bluuebunny/crossref_metadata_2025_split huggingface dataset:
Study of Comicellization of Diblock Copolymers in a Selective Solvent
Authors: Pleštil Josef , Koňák Čestmír , Hu Xuesong , Lal Jyotsana 
Published: January 2006

AbstractSummary: The size, aggregation number and other quantities which characterize the formation of micelles in a bidisperse solution of block copolymers which are chemically identical but have different block asymmetries has been studied in a selective solvent using LS and SANS techniques. Experimental results for the comicellization of two chemically identical block copolymers (high molecular weight, PS‐PI, and a low molecular weight dPS‐PI with a deuterated PS block) and two slightly incompatible copolymers (high molecular weight PS‐HPI, and dPS‐PI) in decane, a selective solvent for PI, are reported. Individually, each of the PS‐HPI and PS‐PI copolymers formed micelles with a PS core, which were stable over the entire temperature range covered by the experiments (25–70 °C). The small copolymer, dPS‐PI, formed micelles with a highly swollen core at low temperatures and was molecularly dispersed above the critical micelle temperature (47 °C). Comicellization was observed for both pairs of copolymers studied over a broad range of mixing ratios. The mixed micelles were comprised of large copolymer (PS‐HPI or PS‐PI) and a portion of the small copolymer (dPS‐PI). The amount of adsorbed dPS‐PI copolymer increased with increasing weight fraction of this copolymer and decreased with increasing temperature. The critical comicellization temperature was estimated as 70 and 60 °C for the comicelles based on PS‐HPI and PS‐PI copolymers, respectively. The SANS data suggest that the small copolymer does not form a shell coating the PS core of the initial micelle, but is instead incorporated into the core where it forms a layer of mixed dPS and PS chains.
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First Poly(2‐oxazoline)s with Pendant Amino Groups
Authors: Cesana Sonia , Auernheimer Jörg , Jordan Rainer , Kessler Horst , Nuyken Oskar 
Published: January 2006

AbstractSummary: A new 2‐oxazoline monomer with a Boc protected amino function, 2‐[N‐Boc‐5‐aminopentyl]‐2‐oxazoline; (Boc‐AmOx), was synthesized from commercially available compounds. With an initiator salt system (N‐methyl‐2‐methyl‐2‐oxazolinium triflate; MeOxOTf), the monomer could be converted via living cationic ring‐opening polymerization to well‐defined homopolymers with narrow molar mass distributions and targeted polymer chain length. After a quantitative deprotection, poly(2‐oxazoline)s with pendant amino functions were obtained. In order to vary the polymer functional group density and solubility of the polymer, copolymerization with different monomer ratios of Boc‐AmOx and 2‐ethyl‐2‐oxazoline (EtOx) was performed. Ex‐situ NMR spectroscopy studies verified the randomness of the cationic copolymerization. The accessibility of the pendant amino side functions was confirmed in polymer analog thiourea formation with different isothiocyanates, such as benzyl isothiocyanate (BzNCS), or a fluorescence dye, tetramethyl rhodamine isothiocyanate (TRITC). A cross‐linking reaction with a bifunctional isothiocyanate (Ph(NCS)2) resulted in poly(2‐oxazoline) hydrogels.
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Insights into Bridging Flocculation
Authors: Fellows Christopher M. , Doherty William O. S. 
Published: January 2006

AbstractThe phenomenon of bridging flocculation is very widely encountered in many industrial applications, but is rarely explained with any clarity. In this paper, a cohesive mechanistic model is used to explain the extraordinary effectiveness of bridging flocculation and to guide a body of work on synthesis and application of cationic polymers for the cane sugar industry.
Fluorocarbon End‐functionalized Polymers from Poly(arylether) Dendritic Initiators
Authors: Narrainen A. Pillay , Hutchings L. R. , Feast W. J. , Thompson R. L. , Ansari I. A. , Clarke N. 
Published: January 2006

AbstractFréchet‐type poly(arylether) first and second generation (G1 and G2 respectively) dendrons were prepared from 1‐(bromomethyl)‐3,5‐bis(trifluoromethyl)benzene. The latter and the brominated versions of the two dendrons were successfully employed in the copper mediated living radical polymerization (LRP) of styrene‐d8 giving polymers of predictable molecular weights and narrow polydispersities. Contact angle measurements and ion beam analysis were used to explore the adsorption of these materials to the air‐polymer surface in blended films with unfunctionalized hydrogenous polystyrene. Although contact angle analysis indicated only modest changes in the hydrophobicity and lipophobicity of the surface, ion beam analysis clearly showed the formation of an excess layer of dendron functionalized polymer at the exposed surface that increased with increasing fluorine content.
Microscopic and Molecular Insights into Heterogeneous Phase Degradation of Agars and Carrageenans by Marine Bacterial Galactanases
Authors: Helbert William , Nyvall‐Collen Pi , Michel Gurvan , Czjzek Mirjam 
Published: January 2006

AbstractAgars and carrageenans are sulfated galactans and are the main matrix component of the cell wall of red algae. They form gels made of a 3D network of fibres built by the aggregation of polysaccharide double‐helices. Agarases and carrageenase are enzymes produced by marine bacteria involved in the conversion of algal biomass. We have analyzed the structures and the modes of action of these enzymes adapted to the degradation of anionic polysaccharides in heterogeneous phase. We found that κ‐ and ι‐carrageenases proceed via an endo‐processive mode of action as it was already described for other enzymes active on neutral polysaccharides (cellulose, starch).
Investigation of the Reaction Between Benzophenone and Trimethylaluminium: A Source of Novel Aluminic Activator for Single‐site Olefin Polymerization Catalysts
Authors: Dalet Thomas , Cramail Henri , Deffieux Alain 
Published: January 2006

AbstractThe reaction between benzophenone and TMA was investigated in details at 20 °C for different TMA/benzophenone (r) ratios. For r = 2, a heterodimer µ‐(1,1‐diphenylethoxy)‐µ‐methyl‐tetramethyldialuminium (B) is only formed. The latter was found able to activate MeDIP(2,6‐iPrPh)2FeCl2 catalyst towards ethylene polymerization. Such catalytic system leads to the formation of high molar mass polyethylene with a broad molar mass distribution, without the presence of oligomers, that is attributed to a strong reduction of the transfer reaction to TMA.
Structure and Properties of Nanocomposites Based on SBS Block Copolymer and Alumina
Authors: Adhikari R. , Henning S. , Lebek W. , Godehardt R. , Ilisch S. , Michler G. H. 
Published: January 2006

AbstractThe addition of inorganic filler into commodity plastics has a long history. Today, polymer composites based on nanosized filler are popular among polymer scientists from academia and industries due to their ability to enhance a number of physical properties. In this work, we investigate the dispersion and reinforcing effect of alumina nanoparticles using a polystyrene‐polybutadiene based block copolymer (SBS) and organically modified alumina nanofiller. With the aid of solution casting procedures, polymer composites with good dispersion of nanoparticles could be produced. It has been demonstrated that with suitably coated nanoparticles, polymer composites with optimum dispersion of nanofiller ensuring marked reinforcement effect can be achieved.
Catalytic and Optical Behavior of Polymer Embedded Metal Nanoparticles
Authors: Ciardelli Francesco , Pertici Paolo , Vitulli Giovanni , Giaiacopi Simone , Ruggeri Giacomo , Pucci Andrea 
Published: January 2006

AbstractVery small metal aggregates (nanoaggregates) embedded in an inert polymer matrix, which simply stabilizes the nanodispersion, show unique catalytic and optical behaviour.Indeed Ru‐nanoparticles in vinyl‐aromatic polymers or polyphosphazenes display an enhanced reactivity for hydrogenation of different groups, such as aromatic rings, keto and nitro groups, oximes and nitriles which are converted into the corresponding saturated derivatives under mild conditions.The optical properties of terthiophenethiol‐coated gold nanoparticles in UHMWPE (concentration lower than 4 wt.%) are characterized by poor dichroism due to their centrosymmetric structure. High dichroism (R = 30 at 400 nm, DR = 30) is on the contrary recorded for the terthiophene band showing the chromophores to be sensitive to mechanical orientation also when complexed with gold. On the other hand, nanocomposites based on polymers containing vinyl alcohol units and dispersed gold nanoparticles with average diameter ranging from 3 to 20 nm have been efficiently prepared by an UV photo‐reduction process. Uniaxial drawing of the irradiated Au/polymer nanocomposites favours the anisotropic distribution of packed assemblies of gold particles, providing oriented films with polarization‐dependent tunable optical properties.
Characterization of Polymers by Liquid Chromatography
Authors: Held Daniela , Kilz Peter 
Published: January 2006

AbstractLiquid chromatography (LC) is well established for the comprehensive characterization of complex macromolecules with multiple distributions. Hyphenated chromatographic methods in their various forms are currently one of the most promising and powerful methods for the fractionation and characterization of complex sample mixtures in different property coordinates. Modern detector technologies open up new ways to investigate various properties with high sensitivity even in the low concentration ranges used in chromatography. This paper discusses possibilities and applications for the advanced characterization of macromolecules.
Biopolymers from the Mauritian Marine Environment
Authors: Jhurry D. , Bhaw‐Luximon A. , Mardamootoo T. , Ramanjooloo A. 
Published: January 2006

AbstractTo the best of our knowledge, the extraction of biopolymers from algae and seaweeds still remains untapped. Prior studies in this area have been limited to a taxonomic survey of algae and seaweeds found around our coastal regions. In this paper, we report on the extraction of biopolymers from Hypnea, Eucheuma and Gracilaria species collected around the coastal regions of Mauritius. Various extraction conditions were used and their effects on yield and structure of the corresponding biopolymers were investigated. The extracted polysaccharides were characterized by a combination of IR, NMR, SEC, viscometry and elemental analyses. These revealed that polysaccharide extracted from Gracilaria is a highly methylated agar and Hypnea/Eucheuma contain κ‐carrageenan.
New Chromatographic and Hyphenated Techniques for Hydrophilic Copolymers
Authors: Pasch Harald , Adler Martina , Knecht Daniela , Rittig Frank , Lange Ronald 
Published: January 2006

AbstractMost synthetic polymers are distributed in more than one parameter of molecular heterogeneity. For hydrophobic copolymers there are different chromatographic techniques available to analyse these distributions. As a result of the increasing interest in hydrophilic polymers and copolymers new chromatographic techniques are developed for the characterization of these polymers as well. However, very frequently these polymers contain highly polar or charged functional groups making them soluble only in aqueous mobile phases. There are several problems related to the use of aqueous mobile phases in polymer chromatography. Even the SEC analysis of such copolymers is not straightforward. As for HPLC in aqueous mobile phases, there are only a few applications in the literature so far. In addition to the fact that only a very limited number of stationary phases is available for aqueous HPLC of polymers, the interactions of polyelectrolytes in such chromatographic systems are not well understood.The present paper addresses the problems related to the application of SEC and HPLC in aqueous mobile phases. For graft copolymers with a polyethylene oxide backbone, e.g. PEG‐g‐polymethacrylic acid and PEG‐g‐polyvinyl alcohol, it will be shown that methods can be developed that give accurate molar mass and chemical composition information. Two‐dimensional chromatography where aqueous HPLC and SEC are coupled on‐line will be shown to be the most powerful analysis tool for the analysis of such copolymers. The hyphenation of the chromatographic separation techniques with spectroscopic detection techniques provides further insight into the molecular complexity of these copolymers.
The Progress of Ageing of Lignin‐containing Paper Induced by Light and its Relation to Chemiluminescence – Temperature Runs
Authors: Rychlý Jozef , Matisová‐Rychlá Lyda , Bukovský Vladimír , Pleteníková Martina , Vrška Milan 
Published: January 2006

AbstractLignin‐containing papers from different sources and of different age were irradiated by the visible light and the progress of the degradation reaction was followed by non‐isothermal chemiluminescence method. Kinetic data obtained for papers degraded in oxygen were compared with double fold endurance test and carbonyl groups concentration. The effect of lignin on degradation of cellulose after deacidification treatment of the paper by methoxymagnesium methylcarbonate (MMMC) was ascertained and a mechanism of co‐oxidation of lignin and cellulose in originally alkaline conditions was outlined.
Properties of a Water‐Soluble Paclitaxel Conjugate in Aqueous Solution and its Interaction with Serum Albumin
Authors: Hess M. , Jo B.‐W. , Wermeckes B. , Dehne S. , Sohn J.‐S. , Wunderlich S. , Zähres M. 
Published: January 2006

AbstractA summary of the most recent investigations of conformation and solution properties of a polymer conjugate of the anti‐cancer drug paclitaxel is given. First results of spectroscopic studies of interaction with model proteins in the solid state and in solution are discussed.
Improvements in Polysaccharides for use as Blood Plasma Expanders
Authors: Kulicke W.‐M. , Heinze T. 
Published: January 2006

AbstractModern blood plasma volume expanders consist of water‐soluble polysaccharides that are compatible with the human body. They are more effective for the treatment of intravasal volume deficiency compared to synthetic polymers. These colloidal blood plasma volume expanders, for example pullulan, dextran or hydroxyethyl starch (HES) are used in blood isotonic electrolyte solutions. HES has the lowest tendency to remain in the liver or other organs of the human body in comparison to other expanders.The knowledge of the molar mass and coil dimensions as well as their distribution are essential, since products of low molar masses do not have the desired effect and parts of large molar masses can lead to an anaphylactic shock. Injection of HES enhances the microcirculation and leads to a better oxygen transport into the tissue and the muscle. Because of this, HES was identified as a doping agent in 02/2002. In addition to this it will be shown that starch acetates have an even better physiological compatibility and are an interesting alternative to HES. We will present investigations on the shelf life of a new acetyl starch, which may be an alternative to the blood plasma expanders used to date.
Polymerization of ε‐Caprolactone and its Copolymerization with γ‐Butyrolactone using Metal Complexes
Authors: Bhaw‐Luximon Archana , Jhurry Dhanjay , Motala‐Timol Shaheen , Lochee Yemanlall 
Published: January 2006

AbstractSolution polymerization of ε‐caprolactone (ε‐CL) was performed using four different initiators namely: tin(II) octanoate (Sn(Oct)2)/ethanolamine, aluminium Schiff's base complex‐HAPENAlOiPr, lithium diisopropyl amide (LDA) and aluminium isopropoxide. The reaction conditions varied with the initiator used. LDA gave rise to the most rapid polymerization with the highest amount of cyclic species as detected by 13C NMR. However, no cyclic species were detected when HAPENAlOiPr was used as initiator. The tin(II) octanoate/ethanolamine system lead to an α,ω‐dihydroxy‐polycaprolactone (PCL). The copolymerization of ε‐CL was then performed with the hard to oligomerize γ‐butyrolactone using the four initiators. GPC (Gel Permeation Chromatography) analyses showed the formation of copolymers. The highest incorporation of polybutyrolactone (PBL) in the copolymer was obtained using HAPENAlOiPr as evidenced by 1H NMR. 13C NMR indicated the presence of pseudoperiodic random copolymers with short blocks of PCL whose block length varied with initiator used. The longest and shortest block length were obtained using Sn(Oct)2 and HAPENAlOiPr respectively as calculated from 13C NMR. The reactivity ratios were determined using the Finemann‐Ross method at low conversion with HAPENAlOiPr as initiator. The values obtained, rCL = 19.4 and rBL = 0.11, confirmed the presence of long blocks of CL units in the copolymer.
Kinetic Study of the Al‐Schiff's Base Initiated Polymerization of ε‐caprolactone and Synthesis of Graft Poly(methylmethacrylate‐g‐caprolactone)
Authors: Motala‐Timol Shaheen , Bhaw‐Luximon Archana , Jhurry Dhanjay 
Published: January 2006

AbstractGraft copolymers of polycaprolactone (PCL) on polymethacrylate (PMMA) backbone have been successfully synthesized and characterized by SEC, 1H and 13C NMR spectroscopy. The strategy used consisted of polymerizing ε‐CL, followed by end‐functionalization of the resulting PCL using methacryloyl chloride. Free radical polymerization of the methacryl double bond lead to the C‐C polymer backbone and an overall graft copolymer. The polymerization of ε‐caprolactone was achieved using Al‐Schiff's base isopropoxide (HAPENAlOiPr) in DCM at ambient temperature. SEC and MALDI analysis of the polymers confirmed that mostly linear chains were obtained with the Al initiator, up until high monomer conversion. The low molar mass PCL was then end‐capped with a methacryloyl group, in a quantitative manner, as evidenced by 1H NMR. The macromonomer thus obtained was copolymerized in small proportions with methyl methacrylate by conventional free radical polymerization and atom transfer radical polymerization (ATRP). Analysis of the products by NMR and SEC showed the presence of true graft copolymers and the absence of homopolymers.
Polydioxanone Polymers for Annuloplasty in Valve Repair
Authors: Kalangos Afksendiyos 
Published: January 2006

AbstractThe Kalangos biodegradable ring® was recently developed fpr mitral and tricuspid annuloplasty to allow for flexibility, remodeling and preservation of growth potential of the native annulus. In this article, the results of the experimental trials carried out to assess its safety and potential advantages will be discussed.
Molecular Watchmaking: ab initio Emulsion Polymerization by RAFT‐controlled Self‐assembly
Authors: Sprong Ewan , Leswin Joost S.K. , Lamb David J. , Ferguson Christopher J. , Hawkett Brian S. , Pham Binh T.T. , Nguyen Duc , Such Christopher H. , Serelis Algirdas K. , Gilbert Robert G. 
Published: January 2006

AbstractControlled radical polymerization using RAFT has the potential to make polymers with virtually any desired molecular architecture. For this to be implemented on an industrial scale, it must be performed by polymerization in disperse media. However, simply adding a RAFT agent to a conventional emulsion polymerization recipe leads to a loss of molecular weight control and formation of coagulum, probably because of nucleation in droplets, which is normally an unlikely phenomenon in emulsion polymerizations. Recently, a method has been devised for implementing RAFT in ab initio emulsion polymerization that avoids droplets in the particle formation stage. The molecular weight distribution of the polymer thus formed shows that molecular weight control is maintained throughout the polymerization. A model is developed to predict the particle size formed in this new type of emulsion polymerization. The new methodology enables synthesis of novel dispersions where molecular architecture can be precisely controlled, such as structured core‐shell particles.
Change in Physico‐chemical Properties of PMMA and PS by Copolymerization with an Anionic Amphiphilic Comonomer: Sodium 11‐(methacryloyloxy) undecanylsulfate (MET)
Authors: Hartmann P. C. , Lupo M. , Weber W. , Sanderson R. D. 
Published: January 2006

AbstractSodium 11‐(methacryloyloxy) undecanylsulfate (MET) monomer units were incorporated in polystyrene (PS) and poly(methyl methacrylate) (PMMA) by free radical copolymerization in solution with styrene and methyl methacrylate, respectively. Experimental compositions, thermal degradations, average molecular weights, glass transitions and affinities for moisture were experimentally determined for copolymers of various compositions. Both styrene and methyl methacrylate copolymerized well with MET. An increase in the moisture affinity and a change in the glass transition were observed with increasing MET content in the respective copolymers.
Effects of Laplace Pressure on Propagation and Termination in Aqueous Heterogeneous Free Radical Polymerization
Authors: Zetterlund Per B. , Okubo Masayoshi 
Published: January 2006

AbstractSummary: The influence of the Laplace pressure in polymer emulsion particles during aqueous heterogeneous free radical polymerization on the polymerization kinetics has been investigated. Calculations were carried out based on experimentally reported pressure dependences of propagation and termination rate coefficients. The results suggest that in most cases the effects are not likely to be significant, although under conditions of very small particles (diameter <20 nm) and high interfacial tensions effects of the order of a few percent on propagation (increase in rate) and termination (decrease in rate) were predicted.(kp/kt0.5)/(kp/kt0.5)0 as a function of particle radius as a result of the Laplace pressure.magnified image(kp/kt0.5)/(kp/kt0.5)0 as a function of particle radius as a result of the Laplace pressure.
Differential impairment of the sudomotor and nociceptor axon‐reflex in diabetic peripheral neuropathy
Authors: Berghoff Martin , Kilo Sonja , Hilz Max J. , Freeman Roy 
Published: January 2006

AbstractIt is not known whether C‐fiber functional subclasses are differentially affected by diabetes mellitus or whether the patterns of C‐fiber dysfunction are different between type 1 and type 2 diabetes. We therefore examined efferent sympathetic sudomotor and primary afferent nociceptor C‐fiber function in diabetic patients. Acetylcholine (10%) was used to evoke C‐fiber (axon‐reflex)–mediated responses. The nociceptor (flare) response was measured using a laser Doppler device. The sudomotor response was quantified with silastic imprints. The nociceptor C‐fiber–mediated flare response was reduced in type 2 diabetic patients (P < 0.008) but was similar to controls in type 1 diabetic patients. The sympathetic C‐fiber–mediated responses, including sweat volume (P < 0.05) and the number of activated sweat glands (P = 0.003), were increased in patients with type 1 diabetes. There also was a trend toward a larger axon‐reflex sweat area in patients with type 1 diabetes (P = 0.09). No differences in these sweat responses were found in patients with type 2 diabetes compared to controls. These findings suggest that the functional abnormalities in diabetic peripheral neuropathy are not homogeneous and that C‐fiber subclasses are differentially affected in type 1 and 2 diabetes mellitus. Muscle Nerve, 2006