bluuebunny/crossref_metadata_2025_split huggingface dataset:
Poly(4‐vinylpyridine) Nanocrosslinked by Polyhedral Oligomeric Silsesquioxane
Authors: Liu Yonghong , Meng Fanliang , Zheng Sixun 
Published: June 2005

AbstractSummary: Octa(propylglycidyl ether) polyhedral oligomeric silsesquioxane (OpePOSS) was used as the crosslinking agent to prepare the nanocrosslinked poly(4‐vinylpyridine) (P4VP) with POSS content up to 55.2 wt.‐%. The formation of the crosslinked structure is ascribed to the macromolecular reaction between pyridine rings of P4VP and epoxide groups of OpePOSS. The POSS‐crosslinked P4VP displayed enhanced glass transition temperatures (Tgs) and an improved thermal stability in terms of the results of thermal analysis.Crosslinking of poly(4‐vinylpyridine) with octa(propylglycidyl ether) polyhedral oligomeric silsesquioxane.magnified imageCrosslinking of poly(4‐vinylpyridine) with octa(propylglycidyl ether) polyhedral oligomeric silsesquioxane.
Polymer Protein Hybrids
Authors: Smeenk Jurgen M. , Ayres Lee , Stunnenberg Henk G. , van Hest Jan C.M. 
Published: June 2005

AbstractStructural proteins form an important source of inspiration for materials scientists, because of the well‐defined relationship between their three‐dimensional folding pattern and their physical properties. Incorporation of structural peptide elements in synthetic polymers allows the combination of natural structural control with synthetic versatility. In this report, two approaches to introduce silk‐inspired β‐sheet elements in hybrid block copolymers are described. In our first approach we have successfully applied the controlled radical polymerization technique Atom Transfer Radical Polymerization (ATRP) to construct ABA triblock copolymers, of which the A blocks consist of PMMA and the B block consists of Ala‐Gly‐Ala‐Gly‐methacrylate moieties. This method leads to triblock copolymers with the structural peptide elements in the side chain of the middle block.Our second approach uses protein engineering for the construction of the β‐sheet element. The latter is converted into a triblock copolymer architecture by modification of both the N and C ends with poly(ethyleneglycol) chains. In this case the B block consists solely of the β‐sheet peptide element. It was demonstrated that it is possible to introduce β‐sheet characteristics in the hybrid material by means of both approaches.
Stereocomplexes of Triblock Poly(lactide‐ PEG2000‐lactide) as Carrier of Drugs
Authors: Bishara Ashgan , Kricheldorf Hans R. , Domb Abraham J. 
Published: June 2005

AbstractTriblock copolymers of poly(lactide)‐poly(ethylene‐glycol)‐poly(lactide) (PLA‐PEG2000‐PLA) were synthesized by ring‐opening polymerization of lactide and PEG2000 diol as co‐catalyst. Stereocomplexes with particle sizes ranging from nanometers to microns were obtained by mixing acetonitrile solutions of pairs of enantiomeric homopoly(lactide) and the triblock copolymers. The stereocomplexes exhibited higher crystalline melting temperatures than the optically pure polymers. The ratio of PLA terminals in the copolymers had a significant effect on their stereocomplex degradation and drug release. These stereocomplexes were used for the encapsulation of dexamethasone for controlled release applications. Dexamethasone phosphate loading capacity, in vitro release, degradation and stability of polymers and formulation were investigated for one month. An increase in the dexamethsone phosphate content in the stereocomplex or a decrease in the PLA ratio in the copolymer resulted in a faster release of drug and polymer degradation.
Effects of Polymer Modification of an Anti‐Cancer Drug with Poly(ethylene oxide)
Authors: Sohn Jung‐Sun , Jo Byung‐Wook , Hess Michael , Schwark Kirsten , Dehne Stephanie , Zähres Manfred 
Published: June 2005

AbstractThe hydrophobic anti‐cancer drug paclitaxel was modified with the hydrophilic poly(ethylene oxide) to a water‐soluble predrug. The modification of the polymer chain results in a different solution behaviour of the macromolecules compared with the unmodified polymer. The phase diagram of the (quasi)binary system predrug‐water was investigated, and molecular simulations of the predrug were executed in vacuum and in the presence of water. The results are important for further engineering on active drug systems.
Preparation and Characterization of Magnetic Targeted Drug Controlled‐Release Hydrogel Microspheres
Authors: Chen Jie , Yang Liming , Liu Yinfeng , Ding Guowei , Pei Yong , Li Jian , Hua Guofei , Huang Jian 
Published: June 2005

AbstractMagnetic targeted drug controlled release hydrogel microspheres were prepared by a radiation technique. Ferric oxide granules (size around 50 nm) were used as the core for magnetic target. The PVP ferrogels (ferromagnetic nanoparticles in hydrogel microsphere) were obtained by irradiating an emulsion of Poly (N‐vinylpyrrolidone) PVP/ferromagnetic granule with cobalt 60 γ–ray. The morphology of the PVP ferrogel was studied by both optical and electronic microscopy, respectively. A broad‐spectrum anticancer drug, Bleomycin A5 Hydrochloride (BLM), was immobilized in the ferrogel and the release property of the drug in vitro was studied. The function of targeting and anti‐cancer was studied on the New Zealand White rabbits, based on the implantation of experimental VX2 squamous cell carcinoma in the auricles of the rabbits.
The Role of Synthetic Pharmaceutical Polymer Excipients in Oral Dosage Forms – Poly(ethylene oxide)‐graft‐poly(vinyl alcohol) Copolymers in Tablet Coatings
Authors: Gutzler Rainer , Smulders Maarten , Lange Ronald F.M. 
Published: June 2005

AbstractA number of tablet coatings are available to provide a controlled release of pharmaceutically active compounds in the stomach or intestine using both instant or sustained released systems. The preferred properties of these tablet coatings are a low solution viscosity (preferable in water) combined with a phase separated morphology, showing good mechanical properties. PEO‐g‐PVAl copolymers have been developed as an instant‐release tablet coating, and were obtained via a conventional radical polymerisation of VAc in the presence of PEO. No free PEO was observed in the PEO‐g‐PVAl copolymers 1f and 1i using 2D LCCC‐SEC and MALDI‐TOF analysis. Next to the requirement of being PEO free, the PEO‐g‐PVAl copolymers show a good combination of film forming properties, a fast dissolution and a low solution viscosity in water. The phase separated morphology, as demonstrated by TEM, DSC, DMTA, and WAXS experiments, should provide the PEO‐g‐PVAl copolymers with relatively constant mechanical properties. A model reaction, using 2‐methoxyethyl‐ether and 1,4,7,10‐tetraoxacyclododecane, has been developed to imitate the grafting reaction of VAc on PEO. Using this model reaction and using the same reaction conditions (temperature, initiator, concentration, VAc:“PEO” ratio, etc.) as applied in the PEO‐g‐PVAl polymerisation procedure, a degree of grafting for PEO of 13±3% was found. Comparing this figure with the results of LCCC‐SEC and MALDI‐TOF measurements, this figure seems a few percent too high, pointing to a slightly increased reactivity of the two model compounds compared to the PEO used.
Preparation and Characterization of pH‐sensitive Hydrogel Film of Chitosan/Poly(acrylic acid) Copolymer
Authors: Yang Liming , Shi Lili , Chen Jie , Pei Yong , Zhu Feng , Xia Yiben 
Published: June 2005

AbstractA hydrogel film of chitosan/poly(acrylic acid) (CS/PAAc) copolymer with the property of pH sensitivity, was prepared by irradiating the chitosan film, which was then swelled by aqueous AAc solutions of different concentrations. The effects of the feed ratio of chitosan and AAc on the properties of the hydrogels, such as swelling ratio and pH‐sensitivity, were determined. Fourier transform infrared (FT‐IR) spectroscopy was applied in the attenuated total reflectance (ATR) mode for analyzing the structure change of the hydrogels after the treatment in buffer solutions of different pHs.
Synthesis and Properties of Poly(N‐isopropylacrylamide‐co‐acrylamide) Hydrogels
Authors: Chen Jie , Pei Yong , Yang Li‐Ming , Shi Li‐Li , Luo Hao‐Jie 
Published: June 2005

AbstractPoly (N‐isopropylacrylamide‐co‐acrylamide) [Poly(NIPAAm‐co‐AAm)] with different feed ratios were obtained by radiation polymerization using Co60γ‐rays. Swelling equilibrium data in various media: deionized water, aqueous NaCl solutions and different pH buffer solutions, were determined. It appeared that the lower critical transition temperature (LCST) of the hydrogels increased with an increasing acrylamide content and decreased with increasing ionic strength. Moreover, LCST was affected by pH.
Synthesis of Chain‐End Functionalized PP and Applications in Exfoliated PP/Clay Nanocomposites
Authors: Wang Z.M. , Han H. , Chung T.C. 
Published: June 2005

AbstractThis paper summarizes our research to the preparation of chain‐end functionalized isotactic polypropylene (i‐PP) having a terminal functional group, such as an OH and an NH2. The chemistry involves metallocene‐mediated propylene polymerization using the rac‐Me2Si[2‐Me‐4‐Ph(Ind)]2ZrCl2/MAO complex in the presence of styrene derivatives (St‐f) and hydrogen, which serve as the chain transfer agents. The molecular weight of the resulting i‐PP polymers with terminal OH or NH2 groups (i.e., PP‐t‐OH and PP‐t‐NH2) are inversely proportional to the molar ratio of [St‐f]/[propylene]. Despite the extremely low concentration of functional groups, the high molecular weight NH3+‐terminated PP (PP‐t‐NH3+) exhibits a distinctive advantage over other functional PP polymers containing side chain functional groups or long functional blocks. The terminal hydrophilic NH3+ cation, with good mobility and reactivity, effectively ion‐exchanges the cations (Li+, Na+, etc.) located between the clay interlayers, and anchors the PP chain to the clay surfaces. On the other hand, the remaining rest of the unperturbed, end‐tethered, high molecular weight PP tail exfoliates the clay layers. This exfoliated structure is maintained even after further mixing of the PP‐bearing platelets with pure, neat PP polymers.
Basic Aspects of Polymer Degradation
Authors: Rivaton Agnès , Gardette Jean‐Luc , Mailhot Bénédicte , Morlat‐Therlas Sandrine 
Published: June 2005

AbstractKnowledge on the mechanisms by which polymers degrade on exposure to natural or artificial ageing has considerably increased during the past few years. One reason for this is the development of novel experimental procedures and analytical techniques. The analyses of the chemical changes permit determining the main degradation routes applicable to the degradation of the properties of materials and ensures the relevance of the laboratory experiments.
Organic Phosphites as Polymer Stabilizers
Authors: Habicher Wolf D. , Bauer Ingmar , Pospíšil Jan 
Published: June 2005

AbstractThe antioxidative action of phosphonites and phosphites depends on their structure, the nature of the polymer to be stabilized and the aging conditions. Phosphorus compounds can act in different ways: as hydroperoxide decomposers (secondary antioxidants), as free‐radical scavengers (primary antioxidants), as well as metal‐complex forming agents. The stabilizing action of phosphites and phosphonites is due to three basic mechanisms: oxidation by hydroperoxides, substitution by alkoxyl radicals and hydrolysis to acidic phosphorus compounds and phenols. Modification of phosphites with additional functional groups such as hindered amine moieties leads to new stabilizing properties. An intramolecular synergistic effect is observed.
Migration of Additives from Poly(vinyl chloride) (PVC) Tubes into Aqueous Media
Authors: Wang Qian , Storm Birgit K. 
Published: June 2005

AbstractThe stability and migration product of medical PVC tubes plasticized with polyadipates were investigated by ageing in phosphate buffer at pH 1.679 and water at different temperatures. Changes in the PVC tubes were studied by water absorption, weight loss, Fourier infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). The low molecular weight migration product that was released was extracted and silylanized before gas chromatography/mass spectroscopy (GC/MS) identification and quantification. After 70 days, the weight loss was less than 0.5% and only a small amount of adipic acid migrated when a tube was aged at 37°C in water and phosphate buffer (pH 1.679), and at 70°C in water after 56 days. However, when aged at 70 and 110°C, gradual deactivation of heat stabilizer after 21 days of ageing in buffer solution and separation of plasticizer from PVC matrix occurred. When the tube was aged at 110°C, significant degradation of both polyadipates and PVC were observed. Adipic acid and 1,4‐butanediol monomers and oligomers of polyadipate were the major migration products from polyadipates in the water ageing solution, while only a relatively high amount of adipic acid was identified as the main product in the buffer ageing solution.
Investigation of Degradation of Structural Adhesives under Influence of Chemicals
Authors: Kjærside Storm Birgit , Gwisdalski Milosz , Lindvang Dan , Rann Michael 
Published: June 2005

AbstractStructural adhesives are used for joining materials also under conditions, where they through the application will be influenced by many different chemicals. The adhesives can – if not protected from the chemical influence – be degradated of the chemicals. The degradation can because of the different structures of the polymers in the adhesives result in lower strength of the joining area, but can also give higher strength but brittleness.Information of the structures of the structural adhesives used in the project have been taken from the data sheets from the manufacturers and have been compared with investigation of the structures by FTIR and DSC. In the laboratory the HSP's (Hansen Solubility Parameters) of the adhesives has been determined and compared with the theoretically estimated HSP's. The estimation has mainly been done by Lydersens group contribution method.The chemical resistance of the adhesives have been foreseen by using HSP's of the adheisves and compared them with the HSP's of the chemicals.The structural adhesives were most of the epoxy types and of the polyurethane types with different curing systems. The structural adhesives should all have high strength and an opening time of more than 30 minutes. They were in the laboratory cured up after the specifications from the manufacturer and were stored one week after curing before they were influenced by hte chosen chemicals. The chemicals were chosen from their functional groups.In the laboratory the adhesives were influenced by different chemicals at room temperarture and under elevated temperature and under different periods to develope the degradation curves for the different chemicals and to foresee the degradation time of the adhesives before their properties were not acceptable any more. The structure after influence of the chemicals is studied by FTIR. The results of the investigations have been that it is possible to estimate the degradation by using the HSP's of the adhesives and the chemicals, but to estimate the time before degradation has been so serious that the properties of the adhesives are not acceptable any more, it is necessary to add laboratory investigations to the HSP comparisons of adhesives and chemicals. The comparison of the HSP and of the chemicals by which the adhesives can be in its lifetime has seen to be usefull especially if the chemicals are pesticides.
Floating Diamonds with Nanomagnetic Particles
Authors: Vatta Laura L. 
Published: June 2005

AbstractIn the diamond industry, ferrofluids are used in ferrohydrostatic separators for the density separation of diamonds from gangue material. The size of the magnetic core of the coated particles forming the ferrofluid suspension is vital in ensuring the stability of the fluid. The particle size must be small enough such that sedimentation does not occur in a magnetic field gradient and under the influence of a gravitational field and such that magnetic agglomeration can be overcome. This paper discusses the particle size requirements for fluid stability under the influence of these effects.
Templating Polymerization of Dodecylammonium Surfactants with Polymerizable (Meth)acrylate Counter Ions
Authors: Hartmann Patrice C. , Sanderson Ronald D. 
Published: June 2005

AbstractBoth dodecylammonium acrylate (I) and dodecylammonium methacrylate (II) are reactive surfactants in which the polymerizable group is the organic counterion. Templating polymerization of I and II from the lyotropic liquid crystalline (LLC) lamellar phase was successfully performed with conservation of the supramolecular structure. A 20 wt% aqueous solution of II formed cubic bicontinuous phases, even upon addition of divinyl benzene (DVB). Polymerization from the cubic phases was attempted without and with DVB (3 wt%). Bicontinuous cubic phases always evolved toward lamellar structures upon polymerization.
Comprehensive Study of Free Radical Copolymerization Using a Monte Carlo Simulation Method, 1
Authors: Mohammadi Yousef , Najafi Mohammad , Haddadi‐Asl Vahid 
Published: June 2005

AbstractSummary: In order to investigate the influence of reactivity ratios and initial feed composition on the microstructure of macromolecules in free radical copolymerization, a comprehensive study was carried out using a Monte Carlo simulation method. As a result, a new procedure was introduced to modify the works of others on the initiation step. The variation of the copolymer composition and the fashion of the arrangement of monomers in simulated chains were evaluated as a function of copolymerization parameters. The model was capable of monitoring any change in azeotropy as well as the magnitude and direction of composition drift from the azeotrope point. The maximum reachable conversion (MRC) was predicted for different combinations of initial feed compositions and reactivity ratios. According to the simulation results, a critical conversion where the macromolecules produced inherited the maximum allowed alternation was obtained for the reactivity ratios given.Change of sequence distribution of simulated copolymer chains with conversion for various initial feed compositions on a triangular graph (rA = 0.5, rB = 0.9).magnified imageChange of sequence distribution of simulated copolymer chains with conversion for various initial feed compositions on a triangular graph (rA = 0.5, rB = 0.9).
Singularity‐Free Brownian Dynamics Analyses of Rotational Dynamics: Non‐Spherical Nanoparticles in Solution
Authors: Naess Stine Nalum , Elgsaeter Arnljot 
Published: June 2005

AbstractSummary: From kinetic theory we have rigorously derived singularity‐free Brownian dynamics analyses of nanoparticle rotational dynamics. The rigid non‐spherical nanoparticles incorporate all three rotational degrees of freedom. This was achieved by using the components of Cartesian rotation vectors as the generalized coordinates describing angular orientation. The new results constitute an important advance compared to the situation when Eulerian angles specify angular orientation. Our finding eliminates one of the main longstanding obstacles to detailed studies of nanoparticle rotational dynamics in the diffusion time domain. The described formalism is applicable to a wide range of nanoparticle systems including liquid crystals, biopolymers, and colloids.
magnified image
Bernoullian, Terminal, Penultimate or Third Order Markov Statistics?
Authors: Karssenberg Frederik G. , Piel Christian , Hopf Andreas , Mathot Vincent B. F. , Kaminsky Walter 
Published: June 2005

AbstractSummary: A series of 7 homogeneous ethylene‐propylene copolymers is modeled by a Bernoullian, a terminal, a penultimate and a third order Markov model and it is found that the penultimate model describes this series best. The Bernoullian and terminal model prove to be insufficient and the third order Markov model is statistically not justified. Based on these results, a criterion to select the optimal Markovian order of homogeneous, single site catalyst produced copolymers is developed.Schematic of the [(3‐MePh)(4‐MePh)C(2,7‐di‐tert‐BuFlu)(Cp)]ZrCl2 metallocene copolymerizing ethene and propene.magnified imageSchematic of the [(3‐MePh)(4‐MePh)C(2,7‐di‐tert‐BuFlu)(Cp)]ZrCl2 metallocene copolymerizing ethene and propene.
Molecular and cell biology of the sarcoglycan complex
Authors: Ozawa Eijiro , Mizuno Yuji , Hagiwara Yasuko , Sasaoka Toshikuni , Yoshida Mikiharu 
Published: June 2005

AbstractThe original sarcoglycan (SG) complex has four subunits and comprises a subcomplex of the dystrophin–dystrophin‐associated protein complex. Each SG gene has been shown to be responsible for limb‐girdle muscular dystrophy, called sarcoglycanopathy (SGP). In this review, we detail the characteristics of the SG subunits, and the mechanism of the formation of the SG complex and various molecules associated with this complex. We discuss the molecular mechanisms of SGP based on studies mostly using SGP animal models. In addition, we describe other SG molecules, ϵ‐ and ζ‐SGs, with special reference to their expression and roles in vascular smooth muscle, which are currently in dispute. We further consider the maternally imprinted nature of the ϵ‐SG gene. Finally, we stress that the SG complex cannot work by itself and works in a larger complex system, called the transverse fixation system, which forms an array of molecules responsible for various muscular dystrophies. Muscle Nerve, 2005
Serial electrophysiologic studies in rhesus monkeys with Krabbe disease
Authors: Weimer Maria B. , Gutierrez Amparo , Baskin Gary B. , Borda Juan T. , Veazey Ronald S. , Myers Leann , Phillippi‐Falkenstein Kathrine M. , Bunnell Bruce A. , Ratterree Marion S. , England John D. 
Published: June 2005

AbstractKrabbe disease is a progressive leukodystrophy that results in demyelination in the central and peripheral nervous systems in humans. It has been described in a number of mammalian species including the rhesus monkey. We performed serial nerve conduction studies beginning within the first 2 months of life in four homozygous, two heterozygous, and two normal rhesus monkeys (Macaca mulatta) to characterize the peripheral neuropathy. Mean conduction velocities of the median, ulnar, and tibial nerves were significantly slower in the affected than unaffected monkeys at all ages (P < 0.0001). The conduction velocity differences became more apparent between the affected and unaffected as the monkeys aged. When compared to the unaffected monkeys, the serial conduction velocities suggested occurrence of dysmyelination followed by demyelination in the affected monkeys. These observations provide further insight into the disease process and suggest an early window of opportunity for treating Krabbe disease. Muscle Nerve, 2005
Chronic exercise accelerates the degeneration–regeneration cycle and downregulates insulin‐like growth factor‐1 in muscle of mdx mice
Authors: Okano T. , Yoshida K. , Nakamura A. , Sasazawa F. , Oide T. , Takeda S. , Ikeda S. 
Published: June 2005

AbstractThe aim of this study was to examine the effects of chronic running exercise on degenerative–regenerative processes in the hindlimb muscles of dystrophin‐deficient mdx mice. The number of large‐sized degenerative–regenerative groups (DRGs) was markedly decreased, whereas that of small‐sized DRGs was unchanged by exercise. Expression of insulin‐like growth factor‐1 (Igf1), as well as a myogenic factor MyoD (Myod1), was downregulated in mdx muscles by exercise. The downregulation of Igf1 may well correlate with the decrease in the population of early regenerating fibers, which existed predominantly in DRGs, because IGF‐1 was mainly localized in these fibers. Our data indicate that chronic exercise may accelerate the active cycle of degeneration–regeneration in mdx skeletal muscles. This means that mdx skeletal muscles can temporarily cope with work‐induced injury by enhancing muscle regeneration and repair, but we speculate that an early decline of IGF‐1 will accelerate age‐dependent muscle wasting and weakness in the later stage of life in mdx mice. Muscle Nerve, 2005