bluuebunny/crossref_metadata_2025_split huggingface dataset:
Biodegradation of ldpe/cellulose blends by common fungi
Authors: Foust Christopher J. , Mills Richard R. , Haas Thomas , Castevens Charles , Ottenbrite Raphael M. 
Published: March 2011

AbstractWe have developed a cellulose‐polyethylene blend polymer film for degradative susceptibility to brown rot or cellulasic fungi. Paxon low‐density polyethylene (LDPE) polymer pellets were melt‐blended with 8855 cellulose. A pure polyethylene sample was melted, pressed and used as the control. Naturally occurring fungi were harvested from decaying wood and cultured on full nutrient agar until individual phenotypes developed. The discrete fungal colonies were isolated and transferred to bacteriological agar with carboxymethylcellulose as the only carbon source. Surviving fungi were subjected to an indirect cellulase assay to confirm cellulolytic properties. Trichoderma viride showed 100% surface area growth on low‐density polyethylene (LDPE) blended with 8% (w/w) cellulose in 90 days. Growth coverage by Gliomastix on LDPE blended with 8% cellulose reached 100 % in 150 days, and up to 72% growth activity on blends with 1.5% cellulose, 1% cellulose, and the control LDPE.
Microspheres by dispersion polymerization of lactides and ϵ‐caprolactone
Authors: Slomkowski Stanislaw , Sosnowski Stanislaw , Gadzinowski Mariusz 
Published: March 2011

AbstractPolyester microspheres were synthesized by the ring‐opening polymerization of lactides (racemate or optically active L,L‐isomer) and ϵ‐caprolactone. Polymerizations were carried out in the 1,4‐dioxane‐heptane mixed solvents in the presence of poly(dodecyl acrylate)‐g‐poly(ϵ‐caprolactone) (poly(DA‐CL)) used as surface‐active agent. Polymerizations were initiated with tin(II) 2‐ethylhexanoate (lactides), diethylaluminum ethoxide or sodium trimethylsilanolate (ϵ‐caprolactone). In the studies of the polymerization of lactides, relations were determined between diameters, the distribution of diameters of synthesized microspheres, and the structure of poly(DA‐CL). It was found that it is possible, depending on thermal treatment of microspheres after synthesis, to obtain polylactide microspheres differing in the degree of crystallinity. Kinetics of the dispersion pseudoanionic and anionic polymerizations of ϵ‐caprolactone were also investigated and the results of these studies were compared with the data for the corresponding polymerizations of ϵ‐caprolactone in solution.
Quantitative comparison of selectivities in the polymerization of cyclic esters
Authors: Baran Jolanta , Duda Andrzej , Kowalski Adam , Szymanski Ryszard , Penczek Stanislaw 
Published: March 2011

AbstractChain transfer processes (ktr) taking place in the polymerization (anionic and pseudoanionic) of cyclic esters (lactones) are reviewed. These reactions are mostly responsible for the departure of these systems from the fully controlled (living) polymerizations. The ratios of kp/ktr have been determined for a number of initiating systems and the structures of the growing species are related to their selectivity, expressed by kp/ktr. It has been shown that the less reactive and more sterically crowded active species polymerize more selectively.
Ultrahigh‐strength self‐reinforced polylactide composites and their surgical applications
Authors: Törmälä Pertti , Pohjonen Timo , Rokkanen Pentti 
Published: March 2011

AbstractBioabsorbable lactide polymers and copolymers were self‐reinforced by die‐drawing to increase their strength and ductility. Self‐reinforced materials were applied in manufacturing ultrahigh‐strength implants, like pins, screws, tacks and stents, for tissue management in different disciplines of surgery.
Processing and in vitro degradation of poly(l‐lactic acid) fibres
Authors: Migliaresi Claudio , Fambri Luca 
Published: March 2011

AbstractHigh‐strength poly(L‐lactic acid) fibres were produced by dry spinning from chloroform solution or melt spinning. Fibres were characterised by viscometric molecular weight, thermal analysis and mechanical properties. Different sets of fibres were subjected to in vitro degradation in Ringer solution at 37°C for up to 16 weeks.
Molecular designing of biodegradable copolypeptide membranes
Authors: Hayashi Toshio , Oka Masahito , Miyachi Yasuyoshi 
Published: March 2011

AbstractTwo‐component random copolypeptide membranes consisting of N‐(hydroxyalkyl)‐ L‐glutamine and L‐leucine or L‐alanine were prepared by carrying out aminolysis reactions with 3‐amino‐l‐propanol (P) together with crosslinking reaction with octamethylenediamine (OMDA) on membranes of the starting copolymers consisting of γ‐methyl L‐glutamate (M) and L‐leucine (L) or L‐alanine (A). The relation between their bulk structure and properties was investigated with regard to the swelling ratio in water (q), the rate of water vapor permeability (Vf), tensile properties, and enzymatic degradation behavior in a pseudo‐extracellular fluid (PECF). The tensile property of the membranes was highly dependent on q in PECF, and on the hydrophobicity of the side chains. It was shown that a common relation was obtained between Vf and q of membranes in PECF regardless of the difference of the nature of side chains. Biodegradation of the membranes in vitro by bromelain indicated that degradation took place in bulk rather than on a surface, and that the rate of degradation was also highly dependent on q of samples as well as on the hydrophobicity of side chains of samples.
Evaluation of biodegradable hydrogels for colon‐specific drug delivery
Authors: Hovgaard Lars , Brøndsted Helle 
Published: March 2011

AbstractThis paper summarizes the work carried out in our group over the last five years on biodegradable dextran hydrogels for colon‐specific drug delivery. Emphasis is placed on the recent developments in the design of dextran hydrogel capsules. The dextran hydrogels were shown to remain intact in the stomach and small intestine but were degraded by microbial dextranases in the colon. A large number of hydrogels with different structures have been studied and characterized in detail with respect to crosslinking density, equilibrium degree of swelling and modulus of elasticity. The release of hydrophilic and hydrophobic model drug molecules from dextran hydrogel discs and capsules have been studied. Biodegradation of the hydrogels was studied using a pure dextranase preparation, in vivo in rats and in vitro in human colon. Degradability was evaluated by measuring the time for complete dissolution of the hydrogels, the change in thickness and dry weight of the hydrogel discs and the production of short‐chain fatty acids. The surface characteristics of gels before and after degradation were studied by scanning electron microscopy.
Polymer liquid dynamics studied via dielectric normal mode spectroscopy
Authors: Kotaka Tadao , Adachi Keiichiro 
Published: March 2011

AbstractDielectric spectroscopy was applied to study dynamics of cis‐polyisoprenes (PI), used as type‐A probe, in blends with polybutadiene (PB) and in block copolymers with polystyrene (PS) of SI‐ and SIS‐type. For dilute high‐molecular weight (M) PI/low‐ M PB blends we identified Rouse mode with M2‐dependent relaxation time τ, while for low‐ M Pi/high‐ M PB blends, we identified pure reptation mode with M3 ‐dependent τ. In between τ ∞ Mα with the exponent α varying from 2 to 3 as MB was increased, as suggested by Graessley with constraint release via tube renewal mechanism. For the blends with the MW ratio MI/MB = 2.5, we found bulk polymer behaviour with τ ∞ M3.5, in which competition between pure reptation and tube renewal appear to be essential and the contribution of contour length fluctuation may be ruled out. For SI‐diblock copolymers between Tg(I) < T < Tg(S) we observed normal modes of I‐block chains tethered on rigid S‐domains. The mode distribution as judged from the dielectric loss ε” curves was dependent on the domain morphology, reflecting restricted motions of crowded I‐tethered chains. For SIS‐triblock copolymers normal modes became appreciable, even below their critical solution temperature, in the range of T > Tg(S), exhibiting broadening due presumably to their micro‐phase‐separated structure. The relaxation mechanisms for such end‐capped I‐chains in SIS‐triblock copolymers could be junction hopping in those with isolated S‐domains but chain rotating in those with S continuous morphologies.
Orientation of amorphous polymers
Authors: Monnerie L. , Jasse B. , Bokobza L. 
Published: March 2011

AbstractOrientation of amorphous polymers stretched at a temperature above their glass‐transition temperature, is involved in thermoforming processing.The molecular processes controlling the orientation and chain relaxation of polymers have been investigated by infrared dichroism in a large series of materials: polystyrene, polymethylmethacrylate of various tacticity and its copolymers with styrene and acrylonitrile.Polystyrene with hydrogenated and deuterated blocks leads to information on the behavior of each block (central part, chain ends) and allows a quantitative comparison with the Doi‐Edwards model for chain relaxation. In order to analyse the effect of polydispersity, blends of hydrogenated and deuerated polystyrene chains with various molecular weights have been studied. Short chains with molecular weights smaller than the molecular weight between entanglements, enhance the relaxation of long chains. Furthermore an anisotropic orientational coupling effect exists between a chain segment and its oriented surrounding.By comparing the orientation of polymers with different chemical structures, it results that they behave differently under temperature conditions where T ‐ Tg = const, but they undergo identical relaxations when the experiments are performed at temperatures chosen in such a way that the monomer friction coefficients are identical.In copolymers of styrene and methylmethacrylate, the two monomer units have different orientations due to local conformational constraints. This effect also accounts for the difference observed between an alternated and a random copolymer.
Improved red dopants for organic electroluminescent devices
Authors: Chen C. H. , Tang C. W. , Shi J. , Klubek K. P. 
Published: March 2011

AbstractA t‐butyl substituted red fluorescent dye, 4‐(dicyanomethylene)‐2‐t‐butyl‐6‐(1,1,7,7‐tetramethyljulolidyl‐9‐enyl)‐4H‐pyran (DCJTB), has been found to be an excellent dopant in AIQ3 which produces a highly efficient organic EL device with improved red chromaticity. Unlike 4‐(dicyanomethylene)‐2‐methyl‐6‐(1,1,7,7‐tetramethyljulolidyl‐9‐enyl)‐4H‐pyran (DCJT), DCJTB can be synthesized in a pure form directly from the unsymmetrical 4‐(dicyanomethylene)‐2‐(t‐butyl)‐6‐methyl‐4H‐pyran without the contamination of the non‐fluorescent bis‐condensation byproduct which is prevalent in the DCJT preparation. Both photoluminescence and electroluminescence in the solid films of DCJTB in AlQ3 are modestly enhanced by the extra t‐butyl substitution as a result of a reduction in the effect of concentration quenching. The operation stability of the DCJTB doped EL device is superior, having a half‐life of over 5,000 h driven at an initial brightness > 400 cd/m2.
Improved stability of molecular organic EL devices
Authors: Fujii Hiroyuki , Sano Takeshi , Nishio Yoshitaka , Hamada Yuji , Shibata Kenichi 
Published: March 2011

AbstractInfluence of emission sites on emission efficiency and running durability of molecular organic electroluminescent devices was investigated. When fluorescent dye rubrene was doped into TPD diamine hole transport layer, rubrene molecule emitted bright yellow light with a max. luminance of 61 000 cd/m2. The device had the highest efficiency of 9.8 Im/W at 100 cd/m2. Half‐decay time of the device from initial luminance of 530 cd/m2 under constant direct current was 3 600 h. On the other hand, when rubrene was doped into BeBq2 complex electron transport layer, the efficiency was 4.4 Im/W and the half‐decay time was 110 h. Thus doping site is found to exert significant influence both on the emission efficiency and the running durability.
Synthesis and properties of novel hole transport materials for electroluminescent devices
Authors: Thelakkat Mukundan , Fink Ralf , Haubner Frank , Schmidt Hans‐Werner 
Published: March 2011

AbstractWe synthesized low molecular weight triphenyldiamines (TPDs), novel 1,3,5‐tris(diarylamino)benzenes (TDABs), polymeric triphenyldiamines and insoluble triphenylamine networks based on tris(4‐ethynylphenyl)amine as hole transport materials for electroluminescent displays. The HOMO energy values as determined from cyclic voltammetry measurements for TPDs and TDABs are between −4.97 and −5.16 eV. By using a polymeric TPD as hole transport layer and tris(8‐quinolinolato) aluminium as emitter, LEDs with an onset voltage of 3V and a luminance up to 900 cd/m2 were obtained under ambient conditions.
A general approach to precursors for poly(arylene vinylene) derivatives: Mechanism, scope and modifications
Authors: Vanderzande Dirk J. , Issaris Anna C. , van Der Michael J. , Borght Albert , van Breemen J. , De Kok Margreet M. , Gelan Jan M. 
Published: March 2011

AbstractA new precursor route for poly(arylene vinylene) derivatives will be presented. In this way non‐ionic precursor polymers are obtained which show an enhanced thermal stability and are soluble in organic solvents. This enables a thorough structural characterization and the study of the mechanism. Experiments have been performed to differentiate between a radical or an ionic polymerization mechanism. Furthermore possibilities to tune solubility characteristics and to introduce defects in the polymer backbone will be discussed. Also the scope for this new route was explored. The first results indicate that the versatility exceeds that of the Wessling route, e.g. the synthesis of precursors for poly(p‐biphenylene vinylene) and poly(2,6‐naphthylene vinylene) could be accomplished in our case, whereas it failed in the case of the Wessling route.
Modification of polymers by adsorption phenomena
Authors: Weidenhammer Petra , Jacobasch Hans‐Jörg 
Published: March 2011

AbstractThe adsorption of ions and amphiphilic molecules on solid polymers is investigated by direct force measurements using an atomic force microscope (AFM). It is shown that electrolyte ions are changing the surface potentials of the solid polymers as well as their adhesive properties. The experiments show that the interaction with a negatively charged probe is dramatically decreased by the adsorption of anions. The adsorption isotherms are determined by zeta potential measurements (streaming potential of flat plates). In presence of adsorbing anions, the attractive interaction and the adhesion are reduced and can be eliminated completely.So, even solutions of simple electrolyte ions can be applied intentionally in order to modify the interaction of polymer surfaces. A wide variety of technological applications becomes accessible.
The combination of ionic surfactants with polyelectrolytes‐a new material for membranes?
Authors: Schwarz Hans‐Hartmut , Richau Klaus , Apostel Regine 
Published: March 2011

AbstractThe combination of two oppositely charged polyelectrolytes results in polyelectrolyte complexes. The simultaneous interfacial reaction between the different polyions leads to formation of polyelectrolyte complex membranes. Some of these have a very good performance in the membrane process pervaporation, especially for dehydration of organic liquids. The combination of a polyelectrolyte with an ionic surfactant of opposite charge results like‐wise membranes but with other separation properties. The differences between the two types of membranes, formed from cellulosesulfate in combination with cationic polyelectrolytes or cationic surfactants, will be discussed.
Multilayers by adsorption of functional polyelectrolytes
Authors: Charlier Valery , Laschewsky André , Mayer Bernd , Wischerhoff Erik 
Published: March 2011

AbstractThe synthesis of polycations bearing reactive groups, namely tertiary anilines located in the side chain or in the main chain, is described. These polyions are employed in conventional alternating polyelectrolyte multilayer assembly or in a modified build‐up process including an azo coupling reaction on the topmost layer after every polycation adsorption step, which offers the potential to create multilayer structures with a non‐centrosymmetric structure. The characterization of these modified assemblies by UV/VIS spectroscopy reveals significant differences in the spectral data in dependence of the polycation structure.
Anew technique for determining the adsorption energy of terminally adsorbed polymer
Authors: Chen Ming‐Hua , Furusawa Kunio 
Published: March 2011

AbstractUsing a new experimental technique, “Continuous Elution Method”, the desorption behavior of polystyrene(PS) and polystyrene (PS‐X) functionalized by a terminal iminium ion (‐X) from α‐Al2O3 and γ‐Al2O3 surface were investigated, and found that PS‐X is forming a terminally adsorbed polymer layer on α‐Al2O3, surface. Furthermore, it was found that the adsorption force of terminally adsorbed polymer is balanced with the desorption force which is contributed from the osmotic pressure in the adsorption layer. Based on this concept, the adsorption energy of the end‐functionalized polystyrene terminally adsorbed on the α‐Al2O3, surface was evaluated to be 4.2 ˜4.3 kT.
Application of cationic polymerization to grafting and coating of silica particles
Authors: Spange Stefan , Eismann Ulrike , Höhne Susanne , Langhammer Elke 
Published: March 2011

AbstractThe cationic polymerization of electron rich monomers such as vinyl ethers, vinyl furane, and cyclopentadiene on silica surfaces can be initiated by aryl methyl halides. The reactions yield always soluble polymers (by heterogeneous catalysis) and novel polymer/silica hybrid materials. The link between polymer and solid is caused by covalent Si‐O‐C bonds, by network formation of the polymers during the chain growth, or by a combination of both of them. The analysis of the polymer structures on the surface by 1H MAS NMR spectroscopy in suspension and by solid state 13C CP MAS NMR spectroscopy is described. Proof of Si‐O‐C bonds via DRIFT spectroscopy and 13C CP MAS NMR spectroscopy is given. The most effective method of irreversibly linking the polymer to the silica surface is the network formation. Polyvinyl ethers are bound strongly to the surface, as can be shown by FTIR measurements, but the linkage is not stable due to the Si‐O‐C bonds' susceptibility to hydrolysis.Poly‐cyclopentadienes (PCPD) are linked to the surface by Si‐O‐C bonds, which show an extraordinary high resistance to acids and bases. Si‐O‐C bond formation of poly‐2‐vinyl furane could not yet be detected by 13C CP MAS NMR spectroscopy and DRIFT spectroscopy. In this case the high degree of coating derives from the bifunctionality of 2‐vinyl furane: it may undergo Friedel‐Crafts‐alkylation at the 5‐position of the furane ring as well as chain polymerization via the vinyl group at the 2‐position.
Direct filature of bacterial cellulose from culture medium
Authors: Tokura Seiichi , Asano Hisashi , Sakairi Nobuo , Nishi Norio 
Published: March 2011

AbstractThe continuous Filature of bacterial cellulose has been achieved directly from culture medium using shallow culture pan newly designed. A remarkable progress of fiber properties was observed comparing with regenerated cellulosic filaments on the filament of bacterial cellulose dependently on the rinsing process with water or ethylene glycol. The progress of fiber properties was also shown on the filament of N‐acetylglucosamine(GlcNAc) incorporated bacterial cellulose probably due to enforcement of fiber interactions. A copolymer of carboxymethylglucose (CM‐Glc) and glucose has been achieved successfully to increase the adsorption capacity for lead ion comparing with original carboxymethyl cellulose (CMC).
Industrial proteins as a green alternative for ‘petro’ polymers: Potentials and limitations
Authors: De Graaf Leontine A. , Kolster Peter 
Published: March 2011

AbstractFor the development of technical applications of polymers from renewable resources, various biopolymers are being studied. In this paper, the opportunities for industrial proteins on this market are discussed e.g. for use in (technical) coatings, adhesives, surfactants and plastics. The use of protein modifications for the improvement of functional properties relevant for technical applications is addressed.
Development and application of highly efficient ruthenium‐based catalysts for the ring opening metathesis polymerization
Authors: Glander S. C. , Nuyken O. , Schattenmann W. C. , Herrmann W. A. 
Published: March 2011

AbstractVarious bisallylic ruthenium(IV) complexes were synthesized and tested as catalysts for the ring opening metathesis polymerization (ROMP) of norbornene. In presence of cocatalysts such as silanes or certain diazoalkanes a significant increase of the catalytic activity could be observed. With these highly efficient systems the ROMP of diolefinic norbornene derivatives (dicyclopentadiene, 5‐ethylidene‐2‐norbornene, norbornadiene) and monomers containing functional groups was achieved (e.g. alcohols, acids, esters, amides, imides, ketones, aldehydes, …).
Copolymerization of CO2 and cyclohexene oxide
Authors: Super M. , Beckman E. J. 
Published: March 2011

AbstractGeneration of high value polymers from carbon dioxide is of general technological interest given that CO2 is both inexpensive and relatively easy to handle on an industrial scale. Previous work on the use of CO2 as a comonomer has focused primarily on development of new catalysts, and the effects of conventional process variables such as temperature and concentration on the polymerization outcome have not been examined in great detail. Recently, we, as well as Darensbourg and colleagues, have shown that one can generate zinc‐based catalysts for the polymerization of CO2 and cyclohexene oxide which produce over 400 grams of polymer per gram of metal. In this paper, we use a product of the reaction between zinc oxide and the fluorinated half‐ester of maleic anhydride to generate copolymers of CO2 and cyclohexene oxide where CO2 is both reactant and sole solvent. In general, we found that the outcome of the polymerization depends greatly on the proximity to the ceiling temperature and the critical cyclohexene oxide concentration, and also on the phase behavior of the cyclohexene oxide‐CO2 binary.
Effect of thermooxidation on tinuvin 783 in LDPE films: Characterization by UV and ftir spectroscopy
Authors: Kaci Mustapha , Rezgui Farouk , Sadoun Tahar 
Published: March 2011

AbstractThe effect of thermooxidation on Tinuvin 783 which is a hindered amine light stabilizer in LDPE films has been investigated by UV and FTIR spectroscopy. Initially, a standard curve describing the variation of the concentration of Tinuvin 783 in LDPE films was plotted using the method of integration of the band area. The relation obtained was: band area = 19.6249 × [Tinuvin 783]. This equation was then applied to measure the variation of the concentration of Tinuvin 783 in the 0.2%wt stabilized samples which have undergone thermooxidation at 90°C for 98 days. The results showed a considerable decrease in the concentration of Tinuvin 783 by 35% during the first 30 days due to probably the formation of nitroxyl radicals. After this, the concentration was observed to be unchanged and may correspond to the phase of nitroxyl radical regeneration. On the other hand, no chemical change in the stabilized LDPE films was observed by FTIR spectroscopy at 90°C during 98 days while the band characteristic of ketone groups (1720 cm−1) was detected for the unstabilized samples after only 11 days. (LDPE: low density polyethylene; HALS: hindered amine light stabilizer)