bluuebunny/crossref_metadata_2025_split huggingface dataset:
A polymer as an active ingredient in a drug – the development of Copolymer 1 as a drug against multiple sclerosis
Authors: Sela Michael 
Published: January 2003

AbstractA polymer of four amino acids, L‐lysine, L‐glutamic acid, L‐tyrosine and L‐alanine, prepared from their respective N‐carboxy‐amino acid anhydrides, has been approved by the regulatory agencies in the United States and forty other countries as a drug/vaccine against the exacerbating‐remitting type of multiple sclerosis. The drug, Copolymer 1 (Cop1), is called Copaxone by the industry. It is a specific drug for multiple sclerosis and is not active against other autoimmune diseases. Thus, it serves as a prototype of specific drugs/vaccines against autoimmune diseases. In the case of Cop1, this is due to its immunological cross‐reaction with the myelin basic protein, a substance in the myelin sheath of the brain that seems to be the main cause of the autoimmune phenomenon in multiple sclerosis. From the point of view of polymer chemistry, it is of interest that Copaxone is the first drug of a polymeric nature approved for treatment of a disease. Copyright © 2003 John Wiley & Sons, Ltd.
Synthesis and preliminary in vitro evaluation of polymeric dicarboxylato‐ and dihydroxylatoplatinum(II) chelates as antiproliferative agents
Authors: Neuse Eberhard W. , Mphephu Ntshengedzeni , Netshifhefhe Humphrey M. , Johnson Mark T. 
Published: January 2003

AbstractDespite much progress in the chemotherapy of cancerous diseases, antitumor drugs in current clinical use suffer from major pharmacological deficiencies. The platinum drug family, represented by the parent drug cisplatin, falls directly into this category of medicinal agents, with toxicity and resistance problems implicated as key factors leading to suboptimal therapeutic effectiveness. Polymer–drug conjugation, a technique involving the bioreversible drug binding to suitably designed, water‐soluble carrier polymers, ranks as one of the most promising tools in advanced drug research for the enhancement of a drug's therapeutic index through modification of its pharmacokinetic pathway. The conjugate acts as a prodrug, transporting the bioactive constituent from central circulation to, and into, the transformed target cell, where it is released from the carrier for biological action. This technique is utilized here as a means to enhance the therapeutic effectiveness of selected platinum drug species. Platinum is polymer‐bound (conjugated) through chelation with carrier‐attached pairs of carboxyl or hydroxyl functionalities carrier‐attached in 1,1‐ or 1,2‐geometry, acting as leaving group ligands upon metal coordination. Within the carrier's structural framework, the ligand pairs are arranged either as main‐chain constituents or else as side‐chain functionalities. Platinum chelation with these functionalities is accomplished by treatment of the carrier in aqueous solution with trans‐diaminocyclohexanediaquaplatinum(II) dinitrate (DACH‐Pt), used here as the platination agent. Molar reactant ratios are chosen so as to achieve platinum incorporation in the range from about 4% to 7% by mass. Under these conditions the conjugates, purified by dialysis and isolated by freeze‐drying, are found to retain solubility in water. Selected conjugates submitted to a preliminary in vitro screen show antiproliferative activities on a par with cisplatin against the (sensitive) HeLa cancer line, and up to ten times higher than cisplatin against the (multidrug‐resistant) Colo 320 DM Line. Copyright © 2003 John Wiley & Sons, Ltd.
Integrated device based on conjugated oligoaniline
Authors: Kuo Chin‐Tsou , Weng Shou‐Zheng 
Published: January 2003

AbstractAn integrated optoelectronic device is demonstrated with a high–mobility conjugated oligoaniline field‐effect transistor (FET) driving a poly(2‐methoxy‐5‐(2′‐ethylhexyloxy)‐1,4‐phenylene)vinylene (MEH‐PPV) light‐emitting diode (LED). The FET fabricated with oligoaniline (16‐mer) thin film as the semiconductor layer exhibits ideal source current–drain‐source voltage characteristics. Its performance is close to those of inorganic amorphous silicon FETs, with field‐effect mobilities of 0.1–1.0 cm2/V s and on–off current ratio of 106. The FET‐LED integrated device exhibits a current of 8 × 10−4 A with the maximum brightness on the order of 10 cd/m2 at gate voltage of −100 V and drain‐source voltage of 60 V. Copyright © 2003 John Wiley & Sons, Ltd.
Water‐soluble acidic polyelectrolytes with metal‐removing ability
Authors: Rivas Bernabé L. , Pereira Eduardo D. , Gallegos Paola , Geckeler Kurt E. 
Published: January 2003

AbstractWater‐soluble polymers containing carboxylic acid, phosphonic acid, and sulfonic acid groups were investigated as polychelatogens under different experimental conditions. The maximum retention capacity (MRC) of these polymers was determined at different pH and polymer–metal ion ratios. The metal ions investigated were: Ag(I), Cu(II), Co(II), Ni(II), and Cr(III). The MRC values of the divalent metal ions were found to be very similar and higher than those of the trivalent cations, and there was an important effect of the pH on the MRC. This indicates that the polymer–metal ion interactions were dominated by electrostatic forces. Copyright © 2003 John Wiley & Sons, Ltd.
Degradation of polyamide‐6 by using metal salts as catalyst
Authors: Klun Urša , Kržan Andrej 
Published: January 2003

AbstractPolyamide‐6 (PA‐6) is a widely used polycondensation polymer that can be recycled by hydrolysis to its monomer ϵ‐caprolactam. The reaction is normally catalyzed by mineral acids. Using microwaves as the source of heating, zinc chloride, acetate and triflate were evaluated as non‐acid catalysts for the reaction. Gravimetric and electron spray ionization mass spectrometry analysis of reaction products showed ZnCl2 as the most effective salt catalyst. A 50wt% (versus PA‐6) addition gave 75% water‐soluble, low‐molecular‐weight oligomers, which is approximately 25% lower than when using phosphoric acid. The triflate salt was effective only when used as an addition to a mineral acid, whereas the acetate was ineffective. FTIR and NMR spectroscopy of degradation products showed that dissociated ions from ZnCl2 bind to the amide group of the polymer. Using the triflate salt no such interaction could be observed, indicating that the degradation and catalysis mechanisms differ with the chloride and triflate salt. Five water‐stable lanthanide triflates showed no catalytic effect on the reaction. Copyright © 2003 John Wiley & Sons, Ltd.
Composite membranes with conducting polymer microtubules as new electroactive and transport systems
Authors: Elyashevich G. K. , Kuryndin I. S. , Rosova E. Yu. 
Published: January 2003

AbstractComposite membranes consisting of microporous polyethylene films and the layers of electroconducting polymers have been elaborated. Polyethylene films were prepared in the process based on melt extrusion with subsequent annealing, uniaxial extension, and thermofixation. Permeability, the size distribution of the through flow channels, and mechanical characteristics of porous films have been determined. Polypyrrole and polyaniline were used as conducting polymers which were deposited onto porous films by oxidative polymerization from a gas (polypyrrole) or liquid (polyaniline) phase of a monomer. It has been shown that the relief‐like character of the surface and the porous structure of polyethylene films provide very high adhesion of conducting layer to porous support. Conducting layers were deposited onto the surface of the porous support and also on the pore walls of pores. The layers inside through flow channels in the porous support form microtubules connecting two membrane surfaces. Surface and volume electrical conductivity, resistance of composite membranes in electrolytes, and their mechanical characteristics have been measured. Shrinkage and thermodeformational behavior of the polyethylene support and composites have been compared and analyzed. Atomic force microscopy, IR spectroscopy, electrochemical measurements, and mechanical and thermomechanical tests have been used for investigation of the structure and properties of porous films and composite membranes. Copyright © 2003 John Wiley & Sons, Ltd.
An X‐ray method for determination of crystallinity as a function of depth from a polymer surface
Authors: Khalfin Rafail L. , Cohen Yachin 
Published: January 2003

AbstractManufactured articles of semicrystalline polymers usually have a variation in texture (degree of crystallinity and crystal orientation) as a function of the depth from the external surface. This is often due to the fact that the crystallization process near the surfaces occurs at different conditions and rates relative to the bulk of the material. In this report we present an X‐ray diffraction technique to elucidate the changes in the degree of crystallinity as a function of depth from the surface. Changes in the scheme of X‐ray diffractometer (reflection or transmission, slit width, etc.), the linear material absorption coefficient (using different wavelengths) and the diffraction angle have different effects on the scattering from layers at different depths. It is thus possible to define the material heterogeneity as a function of depth. This method is demonstrated using a film of vinylidene fluoride–tetrafluoroethylene (5 mol%) copolymer that has been crystallized asymmetrically by quenching on one side. The increase in crystallinity from a negligible value on the quenched side to the bulk value is presented. Copyright © 2003 John Wiley & Sons, Ltd.
Oligophenylazomethines: synthesis, structure, electrochemical property and photocyclization
Authors: Higuchi Masayoshi , Yamamoto Kimihisa 
Published: January 2003

AbstractOligophenylazomethines (OPAs) and the aniline‐capped OPAs (OPA's) as soluble model compounds of polyphenylazomethine (PPA) were synthesized via dehydration of 4‐aminobenzophenone in the presence of TiCl4 or PTS as a Lewis acid. The 1H‐NMR spectra of OPAs revealed that OPAs have some isomers, which are based on the E/Z conformation of the azomethine moieties, and the formation ratio of the E/Z isomers changes due to the intramolecular steric hindrance of the oligomers. The cyclic voltammograms of OPA's showed irreversible redox waves in the presence of trifluoroacetic acid. Photocyclization of OPA's proceeded in concentrated sulfuric acid. Copyright © 2003 John Wiley & Sons, Ltd.
Design your own elastomeric or stereoregular polymer
Authors: Shmulinson Michal , Volkis Victoria , Lisovskii Anatoli , Nelkenbaum Elza , Eisen Moris S. 
Published: January 2003

AbstractThis study reports the synthesis and activity as precatalysts for the polymerization of propylene of five racemic group 4 complexes, cis‐[p‐R′C6H4C(NR)2]2MX2 (R′ = CH3, R = SiMe3, M = Ti, X = Cl (1); R′ = CH3, R = SiMe3, M = Zr, X = Cl (2); R′ = H, R = i‐pr, M = Zr, X = Cl (3); R′ = CH3, R = SiMe3, M = Zr, X = CH3 (4)) and (acac)2MCl2 (M = Ti (5), M = Zr (6)) (acac = acetylacetone). The hydrocarbyl complex 4 was prepared by the alkylation of the corresponding complex 2 with MeLi·LiBr. Reaction of complex 4 with B(C6F5)3 or all complexes with MAO (MAO = methylalumoxane) results in the formation of a “cationic” intermediate complex which rapidly reacts with the incoming monomer. Some of the complexes catalyze the stereoregular polymerization of propylene only under pressure in either toluene or CH2Cl2, producing polypropylene with very large isotacticities (mmmm % = ∼95–98), high melting points (140–154 °C) and similar molecular weights as compared with cyclopentadienyl complexes, whereas complex 5 is active for the polymerization of elastomeric polypropylene. Copyright ­© 2003 John Wiley & Sons, Ltd.
Synthesis of high‐molecular‐weight cyclic and multicyclic polystyrenes
Authors: Lepoittevin Bénédicte , Hémery Patrick 
Published: January 2003

AbstractDifferent cyclic architectures were prepared by combination of living anionic polymerization and coupling reactions. Well‐defined macrocyclic polystyrenes were obtained by reaction of a two‐ended living precursor dianion with an electrophile compound. Two types of coupling agent (diethylenic and dihalogeno compounds) were used and their influence on the cyclization yield was studied. Cyclization with a diethylenic product is preferred as it generates a macrocycle with two living centers and is able to react with a (multifunctional) nucleophile leading to more complex architecture. Cyclic polystyrenes with two attached linear branches were obtained by consecutive coupling of monofunctional and difunctional living chains with DDPE (1,3‐bis(phenyl‐ethylenyl)benzene). High molar mass multicyclic polystyrene was prepared by reaction of living macrocycles with poly(chloromethylstyrene). Size exclusion chromatography and matrix‐assisted laser desorption ionization time of flight (MALDI‐TOF) mass spectrometry analyses have confirmed the high efficiency of these coupling reactions. Copyright © 2003 John Wiley & Sons, Ltd.
Highly conductive, oriented polymer electrolytes for lithium batteries
Authors: Golodnitsky D. , Livshits E. , Ulus A. , Peled E. 
Published: January 2003

AbstractIn semicrystalline complexes of poly(ethylene oxide) (PEO) with different salts, such as lithium iodide, lithium trifluoromethanesulfonate (LiTF) and lithium trifluoromethanesulfonimide (LiTFSI), stretching induced longitudinal DC conductivity enhancement was observed, in spite of the formation of more ordered polymer electrolyte (PE) structure. It was found that the more amorphous the PE, the less its lengthwise conductivity is influenced by stretching. The results of our investigation suggest that ionic transport occurs preferentially along the PEO helical axis, at least in the crystalline phase, and that the rate‐determining step of the lithium ion conduction in LiI:P(EO)20, LiTF:­P(EO)20 polymer electrolytes below Tm is “interchain” hopping. Understanding ion transport processes is clearly a fertile field for research and development in the synthesis of new rigid polymers with ordered channels and composition appropriate for enhanced ionic conductivity. Copyright © 2003 John Wiley & Sons, Ltd.
Controlling the properties of single‐polymer composites by surface melting of the reinforcing fibers
Authors: Rein D. M. , Vaykhansky L. , Khalfin R. L. , Cohen Y. 
Published: January 2003

AbstractAll‐thermoplastic single‐polymer composites are materials in which both the reinforcing fibrous phase and the matrix between them are made of the same thermoplastic polymer. Excellent bonding is achieved by mutual entanglement macromolecules due to controlled surface melting of the fibers. This results in a uniform structure of a single chemical entity. The physical properties of the consolidated material, such as modulus and coefficient of thermal expansion (CTE), can be controlled by the extent of melting effected in the process, which determines the fiber/matrix ratio. The fabrication technology utilizes oriented polymer fibers in various forms: unidirectional lay‐up, woven fabric or chopped fibers/non‐woven felt. The key element in the processing scheme is the control of the fibers' melting temperature by hydrostatic pressure. The fibers are heated under high pressure to a temperature that is below their melting point at the high pressure but above the melting temperature at some lower pressure. Reduction of pressure for controlled time results in melting of the fibers, which starts at the fiber surface. This surface melting under controlled pressure followed by crystallization produces the consolidated structure. We illustrate and describe this process using fibers of ultra‐high‐molecular‐weight polyethylene (UHMWPE), showing the effect of the processing conditions on the flexural modulus, fiber/matrix ratio, and CTE in plane and in the thickness direction. These properties are relevant to the use of such composites as substrates for microwave antennae. Copyright © 2003 John Wiley & Sons, Ltd.
Gel point prediction of metal‐filled castor oil‐based polyurethanes system
Authors: Srivastava Anil , Singh P. 
Published: January 2003

AbstractPrediction of gel point conversion and network formation is of great importance in polycondensation during synthesis as well as processing. It enables one to estimate the safe conversions for reactor operation without gelation and the cycle time during processing, and plays an important role in controlling the molding parameters used for reinforced reaction injection molding (RRIM), reaction injection molding (RIM) and compression molding. Theories of gelation have been extensively published in the literature and supported by experimental data for various polycondensation systems. However, most such studies relate to unfilled systems. In this work, metal‐filled polyurethanes have been synthesized in bulk by reacting toluene di‐isocyanate with castor oil and its polyols possessing different hydroxyl values. Metallic aluminum powder (10–40% by weight) was dispersed thoroughly in castor oil and its polyols before reacting at different temperatures (30–60 °C) in a moisture‐free, inert environment. The gel point conversions were measured experimentally and an empirical model from the experimental data has been developed to predict the gelation behavior. The proposed model could be of immense importance in the paints, adhesives and lacquers industries, which use castor oil in bulk. From these experiments it was concluded that: (i) fine metal powder gives a rise in viscosity; (ii) metal fillers not only restrict the molecular motion due to the increase in viscosity, but also lower the conversion; (iii) the vegetable oil and its polyols have a number of bulky groups, which also impart the delay tendency in gel time; (iv) there is a change in gelation dynamics at 50 °C – this is due to the change in reactivity of di‐isocyanates; (v) the presence of metal filler does not initiate the intermolecular condensation; (vi) there is a gap between theoretical and experimental gel point owing to the unequal reactivity of the secondary alcohol position; (vii) there is an inverse relationship of gel time with the reaction temperature and hydroxyl value of polyols. An empirical model based on process parameters, i.e., hydroxyl value, temperature, shape factor and filler concentration, has been derived and found to be adequate for the metal‐filled system. The correlation coefficient on the data is on the lower side in some cases because the following were not taken into account: (i) the first‐order kinetics followed by the reaction in the second half while it is tending towards gelation; (ii) the error in observing the gel point viscosity; (iii) errors in assuming the spherical shape of aluminum metal powder; (iv) errors due to failure to maintain the constant speed in agitation. Copyright © 2003 John Wiley & Sons, Ltd.
The use of polymers for coating of cells
Authors: Kampf Nir 
Published: January 2003

AbstractBare cells or tissues are sometimes exposed to external hazardous conditions, physical (thermal changes), chemical or biological (such as enzymes, bacteria and viruses). Liquids, semi‐liquids (e.g. gels) or solid films are often used to surround individual cells or tissues in order to protect them and to achieve greater stability in laboratory and industrial uses. On the one hand there is a need for isolation and creating a barrier between the cell and its surroundings, and on the other hand this should not affect the metabolism and viability of the cell used. Polymers are major substances for cell encapsulation and entrapment. These preparations are often used for the manufacture of drugs and other cell metabolites. There are only a few publications describing single‐cell coating. We can consider a definition of coating as a process of surrounding an object with a thin film, having a thickness of only a small fraction of the object's dimensions. Taking this definition into account, in fact, most coating experiments actually deal with entrapment or immobilization rather than coating. The latest research shows for the first time the ability to coat a single cell by producing a thin gel layer around it. Xenopus laevis eggs and embryos were used as a model system for coating with thin films composed of low‐methoxy pectin (LMP), alginate, and ι‐ and κ‐carrageenans. These gums have different compositions and structures and accordingly created different coatings around the cells. The first goal was to achieve a thin film (∼50 µm) around an individual non‐fertilized egg (one cell). Next, the influence of coating an early‐stage toad embryo was tested. All coated embryos appeared to develop normally, similar to non‐coated embryos. The survival percentages after hatching of coated embryos were significantly higher than of the non‐coated control. In addition, the coating served as a barrier to microbial contamination and thus improved survival prospects. The coatings delayed hatching by 18 to 24 hr. At hatch, the embryos were at a more developed stage than their non‐coated counterparts. Thus, coating cells by polymeric thin film appears to be a suitable tool for laboratories interested in performing longer‐term experiments with cells or embryos. Copyright © 2003 John Wiley & Sons, Ltd.
Process–structure–property relationships of erodable polymeric biomaterials, I: Poly(desaminotyrosyl arylates)
Authors: Jaffe Michael , Pai Vaishali , Ophir Zohar , Wu Jing , Kohn Joachim 
Published: January 2003

AbstractPolymeric biomaterials, especially new compositions, are often tested for biocompatibility, bioerosion rate or cell growth specificity without regard to the morphological structures introduced during materials processing. It will be shown that in addition to the potential influence on biological response, processing induced structure profoundly influences materials properties under bio‐relevant conditions. Using a combinatorial library of erodable Polyarylates, these issues will be explored with emphasis on in‐vivo dimensional stability and mechanical property retention. Copyright © 2003 John Wiley & Sons, Ltd.
ATR‐FTIR studies on the effect of strong salting‐out salts on the phase separation scenario in aqueous solutions of poly(N‐isopropylacrylamide) [PNIPA]
Authors: Kesselman Ellina , Ramon Ory , Berkovici Ronen , Paz Yaron 
Published: January 2003

AbstractAttenuated total reflectance (ATR) FTIR spectroscopy was used to investigate the effect of two strong salting‐out salts (Na2SO4 and K2SO4) on the temperature‐induced phase separation process in aqueous solutions of poly(N‐isopropylacrylamide) [PNIPA]. It was found that the addition of these salts not only depresses the phase transition temperature (as was pointed out by other groups in the past) but, in fact, changes the whole scenario below, at, and above the aggregation temperature. Deconvolution of the amide II peak into three sub‐bands reflecting three types of populations that differ by their hydrogen bonding types revealed that the sulfate ions decreased the amount of amide–water hydrogen bonds, while increasing the amount of amide–amide intramolecular H‐bond population. This led to a relatively compact structure even at low temperatures. Based on the behavior of the hydrophobic IR peaks it is suggested that addition of sulfate ions increases the importance of hydrophobic interactions below the phase separation temperature. This study demonstrates the potential of ATR‐FTIR in providing information at a molecular level on phase separation phenomena in aqueous solutions of hydrophobic polymers and, in particular, on the effects of co‐solutes in such systems. Copyright © 2003 John Wiley & Sons, Ltd.