bluuebunny/crossref_metadata_2025_split huggingface dataset:
Controlled Release of Goserelin from Microporous Polyglycolide and Polylactide
Authors: Kovalchuk Andrey , Fischer Wilfried , Epple Matthias 
Published: April 2005

AbstractSummary: Two microporous biodegradable polyesters, i.e., PGA and PDLLA, were obtained by solid‐state polymerization reaction from the sodium salts of the corresponding α‐hydroxycarboxylic acids after washing out the by‐product sodium chloride. The polymers were shaped by cold uniaxial pressing, by hot uniaxial pressing, and by extrusion at elevated temperature. Due to the special microporosity of the polymers, the introduction of drugs is possible at moderate temperature. The release kinetics of the model drug Phe and of the anti‐tumor drug goserelin (an LH‐RH agonist) from compacted polymer samples were fast (approx. 2 d). The release kinetics of goserelin were corrected for the decomposition of the drug. External coatings with PDLLA or PLLA obtained by immersion in polymer solution strongly slowed down the release kinetics in the case of the PDLLA coating, giving an almost linear release during 100 d. A coating with PLLA was unsuitable to slow down the release kinetics.SEM picture of the surface of a PDLLA‐coated extruded sample (#9).magnified imageSEM picture of the surface of a PDLLA‐coated extruded sample (#9).
Reactive Compatibilization of PA6/LDPE Blends with Glycidyl Methacrylate Functionalized Polyolefins
Authors: Wei Qian , Chionna Donatella , Pracella Mariano 
Published: April 2005

AbstractSummary: Blends of polyamide‐6 (PA6) and low density polyethylene (LDPE) were compatibilized by melt mixing with various polyolefins functionalized with glycidyl methacrylate (GMA), i.e., GMA grafted LDPE (LDPE‐g‐GMA), GMA grafted styrene‐ethylene/butylene‐styrene block copolymer (SEBS‐g‐GMA) and ethylene‐co‐glycidyl methacrylate copolymer (E‐GMA). Blends with PA6/LDPE composition ratios of 25/75 and 75/25 wt.‐%/wt.‐% were prepared in a Brabender internal mixer and their properties were evaluated by SEM, rheological measurements and DSC. Morphological investigation by SEM showed a neat improvement of phase dispersion and interfacial adhesion in all compatibilized blends when compared to PA6/LDPE binary blends. The variation of the dispersed phase size was analyzed as a function of blend composition, compatibilizer concentration and GMA content. The emulsification curves of compatibilized blends showed that the equilibrium size of dispersed particles at the saturation concentration of copolymer was lower when PA6 was the major component. The finest dispersion of the LDPE phase (<0.25 μm) was observed in the presence of SEBS‐g‐GMA copolymer. LDPE‐g‐GMA and E‐GMA displayed a similar compatibilizing efficiency. In all cases, the blends with a polyamide matrix presented a marked rise in torque and melt viscosity with increasing compatibilizer content. These effects were accounted for by a reaction between the epoxide groups of LDPE‐g‐GMA and the carboxyl/amine end‐groups of PA6, leading to the formation of an interchain graft copolymer. The phase transition processes of PA6 in the blends were influenced by the compatibilizer content and the interfacial interactions between the polymer components, suggesting a different role for the compatibilizer at the PA6/LDPE interface.SEM micrograph of PA6/LDPE 25/75 blend compatibilized with 2.5 phr SEBS‐g‐GMA.magnified imageSEM micrograph of PA6/LDPE 25/75 blend compatibilized with 2.5 phr SEBS‐g‐GMA.
Preparation of a Siloxane Acrylic Functional Siloxane Colloid for UV‐Curable Organic‐Inorganic Hybrid Films
Authors: He Jianyun , Nebioglu Ahmet , Zong Zhengang , Soucek Mark D. , Wollyung Kathleen M. , Wesdemiotis Chrys 
Published: April 2005

AbstractSummary: A new siloxane colloid was developed, for the use in UV‐curable inorganic‐organic hybrid films. The UV‐crosslinkable silica‐colloids were prepared from vinyltrimethoxysilane (VTMS) via a sol‐gel method. The structure of silica‐colloids was characterized using 1H NMR, 29Si NMR, FT‐IR, and matrix‐assisted laser desorption/ionization (MALDI‐TOF) mass spectrometry (MS). The particle size of the siloxane colloid was evaluated using atomic force microscopy (AFM) and small angle light scattering (SALS). Organic phase was based on an acrylated polyester which was synthesized using 1,4‐cyclohexane dimethanol (1,4‐CHDM), neopentyl glycol (NPG), 1,6‐hexanediol (1,6‐HD), maleic anhydride (MA), adipic acid (ADA), and acrylic acid (AA). The acrylated polyester was characterized by gel‐permeation chromatography (GPC) and acid titration. A photo‐initiator was added to the formulation and the UV‐crosslinking reaction of hybrid film was monitored via photo‐differential scanning calorimetry (Photo‐DSC) and real‐time infrared spectroscopy (RT‐IR). The effect of the concentration of VTMS colloids, UV‐light intensity, and exposure time on the polymerization rate was investigated and compared with an inorganic‐organic hybrid film based on TEOS oligomers. Photo‐DSC and RT‐IR results indicated that VTMS colloids can greatly increase free radical polymerization rate and the VTMS colloids functioned effectively as cross‐linker and reactive diluent. AFM and small angle light scattering (SALS) data showed that the silica‐colloids were well dispersed in the organic phase.
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Synthesis of Poly(urethane acrylate‐co‐styrene) Films Containing Silver Nanoparticles by a Simultaneous Copolymerization/in situ Electron Transfer Reaction
Authors: Kim Ju‐Young , Shin Dong‐Hyun , Ihn Kyo‐Jin 
Published: April 2005

AbstractSummary: A novel process for the synthesis of nanocomposite films containing silver nanoparticles is presented. Unlike conventional synthetic processes, silver nanoparticles and the polymer film constituting the nanocomposite film were synthesized simultaneously through an in situ electron transfer reaction and the copolymerization of styrene and amphiphilic urethane acrylate nonionomer (UAN), which contains hydrophobic poly(propylene oxide) segments and hydrophilic poly(ethylene oxide) segments along the same backbone. Silver nitrate crystals were first dissolved in a UAN/styrene solution through the formation of a complex between silver salts and the poly(ethylene oxide) chains of UAN, and then the transparent solutions obtained were directly converted to transparent free‐standing films containing silver nanoparticles by copolymerization and an electron transfer reaction by radicals. The amount of radical initiator strongly influenced the size and number of silver nanoparticles formed within the polymer films. The formation of silver nanoparticles was confirmed by transmission electron microscopy (TEM) and characteristic UV absorbance spectra. Hydrophobic/hydrophilic microphase separation in the UAN/styrene solution was also confirmed by TEM and mechanical property measurements.TEM image of poly(urethane‐co‐styrene) film containing silver nanoparticles.magnified imageTEM image of poly(urethane‐co‐styrene) film containing silver nanoparticles.
Enthalpy Relaxation in Poly(4‐hydroxystyrene)/Poly(methyl methacrylate) Blends
Authors: Cowie Iain M. G. , Arrighi Valeria , McGonigle Elizabeth‐Anne 
Published: April 2005

AbstractSummary: The influence of blend composition on enthalpy relaxation behaviour was assessed for miscible blends of poly(4‐hydroxystyrene)/poly(methyl methacrylate) (PHS/PMMA). Values of enthalpy lost (ΔH(Ta, ta)) were calculated from experimental data plotted against log10(ta) and modelled using the Cowie‐Ferguson (CF) semi‐empirical model. This gives a set of values for three adjustable parameters, ΔH∞(Ta), log10(tc) and β. The blends relaxed more slowly than PMMA, but more quickly and less co‐operatively than PHS. Moreover, the blends released more enthalpy than PMMA, but less than PHS. The enthalpy lost by the fully relaxed glass (ΔH∞(Ta)) was less than the theoretical amount possible on reaching the state defined by the liquid enthalpy line extrapolated into the glassy region (ΔHmax(Ta)). Infrared spectroscopy was used for assessing the hydrogen bonding interactions in the blends. The ageing results are discussed with reference to the hydrogen bonding interactions.Dependence of ΔT (□) and ΔCp (▴) on PHS/PMMA blend composition.magnified imageDependence of ΔT (□) and ΔCp (▴) on PHS/PMMA blend composition.
Telechelic and Star‐Shaped Poly(ε‐caprolactone) Functionalized with Triethoxysilyl Groups – New Biodegradable Coatings and Adhesives
Authors: Kricheldorf Hans R. , Hachmann‐Thießen Heiko 
Published: April 2005

AbstractSummary: Monofunctional poly(εCL) having one CH2OH and one CO2CH3 endgroup was prepared by SnOct2 + MeOH‐initiated polymerizations of εCL at 80 °C. The CH2OH endgroups were reacted with IPTES. In this way, poly(εCL) having one CO2CH3 and one TES endgroup was obtained. Poly(εCL) having two CH2OH endgroups were prepared by means of SnOct2 and Tetra EG or 1,4‐butanediol as coinitiators. The molecular weight distribution significantly broadened when the polymerization temperature increased from 80 to 120 °C. The OH endgroups were quantitatively functionalized by addition of IPTES. Star‐shaped poly(εCL)s having three or four OH endgroups were prepared with 1,1,1‐tris(hydroxymethyl)propane or pentaerythritol as coinitiators. All endgroups were modified with IPTES. The lengths of the poly(εCL) segments were varied via the monomer/coinitiator ratio. All functionalized oligomers were characterized by 1H NMR spectroscopy and MALDI‐TOF mass spectrometry. Preliminary studies of film formation and adhesive properties were performed.MALDI‐TOF mass spectrum of a poly(εCL) initiated with Sn(Oct)2 and 1,4‐butanediol and functionalized with IPTES.magnified imageMALDI‐TOF mass spectrum of a poly(εCL) initiated with Sn(Oct)2 and 1,4‐butanediol and functionalized with IPTES.
Morphological Studies of Epoxy/Polyaniline Blends
Authors: Tsotra Panayota , Gryshchuk Oleg , Friedrich Klaus 
Published: April 2005

AbstractSummary: Polyaniline‐dodecybenzenesulfonic acid (PANI‐DBSA)/epoxy resin (EP) blends were prepared by a solution‐in‐toluene process and direct mixing of PANI‐DBSA with EP. The dispersion quality of PANI‐DBSA proved to be strongly related to the final electrical properties of the cured blends. The solution processed blends showed enhanced electrical properties with small PANI‐DBSA contents (percolation threshold determined was around 2.3 wt.‐% PANI‐DBSA). The morphologies of these blends were investigated by atomic force (AFM), scanning electron (SEM) and transmission electron (TEM) microscopy. The existence of a translucent PANI‐DBSA network exists within the EP matrix. The microscopy investigations were in agreement with the results from differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA).SEM image of the PANI‐DBSA‐rich regions (indicated by arrows) surrounded by the conductive EP/PANI‐DBSA matrix (5 wt.‐% PANI‐DBSA).magnified imageSEM image of the PANI‐DBSA‐rich regions (indicated by arrows) surrounded by the conductive EP/PANI‐DBSA matrix (5 wt.‐% PANI‐DBSA).
Vacuum Ultraviolet Photolysis of Hydrocarbon Polymers
Authors: Truica‐Marasescu Florina‐Elena , Wertheimer Michael R. 
Published: April 2005

AbstractSummary: The wavelength‐dependent vacuum ultraviolet (VUV) photolysis of several polymers, low density polyethylene (LDPE), biaxially oriented poly(propylene) (BOPP), atactic polystyrene (PS), and poly(methyl methacrylate) (PMMA), was studied by irradiation in vacuum with the well‐characterized emissions from four different resonant or excimer VUV sources. These lamps comprise radiofrequency (r.f.) discharges in different noble gases, such as krypton, xenon (at low pressures, producing near‐monochromatic resonant line radiations), xenon excimer (at “high” pressure), and a deuterium/argon mixture (producing a broad‐band emission). VUV‐induced mass loss (ablation or etching) was monitored in situ by quartz crystal microbalance measurements. Following irradiation, samples were analysed by ATR‐FTIR and XPS, to evaluate near‐surface structural changes (e.g., creation of unsaturation, cross‐linking) resulting from the VUV‐initiated bond scissions and radical‐creation reactions. PMMA was the most readily ablatable polymer, whereas the mass loss of BOPP was higher than that of LDPE, regardless of the irradiation wavelength, λ. All polymers were found to form double bonds, with the exception of PS, which is rather stable, probably due to energy dissipation by fluorescence.Formation of double bonds in a) vinyl‐, b) vinylidene‐, and c) vinylene‐like unsaturated groups, as a function of the radiation dose, D, for KrL (▪), XeL (▴), and D2Ar‐irradiated (•) PMMA.magnified imageFormation of double bonds in a) vinyl‐, b) vinylidene‐, and c) vinylene‐like unsaturated groups, as a function of the radiation dose, D, for KrL (▪), XeL (▴), and D2Ar‐irradiated (•) PMMA.
2H NMR Study of Aromatic Guest Dynamics in Clathrate Phases of Syndiotactic Polystyrene
Authors: Albunia Alexandra R. , Graf Robert , Guerra Gaetano , Spiess Hans Wolfgang 
Published: April 2005

AbstractSummary: 2H NMR solid‐state spectra of aromatic molecules (benzene, toluene, chlorobenzene, naphthalene) included in clathrate phases of syndiotactic polystyrene (s‐PS) or absorbed in the amorphous phase of s‐PS, have been recorded and analyzed for a broad range of temperature (230–360 K). The dynamic processes accessible to aromatic molecules absorbed in s‐PS clathrate phases are essentially temperature independent for the whole temperature range under investigation. Moreover, the molecular re‐orientations reflected in the NMR line‐shapes are similar to those accessible to the same molecules when absorbed in polystyrene amorphous phase at temperatures substantially lower than the polymer glass transition temperature. A simulation procedure for 2H NMR line‐shape analysis has been used to establish models for the dynamic processes of the different aromatic guest molecules.Solid‐state 2H NMR spectrum of naphtalene‐d8 in the amorphous phase of a semi‐crystalline s‐PS film (A), in the s‐PS clathrate phase (B) and the simulated spectrum for a static CD bond (C).magnified imageSolid‐state 2H NMR spectrum of naphtalene‐d8 in the amorphous phase of a semi‐crystalline s‐PS film (A), in the s‐PS clathrate phase (B) and the simulated spectrum for a static CD bond (C).
FTIR‐Spectroscopy on Segmental Reorientation of a Nematic Elastomer under External Mechanical Fields
Authors: Tammer Michael , Li Jianjun , Komp Ansgar , Finkelmann Heino , Kremer Friedrich 
Published: April 2005

AbstractSummary:Fourier transform infrared (FTIR) spectroscopy with polarized light is employed to study the segmental orientation and the order of a nematic liquid crystalline elastomers (NLCEs) with a monodomain structure in response to an external mechanical field. The reorientation and the order parameter of the different molecular moieties are analyzed in detail, revealing information about angular excursion in the rearrangement of the mesogens, the spacer molecules, and the main‐chain. In case of an elongation of the NLCE films perpendicular to the initial mesogen orientation, no reorientation or change of order is observed for an elongation ratio less than 1.3. At higher strain, a molecular reorientation process is induced on all molecular segments and the order of alignment is decreased. When the NLCE‐films are stretched parallel to the mesogens, no molecular reorientation takes place and the order parameters show no significant change.Angular reorientation of different molecular moieties at mechanical strain perpendicular to the initial mesogen orientation.magnified imageAngular reorientation of different molecular moieties at mechanical strain perpendicular to the initial mesogen orientation.
A Semi‐Batch Process for Nitroxide Mediated Radical Polymerization
Authors: Wang Yanxiang , Hutchinson Robin A. , Cunningham Michael F. 
Published: April 2005

AbstractSummary: A semi‐batch process using nitroxide mediated polymerization, was explored for the design of low molecular weight solvent‐borne coatings, typical of those used in the automotive industry. While living radical polymerization (LRP) offers many advantages in the control of polymer chain microstructure that may confer important physical and chemical property benefits to coatings, adapting LRP to a semi‐batch process poses significant challenges in the design and operation of the process. Using styrene monomer, various two‐component initiating systems (free radical initiator, 4‐hydroxy‐TEMPO) were studied to understand the effects of different initiators on the course of polymerization. In addition, an alkoxyamine was synthesized and used as the initiating source. The initiators Luperox 7M75 and Luperox 231 give higher polymerization rates and reasonable control over polymerization, while benzoyl peroxide (BPO), Vazo 67, and the alkoxyamine are less effective. The number of polymer chains in the final product is always less than the theoretical value, reflecting poor initiation efficiency, probably resulting from undesirable termination reactions that become important due to the nature of the semi‐batch process. Adding camphorsulfonic acid (CSA) or charging initiator concurrently with monomer during semi‐batch feed, can increase the polymerization rate while maintaining the living character of the polymerization. The copolymerization of styrene and butyl acrylate is also shown to exhibit living character.Schematic representation of the exchange reaction to produce N‐TEMPO capped polymer chains.magnified imageSchematic representation of the exchange reaction to produce N‐TEMPO capped polymer chains.
A New Heterogenization Technique for Single‐Site Polymerization Catalysts
Authors: Bartke Michael , Oksman Marita , Mustonen Marja , Denifl Peter 
Published: April 2005

AbstractSummary: Silica‐supported single‐site catalysts show limitations with respect to catalyst homogeneity and maximum metal content. A novel emulsion‐based catalyst heterogenization concept is described, which allows these limitations to be overcome. The method produces catalyst particles with an inherently perfect spherical shape and unique intra‐ and inter‐particle homogeneity. The catalyst particles are very compact and have a low surface area. Video microscopic studies confirm that the improved catalyst homogeneity leads to a more uniform polymerization behavior on a single particle level. The catalysts contain significantly more complex, compared to silica‐supported catalyst systems, which leads to correspondingly higher catalyst activities. No differences, in terms of the mass‐transfer kinetics of these low‐porosity catalysts, compared to porous catalyst systems have been observed.Electron microscopy image of self‐supported single‐site catalyst prepared by the emulsion‐based method.magnified imageElectron microscopy image of self‐supported single‐site catalyst prepared by the emulsion‐based method.
Production of Polymeric Materials with Controlled Pore Structure: the “Reactive Gelation” Process
Authors: Marti Nadia , Quattrini Francesca , Butté Alessandro , Morbidelli Massimo 
Published: April 2005

AbstractSummary: A new approach for the production of macroporous polymer materials is presented. Cross‐linked polystyrene particles are first produced by emulsion polymerization. This latex is then swollen by a further addition of monomer and it is successively destabilized, by addition of salt, in such a way that a controlled aggregation is achieved. The system is left aggregating until a gel is obtained. Although polymer gels have their own consistency, latex particles are kept together by weak interactions only, e.g. Van der Waals' forces. In order to impart enough mechanical resistance to the material, the residual monomer is polymerized, thus bridging the polymer particles with cross‐linked polymer. Accordingly, the process has been named “reactive gelation”. In this work, it is shown how it is possible to obtain an accurate control upon the pore structure of the material by properly tuning each step of the process. An application of the obtained material as stationary phase in a separation carried out by high performance liquid chromatography is presented.SEM picture of the macroporous material obtained by reactive gelation.magnified imageSEM picture of the macroporous material obtained by reactive gelation.
Down‐regulation of a morphogen (sonic hedgehog) gradient in the gastric epithelium of Helicobacter pylori‐infected Mongolian gerbils
Authors: Suzuki Hidekazu , Minegishi Yuriko , Nomoto Yohei , Ota Takayuki , Masaoka Tatsuhiro , van den Brink Gijs R , Hibi Toshifumi 
Published: April 2005

AbstractSonic hedgehog (Shh) is a morphogen involved in many aspects of patterning of the gut during embryogenesis and in gastric fundic gland homeostasis in the adult. Intestinal metaplastic change of the gastric epithelium is associated with the loss of Shh expression, and mice that lack Shh expression show intestinal transformation of the gastric mucosa. The present study was designed to investigate the alteration of Shh expression in the stomach of an experimental model of Helicobacter pylori (H. pylori) colonization. Male Mongolian gerbils were inoculated with H. pylori and examined 4 and 51 weeks later. The level of Shh mRNA expression was determined by quantitative RT‐PCR and in situ hybridization. Shh protein expression was determined by immunoblotting and immunohistochemistry. Shh was expressed in the parietal cells, zymogenic cells, and mucous neck cells of the gastric fundic glands of gerbils. Prolonged colonization by H. pylori led to extension of the inflammation from the antrum to the corpus of the stomach, with loss of Shh expression. Loss of Shh expression correlated with loss of parietal cells, disturbed maturation of the mucous neck cell–zymogenic cell lineage, and increased cellular proliferation. Shh expression is significantly reduced in H. pylori‐associated gastritis. These data show for the first time that H. pylori infection leads to down‐regulation of the expression of a morphogen with an established role (Shh) in gastric epithelial differentiation. Copyright © 2005 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.