phase the bulk polymerization is fast and complete. In this temperature region the transition from nematic1to smectic poly(1) is passed during which temporary segregation may occur, affecting the molecular ordering. Starting with isotropic1, the polymerization proceeds considerably more slowly.
Propene polymerization with MgCl2‐supported transition metal catalysts activated by Cp2MtMe2(Mt = Ti, V, Zr, Hf)
Authors: Soga Kazuo , Uozumi Toshiya , Yanagihara Hisayoshi 
Published: April 2003

AbstractSeveral kinds of MgCl2‐supported catalysts were prepared by grinding the mixtures of MgCl2 and MtCln(MtCln = TiCl4, ZrCl4, HfCl4, VCl3). Polymerization of propene was conducted at 40°C and 1 atm with these solid catalysts by using Cp2MtMe2 (Mt = Ti, Zr, Hf, V) as cocatalyst. Polymerization took place only with the use of the TiCl4/MgCl2 catalyst. Both the activity and isospecificity were found to strongly depend upon the cocatalyst used. The polymers produced were fractionated with boiling heptane and analyzed by means of 13C NMR, the results of which suggested the existence of two types of catalytic centers, isospecific and aspecific. Plausible models of these catalytic centers are proposed.
Evaluation of olefin reactivity ratios over highly isospecific Ziegler‐Natta catalyst
Authors: Soga Kazuo , Yanagihara Hisayoshi , Lee Dong‐ho 
Published: April 2003

AbstractThe recently found catalyst system, composed of Solvay‐type TiCl3 and (RCp)2TiMe2, producing extremely high isospecific polyolefins, was used for copolymerizations of ethylene with various α‐olefins (propene, 1‐butene,1‐hexene and 4‐methyl‐1‐pentene) to obtain monomer reactivity ratios for isospecific centers. It was found that no homopolymer was formed actually. Using the copolymer composition obtained by 13C NMR, the monomer reactivity ratios were calculated according to the Fineman‐Ross and Kelen‐Tüdős method. For the ethylene/propene pair the same values of reactivity ratio were also obtained from the diad distribution of comonomers. The relative reactivity of these olefins was found to decrease in the following order; ethylene > propene > 1‐butene > 1‐hexene > 4‐methyl‐1‐pentene.
Anionic block polymerization initiated by potassium solutions, 2. Synthesis of poly(2‐oxetanone)‐block‐polystyrene‐block‐poly(2‐oxetanone)
Authors: Jedliński Zbigniew , Kurcok Piotr , Adamus Grazyna 
Published: April 2003

AbstractThe block polymerization of styrene with 2‐oxetanone (β‐propiolactone) proceeds fast with a yield of more than 90%, in the presence of potassium solutions in THF containing 18‐crown‐6. Poly(2‐oxetanone)‐block‐polystyrene‐block‐poly(2‐oxetanone) ABA triblock polymers having the expected molecular mass and composition are formed. Their glass transition and melting temperatures as well as their melting enthalpies determined by DSC show a strict correlation with block polymer composition. The mechanism of this block polymerization involving acyloxygen and alkyl‐oxygen bond scission in 2‐oxetanone is in good agreement with previous results of the homopolymerization of β‐lactones by alkali metal solutions abounding in potassium anions.
Controllable specific interaction and miscibility in polymer blends, 1. Hydrogen bonding and morphology
Authors: Cao Xianyi , Jiang Ming , Yu Tongyin 
Published: April 2003

AbstractThis paper concentrates on the effect of introducing hydrogen bonding into otherwise immiscible blends on their miscibility and morphology. 1,1,1,3,3,3‐Hexafluoro‐2‐hydroxypropyl‐containing units are incorporated in polystyrene which is then mixed with carbonyl‐containing polymers such as poly(methyl methacrylate) and poly(butyl acrylate). The infrared study confirms the formation of hydrogen bonding and shows that the frequency shifts of hydroxyl stretching caused by the H‐bonds are independent on whether the hydroxyl‐containing units are in the monomer or connected to polystyrene or polyisoprene chains and whether they are randomly distributed along the chains or only located at the ends of the polymers. Hydrogen bonding in the blends dramatically enhances miscibility judged by differential scanning calorimetry and transmission electron miscroscopy (TEM). TEM observations reveal apparent and regular variations of the morphology in the blends with the content of the hydroxyl‐containing groups, which implies that the morphological features of the blends, such as size of the dispersed phase, or extent of interpenetrating between the components are controllable simply by changing the structure and/or amount of the introduced groups forming the specific interaction in the blends.
Compatibility of poly(ethylene oxide) and poly(methyl methacrylate) chains in solutions of their blends, diblock and triblock copolymers
Authors: Wohlfarth Christian , Regener Erhard , Rätzsch Margit T. 
Published: April 2003

AbstractSolvent activity data were obtained from vapour pressure measurements at 50°C, 70°C, 100°C and reduced to χ‐functions in systems consisting of benzene or toluene on the one hand and blends or block copolymers of poly(ethylene oxide) and poly(methyl methacrylate) on the other. The χBC‐values are negative for all polymer subsystems, but miscibility on a segmental scale is somewhat different for block copolymers and blends. χBC depends on the concentration of solvent and is mainly influenced by the Δχ‐effect in solution and correlated with the syndiotacticity of the PMMA chains. There is only a small influence of temperature and blend composition or block ratio.
Effect of the degree of saponification on the rheological and thermal properties of poly(vinyl alcohol) gels
Authors: Watase Mineo , Nishinari Katsuyoshi 
Published: April 2003

AbstractThe rheological and thermal properties of poly(vinyl alcohol) (PVA) gels prepared through freezing‐thawing cycles were studied, in order to clarify the relation between structure and functional properties. The breaking strength of PVA gels increases with increasing the degree of saponification (DS), i.e. the degree of deacetylation, while the breaking deformation decreases. The endothermic differential scanning calorimetry (DSC) peak accompanying the transition from gel to sol shifts to higher temperatures with increasing concentration and DS. The endothermic enthalpy as a function of concentration increases gradually up to 25 wt.‐%, then it increases rapidly for PVA with DS = 96,0,97,5 and 98,5 mol‐%. A sharp diffraction peak is observed in the X‐ray pattern for PVA gels with DS = 99,9 mol‐% but not for PVA gels with DS = 96,0 mol‐%. All results from rheology, DSC and X‐ray analysis show that only a slight increase in DS from 96,0 mol‐% to 97,5 mol‐% promotes the formation of ordered regions in PVA remarkably.
Determination of the reinitiation constants and other kinetic parameters of free‐radical polymerization by gas‐chromatography/mass spectrometry
Authors: Farina Mario , Silvestro Giuseppe Di , Sozzani Piero 
Published: April 2003

AbstractGC‐MS analysis of oligomers obtained by using a high concentration of chain transfer agents permits the identification and determination of the concentrations of all the compounds formed in the early propagation steps. From these data the exact structure of the starting chain end and the evaluation of a series of kinetic and probabilistic parameters can be obtained, thus allowing a more detailed description of the polymerization mechanism. Applying this method to the copolymerization of styrene (1) and methyl methacrylate (2), a value of 6 was obtained for the ratio of the reinitiation rate constants kr1/kr2 in the presence of 1‐butanethiol at 60°C.
Synthèse de polysiloxanes téléchéliques, 1. Synthèse de diols et diépoxydes
Authors: Boutevin Bernard , Youssef Boulos 
Published: April 2003

AbstractTelechelic poly(dimethylsiloxane)s (4, 5, 6) with acetoxy, hydroxyl or 2,3‐epoxypropoxy functions as end groups were synthesized. As starting materials chloro‐3‐acetoxy‐[or 3‐(2,3)‐epoxypropoxy]‐propyldimethylsilanes (2 and 3) were prepared by hydrosilylation of the corresponding allylic derivatives with chlorodimethylsilane, and subsequently condensed with α‐hydro‐ω‐hydroxyoligo‐ (or poly‐) dimethylsiloxanes (1b – d) in the presence of pyridine. The hydroxyl derivatives 5a – d were obtained by hydrolysis of the acetoxy derivatives, and the 3‐(2,3‐epoxypropoxy)propyl derivatives 6a, b by reaction of the diols with 1‐chloro‐2,3‐epoxypropane.
Synthèse de polysiloxanes téléchéliques, 2. Synthèse de diamines aromatiques
Authors: Boutevin Bernard , Robin J. J. 
Published: April 2003

AbstractTelechelic aromatic diamines (11) containing an oligo‐ or polysiloxane chain were prepared in a 4‐step synthesis. In the first step 1‐allyloxy‐4‐nitrobenzene (6) was synthesized and subsequently hydrosilylated with chlorodimethylsilane. In the third step the product (7) was hydrolyzed or condensed with α‐hydro‐β‐hydroxyoligo‐ or polydimethylsiloxane (9a or 9b). In the last step the nitro groups were reduced into amino groups. The steps were controlled by means of 1H and 29Si NMR spectroscopy.
Polymerization of bis[4‐bis(2,3‐epoxypropyl)aminophenyl]methane. Identification of new derivatives of 3‐hydroxy‐1,2,3,4‐tetrahydroquinoline
Authors: Costes Bruno , Reyx Danièle , Platzer Nicole 
Published: April 2003

AbstractBis[4‐bis(2,3‐epoxypropylamino)phenyl]methane (3) was shown to undergo homopolymerization when heated without or with an accelerator such as N,N‐dimethylbenzylamine (10). When 3 was polymerized without accelerator, no ether formation was found. A new type of curing process involving opening of the epoxy ring by reaction at the phenyl ring in ortho position to the tertiary amino substituent allows one to explain the formation of compounds containing the 3‐hydroxy‐1,2,3,4‐tetrahydroquinoline moiety. The corresponding derivatives 4–7 were isolated for the first time and their structures established by different spectroscopic methods such as 1H, 13C, 2D δ‐δ NMR, and FT‐IR. Intermolecular reaction at the orthocarbon of the tertiary amino group with an epoxy group may explain the resin formation by curing 3 without accelerator. Polymerization of 3 with accelerator 10 led to polyetherification. This result may be explained in terms of difference in the reactivity of the tertiary amines 3 and 10 towards the epoxy group. The former gives an unstable “zwitterion” by reaction at the nucleophilic carbon, subsequently leading to the stable hydroquinoline system by proton transfer. The latter also gives an unstable “zwitterion” by reaction at the nucleophilic nitrogen, however, it induces epoxy ring‐opening polymerization due to the lack of intramolecular stabilization. Moreover, the results suggest that the hydroxyl functions, formed in the absence of an accelerator, do not react with epoxides under the studied conditions.
Chromatographic cross‐fractionation of statistical copolymers of styrene and 2‐methoxyethyl methacrylate
Authors: Glöckner Gottfried , Stejskal Jaroslav , Kratochvíl Pavel 
Published: April 2003

AbstractChromatographic cross‐fractionation (CCF) by preparative size‐exclusion chromatography (SEC) and gradient high‐performance liquid chromatography was applied to stat‐copoly‐(styrene/2‐methoxyethyl methacrylate). Two specimens were analyzed, which had been polymerized from the same batch of monomer mixture in benzene solution to either low or high conversion (10,1 or 86,4 mass‐%, respectively). The initial monomer mixture contained more styrene (76,7 mass‐%) than the azeotropic one (39,4%). The integral chemical composition distribution (CCD) of the low‐conversion sample agreed with the theoretical curve, whereas the calculated CCD of the high‐conversion specimen was broader than the one determined experimentally. The contour map of the low‐conversion sample exhibited the tapering effect of molar mass predicted by theory. The corresponding map of the high‐conversion sample showed that the composition shift towards the initial monomer ratio induced production of macromolecules of higher molar mass.
Azo polymers — syntheses and reactions, 3. Photolysis of monomeric and polymeric azo compounds
Authors: Nuyken Oskar , Weidner Richard , Dörner Barbara , Grunow Arthur 
Published: April 2003

AbstractUnsymmetrical azo compounds of the general structure m‐RC6H4NNC(OCOCH3) (R1) (R2) (2–4), in which R stands for H, CH3, CHCH2 or a polymeric residue, were irradiated with light of λ ≥ 330 nm. Depending on the substituents R1 and R2 and the reaction temperature trans‐cis isomerization or/and decomposition was observed. Polymers containing azo groups and CC‐double bonds can be crosslinked by irradiation.
Chain extension of poly(dimethylsiloxane) having hydroxyl or vinyl terminal groups
Authors: Shara Mohammed A. , Mark James E. 
Published: April 2003

AbstractChain extension of hydroxyl‐ or vinyl‐terminated poly(dimethylsiloxane) was carried out with difunctional end‐linking agents that are similar in their structure to the higher functionality end linkers used for model network formation. Values of the number‐average molecular weight of the polymers before and after chain extension were determined by gel permeation chromatography. In this way, values of the extent of reaction, p, were determined for different stoichiometric ratios, r. They were found to be in the range 0,5–1,0, with the largest values generally corresponding to r closest to unity. Increase in reaction time increases p, but increase in the amount of catalyst did not show any discernible effect. The overall results show that at least under some conditions, the analogous reactions using end linkers of functionality three or higher should produce nearly perfect model networks.
Microstructure of syndiotactic polypropylenes prepared with heterogeneous titanium‐based Ziegler‐Natta catalysts
Authors: Kakugo Masahiro , Miyatake Tatsuya , Naito Yukio , Mizunuma Kooji 
Published: April 2003

AbstractPolypropylenes produced with various heterogeneous titanium‐based Ziegler‐Natta catalysts were fractionated by solvent extraction technique. The infrared analysis of the fractions indicates the presence of a crystalline syndiotactic sequence, soluble in xylene at 20°C, and boiling hexane soluble fractions of all samples examined. Highly syndiotactic polypropylene (proportion of rrrr pentad is 0,50), comparable in syndiotacticity to the syndiotactic polymer prepared at −78°C with a homogeneous vanadium catalyst, was separated from the xylenesoluble fraction of the polymer prepared with the system TiCl3‐Al(C2H5)2Cl by means of elution column fractionation. The steric irregularities are mainly rrrm and rrmr (ratio ≈ 1:1), suggesting that the propagation is controlled mainly by end‐groups. Chemical inversions, i. e., head‐to‐head or tail‐to‐tail linkages of propylene units, are practically absent, though they are seen in syndiotactic polypropylenes prepared with vanadium catalysts.
The ability of macromonomers to copolymerize: A critical review with new developments
Authors: Gnanou Yves , Lutz Pierre 
Published: April 2003

AbstractThe first part of this article critically examines the various studies dealing with the ability of macromonomers to copolymerize. The conclusions drawn from these investigations, concerning the influence of the molecular weight of the macromonomer on its reactivity, are contradictory. Owing to the systems selected, other parameters are also involved in the reactivity of macromonomers that make it difficult to settle the controversy. In the second part, our own results on the reactivity of macromonomers are reported. The system chosen exhibits the advantage to remove all the complicating features connected with the incompatibility between polymers. It results that the side group associated with the unsaturation plays the major role in decreasing the reactivity of the macromonomer which is shown in addition to be independent of the macromonomer chain length. The criteria allowing to predict, for a given system, the macromonomer behaviour in a copolymerization process are also given.
Spatial organization of homopolymer chains inside spherical polybutadiene domains of styrene‐butadiene diblock copolymers
Authors: Cheng Pao‐Luo , Berney Charles V. , Cohen Robert E. 
Published: April 2003

AbstractBlends of perdeuterated polybutadiene and a styrene‐butadiene diblock copolymer (polystyrene‐block‐polybutadiene) were prepared by solution‐casting techniques. Small‐angle neutron scattering and transmission electron microscopy experiments on blends containing homopolymer with chain length smaller than the corresponding block sequence showed that homopolymer chains are solubilized by the spherical microdomains up to a homopolymer content of about 15 mol‐percnt;. The solubilized homopolymer is distributed in a spatially uniform manner throughout the domain volume and the radius of gyration of the homopolymer is only slightly larger than that of an unperturbed chain in bulk. At about 18 mol‐percnt;, pools of homopolymer appear outside the microdomains; the change in scattering intensities indicates that pool formation is a kinetic phenomenon rather than a thermodynamically controlled event. Experiments on blends containing longer homopolymer chains revealed a lower concentration, between 3 and 6 mol‐percnt;, for the onset of homopolymer pool formation.
Anionic polymerization of one‐ended “living” strontium‐polystyrene in tetrahydropyran in the presence of tetraglyme and in benzene
Authors: De Smedt Constant , Van Beylen Marcel 
Published: April 2003

AbstractThe anionic polymerization of the strontium salt of one‐ended living polystyrene (SrS2) was investigated at 20°C in tetrahydropyran (THP) in the presence of two different concentrations of added tetraglyme. Similarly to BaS2 in tetrahydrofuran (THF) and to SrS2 in THF and in pure THP, the observed pseudo‐first‐order rate constant of propagation, kobs, was nearly independent of the total concentration of salt, their values being 7,5.10−3 s−1 and 9 · 10−3 s−1, respectively, i. e. about 100 to 120 times higher than in pure THP. This indicates that the propagation occurs mainly via an increased but constant amount of free S− anions resulting from the two already known equilibria SrS2 ⇌ (SrS)+ + S−(K1) and 2 SrS2 ⇌ (SrS)+ + (SrS3)− (K2) and the equilibrium of glymation (SrS+) + G ⇌ G, (SrS)+ (Ki). A small not exactly determinable contribution of glymated ion‐pairs and/or triple ions, whose rate constants would then probably be of the order of 18 l · mol−1 · s−1 and 80 l · mol−1 · s−1, respectively, could not be excluded. The glymation constant Ki was found to be about 3 · 106 1 · mol−1, i.e., approximately 17 times greater than for the Na+ cation. Finally, a kinetic experiment with SrS2 at 20°C in pure benzene (contaminated, however, with some remaining THP from the preparation of SrS2) indicated that propagation by ion‐pairs is possible with a bimolecular apparent rate constant Kapp = 1,1 · 10−1 l · mol−1 · s−1.
Thermal behavior, morphology and the determination of the polymer‐polymer interaction parameter of polycarbonate‐poly(butylene terephthalate) blends
Authors: Kim Woo Nyon , Burns Charles M. 
Published: April 2003

AbstractBlends of bisphenol‐A polycarbonate (PC, poly(oxycarbonyloxy‐1,4‐phenylene‐2‐isopropylidene‐1,4‐phenylene)) and poly(butylene terephthalate) (PBT, poly(oxytetramethyleneoxy‐terephthaloyl)) have been investigated by differential scanning calorimetry and scanning electron microscopy. Blends were prepared by screw extrusion and solution casting with mass fractions of PC in the blends varying from 0,90 to 0,10. From the measured glass transition temperature (Tg) and apparent mass fractions of PC and PBT dissolved in each phase, it appears that the PBT dissolves more in the PC‐rich phase than does the PC in the PBT‐rich phase. Also, compatibility is greater in the case of extruded blends than in the case of solutioncast blends. The values of the Flory‐Huggins polymer‐polymer interaction parameter (χ12) were determined and found to range from 0,042 to 0,033 for extruded blends at 250°C and from 0,054 to 0,039 for solution casting at 25°C. The χ12 decreases with increase of PBT content throughout the investigated composition range. From the Tg's, the microscopy study and the extrudate swell ratios, it is concluded that compatibility is achieved in the blends having mass fractions 0,90, 0,20 and 0,10 of PC, but that these blends are not microscopically homogeneous.