bluuebunny/crossref_metadata_2025_split huggingface dataset:
Tailoring of macromolecule conjugates using reversed micelles as matrix microreactors
Authors: Kabanov Alexander V. , Levashov Andrey V. , Khrutskaya Maria M. , Kabanov Victor A. 
Published: April 2003

AbstractBeing solubilized in systems of reversed micelles of a surfactant, the macromolecules incorporate into the inner cavities of the micelles, whose size can be changed by varying the degree of hydration, w0 = [H2O]/[surfactant]. The conjugates of proteins (α‐chymotrypsin, bovine serum albumin (BSA), monoclonal antibodies to insulin) with linear polyelectrolytes (poly(methacrylic acid), quaternized poly(4‐vinylpyridine)) are synthesized in reversed micelles of Aerosol OT (sodium bis(2‐ethylhexyl)sulfosuccinate) in the octane with 100% yield. The yield critically depends on the degree of hydration: the reaction does not proceed at low w0, but if w0 exceeds a threshold value (which differs for various macromolecules) the yield increases sharply and reaches 100%. Using the ultracentrifugation it was demonstrated that at low w0 the polyelectrolyte represents a compact globule compressed by the micellar matrix in the inner cavity of a micelle. Under these conditions, there is no space for the protein in a micelle which contains polyelectrolyte, and therefore reaction does not proceed. If w0 exceeds a threshold value the micelles become large enough to entrap the conjugated macromolecules simultaneously. The possibility of regulation of the conjugate composition by variation of w0 (via the size of the micellar matrix) was demonstrated by a conjugate of BSA with quaternized poly(4‐vinylpyridine).
Polyarylenes and poly(arylenevinylene)s, 4. Novel anthracene‐containing poly(arylenevinylene)s via poly‐Heck reaction
Authors: Weitzel Hans‐Peter , Müllen Klaus 
Published: April 2003

AbstractHeck reactions with anthracene‐containing compounds are investigated. Some oligomeric model compounds as well as polymers were synthesized. The reason for the failure of 9,10‐divinylanthracene to undergo the Heck reaction are described. The solution of the synthetic problem was achieved by using the yet unknown 9,10‐bis(1,3‐butadienyl)anthracene.
Effect of catalyst isospecificity on olefin copolymerization
Authors: Soga Kazuo , Uozumi Toshiya , Park Joon Ryeo 
Published: April 2003

AbstractCopolymerizations of ethylene with propene, ethylene with 1‐hexene, and propene with 1‐hexene were performed at 40°C under atmospheric pressure by using the aspecific catalyst composed of TiCl3/MgCl2 and Al(C2H5)3 and the isospecific Solvay‐type catalyst composed of TiCl3 and Cp2Ti(CH3)2. In case of ethylene‐propene copolymerization, the catalyst isospecificity affects neither the monomer reactivity ratios nor the monomer distribution in poly(ethylene‐co‐propene). The thermal properties of poly(ethylene‐co‐propene) are, however, not the same for the two catalysts due to the different tacticity of long propylene sequences contained in the copolymers. In the copolymerizations of ethylene and 1‐hexene and of propene and 1‐hexene, the monomer reactivity ratios differ to some extent between the two catalyst systems. The aspecific catalyst facilitates incorporation of 1‐hexene both in poly(ethylene‐co‐1‐hexene) and poly(propene‐co‐1‐hexene). The monomer distributions are also different in these copolymers. The aspecific and isospecific catalysts show a tendency to give random and blocky copolymers, respectively.
Polycondensation versus metal template condensation of 2,2′‐ethylenedithiodianiline with glyoxal
Authors: Biçak Niyazi , Hizal Gurkan , Yagci Yusuf , Barlas Hulusi 
Published: April 2003

AbstractA polymer with azomethine linkages is formed upon reaction of 2,2′‐ethylenedithiodianiline (1) with glyoxal. The same reaction in the presence of Ni(II) and Cu(II) ions yields the corresponding metal complexes of the macrocyclic ligand. The driving force for the selectivity of this reaction may be attributed to the template effect of the metal ions. In the case of Co(II) ions, the polymer is formed as a by‐product, together with the macrocyclic complex.
Contribution to the study of the kinetics of radical homo‐ and copolymerization of fluoroalkyl methacrylates, 2. 2,2,3,4,4,4‐hexafluorobutyl methacrylate and 2,2,3,3,4,4,5,5‐octafluoropentyl methacrylate
Authors: Kárpátyová Angela , Bartoň Jaroslav , Paleta Oldřich 
Published: April 2003

AbstractThe kinetics of radical homopolymerization of 2,2,3,4,4,4‐hexafluorobutyl methacrylate (HFBMA) and 2,2,3,3,4,4,5,5‐octafluoropentyl methacrylate (OFPMA) was investigated in four different solvents. The rate of polymerization (Rp) of both monomers was found to increase with increasing donor number of the solvents, the increase being more marked in the case of OFPMA. This is probably associated with the leveling of the electron density of the double bonds of HFBMA and OFPMA by the influence of solvents as well as with the gel effect in the polymerization. Copolymerization parameters for HFBMA and OFPMA with butyl acrylate, styrene and methyl methacrylate were determined in benzene at 60°C and the values of resonance and polarity terms, Q and e, were also established.
Thermodynamics of mixing of ethylene oxide oligomers with different endgroups in tetrachloromethane
Authors: Killmann Erwin , Cordt Frank , Möller Friedrich 
Published: April 2003

AbstractEnthalpies and Gibbs energies of mixing of liquid ethylene oxide oligomers with hydroxyl and methoxy end groups in tetrachloromethane are obtained by microcalorimetry and vapour pressure measurements. In this part of the publication the thermodynamic excess quantities ΔH, ΔGE and ΔSE are fitted by power series as functions of the weight fraction. Polymer‐ and solvent‐specific as well as partial thermodynamic quantities are deduced. The qualitative explanation of the strongly end group specific mixing behaviour demonstrated by these quantities is based on the induced dipol interactions of the ethylene oxide middle segments and on the hydrogen bond interactions of the OH end groups.
Zur frage der Existenz ternärer azeotrope bei Donator‐Acceptor Copolymeren
Authors: Schmidt‐Naake Gudrun , Schmidt Hermann , Litauszki Beata , Bieger Wolfgang 
Published: April 2003

AbstractUsing the suitable terpolymerization equations for the copolymerization of donor‐acceptor copolymer systems no ternary azeotrope could be calculated. Copolymerization reactivity ratios taken from literature show that there is no chance to find an azeotrope.
Side‐chain liquid‐crystalline polyacrylates containing heterocyclic mesogenic groups, 2. Influence of the length of the spacer group on the mesomorphous properties
Authors: Legrand Cécile , Borgne Alain Le , Bunel Claude , Lacoudre Nelly , Barny Pierre Le , Spassky Nicolas , Vairon Jean‐Pierre 
Published: April 2003

AbstractThe synthesis of a series of side‐chain liquid‐crystalline polyacrylates having mesogenic groups containing the trans‐2‐(4‐cyanophenyl)‐1,3‐dioxan‐5‐yl moiety is reported. Methylenic spacer groups of different lengths have been used. Polymers were prepared by radical polymerization of the corresponding acrylates. The liquid‐crystalline nature of these polymers has been established by calorimetric measurements and optical texture observations. The phase behaviour is strongly dependent on the length of the spacer group. With (CH2)6, the unusual INSANre sequence is observed.
Photoreactive cellulose derivatives with comb‐like structure, 1. Modification of O‐trialkylsilylcellulose with cinnamic acid‐containing side chains
Authors: Klemm Dieter , Schnabelrauch Matthias , Stein Armin , Niemann Manfred , Ritter Helmut 
Published: April 2003

AbstractTrimethyl‐ and tert‐butyldimethylsilylcellulose were esterified with cinnamic acid, 4‐nitrocinnamic acid, 4‐(hexyloxy)cinnamic acid, 4‐(hexadecyloxy)cinnamic acid and N‐cinnamoyl‐11‐aminoundecanoic acid yielding photosensitive comb‐like cellulose derivatives. The UV‐irradiation of solid films of tert‐butyldimethylsilylcellulose cinnamate, trimethylsilylcellulose 4‐nitrocinnamate and tert‐butyldimethylsilylcellulose‐4‐hexyloxycinnamate were performed and the decrease of the absorption maxima was correlated with E/Z isomerisation and [2 + 2]‐cycloaddition. A possible application of the described photoreactive cellulose esters in the area of membrane technology is discussed.
Chirality of poly(vinyl compounds), 12. α‐(trityloxymethyl)acrylonitrile, a new monomer forming optically active, single‐sense helical polymers
Authors: Wulff Günter , Wu Yonghua 
Published: April 2003

AbstractThe new monomer, α‐(trityloxymethyl)acrylonitrile (2), was prepared. It can be polymerized anionically with optically active initiator systems to yield an insoluble polymer showing strong optical activity. In contrast to trityl methacrylate optically active polymers are obtained from 2 in toluene as well as in tetrahydrofuran. After removal of the trityl groups the optical activity is completely lost in the resulting poly[α‐(hydroxymethyl)acrylonitrile]. It is therefore concluded that an atropisomeric helical arrangement is present in poly[α‐(trityloxymethyl)acrylonitrile]. Compared to trityl methacrylate and its polymer the new monomer 2 and the corresponding polymer show higher stability against splitting off of the trityl groups.
The synthesis of polymers bearing terminal fluorescent and fluorescence‐quenching groups, 1. The incorporation of fluorescent groups at one end of the macromoleculer by means of the initiation process
Authors: Al‐Takrity Emad Taha Bakir , Jenkins Aubrey D. , Walton David R. M. 
Published: April 2003

AbstractSuitably substituted vinylidene compounds, incapable of undergoing anionic polymerisation, are reacted with butyllithium to produce an initiator for the anionic polymerisation of methyl methacrylate. Thus poly(methyl methacrylate)s are obtained, the macromolecules of which carry a single fluorescent (or fluorescence quenching) moiety at the initiating end of each chain.
The synthesis of polymers bearing terminal fluorescent and fluorescence‐quenching groups, 2. The incorporation of fluorescent and fluorescence‐quenching groups by means of a direct termination process
Authors: Al‐Takrity Emad Taha Bakir , Jenkins Aubrey D. , Walton David R. M. 
Published: April 2003

AbstractAttempts to terminate anionic polymerisation by suitably substituted (i. e. chromophoric) compounds, such as 9‐anthrylacetyl chloride, 1‐naphthoyl chloride, 1‐naphthylacetyl chloride, 1‐(1‐naphthyl)‐1‐phenylethylene, 1‐chloromethylnaphthalene or 1‐pyrenylmethyl bromide are described. In combination with the procedure described in part 1 of this series, it is possible to synthesise polymer molecules in which either one or both end‐groups contain the above‐mentioned photophysically‐active moieties. In the difunctional case, the chosen active groups may be either identical or different.
The synthesis of polymers bearing terminal fluorescent and fluorescence‐quenching groups, 3. The incorporation of fluorescent and fluorescence‐quenching groups by means of an indirect termination process
Authors: Al‐Takrity Emad Taha Bakir , Jenkins Aubrey D. , Walton David R. M. 
Published: April 2003

AbstractA useful general method is reported for incorporating specific groups at the terminal unit on a polymer prepared anionically. The living polymer anions are terminated by reaction with allyl iodide, the product converted to the corresponding saturated alcohol through hydroboration, and the alcohol coupled with an acyl chloride RCOCl, where R is the desired specific group. In the examples described here, the chosen terminal moieties are hydroxyl, vinyl, and certain fluorescent (or fluorescence‐quenching) groups, such as pyrenyl.
Amphiphilic properties of synthetic glycolipids based on amide linkages, 4.13C NMR spectroscopic studies on the gelation of N‐octyl‐D‐gluconamide in aqueous solution
Authors: Taravel François R. , Pfannemüller Beate 
Published: April 2003

Abstract13C NMR measurements were taken on cooling of aqueous solutions of N‐octyl‐D‐gluconamide to follow the process of gelation. On cooling from 90°C gelation sharply occurs at 60–62°C. In the pre‐stage of gelation at 64°C an aggregated species, probably a dimeric form of octylgluconamide, is detected. Additional signals for sugar carbons C‐1, C‐4 and C‐6 indicate hydrogen bonding. As a side reaction conversion of the octylgluconamide to the ammonium salt takes place. Assignments of the new signals were made with the ammonium salt formed from D‐gluconamide and the corresponding octylammonium salt of gluconic acid. When the solution of octylgluconamide is kept at 64°C for a longer period, octylgluconamide, free and aggregated, and its ammonium salt coexist. At 64°C relaxation times t1 of the sugar carbons corresponding to the octylgluconamide species are much shorter than those of the salt, indicating a decrease of the mobility of the sugar carbons of the former in the pre‐stage of gelation.
Pervaporation of water‐ethanol mixtures through poly(acrylonitrile‐co‐acrylic acid) membranes
Authors: Lee Young Moo , Wang Wun Jae 
Published: April 2003

AbstractPervaporation performance of poly(acrylonitrile‐co‐acrylic acid) membranes was examined at several feed ethanol concentrations and temperatures. The incorporation of carboxylic acid groups into the glassy polyacrylonitrile membrane made it possible to selectively separate water from aqueous ethanol solution by pervaporation. Carboxylic groups play a role as carriers for water. Concentration dependent diffusion of water through the membranes was assumed and a new permeation equation is proposed and discussed.
Bimechanistic phase transfer catalyzed polythioetherification
Authors: Shaffer Timothy D. , Kramer Michael C. 
Published: April 2003

AbstractRelative concentrations of catalysts, sulfide catalyst structure, and organic phase monomer concentration were studied for the bimechanistic phase transfer catalyzed (BPTC) polymerization of aqueous sodium sulfide with 1,8‐dibromooctane (DBO). BPTC is a new phase transfer mechanism which combines the effects of normal phase transfer with “inverse” phase transfer catalyzed reactions. Two catalysts are used: an ammonium salt and a cyclic or acyclic sulfide. With hexadecyltrimethylammonium chloride (CTMAC) and tetrahydrothiophene (THT), the optimum catalyst concentrations were found to be 10 mol‐% and 5 mol‐%, respectively, per DBO, but each was independent of the other. Diluting the monomer with o‐dichlorobenzene did not significantly alter the mechanism's profile, but expectedly lowered obtainable molecular weight. Of five sulfide catalysts examined, pentamethylene sulfide and dimethyl sulfide were the best, producing the highest molecular weight polyaliphatic sulfides with polydispersities M̄w/M̄n of ca. 1,3.
In‐situ photopolymerization of oriented liquid‐crystalline acrylates, 5.. Influence of the alkylene spacer on the properties of the mesogenic monomers and the formation and properties of oriented polymer networks
Authors: Broer Dirk J. , Mol Grietje N. , Challa Ger 
Published: April 2003

AbstractThe photoinitiated bulk polymerization of macroscopically oriented 1,4‐phenylene bis{4‐(ω‐acryloyloxyalkyloxy)benzoate} produces densely crosslinked oriented polymer networks. The influence of the length of the alkylene spacer between the aromatic central core and the polymerizable acrylate end‐groups on the mesomorphic behaviour of the monomer, the molecular orientation in the monomeric and polymeric state and the process of photoinitiated polymerization in the ordered state is studied. Some optical properties of the oriented networks are presented.
Dispersion of trans‐polyoctenylene in isotactic poly(propylene), 1. Morphology/mechanical properties relationships
Authors: Wenig Werner , Fiedel Heinz‐Werner 
Published: April 2003

AbstractBlends of isotactic poly(propylene) (iPP) and trans‐polyoctenylene (TOR), prepared from solution, exhibit unexpected mechanical properties at specific mass fractions of TOR: While generally the elastic modulus E decreases continuously with increasing TOR content, it surpasses a maximum for mass fractions of TOR around 0,10. The reason for this behaviour is investigated. It turns out that the crystallinity as well as the crystal morphology (which is investigated by evaluating small‐angle X‐ray scattering by interface distribution functions) does not explain the mechanical behaviour. The order of the lamellar stacks (number of orientation‐correlated crystals) proves to be well correlated with the course of the elastic modulus. This order is a consequence of the increasing dispersion of TOR at mass fractions between 0,075 and 0,20 creating interfaces and infecting subsequently the crystallization conditions in the sample.
Dithiocarbamate telechelic polymers: Synthesis and block copolymerization
Authors: Van Kerckhoven Christel , Van den Broeck Hilde , Smets Georges , Huybrechts Jos 
Published: April 2003

AbstractThe iniferter method of Otsu was studied for the synthesis of polyvinyl block copolymers of relatively low molecular weight using tetramethylthiuram disulfide (TD) and benzyl N,N‐diethyldithiocarbamate (BDC) as initiator. Considering the low quantum yield of dissociation (ϕd) of TD (2,5 · 10−3 in cyclohexane), TD was used as thermal initiator (95°C) for the synthesis of dithiocarbamate‐polystyrene (TD‐PS) telechelics. 13C NMR analysis of this TD‐PS shows two 13CS signals corresponding to two different end‐groups: Et2NCSSCH(C6H5)CH2 and Et2NCSSCH2CH(C6H5). Several styrene polymerizations were also carried out in presence of azoisobutyronitrile (AIBN) as thermal initiator and TD as chain‐transfer reagent. Depending on the mole ratio AIBN/TD, mono‐ and difunctional TD‐PS's are formed, as evidenced by NMR analysis. These TD‐PS's were used for the photochemical initiations of ethyl acrylate (EA), acrylic acid (AA) and methyl methacrylate (MMA). It is assumed that the quantum yield of dissociation of the dithiocarbamate end‐group is equal to that of BDC (ϕd : 0,06). TD‐PS nonfunctional polymers were also prepared, either photochemically by dissociation of BDC, or thermally in presence of AIBN and BDC as transfer agent. They were used for block copolymerization with MMA. Inversely, TD‐PMMA's were prepared in a first step; in this case ϕd = 0,026. They were then used for the polymerization of EA. The block copolymers were fractionated; their composition and molecular weights were determined by 1H NMR and gelpermeation chromatography, respectively.
Synthesis and properties of well‐defined multiblock copolymers: poly(4,4′‐isopropylidenediphenyl carbonate)‐block‐polystyrene
Authors: Dems Andrzej , Strobin Grażyna 
Published: April 2003

AbstractWell‐defined poly(4,4′‐isopropylidenediphenyl carbonate)‐block‐polystyrene multiblock copolymers, PC‐b‐PS, were prepared by condensation of PC prepolymers having chloroformyl end‐groups with PS prepolymers having hydroxyl end‐groups. Both prepolymers had narrow molecular weight distribution (PC prepolymer: M̄w/M̄n ≤ 1,31, PS prepolymer: M̄w/M̄n ≤ 1,03). The course of the polycondensation reaction depends on the molecular weight of the prepolymers used as substrates. After fractionation, the obtained multiblock copolymers are homogeneous in chemical composition and have a narrow molecular weight distribution. The mechanical properties of the copolymers depend on the weight fraction of the PS blocks. All copolymers exhibit two glass transition temperatures, close to those of the parent homopolymers.
Optically active comb‐branch liquid‐crystalline polymers having the chiral centre in the flexible spacer, 2.. The synthesis and characterisation of copolymers containing the novel chiral monomer (S)‐2‐[2‐4‐methoxy‐4′‐biphenylyloxy)‐1‐methylethoxy]ethyl methacrylate
Authors: Cowie John M. G. , Hunter Hugh W. 
Published: April 2003

AbstractA new series of optically active liquid‐crystalline comb‐branch copolymers was prepared from (S‐2‐[2‐(4‐methoxy‐4′‐biphenylyloxy)‐1‐methylethoxy]ethyl methacrylate (1) and the nematogenic monomer 4‐cyanophenyl 4‐(6‐acryloyloxyhexyloxy)benzoate (2). These copolymers are characterised by the chiral centre being positioned in the flexible spacer. The copolymers form chiral nematic phases with temperature‐dependent reflection colours at low chiral monomer compositions, and crystalline phases at higher compositions. One of the copolymers of intermediate composition forms a smectic phase in addition to a chiral nematic phase.
Thermotropic polyesters, 6. New approach to the synthesis of segmented liquid‐crystalline polymers with an increased with an increased length of mesogenic and flexible elements
Authors: Bilibin Alexander Yu. , Piraner Olga N. 
Published: April 2003

AbstractA new approach to the synthesis of segmented liquid‐crystalline (LC) polymers with an increased length of both mesogenic and flexible moieties is suggested. It consists in the preparation of intermediate polymeric compounds on the basis of aliphatic diols and a “triade” type complex monomer, 4,4′‐(oxalyldioxy)dibenzoyl dichloride (6), whose central oxalyl unit plays the role of a bifunctional protective group and proves to be the structural element of the main chain of the intermediate polymer. The chemodegradation of the latter to bifunctional alkylene bis(4‐hydroxybenzoate)s (3), which differ from the initial complex monomer, is achieved by selective removal of the oxalyl protective group. The desired LC polymers may be synthesized on the basis of such hydroxy‐bifunctional compounds 3 and another triade type monomer carrying two acyl chloride functions, 4,4′‐(terephthaloyldioxy)dibenzoyl dichloride. The features of each stage of the synthesis are discussed. Special attentional is paid to the selectivity of hydrolysis procedure of the intermediate polymers. A series of segmented LC polyesters containing five or seven 1,4‐phenylene units in the mesogenic group are synthesized, their thermal properties are compared with the properties of LC polymers described earlier.
New thermotropic liquid‐crystalline polyesters with a metalchelated 1,3‐diphenyl‐1,3‐propanedione segment
Authors: Hanabusa Kenji , Tanimura Yoei , Suzuki Takashi , Koyama Toshiki , Shirai Hirofusa 
Published: April 2003

AbstractNew thermotropic liquid‐crystalline polyesters (2–4) containing a mesogenic β‐diketone segment, which can coordinate to a metal ion as bidentate ligand, were synthesized by polycondensation of a mixture of 1,6‐hexanediol (x mol), 1,3‐bis(p‐hydroxyphenyl)‐1,3‐propanedione (y mol), and 4,4′‐hexamethylenedioxydibenzoyl chloride (x + y mol). Homopolyester 1, prepared from 1,6‐hexanediol and 4,4′‐hexamethylenedioxydibenzoyl chloride, and copolyesters 2 and 3 (x/y = 0,8/0,2 and 0,5/0,5, respectively) show a nematic phase, whereas homopolyester 4, prepared from 1,3‐bis(p‐hydroxyphenyl)‐1,3‐propanedione and 4,4′‐hexamethylenedioxydibenzoyl chloride, exhibits a smectic phase. The wide‐angle X‐ray diffraction patterns from the melt‐drawn fibers prepared at mesophase temperatures suggested no orientation for 1, a monoaxial orientation and a crystalline state for 2, a monoaxial orientation and a frozen‐in nematic phase for 3, and a biaxial orientation and a frozen‐in smectic A phase for 4. Introduction of a transition metal (CuCl2 or NiCl2) into copolyesters 2 and 3 gave the corresponding metal‐chelated thermotropic liquid‐crystalline polyesters (5a–c, 6a–c, and 7a–c). Formation of a metal complex among polymer chains by introduction of a metal ion also resulted in better monoaxial orientation according to X‐ray diffraction patterns. The ESR spectra of fibers of copper‐containing polyesters (5a–c and 6a–c) indicated that the plane of the square planar copper complex in the polymers is oriented parallel to the fiber axis.
13C NMR characterization of ethylene oxide/epichlorohydrin copolymer
Authors: Cheng H. N. , Smith David A. 
Published: April 2003

AbstractThe 13C NMR spectra of ethylene oxide/epichlorohydrin copolymers are fully assigned. Information available includes copolymer composition, comonomer sequence distribution, and epichlorohydrin tacticity. The comonomer sequence distribution can be fitted to a two‐component (Bernoullian/Bernoullian) statistical model.