bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermotropic liquid‐crystalline aromatic polyester‐graft‐poly(2,6‐dimethyl‐1,4‐phenylene oxide) copolymers
Authors: Sato Moriyuki , Mangyo Takashi , Mukaida Ken‐ichi 
Published: April 2003

AbstractDicarboxy‐terminated poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO) macromonomers were prepared and subjected to the preparation of tailor‐made aromatic thermotropic liquid‐crystalline (LC) polyester‐graft‐PPO copolymers. The macromonomers were obtained by hydrolysis of dimethyl carboxylate‐terminated PPO macromonomers without cleavage of the PPO chains, which were derived from PPO oligomers with a terminal phenolic OH‐group and a bromo derivative of isophthalate. The tailor‐made aromatic thermotropic LC graft copolymers were prepared by direct polycondensation from the dicarboxy‐terminated macromonomers, p‐hydroxybenzoic acid, aromatic dicarboxylic acids and diphenols at definite mole ratios in pyridine in the presence of diphenyl chlorophosphate as a condensation reagent. The polyester‐graft‐PPO copolymers are thermally stable up to 280–300°C and show a thermotropic LC nematic phase in spite of introduction of PPO grafts on the polyester backbones.
Grafting on polybutadiene with macro or macromonomer initiators containing poly(ethylene glycol) units
Authors: Hazer Baki 
Published: April 2003

AbstractCrosslinked poly(ethylene glycol)‐blockpolybutadience block copolymers were obtained by coupling reaction of polybutadiene (PBd) with macromonomer azo initiators (macroinimers) or polyazoesters (PAE) in moderate yield (22–75%). NMR and FT‐IR spectroscopy measurements were used to characterize and determine the poly(ethylene glycol) (PEG) contents (20–66%). The latter depends on the initial concentration of the azo compounds. Broad melting peaks appear in the DSC curves in a temperature range from about 65–130°C. The crosslinked polymers containing PEG‐1500 units showed sharp melting transitions and the second heating cycle showed that recrystallization rates are very high. Swelling ratios of the polymer networks were determined in water (1,22–2,96) and in CHCl3 (7,81–20,84). The morophology of the cold fractured area of the crosslinked polymers was analyzed by scanning electron microscopy (SEM).
Complex‐radical alternating terpolymerization of maleic anhydride, trans‐stilbene and N‐phenylmaleimide
Authors: Rzaev Zakir M. O. , Medyakova L. V. , Mamedova M. A. , Akovali Güneri 
Published: April 2003

AbstractRadical terpolymerizations of maleci anhydride (MA), trans‐stilbene (Stb) and N‐phenylmale‐imide (PhMI) were carried out in methyl ethyl ketone (MEK) at 60–80°C in the presence of 2,2′‐azoisobutyronitrile (AIBN) as initiator. The terpolymerization was evaluated by using either the free monomer or complex participation models. The relative of MA toward poly(Stb) radical was found to be about 10,6 times lower than that of PhMl. The initial rate of copolymerization, the participation of the charge transfer complex (CTC) monomers and free monomers was quantitatively estimated. It was established that, even with a considerable change in the ratio of electron‐acceptor monomers (MA and PhMI) in the initial reaction mixture, terpolymers possessed always a composition ratio close to 1:2:1. Constants for copolymerization of MA…Stb (M1) and PhMI…Stb (M3) were determined by using the Kelen‐Tüdős equation, and r1 · K1/K3 = 0,03 and r2 · K3/1 =0,08, where K1 and K3 are complex‐formation constants of MA…Stb and PhMl…Stb complexes, respectively, were obtained. The result of kinetic studies of terpolymerization was interpreted as involving mainly alternating copolymerization of two complexomers with predominant participation in chain growth. Thermogravimetric analyses indicated the high thermal stabilities of terpolymers obtained.
Steric stabilization by grafting and copolymerization of water‐soluble oligomers and polymers
Authors: Brown Rebecca , Stützel Bernhard , Sauer Thomas 
Published: April 2003

AbstractDifferent types of nonionic, water‐soluble polymers and macromonomers are investigated as emulsion stabilizers in the batch emulsion polymerization of styrene. A power law dependence of the rate of polymerization vs. stabilizer concentration is observed, in formal accordance to Smith‐Ewart kinetics. For water‐soluble polymers, exponents in the range of 0,6 are found which are close to that of the reference anionic surfactant (0,67). The differences are mainly attributed to the larger initial particle size which is accompanied by secondary agglomeration during polymerization. Several reasons for this agglomeration are discussed which have their origin in the solution and adsorption properties of the water‐soluble polymers. Compared to the non‐functional polymers some macromonomers show a similar kinetic behavior with exponents in the range of 0,4 to 0,5, while others give very small values. These differences strongly depend on the molecular structure of the macromonomers. They are in particular attributed to enhanced homopolymerization as well as solubility in monomer and polymer. No secondary agglomeration takes place when using macromonomers as emulsion stabilizers. This is due to the enhanced colloidal stability because of the defined bonding of the macromonomers to the latex particle surface as compared to the more random grafting of the non‐functional water‐soluble polymers.
Group‐transfer alternating copolymerization of 2‐phenyl‐1,3,2‐dioxaphosphorinane with trimethylsilyl 2‐(acryloyloxy)ethanesulfonate
Authors: Kobayashi Shiro , Kadokawa Jun‐ichi 
Published: April 2003

AbstractThis paper describes a new class of reaction, group‐transfer alternating copolymerization (GTAC), between 2‐phenyl‐1,3,2‐dioxaphosphorinane (1) and trimethylsilyl 2‐(acryloyloxy)ethanesulfonate (2). The copolymerization took place without any added catalyst and proceeded via quantitative trimethylsilyl group‐transfer process to give a 1:1 alternating copolymer 3a having a ketene silyl acetal group in the main chain. Results of spectroscopy as well as alkaline hydrolysis and bromination of the copolymer confirmed the structure.
Exchange reactions between covalent and carbocationic species in polymerization of vinyl ethers in the presence of lewis acids: dynamic NMR studies
Authors: Matyjaszewski Krzysztof , Teodorescu Mircea , Lin Chih‐Hwa 
Published: April 2003

AbstractThe ionization of 1‐chloro‐1‐isobutoxyethane (IBVCI) in the presence of BCI3 in CD2Cl2 and CD2Cl2/CDCl3 mixtures at variable temperatures was studied by 1H NMR spectroscopy. The presence of only one NMR signal for the methine proton in the intermediate stage of ionization indicated a fast exchange between covalent and cationic species. The dependence of its chemical shift on the [BCI3]0/[IBVCI]0 ratio was used to calculate the equilibrium constant of ionization at various temperatures, assuming only the ionization‐recombination process. The dependence of the calculate the equilibrium constant (Kapp) on the [BCI3]0/[IBVCI]0 ratio indicated the involvement of additional side equilibria, including the formation of oxonium ions by the reaction between the carbocation and the ether functionality, and the complexation of Lewis acid by the ether group. The width at half‐height of the methine proton signal was used to calculate the apparent rate constant of the recombination of the counterions in the ion pairs (K). It was found that K is larger in CDCI3/CD2CI2 mixtures than in CD2CI2. When BCI3 is present in excess, the calculated rate constants for ionization and recombination are higher than the reported rate constant of propagation for the cationic polymerization of isobutyl vinyl ether (IBVE). Attempts to use this finding in order to prepare well‐defined polymers were unsuccessful because of the consumption of BCI3 through the addition reaction to the double bond of the monomer.
Interpolymer complexes of (co)poly(vinyl ethers) of glycols and poly(carboxylic acids)
Authors: Kudaibergenov Sarkyt E. , Nurkeeva Zauresh S. , Mun Grigorii A. , Ermukhambetova Bayana B. , Akbauova Akzhan T. 
Published: April 2003

AbstractThe complex formation reaction of poly(vinyl ethers) of ethylene glycol (1), poly(vinyl ether) of diethylene glycol (2), copolymers of vinyl ether of ethylene glycol and vinyl butyl ether (3a–3c) with poly(acrylic acid) (PAA) and poly(methacrylic acid) (PMAA) was studied by conductimetric, viscometric and spectroturbidimetric methods in aqueous solution. It is shown that 1 and 2 do not form polycomplexes with PAA. While an introduction of hydrophobic vinyl butyl ether fragments into the structure of 1 enhances the complexation processes with respect to poly(carboxylic acids), the composition of the polycomplexes is independent of the mixing order of interacting components, temperature and composition of the copolymers. An addition of organic solvents to the aqueous solution of the polycomplexes leads to the cooperative destruction of polycomplex particles. An analysis of IR spectra of the polycomplex films shows the existence of COOH dimers, hydrogen bonds between hydroxyl groups and carboxylic groups as well as ester bonds.
Polymerizable dendrimers. Synthesis of a symmetrically branched methacryl derivative bearing eight ester groups
Authors: Draheim Georg , Ritter Helmut 
Published: April 2003

AbstractThe synthesis of chiral acryl and methacryl derivatives containing four ester groups, tetramethyl 5‐((meth)acryloylamino)isophthalamido‐di‐2L‐succinate (2a and 2b), was done by condensation of 5‐(N‐acryloylamino)isophthalic acid (1a) or 5‐(N‐methacrylamino)isophthalic acid (1b) with L‐aspartic acid dimethyl ester in a mole ratio of 1:2. In a similar way, a methacryl monomer bearing eight ester groups, octamethyl 5,5′‐[5‐(methacryloylamino)‐isophthalamido]bis(isophthalamido)tetra‐2L‐succinate (6b), was obtained using the Z‐protected intermediate tetramethyl 5‐(benzyloxycarbonylamino)isophthalamido‐di‐2L‐succinate (4). The monomers were homopolymerized radically with AIBN as initiator, yielding optically active polymers and oligomers (2a′, 2b′ and 6b′) with branched side groups and degree of polymerization Pn between 2 and 23, depending on the architecture of the monomers.
Orientational behavior of side‐chain liquid‐crystalline polysiloxanes deduced from measurements of second harmonic generation
Authors: Nemoto Nobukatsu , Nagase Yu , Abe Jiro , Matsushima Hiroshi , Shirai Yasuo , Takamiya Nobuo 
Published: April 2003

AbstractSide‐chain functionalized polysiloxanes were prepared via polymer‐analogous esterification of poly[(3‐chloroformylpropyl)methylsiloxane] with 4‐(4‐hydroxyphenylazo)nitrobenzene (P1), 4‐[4‐(ω‐hydroxyalkyloxy)phenylazo]nitrobenzene (P2–P4), 4‐{4‐[N‐(2‐hydroxyethyl)‐N‐methyl]anilinoazo}nitrobenzene (P5), 4‐(4‐hydroxypiperidino)nitrobenzene (P6), or 4‐[4‐(2‐hydroxyethyl)piperidino]nitrobenzene (P7)., P1, P3, P4 and P5 exhibit liquid crystallinity, as deduced from differential scanning calorimetry, polarized microscopic observations and X‐ray diffraction measurements. The liquid‐crystalline phase of P1 and P5 is a nematic phase, and that of P3 and P4 is a smectic one. The second harmonic generation (SHG) measurement of a spin‐coated film of P1 was carried out by the Maker fringe method using a Q‐switched Nd:YAG laser (1064 nm). The SHG profile after the heat treatment of a spin‐coated film suggests a perpendicular orientation of the mesogenic molecules to the glass substrate. The SH light intensity of a corona‐poled film was 20‐fold higher than that of a film which was only heated, though no differences were observed in their UV‐vis absorption spectra. These findings suggest that the mesogenic‐molecular dipole moments are aligned to the same direction in the crystalline or liquid‐crystalline phase by a poling treatment.
Kinetic aspect of the emulsion polymerization of cyclothexyl methacrylate
Authors: Chu Hou‐Hsein , Gau Juen‐Hsien 
Published: April 2003

AbstractThe emulsion polymerization kinetics of cyclohexyl methacrylate (CHMA) at 50°C using a mixture of anionic and nonionic surfactants was investigated. The product of the propagation rate constant (Kp) and the number of radicals per particle (n̄) increased monotonously with the volume‐average particle diameter (Dv). The value of Kp was estimated to be 260 L/(mol · s). Changing the monomer mass fraction in the recipe (from 0,14 to 0,40), the value of n̄ remained constant and close to 0,5. On the other hand, increasing the initiator concentration ([I]), the value of n̄ increased rapidly and then leveled off.
Herstellung und Molmassencharakterisierung von poly[(dimethyliminio)ethylen(dimethyliminio)methylen‐1,4‐phenylenmethylen‐dichlorid]
Authors: Beyer Peter , Lechner M. Dieter , Nordmeier Eckhard , Mächtle Walter 
Published: April 2003

AbstractThe ionene poly[(dimethyliminio) ethylene(dimethyliminio) methylene‐1,4‐phenylenemethylene dichloride] was synthesized and characterized. Number‐, mass‐ and z‐average molar masses Mn, Mw and Mz, and molar mass distribution were determined using equilibrium ultracentrifugation. With detection by means of Schlieren, interference, and UV optics. Mw was additionally determined by static light scattering. All measurements yield within the experimental error the same value of Mw viz. Mw = 12,2 · 103 g/mol. This value agrees well with the value from an analysis of kinetical data, viz. Mw = 11,4 · 103 g/mol. Molar mass distribution w(M) was determined from the concentration profile extrapolated to concentration γ0 = 0; it is of a Wesslau‐type and relatively broad. The non‐uniformity U = Mw/Mn − 1 ≈ 3. According to the theory of polycondensation a Schulz‐Flory type of distribution should be obtained. A Schulz‐Flory distribution is not achieved because the monomers p‐xylylene dichloride and N,N,N′,N′‐tetramethylethylenediamine exhibit higher reactivity in the initiation reaction than the homologs during chain propagation which results in a broader molar mass distribution than a Schulz‐Flory distribution.
Molecular motions in a side‐chain liquid‐crystalline polymethacrylate. A thermally stimulated currents study of the dipolar relaxations in the vitreous and liquid‐crystalline phases and at the glass transition
Authors: Mano João F. , Correia Natália T. , Ramos Joaquim J. Moura , Coates David 
Published: April 2003

AbstractIn the present work we report the results of a Thermally Stimulated Discharge Currents (TSDC) study of a side‐chain liquid‐crystalline polymer. The different discharges observed in the TSDC spectrum have been analysed by the thermal sampling technique and have been attributed to specific relaxation mechanisms at the molecular level. A particular feature of the polymer studied in this work is that the mesogenic side group presents both longitudinal and transverse components of the dipole moment, and this seems to be at the origin of the presence of two separated relaxations in the liquid‐crystalline phase.
Poly[n]acene precursors via repetitive Diels‐Alder reactions with dehydrobenzenes
Authors: Horn Thomas , Wegener Stefan , Müllen Klaus 
Published: April 2003

AbstractDue to their instability, higher [n]acenes are even poly[n]acenes are still elusive in solution. In the present paper the synthesis of new poly[n]acene precursors (7, 9) is described from which the fully aromatic structures should be available by pyrolysis in the solid state via cycloreversion. Polymer syntheses were carried out via repetitive Diels‐Alder reaction of a bicyclic bis‐diene precursor with dehydrobenzenes. Repetitive [4 + 2]cycloaddition was employed because of its potential for constructing defect‐free ladder‐type polymers. Arynes have only been used once before in the actual polymerization step of a polymer synthesis, but this case involved an AA‐type diazotated anthranilic acid. The present approach deals with AB‐type monomers containing dehydrobenzenes as active dienophilic species prepared from dibromobenzenes with butyllithium at low temperatures (−40°C). Aromatization of the precursor polymers 6 and 8 with tetrachloro‐p‐benzoquinone provides the aromatized polymers 7 and 9 interrupted only by the bicyclo[2.2.2]octadiene resp. ‐triene units.
Synthesis of N‐acryloyl‐N′‐4‐tolylurea copolymers and their grafting reaction with ceric ion
Authors: Qiu Kun Yuan , Li Zhao Yang , Zhao Tong 
Published: April 2003

AbstractN‐Acryloyl‐N′‐4‐tolylurea (ATU) and N‐methacryloyl‐N′‐4‐tolylurea (MTU) were prepared via the reaction of 4‐tolyl isocyanate with acrylamide or methacrylamide. In conjunction with ceric ammonium nitrate (CAN), ATU and MTU promote the rate of acrylamide polymerization. Macromolecules having 4‐tolylureido pendant groups, such as poly(ATU‐co‐EA) and poly(MTU‐co‐EA), were synthesized by radical copolymerization of ATU and MTU with EA (ethyl acrylate), respectively. In the presence of CAN, a graft copolymerization of acrylamide onto the surface of these two copolymer films took place. The grafted copolymer was characterized by means of XPS and SEM and with respect to water absorption.
Small‐ and wide‐angle X‐ray scattering characterization of 1‐hexene linear low‐density polyethylene
Authors: Marigo Antonio , Cingano Gianmatteo , Marega Carla , Zannetti Roberto , Ferrara Giuseppe , Paganetto Guglielmo 
Published: April 2003

AbstractFour ethylene‐1‐hexene copolymer samples were studied by small‐angle X‐ray scattering in order to investigate the correlation between the crystalline lamellar thickness and the comonomer content. The lamellar thickness was determined from the identity period of the one‐dimensional scattering function and from the analysis of the one‐dimensional correlation function. The crystallinity and the volume of the crystalline unit cell were determined by wide‐angle X‐ray scattering. Some considerations are reported on the effect of the side chains during the crystallization and on the polydispersity of the lamellar thickness.
Crystallization of a copolyester in microlayers and blends with polycarbonate
Authors: Haderski Denise , Nazarenko Sergey , Cheng Chih‐Min , Hiltner Anne , Baer Eric 
Published: April 2003

AbstractThe crystallization behavior of coextruded microlayered sheets comprised of 657 alternating layers of polycarbonate (PC) and a miscible copolyester of mainly 1,4‐cyclohexanedimethanol and terephthalic acid (KODAR) was investigated as a function of annealing time when the KODAR was crystallized isothermally from the glass at 195°C. Comparisons were made with crystallization of KODAR alone, and with crystallization of KODAR from melt blends with PC. The kinetics of crystallization and the morphology of the crystallized KODAR were characterized with differential scanning calorimetry, and by examination of thin sections microtomed from annealed specimens in the polarized light microscope and the transmission electron microscope. The growth rate of small, birefringent KODAR spherulites was non‐linear, and was strongly affected by diffusion of PC into the KODAR layers. Diffusion of amorphous PC into the KODAR layers retarded nucleation and spherulite growth and decreased spherulite density. The effect became more pronounced as the KODAR layer thickness was reduced. Spherulities nucleated randomly throughout the KODAR layers in the PC/KODAR 20/80 (w/w) microlayer and grew rapidly to form a continuous layer of impinged spherulites. In contrast, spherulites in the PC/KODAR 40/60 and 60/40 microlayers nucleated and grew along the center of the KODAR layers where the KODAR concentration was highest.
Study of the dielectric properties of ferroelectric liquid crystals and related side chain liquid crystalline polymers
Authors: Hsiue Ging‐Ho , Lee Kuang‐Rong , Chen J.‐Hong 
Published: April 2003

AbstractBroadband dielectric spectroscopy (frequency range 10−1–106 Hz) was used to analyze the frequency and temperature dependence of the molecular dynamics of a series of ferroelectric liquid crystals (FLCs) and polymers which exhibit a chiral smectic C (S) phase in a wide temperature range (about 190°C) including room temperature. Two ferroelectric modes, Goldstone and Soft mode, were observed in the low‐molar‐mass FLCs. Both of these modes were found in the S phase; however, only the soft mode was present in the smectic A (SA) phase. On the other hand, two collective relaxation processes (Soft and Goldstone mode) and four molecular relaxations (δ, α, β and γ‐relaxation) of the side chain liquid crystalline polymer were demonstrated.
The anionic copolymerization of 5‐(N,N‐diisopropylamino)isoprene with styrene
Authors: Petzhold Cesar , Stadler Reimund 
Published: April 2003

AbstractThe anionic copolymerization of 5‐(N,N‐diisopropylamino)isoprene (N,N‐diisopropyl‐2‐vinylallylamine) and styrene initiated with alkyllithium compounds is studied. Copolymers obtained from different compositions are characterized by size‐exclusion chromatography (SEC), differential scanning calorimetry and by 1H NMR and 13 C NMR spectroscopy. Under these conditions the dialkylaminoisoprene, similar to butadiene and isoprene, is more reactive than styrene and is incorporated faster into the polymer backbone. The incomplete conversion of the monomers has been attributed to the formation of intra‐or intermolecular complexes between the Li+ counterion at the chain end and amino groups. Because of the polarity of the aminoisoprene, no tapered copolymer is obtained, contrary to the isoprene/styrene system. The reactivity ratios of the monomers calculated according to Kelen‐Tudos show that the styryl anion reacts preferably with an aminoisoprene monomer, while the aminoisoprenyl anion tends to homopolymerize.
Control of molecular weight and molecular weight distribution in ethylene polymerization with metallocene catalysts
Authors: Han Taek Kyu , Choi Hong Ki , Jeung Dong Wook , Ko Young Soo , Woo Seong Ihl 
Published: April 2003

AbstractThe molecular weight (MW) and the molecular weight distribution (MWD) of polyethylene (PE) prepared with various metallocene catalysts were investigated. The weight‐average molecular weight (Mw) of PE prepared with dicyclopentadienyltitanium dichloride/aluminoxane (Cp2TiCl2/MAO) was about 4,0 · 105, while that of PE obtained with dicyclopentadienylzirconium dichloride/aluminoxane (Cp2ZrCl2/MAO) is about 1,0 · 105. PE of bimodal MWD was obtained with the mixed catalyst Cp2TiCl2/Cp2ZrCl2. Narrow MWD PE was obtained with the mixed catalyst Cp2ZrCl2/Et(ind)2ZrCl2, because each catalyst produced an Mw of 1,0 · 105. However, the change of temperature during the polymerization with the mixture Cp2ZrCl2/Et(ind)2ZrCl2 produced PE with a bimodal MWD and a value of the ratio of weight‐ to number‐average molecular weights of Mw/Mn = 4.
Electrochromic behavior and stability of polyaniline composite films combined with a polycation‐bathophenanthroline‐Fe complex
Authors: Morita Mitsuyuki 
Published: April 2003

AbstractThe electromic behavior of polyaniline‐poly(sodium acrylate) composite films (CPAn‐PAcNa) combined with a polycation bound to the disulfonated bathophenathroline ligand‐Fe complex (QDM‐BPDS‐Fe) was investigated in a LiClO4CH3CN non‐aqueous aprotic solution. The combination was achieved by chemial deposition of CPAn‐PAcNa on QDM‐BPDS‐Fe. When the combined film was prepared with appropriately low quantities of QDM‐BPDS‐Fe, they showed much wider color changes than those of the component materials by overlapping of the electrochromic behavior of CPAn‐PAcNa and QDM‐BPDS‐Fe. However, it was difficult to control their spectral changes individually by a simple operation of polarizing the whole combined films, because the oxidation potential of CPAn‐PAcNa and QDM‐BPDS‐Fe were close to each other. Their electrochemical activity was lowered by the combination. From Fourier‐transform infrared measurements, it was deduced that such a low stability of the component materials in the combined films was caused by formation of an electrochemically inactive complex by electrostatic interaction between the first oxidized state of polyaniline and the sulfonato groups in BPDS.