bluuebunny/crossref_metadata_2025_split huggingface dataset:
Gas permeation properties of polyarylates synthesized with bromine‐ and methyl‐substituted bisphenols
Authors: Kharul Ulhas K. , Kulkarni Sudhir S. 
Published: April 2003

AbstractThe effect of bromine substitution on the bisphenol moiety is investigated in terms of the physical and gas permeation characteristics of the resulting polyarylates prepared with aromatic and naphthenic acids. A comparison of polyarylates based on tetrabromobisphenol‐A (TBrbisA) and tetramethylbisphenol‐A (TMbisA) shows that both substituents increase chain rigidity; however, bromine substitution increases packing density while methyl substitution reduces it. The tetrabromo substitution leads to high selectivities for small gases while the tetramethyl substitution leads to high permeabilities. In order to combine both high permeability and selectivity, both bromine and methyl substitutions were combined in the same polyarylate in two ways: (1) A copolymer based on TMbisA and TBrbisA and (2) a polyarylate based on dibromodimethylbisphenol‐A, (DBrDMbisA). These two hybrid polymers have intermediate permeabilities and higher selectivities than either TMbisA‐ or TBrbisA‐based polyarylates. The copolymer is more selective for CO2 while the polyarylate based on DBrDMbisA is more selective for He.
The possibility of living or long‐lived cationic polymerization in the butyl vinyl ether/iodine/liquid sulfur dioxide system
Authors: Oliveria Marcia G. , Moreira Ana C. F. , Brandão Georgia T. , Gomes Ailton S. , Soares Bluma G. 
Published: April 2003

AbstractThe polymerization of butyl vinyl ether (nBuVE) initiated by iodine in the presence of liquid sulfur dioxide has been investigated. The number‐average molecular weight increased with monomer concentration and after the addition of a fresh feed of the monomer at the end of the first polymerization step. This behavior has been observed in media of different polarity, that is, SO2/toluene = 80 : 10 or 50 : 40 v/v and SO2/CH2Cl2 = 20 : 70 v/v 1H NMR spectroscopy revealed the presence of aldehyde terminal group derived from acetal end group, indicating the presence of living or long‐lived propagating species. The average number of polymer chains carrying aldehyde end groups is higher than the initial iodine concentration, suggesting that an additional initiation process by hydrogen iodide is taking place.
The stability of polyelectrolyte complexes of Calf‐Thymus DNA and synthetic polycations: Theoretical and experimental investigations
Authors: Schindler Thomas , Nordmeier Eckhard 
Published: April 2003

AbstractComplexes of Calf‐Thymus DNA and some polycations such as PDADMAC, IONEN, and P4VP were formed and investigated with respect to their stoichiometry and stability. The central part of the study are two theoretical models, the E‐model and the T‐model. It is assumed that a complex molecule consists of two linear polyion strands connected by electrostatic forces. One strand is a DNA molecule and the other is built by the polycations. Both strands carry equal number of charges, so that the complex molecule is electrically neutral. In the E‐model the complex binding distance, r1, is a constant, while in the T‐model r1 depends on the system parameters, such as the concentration, CS, of added salt or the dielectric constant, ε, of the solvent. Both theories predict a critical salt concentration, CS,d where a complex molecule becomes instable and dissociates in its single strands. According to the E‐model CS,d is 0.6 mol/1 for a 1 : 1 salt if the solvent is water and the temperature 298.16 K. This value agrees quite well with those obtained experimentally, which are 0.5 mol/1 for LiCl, 0.6 mol/1 for NaCl, 0.56 mol/l for KCl, and 0.68mol/1 for CsCl. If the dielectric constant of the solvent decreases, CS,d should decrease. This is also confirmed by the experiment. The T‐model predicts that the complex binding distance, rl,d, at which a complex molecule dissociates, is correlated with CS,d r1,d is large at low CS,d and vice versa. Using the experimental data of CS,d the T‐model predicts that r1 increases from r1 ≈ 3.8 · 10−10 m when the complex is built to r1 = r1,d ≈ 8 · 10−10m when the complex dissociates. This value is nearly as large as the average distance of a counterion bound territorial to a DNA molecule. However, for the divalent cations, Ca2+ and Sr2+, r1,d is only 4 · 10−10 m. This may be unrealistic.
Polymerization of acrylamide in aqueous medium initiated with a redox system composed of cysteine and potassium bromate
Authors: Okaya Takuji , Kikuchi Kenji , Morii Yukiko 
Published: April 2003

AbstractAqueous polymerization of acrylamide initiated with a redox initiator system composed by cysteine and potassium bromate was investigated as a model of the redox initiator system composed of poly(vinyl alcohol) having a thiol groups at one end and potassium bromate. The rate of polymerization was proportional to almost the square root of cysteine and potassium bromate concentration, indicating the initiation system is a usual free radical polymerization initiator. On the other hand, the rate was proportional to the 1.8th power of the monomer concentration. The activation energy of the rate of polymerization was about 5 kcal · mol−1, indicating also a typical redox initiation system. Chain transfer constant of polyacrylamide radical to cysteine was calculated to be 0.4. From these results, it is concluded that cysteine exerts two important roles: (1) as a reductant of the redox initiation and (2) as a powerful chain transfer reagent.
Langmuir‐Blodgett films of photochromic polyglutamates, 10. The influence of the side chain architecture on the thermal and monolayer forming properties of “hairy rod”‐like polymers
Authors: Menzel Henning , Rambke Birgit 
Published: April 2003

AbstractThe phase behavior of so called “hairy rod”‐like polymers with mesogenic elements in the side chains was investigated by means of differential scanning calorimetry and X‐ray diffraction and correlated with the properties of their monolayers at the air/water interface. The side chains of the polymers form a highly ordered (crystalline?) structure. The degree of crystallinity and the temperature of the phase transition to a less ordered liquid crystalline structure depend strongly on the side chain architecture. A higher degree of crystallinity is found for a decyloxy tail group than for a hexyl tail group, since alkoxy groups at the mesogenic elements can be packed more tightly. X‐ray diffraction proves that the side chains with a hexyl tail form a liquid crystalline phase, which may provide a fluid matrix for the rigid rod like backbones. The monolayers of these polymers with the side chains in a liquid crystalline phase at room temperature consist of soft domains and can be transferred to homogeneous Langmuir‐Blodgett films. By way of contrast the polymers in which the side chains are in a more highly ordered (crystalline) phase form stiff domains in the monolayers, resulting in isotherms with a shallow increase in surface pressure. Furthermore, a strong temperature dependence is found for the isotherms which can be interpreted to be a result of domain softening. The monolayers of the polymers with highly ordered side chains can be transferred only after inducing some disorder either photochemically or by increasing the temperature.
Polymorphism in an oligo(aryl ether ketone)
Authors: Rueda Daniel R. , Zolotukhin Mikhail G. , André Isabel , Ripoll Martin Martinez , de Abajo Javier , Alvarez Julio C. 
Published: April 2003

Abstract1,3‐Bis(4‐phenoxybenzoyl)benzene (1) shows a single melting peak at T1 = 120°C when rapidly crystallized from a methanol/benzene mixture (10:1 v/v) (sample A) and a double melting peak at T1 = 120°C and T2 = 130°C when crystallized slowly (overnight) (sample B). Slow recrystallization of 1 using ethanol instead of methanol induces the formation of large single crystals which only show a single melting peak at T2 = 130°C (sample C). Analysis of powder X‐ray diffractograms obtained for A, B and C samples clearly point out the coexistence of two crystalline phases in sample B: phase 1 (observed for sample A) and phase 2 (sample C). From optical microscopy and thermal (DSC) observations, it can be concluded that, upon heating, phase 1 melts at T1 and the molten material converts itself into phase 2 if some crystals of phase 2 are present. Single crystal structure determination of, both, phase 1 and 2 reveal conformational differences of the molecule in both phases which pack in an orthorhombic and a monoclinic unit cell, respectively.
Synthesis and properties of polyamides based on a spirobichroman bis(ether‐carboxylic acid)
Authors: Hsiao Sheng‐Huei , Yang Ching‐Yen 
Published: April 2003

AbstractHigh molar‐mass aromatic polyamides were obtained from 7,7'‐bis(4‐carboxyphenoxy)‐4,4,4′,4′‐tetramethyl‐2,2′‐spirobichroman, a novel dicarboxylic acid monomer, by direct polycondensation reaction in N‐methyl‐2‐pyrrolidone (NMP) with various aromatic diamines, using triphenyl phosphite and pyridine as condensing agents. Polyamides having inherent viscosities of 0,73–1,08 dL/g were obtained in quantitative yield. All the polyamides, even that derived from benzidine, are completely amorphous and readily soluble in a variety of organic solvents such as NMP, N,N‐dimethylacetamide (DMAc), N,N‐dimethylformamide (DMF), and m‐cresol. Their solutions can be cast into transparent, flexible and tough films. All the polyamides show distinct glass transitions in the range of 182–235°C on their differential scanning calorimetry (DSC) traces. The 10% weight loss temperatures in nitrogen and air are above 416 and 422°C, respectively.
Multilayer build‐up of a reactive polymer with α,ω‐functionalized chromophores
Authors: Hausch Marcus , Zentel Rudolf 
Published: April 2003

AbstractAlternating multilayers with up to ten layers have been prepared by sequential reaction of a reactive polymer (poly[(1‐methylvinyl isocyanate)‐alt‐(maleic anhydride)]) with α,ω‐functionalized chromophores. For this purpose new chromophores were synthesized varying the length of the hydrophobic spacer. The analysis of the multilayer build‐up shows that physisorption is more important than chemisorption for fixation of new polymer layers. Thus, a multilayer build‐up is only possible with the shorter, more hydrophilic chromophore and not with the long hydrophobic spacer.
Molecular design of biodegradable functional polymers, 5. Enzymatic degradation of polycarboxylates containing vinyl alcohol blocks as biodegradable segment
Authors: Matsumura Shuichi , Shimagami Youko , Kanamaru Minako , Toshima Kazunobu , Tsuji Masao 
Published: April 2003

AbstractPoly(sodium carboxylate)s containing vinyl alcohol blocks were prepared, and their microbial degradability and the poly(vinyl alcohol) (PVA) dehydrogenase activity as a function of vinyl alcohol block length in the polymer chain were analyzed. A clear relationship between the biochemical oxygen demand (BOD) biodegradability using the activated sludge and the relative activity of PVA dehydrogenase of a PVA‐assimilating strain, Alcaligenes faecalis KK314, was observed. A vinyl alcohol block length of about 7 monomer units corresponds to the minimum chain length of the vinyl alcohol block length which acts as a biodegradable segment in the poly[(disodium fumarate)‐co‐(vinyl alcohol)]. The enzymatic cleavability of polycarboxylates containing vinyl alcohol blocks was estimated using the cell‐free extracts of a PVA‐assimilating microbial strain, A. faecalis KK314, as the PVA‐cleaving enzyme source for both PVA dehydrogenase and hydrolase. The molecular weight of the polycarboxylates was reduced depending on the vinyl alcohol block length, and a similar molecular weight reduction tendency was observed with respect to the BOD values and PVA dehydrogenase activities.
The photoactive diazosulfonate group and its role in polymer chemistry
Authors: Nuyken Oskar , Voit Brigitte 
Published: April 2003

AbstractDiazosulfonates are water soluble, highly photoactive but thermally stable compounds which are prepared from appropriate diazonium salts and sodium sulfite in a diazo coupling reaction. Upon irradiation, the stable trans‐isomer is converted into the instable cis‐isomer, followed by decomposition via a radical or an ionic mechanism with phenyl radicals or diazonium salts, respectively, as intermediates, depending on the reaction conditions. These chromophores could be incorporated as side groups into polymers via copolymerization, copolycondensation or via polymer analogous reaction. Reaction conditions as well as advantages and disadvantages of these different techniques and the photochemistry of the polymers are discussed. Diazosulfonate polymers have been applied successfully as photoresins in offset printing techniques. The use in test stripes in quick assays for the detection of phenolic compounds is discussed based on the coupling reaction of the diazonium salt intermediates. In addition, diazosulfonate containing surfactants could be synthesized and were used as photoactive stabilizers in emulsion polymerization and as partners in photoactive polyelectrolyte‐surfactant complexes.
Poly(ether ketone)s with cyclohexyl‐substituted indan groups in the main chain
Authors: Maier Gerhard , Wolf Martin 
Published: April 2003

AbstractPoly(ether ketone)s containing 1,3‐dicyclohexyl‐1‐methyl‐3‐phenylindan groups in the main chain were prepared from different bisphenols and a bisfluoride monomer which contains the indan group. The bisfluoride monomer was synthesized in a three‐step process, starting from cyclohexyl phenyl ketone. All polymers are soluble in tetrahydrofuran, chloroform and N,N‐dimethylpropyleneurea. No melt transitions were detected by differential scanning calorimetry. Glass transition temperatures are relatively high (218°C to 255°C). In gel‐permeation chromatography with polystyrene calibration, 8400 < M̄n < 17900 and 34500 < M̄w < 76600 were found. The thermooxidative stability of these polymers is fairly low with decomposition starting at 400°C in air. This was attributed to the methine group of the cyclohexyl ring since the major decomposition products proved to be cyclohexane and cyclohexene.
Miscibility and specific interactions in blends of poly(vinyl acetate‐co‐vinyl alcohol) with poly(ethyloxazoline)
Authors: Parada Luis G. , Cesteros Luis C. , Meaurio Emilio , Katime Issa 
Published: April 2003

AbstractMiscibility of poly(ethyloxazoline) (PEOX) with poly(vinyl acetate) (PVAC), poly(vinyl alcohol) (PVAL) and poly(vinyl acetate‐co‐vinyl alcohol) (ACAL copolymers) has been investigated over a wide composition range. In some blends, due to the small difference between the glass transition temperatures of the components, the enthalpic relaxation method was used as miscibility criterion. Differential scanning calorimetry (DSC) results indicate that PEOX is immiscible with PVAC and PVAL but is miscible with ACAL copolymers in a certain range of compositions. The ACAL/PEOX phase diagram for different copolymer compositions has been determined. The variation of the glass transition temperature with blend composition for miscible systems was found to follow the Kwei equation. Infrared spectroscopy studies of blends reveal the existence of specific interactions via hydrogen bonding between hydroxyl groups in vinyl alcohol units and the carbonyl group in the tertiary amide, which appear to be decisive for miscibility.
Synthesis of symmetric and asymmetric carbazolyl monomers and their siloxane polymers. Effect of the 2,3,6,7,9‐substitution in the carbazole unit on its mesomorphic behaviour
Authors: Dobarro Alicia , Velasco Dolores , Arnim Volkmar v. , Finkelmann Heino 
Published: April 2003

AbstractA general synthetic route toward symmetric and asymmetric side‐on and end‐on carbazolyl monomers has been developed. The effect of the nature of the core on the induction of liquid‐crystal phases in side‐on carbazolyl polysiloxanes has been studied. Chromophores have been introduced into the carbazole core to produce materials with improved second‐order non‐linear optical (NLO) properties. The mesomorphic behaviour of all the polymers has been investigated by optical microscopy, differential scanning calorimetry (DSC) and X‐ray diffraction. The side‐on polymers are isothropic or crystalline except one of them that presents a metastable nematic phase.
Oligosaccharide‐based thermotropic liquid crystals, 4. Synthesis of cellobiose‐based twin and triplet derivatives and their mesophase properties
Authors: Takaragi Akira , Sugiura Makoto , Minoda Masahiko , Miyamoto Takeaki , Watanabe Junji 
Published: April 2003

AbstractPrevious work from this laboratory has shown that cellobiose octaalkanoate (COA) functions as a thermotropic discotic mesogen, forming a hexagonal ordered columnar phase (Dho). In this work, we prepared the COA‐based discotic twin and triplet derivatives and examined the mesomorphic properties of the derivatives by DSC, polarization microscopy and X‐ray diffraction. In the former derivative, two cellobiose heptadecanoate (CHD) molecules (monomers) are combined through an alkyl spacer of varying length by ether and ester linkages at the C‐1 position of the reducing end units of the monomers. Three CHD molecules having an alkyl spacer are connected with a coupling agent for the latter derivative. The results revealed that (i) all the twin derivatives form a distinct discotic columnar phase, (ii) the thermal stability of the mesophases of the twins is enhanced, compared with that of the monomer, when the length of the flexible spacer is appropriate, (iii) the twins with a relatively short spacer form a discotic rectangular ordered (Dro) phase, while those with a longer spacer form a pseudo‐Dho phase, (iv) the triplets also form a discotic columnar mesophase, but not a hexagonal ordered columnar (Dho) phase, (v) the thermal stability of the mesophases of the triplets strongly depends on the chemical nature of coupling cores, and (vi) the packing structures of the cellobiose cores within the columns of both derivatives are markedly different from that of the monomer.
New thermotropic copoly(keto esters) based on 3,4′‐disubstituted benzophenones
Authors: Stagnaro Paola , Tavella Flavio , Costa Giovanna , Valenti Barbara 
Published: April 2003

AbstractTwo isomeric benzophenone derivatives, 3‐hydroxy‐4′‐carboxy‐ and 4‐hydroxy‐3′‐carboxybenzophenone, were synthesized and used to prepare new homo‐ and copoly(keto esters) with some commercial comonomers. Polymerizations were performed both by solution and melt polycondensation methods which affect the inherent viscosity and solubility of the resultant products. Yields were always almost quantitative independently of the synthetic method employed. All the samples exhibited very high thermal stability. Phase behaviour and morphology of the polyesters have been investigated by differential scanning calorimetry (DSC) analysis and optical microscopy. A liquid‐crystalline (LC) phase was observed in most of the specimens containing commercial hydroxy acids in percentages higher than 30 mol‐%, while both homopolymers melt to an isotropic liquid. Preliminary gravimetric sorption experiments, using acetone as a penetrant, were carried out on films prepared from some of the copolymers able to give both isotropic non‐crystalline and nematic LC morphologies. The penetrant sorption was strongly reduced by the presence of the frozen nematic LC phase that behaves similarly to the conventional crystalline ordered state.
Study on the cationic polymerization mechanism of 1,3‐dioxepane in the presence of ethylene glycol
Authors: Liu Ye , Wang Hengbin , Pan Caiyuan 
Published: April 2003

AbstractThe cationic polymerization of 1,3‐dioxepane (DOP) initiated with trifluoromethanesulfonic acid (I) in the presence of ethylene glycol (EG) was investigated. At sufficiently low concentration of the initiator ([I] > 0.01 mol/L vs. [EG] < 0.20 mol/L), the molecular weights of the obtained polyacetal oligodiols are controlled by the mole ratio of consumed DOP to initial EG. Gel‐permeation chromatography studies revealed that the concentration of cyclic oligomers in the products are negligible. The mechanism of the polymerization was investigated by means of kinetic studies. The results showed that the polymerization proceeds according to the active chain end mechanism (ACF) in combination with the activated monomer mechanism (AM); thus the cyclic oligomer in the obtained polymer is reduced, and intermolecular chain transfer to EG in ACE is dominant. It was also demonstrated that as [DOP]2[I]/[EG] decreases the contribution of ACE to the polymerization decreases and that of AM increases. In addition, 1H and 13C NMR data illustrated that each macromolecule of polyDOP oligodiols contained one EG unit on average and that no EG end groups exist.
Novel chiral poly(para‐phenylene) derivatives containing cyclophane‐type moieties
Authors: Fiesel Rainer , Huber Joachim , Apel Ute , Enkelmann Volker , Hentschke Reinhard , Scherf Ullrich , Cabrera Karin 
Published: April 2003

AbstractThe introduction of cyclic ansa‐substituents allows for the synthesis of soluble poly‐(para‐phenylene)s PPP's possessing main chain chirality. The novel chiral PPP's represent an attractive combination of π‐conjugated character and chirality. We have synthesized open chain (single‐stranded) as well as ladder‐type chiral PPP's. The single‐stranded chiral PPP's exhibit temperature‐dependent changes of chiroptical properties. The behaviour should be assigned to conformational changes. The chiral ladder polymers contain the cyclophane loops exclusively on one side of the molecular board and are characterized by an unexpectedly high chiroptical activity of the π‐π*‐transition. They are potential candidates to study non‐linear chiroptical properties and to investigate circulary polarized luminescence (photo‐ and electroluminescence) effects.
New polymer syntheses, 91. Hyperbranched poly(ester‐amide)s derived from 3,5‐dihydroxybenzoic acid and 3,5‐diaminobenzoic acid
Authors: Kricheldorf Hans R. , Bolender Oliver , Stukenbrock Thomas 
Published: April 2003

AbstractA new pentafunctional monomer (3a) was prepared by acylation of silylated 3,5‐diaminobenzoic acid (DABA) with 3,5‐bisacetoxybenzoyl chloride. The polycondensation of this monomer or its trimethylsilyl ester yielded a hyperbranched poly(ester‐amide) having a nearly alternating sequence of one DABA and two 3,5‐dihydroxybenzoic acid (DHBA) units. However, due to ester‐amide interchange reactions, ca. 15–25% of the DABA units lose their role as branching units. When 3,5‐bisacetoxybenzoic acid and 3,5‐bisacetamidobenzoic acid were copolycondensed in a 2:1 ratio, the resulting polymer and endgroup structures were different. Furthermore, hyperbranched copoly(ester‐amide)s with a variable DHBA/DABA ratio from 10:0 down to 3:7 were prepared. The glass transition temperature (Tg) increased by approx. 90°C (up to 250°C) at higher molar fractions of DABA. Furthermore, monomer 3a was copolycondensed with 3‐acetoxybenzoic acid or its trimethylsilyl ester. The resulting copoly(ester‐amide)s were again amorphous, showing a continuous decrease of the Tg down to the value of the poly(3‐hydroxybenzoic acid) (poly(3‐HBA)) around 136–140°C.
Novel benzo‐15‐crown‐5 functionalized α‐olefin/CO terpolymers for membrane applications
Authors: Klok Harm‐Anton , Eibeck Peter , Schmid Markus , Abu‐Surrah Adnan S. , Möller Martin , Rieger Bernhard 
Published: April 2003

AbstractThe synthesis of a benzo‐15‐crown‐5 functionalized α‐olefin (4′‐(undec‐10‐enylcarboxylate)benzo‐15‐crown‐5, 5) and its terpolymerization with carbon monoxide and various α‐olefins are described. A decline of the glass transition temperatures (Tg) of the corresponding terpolymers was observed upon incorporating compound 5 into the polymer main chain. Ion‐selective membranes were prepared by encapsulating the benzo‐15‐crown‐5 functionalized α‐olefin/CO terpolymers in a microporous polyethylene support. Preliminary ion‐transport experiments demonstrate the ability of these novel crown ether substituted polyketones to transport NaClO4 across the membranes. Adjusting the polarity of the polyketones via the length of the olefinic side chain offers a means to control the ion‐permeation‐rates.