bluuebunny/crossref_metadata_2025 huggingface dataset:
Upward propagating tidal effects across the E- and F-regions of the ionosphere
Authors: Immel Thomas J. , England Scott L. , Zhang Xiaoli , Forbes Jeffrey M. , DeMajistre Robert
Published: August 2014

Recent far-ultraviolet (FUV) observations of Earth have shown the remarkable spatial correspondence between the amplitude of non-migrating atmospheric tides originating in the troposphere and the density and morphology of the nighttime equatorial ionospheric anomaly (EIA). This is likely a result of the modulation of the E-region dynamo electric field in daytime by the tidal winds. FUV observations around the time of the vernal equinox of 2002 show that the signature of tidal influence, the wave-4 periodicity in the separation and density of the two EIA bands, itself exhibits significant temporal variability. Here, we seek to understand this variability, and whether (or not) it is linked to variations in the strength of the upward-propagating tides. This study relies on tidal measurements provided by the global observations from the TIMED-SABER instrument that measures the temperature variations in the MLT associated with the upward-propagating tides. TIMED-GUVI provides F-region density measurements concurrent to the MLT temperature retrievals. It is found that the atmospheric and ionospheric zonal wave-4 signatures very nearly covary over a 30-day period, strongly supporting the theory that the influence of the the diurnal eastward 3 (DE3) tide originating in the troposphere extends to the F-layer of the ionosphere. Additionally, a 6-day periodicity in the power of the ionospheric wave-4 signature is found that may originate with the tide’s interaction with longer period planetary waves.
Temporal and spatial distributions of atmospheric wave energy in the equatorial stratosphere revealed by GPS radio occultation temperature data obtained with the CHAMP satellite during 2001–2006
Authors: Tsuda Toshitaka , Venkat Ratnam M. , Alexander Simon P. , Kozu Toshiaki , Takayabu Yukari
Published: August 2014

Using stratospheric temperature profiles derived from GPS radio occultation (RO) measurements made by the German CHAMP satellite from June 2001 to May 2006, we studied the climatological behavior of atmospheric wave activity in the tropics. The wave potential energy, E
p, is calculated from temperature fluctuations with vertical scales shorter than 7 km in a longitude and latitude cell of 20° × 10° at 19–26 km. E
p is then averaged every 3 months (June–July–August (JJA), September–October–November (SON), December–January–February (DJF), March–April–May (MAM)), and the averages are compared with the cloud top temperature from outgoing long-wave radiation (OLR) and the convective rain rate from the TRMM precipitation radar (PR). E
p at 19–26 km in the western Pacific to Indian Ocean is found to show a clear seasonal variation, with a large E
p during DJF and MAM and a considerably enhanced E
p in SON; it becomes minimum during JJA near the equator, when the center of the enhanced E
p region appears over north India and the Indochina peninsula. Localized enhancement of E
p seems to be mainly due to atmospheric gravity waves. In addition, the longitudinally elongated portion of E
p is partially affected by Kelvin wave-like disturbances with short horizontal scales. In DJF and MAM, the convective clouds are located over the western Pacific and around Indonesia, at which time the Kelvin wavelike disturbances are effectively generated. The spatial and seasonal variations of E
p are closely related to the distribution of clouds, implying that convective wave generation is very important in the tropics. However, wave-mean flow interactions due to the wind shear of the QBO become important in the lower stratosphere, which considerably modifies our analysis of the E
p distribution at 19–26 km. Therefore, both wave generation and propagation characteristics must be taken into account in describing the climatological behavior of atmospheric wave activity in the equatorial stratosphere.
Changes to magnetic minerals caused by frictional heating during the 1999 Taiwan Chi-Chi earthquake
Authors: Mishima Toshiaki , Hirono Tetsuro , Nakamura Norihiro , Tanikawa Wataru , Soh Wonn , Song Sheng-Rong
Published: August 2014

We carried out magnetic mineral analyses of samples from the shallowest major fault zone within the Chelungpu fault system, which is the zone that previous researchers believe slipped during the 1999 Taiwan Chi-Chi earthquake. Our aim was to gain an understanding of the changes to magnetic minerals during the earthquake. Magnetic hysteresis and low-temperature thermal demagnetization measurements showed that high magnetic susceptibilities in the black gouge zone within the major fault zone could be attributed not to fining of ferrimagnetic minerals but, rather, to their abundance. Thermomagnetic analyses indicated that the strata in and around the fault zone originally contained thermally unstable iron-bearing paramagnetic minerals, such as pyrite, siderite, and chlorite. We therefore concluded that frictional heating (>400°C) occurred in the black gouge zone in the major fault zone during the slip of the Chi-Chi earthquake and that the resultant high temperature induced thermal decomposition of paramagnetic minerals to form magnetite, resulting in the observed high magnetic susceptibilities.
Earthquake fault of the 26 May 2006 Yogyakarta earthquake observed by SAR interferometry
Authors: Tsuji Takeshi , Yamamoto Katsuya , Matsuoka Toshifumi , Yamada Yasuhiro , Onishi Kyosuke , Bahar Alfian , Meilano Irwan , Abidin Hasanuddin Z.
Published: August 2014

We analyzed synthetic aperture radar interferometry (InSAR) to reveal surface deformation associated with the 26 May 2006 Yogyakarta earthquake, for which the fault location and geometry have not been clearly determined. Our results demonstrate that surface deformation occurred ∼10 km east of the Opak River fault thought to be the source of the May 2006 event and that the probable causative fault delineated in this study is consistent with aftershock epicenters determined by a temporary seismic network. The trace of the causative fault bends at its southern termination toward the Opak River fault as if it were a splay. Our data demonstrate that another probable slip plane extends across Yogyakarta and that the heavily damaged areas covered by young volcanic deposits may have undergone subsidence during the earthquake.
What ancient scalar satellite data can tell us about the 1969 geomagnetic jerk?
Authors: Yahiat Y. , Hamoudi M. , Mandea M.
Published: August 2014

The linearity of the secular variation of the Earth’s magnetic field is irregularly broken by sudden changes in its trend, known as geomagnetic jerks. Detecting these events in the temporal variations of the magnetic field components continues to be an exciting topic, mainly recently when their investigation rely not more only on observatory data, but as well as on measurements provided by satellites. We have also been interested by these magnetic events, and one of the central aims of our work has been to determine whether the satellite scalar data, obtained in the sixties and early seventies are able to reveal the existence of such a geomagnetic jerk, previously detected around 1969, in observatory annual or monthly means. For this purpose, we have used available OGO2, OGO4 and OGO6 satellite intensity data covering the period 1965–1971. Another motivation of re-processing and analyzing these old satellite datasets has been to better estimate their role in the global core field modeling, especially in describing the secular variation. Our results indicate that these ancient magnetic satellite datasets contain valuable information to characterize the secular variation over the time-span they are available, and allow to detect the geomagnetic jerk around 1969.
Nighttime D-region equivalent electron density determined from tweek sferics observed in the South Pacific Region
Authors: Kumar Sushil , Deo Anil , Ramachandran V.
Published: August 2014

Atmospherics or sferics that originate from lightning discharges on propagating large distances in the Earthionosphere waveguide, particularly at the night, form dispersed sferics called tweeks. Tweeks are novel diagnostic tool to monitor the nighttime D-region ionosphere. Mean equivalent electron density n
em at mean tweek reflection heights h
m and electron density profile have been estimated using the higher harmonic tweeks recorded in the time between 21–03 hrs LT at Suva (18.2°S, 178.3°E), Fiji, during a period March–December 2006. The values of nem vary from 29–170 cm−3 in the altitude range of about 3.5 km at h
m of about 83 km. In terms of usually used exponential electron density profile, the ionospheric reference height and the exponential sharpness factor are calculated to be 83.1 km and 0.64 km−1, respectively. The scale height is calculated to be 1.9 km. Equivalent electron density profile of the nighttime lower ionosphere, using tweek method, shows lower values of electron density by about 20–45% than those obtained from the IRI-2001 model.
Differences in tsunami generation between the December 26, 2004 and March 28, 2005 Sumatra earthquakes
Authors: Geist Eric L. , Bilek Susan L. , Arcas Diego , Titov Vasily V.
Published: August 2014

Source parameters affecting tsunami generation and propagation for theMw> 9.0 December 26, 2004 and theMw= 8.6 March 28, 2005 earthquakes are examined to explain the dramatic difference in tsunami observations. We evaluate both scalar measures (seismic moment, maximum slip, potential energy) and finite-source representations (distributed slip and far-field beaming from finite source dimensions) of tsunami generation potential. There exists significant variability in local tsunami runup with respect to the most readily available measure, seismic moment. The local tsunami intensity for the December 2004 earthquake is similar to other tsunamigenic earthquakes of comparable magnitude. In contrast, the March 2005 local tsunami was deficient relative to its earthquake magnitude. Tsunami potential energy calculations more accurately reflect the difference in tsunami severity, although these calculations are dependent on knowledge of the slip distribution and therefore difficult to implement in a real-time system. A significant factor affecting tsunami generation unaccounted for in these scalar measures is the location of regions of seafloor displacement relative to the overlying water depth. The deficiency of the March 2005 tsunami seems to be related to concentration of slip in the down-dip part of the rupture zone and the fact that a substantial portion of the vertical displacement field occurred in shallow water or on land. The comparison of the December 2004 and March 2005 Sumatra earthquakes presented in this study is analogous to previous studies comparing the 1952 and 2003 Tokachi-Oki earthquakes and tsunamis, in terms of the effect slip distribution has on local tsunamis. Results from these studies indicate the difficulty in rapidly assessing local tsunami runup from magnitude and epicentral location information alone.
Nuclear Mobility and Activity of FOXA1 with Androgen Receptor Are Regulated by SUMOylation
Authors: Sutinen Päivi , Rahkama Vesa , Rytinki Miia , Palvimo Jorma J.
Published: August 2014

Forkhead box (FOX) protein A1 has been dubbed a pioneer transcription factor because it binds target sites in DNA, thereby displacing nucleosomes to loosen chromatin and facilitating steroid receptor DNA binding nearby. FOXA1 is an important regulator of prostate development, collaborating with androgen receptor (AR). Post-translational modifications regulating FOXA1 are thus far poorly understood. SUMOylation, post-translational modification of proteins by small ubiquitin-like modifier (SUMO) proteins, has emerged as an important regulatory mechanism in transcriptional regulation. In this work, we show by SUMOylation assays in COS-1 cells that the FOXA1 is modified at least in two of its three lysines embedded in SUMOylation consensus, K6 and K389, in proximity to its transactivation domains and K267 proximal to its DNA-binding domain. We also provide evidence for SUMO-2/3 modification of endogenous FOXA1 in LNCaP prostate cancer cells. Based on fluorescence recovery after photobleaching assays with mCherry-fused FOXA1 and EGFP-fused AR in HEK293 cells, the presence of FOXA1 retards the nuclear mobility of agonist-bound AR. Interestingly, mutation of the FOXA1 SUMOylation sites slows down the mobility of the pioneer factor, further retarding the nuclear mobility of the AR. Chromatin immunoprecipitation and gene expression assays suggest that the mutation enhances FOXA1's chromatin occupancy as well as its activity on AR-regulated prostate-specific antigen (PSA) locus in LNCaP cells. Moreover, the mutation altered the ability of FOXA1 to influence proliferation of LNCaP cells. Taken together, these results strongly suggest that the SUMOylation can regulate the transcriptional activity of FOXA1 with the AR.
Insulin resistance, atherogenic disorders and liver fibrosis in patients with metabolic syndrome
Authors: Chesnokova L V , Petrov I M , Troshina I A , Medvedeva I V
Published: August 2014

The increased interest in non-alcohol liver disease research is due to the increased incidence of obesity in developed countries. Thus liver disease is prevalent in 20-40 % of population. Nevertheless fibrosis is found not in every patient, which makes the importance to investigate the factors that are associated with fibrosis. Aim. The purpose of our research was to investigate lipid and glucose metabolism in patients with metabolic syndrome in dependence of liver fibrosis intensity. Materials and methods. We investigated 129 patients with obesity and metabolic syndrome aged 18-59 years old (average age 44 (38+47) years), who underwent elastometry and fibrosis intensity was estimated in dependence of accompanying metabolic disorders (lipid and glucose). Results. Glucose metabolic disorders are accompanied by non-alcohol fatty liver disease in 100%, and elastometric fibrosis features are present in 61% of these patients. If liver fibrosis is present, independently of its intensity, in patients without glucose metabolism disturbances insulin resistance is twofold more often (HOMA index 2.7), while there was no significant correlation of fibrosis with atherogenic profile changes. Conclusion. According to elastometry lipid and glucose disorders are not associated with liver fibrosis intensity.
The role of the lipotoxicity in the pathogenesis of type 2 diabetes mellitus and obesity
Authors: Abdulkadirova F R , Ametov A S , Doskina E V , Pokrovskaya R A
Published: August 2014

Obesity is a major risk factor for diabetes mellitus type 2, cardiovascular diseases and associated comorbid conditions. It is traditionally considered that insulin resistance is dependent on glucose metabolism. However, in recent years more and more attention is devoted to the fatty acids metabolism, the increase in concentrations of which plays a significant role in the pathophysiological mechanisms associated with insulin resistance.
Block copolymers comprising a polytetrahydrofuran block and one or two [5]-polyurethane block(s): synthesis and characterization
Authors: Kušan Jacqueline , Keul Helmut , Höcker Hartwig
Published: August 2014

A-B Di- and B-A-B triblock copolymers with poly(tetramethyleneoxy) (poly(THF)) and poly(tetramethyleneoxycarbonylimino) (poly(TeU)) blocks were prepared by sequential polymerization of tetrahydrofuran (THF) and tetramethyleneurethane (TeU) with the monofunctional initiator methyl trifluormethylsulfonate and the bifunctional initiator trifluoromethanesulfonic acid anhydride, respectively. The block copolymers obtained after purification exhibit a monomodal narrow molecular weight distribution and a uniform microstructure of the two blocks as was deduced from gel permeation chromatography and NMR analysis. The block copolymers are semicrystalline materials with distinct melting points of the poly(THF) and the poly(TeU) domains.
Photosensitive polyrotaxanes: New comb-like polymethacrylamides containing 1,3- diphenyl-2-propen-1-one (chalcone) functions and noncovalently bound cyclodextrin in the side-chains
Authors: Goretzki Christian , Ritter Helmut
Published: August 2014

The synthesis and free radical polymerization of a methacrylamide monomer, 5, bearing non-covalently attached cyclodextrins and the chalcone function with a barrier group, is described. The first step of preparation of the monomer was the condensation of 4-(N-methacryloyl-6-aminohexanoylamino)- acetophenone, 1, with 4-nitrobenzaldehyde. The resulting 1-(N-methacryloyl-6- aminohexanoyl-4-aminophenyl)-3-(4-nitrophenyl)-2-propen-1-one, 2, was reduced with tin(II) chloride dihydrate to the corresponding 1-(N-methacryloyl-6-aminohexanoyl- 4-aminophenyl)-3-(4-aminophenyl)-2-propen-1-one, 3. After this, the aminochalcone was condensed with a barrier group, triphenylacetyl chloride, yielding 1-(N-methacryloyl-6-aminohexanoyl-4-aminophenyl)-3-(N’-triphenylacetyl- 4-aminophenyl)-2-propen-1-one, 4. Monomer 4 was copolymerized with methyl methacrylate to the model polymer poly[4-co-methyl methacrylate], 6, and also complexed with dimethylated β-cyclodextrin to the semi-rotaxane (4 / 2,6-Me2-β- CD) 5, which was copolymerized with methyl methacrylate, yielding a polyrotaxane (5-co-methyl methacrylate) 7, containing a cyclodextrin ring in the side-chain. The semi-rotaxane 5 and both copolymers 6 and 7 were characterized spectroscopically and also by means of differential scanning calorimetry, gel permeation chromatography and thermogravimetrical analysis, and - in the case of 5 - by mass spectrometry. Furthermore, the UV-induced E/Z-isomerization of both polymers 6 and 7 was examined in tetrahydrofuran solution. A retarding effect of the noncovalently attached cyclodextrin was finally detected.
The iniferter technique in radical polymerization under UV and thermal conditions: a comparative study
Authors: Suwier Davy R. , Monteiro Michael J. , Vandervelden Alexander , Koning Cor E.
Published: August 2014

UV and thermal polymerisations of styrene were carried out in the presence of conventional ‘iniferters’. The mechanisms of the two methods were investigated and provided new insight into the livingness of the so-called iniferter technique. Chain extension polymerisations were performed using symmetrical iniferters to check the living character of this technique under UV and thermal polymerization conditions. In accordance with the work of Otsu, we have shown that polymerisation under UV irradiation initiated by iniferters proceeds via the classical iniferter living (controlled) mechanism. On the other hand, thermal polymerisations were predominantly controlled by the reversible additionfragmentation chain transfer (RAFT) mechanism.
Supramolecular poly(L-lactide)s containing terpyridine metal complexes
Authors: Heller Marcel , Schubert Ulrich S.
Published: August 2014

Chiral poly(L-lactide)s end-capped with a novel terpyridine ligand are synthesized by a controlled coordinative polymerization procedure. The resulting well-characterized macroligands can be complexed under phase-transfer conditions with iron(II) ions to form well-defined supramolecular poly(L-lactide) complexes. The outstanding stability of such coordinative polymers enables the full characterization by gel permeation chromatography (GPC) and MALDI-TOF mass spectrometry. In addition, in-line diode array UV-Vis spectroscopy coupled to GPC was carried out to verify the formation of the poly(ester) complexes.
Synthesis and characterization of a polyester/styrene resin obtained by frontal polymerization
Authors: Fiori Stefano , Malucelli Giulio , Mariani Alberto , Ricco Laura , Casazza Elena
Published: August 2014

The frontal polymerization technique has been successfully applied, for the first time, to obtain an unsaturated polyester/styrene resin. The effect of the ratio of the two aforementioned components, as well as of the type and amount of free-radical initiator on both front velocity and maximum temperature reached by the front, has been thoroughly studied. The resulting products have been characterized in terms of their thermal and dynamic-mechanical behaviour. A comparison of such products with the corresponding materials obtained by the classical batch polymerization technique has evidenced that frontal polymerization allows to reach a higher degree of crosslinking with respect to batch copolymerization and hence a better thermal and mechanical behaviour.
Surface-directed phase separation in nanometer polymer films: self-stratification and pattern replication
Authors: Budkowski Andrzej , Bernasik Andrzej , Cyganik Piotr , Rysz Jakub , Brenn Rüdiger
Published: August 2014

Phase separation occurs in thin films of polymer blends when molecular mobility is promoted by a temperature above the glass transition but inside the twophase region (temperature quench), or a common solvent added to the polymers (solvent quench). This phenomenon can be altered by a homogeneous surface or pre-patterned substrate, resulting, e.g., in self-stratification or pattern replication, respectively. Such self-organisation processes ordering polymer phases were observed for model polymer blends (deuterated/hydrogenated polystyrene, dPS/hPS, and deuterated/partially brominated PS, dPS/PBrS, both with hPSpolyisoprene diblocks added; dPS/poly(vinylpyridine) and PBrS/PVP) with highresolution ion beam techniques (Nuclear Reaction Analysis, profiling and mapping mode of dynamic Secondary Ion Mass Spectrometry) and Atomic Force Microscopy. The self-stratification process is strongly affected by both the range as well as the strength of the surface/polymer interactions. This is illustrated for the temperature-quenched blends with surface-active copolymer additives tuning the interactions exerted by both external surfaces. The pattern transfer from the substrate to the films is demonstrated for the solvent-quenched blends. Patterndirected composition variations (SIMS maps) coincide with free surface undulations (AFM images). The most effective pattern replication is achieved for the length scale of phase domain morphology comparable with the pattern periodicity and for carefully adjusted polymer/substrate interactions.
Alternating poly(ester amide)s from glutaric anhydride and α,ω-aminoalcohols: synthesis and thermal properties
Authors: Fey Thomas , Keul Helmut , Höcker Hartwig
Published: August 2014

Alternating poly(ester amide)s 6a - e were prepared by polycondensation of α-carboxyl-ω-hydroxyamides 3a - e which were obtained by aminolysis of glutaric anhydride (1) and α,ω-aminoalcohols, H2N-(CH2)x-OH (x = 2 - 6) 2a - e. The polycondensation was performed in dimethylformamide solution using a carbodiimide as activating agent, or in bulk with Bu2Sn(OMe)2, Ti(OBu)4 and Sn(octoate)2 as a catalyst. For the polycondensation in bulk, the influence of catalyst and of temperature on the number-average molecular weight was studied. 1H NMR analyses of the poly(ester amide)s clearly show the alternating microstructure. The poly(ester amide)s from glutaric anhydride and the homologous series of α,ω-aminoalcohols are semicrystalline materials; their melting points show the odd/even effect observed for other poly(ester amide)s.
Fine structure formation and physical properties of poly(butylene terephthalate) fibres in high-speed melt spinning
Authors: Sun Hee Lee , Kyoung Hou Kim , Takeshi Kikutani , Hyun Hok Cho
Published: August 2014

Poly(butylene terephthalate) (PBT) fibres were obtained by high-speed melt spinning up to a take-up velocity of 8 km/min. Fine structure formation and physical properties of these fibres were investigated. The increase of take-up velocity caused raises in both density and birefringence. In wide-angle X-ray diffraction equatorial profiles, the increase of take-up velocity can be observed in the (010) and (100) reflections of β-crystals; the reflection peaks are the sharpest at a take-up velocity of 6 km/min. The initial modulus of the fibres arises when the fraction of β-crystals is increased, while the tenacity depends more on the fraction of α-crystals, i.e., the total crystallinity. Thermal properties of high-speed spun PBT fibres were measured with differential scanning calorimetry, dynamic mechanical and thermo-mechanical analysis, etc. Endothermic curves become sharper with increasing take-up velocity, and endothermic melting peaks are shifted to higher temperature. Crystal structures are well developed in fibres obtained at higher take-up velocities. The tan δ peaks of PBT fibres tend to shift to higher temperature and the peak intensity is decreased with increasing take-up velocity, i.e., the packing density of PBT fibres is high when the take-up velocity and thus the orientation of amorphous regions is increased. The shrinkage has a tendency to decrease with increasing take-up velocity.
Preparation, characterisation and enantioselective separation properties of a chiral stationary phase based on silica beads coated with a 2-hydroxypropyl-β-cyclodextrin polymer
Authors: Carbonnier Benjamin , Janus Ludovic , Deratani André , Morcellet Michel
Published: August 2014

This paper describes the preparation of a chiral stationary phase based on a 2-hydroxypropyl-β-cyclodextrin polymer coated on porous silica. This method requires first the synthesis of a water-soluble cyclodextrin polymer carried out by the polycondensation of 2-hydroxypropyl-β-cyclodextrin with epichlorohydrin under controlled conditions. In the second step, the obtained copolymer was immobilised onto the porous silica surface by physisorption. The macromolecular features of the copolymer were investigated by size exclusion chromatography coupled with a multiple angle laser-light scattering detector. The evolution of the structural parameters of the modified silica beads (specific surface area and pore size distribution) was determined using a nitrogen adsorption method. The enantio-separation capability of the coated silica phase was evaluated for different polycyclic molecules. It was found that the enantioselectivity was strongly influenced by the geometry and shape of the solutes under study and the presence of an acidic modifier in the mobile phase.
Adsorption of monodisperse polybutadienes on carbon black, 2 Bulk adsorption
Authors: Vuillaume Kathy , Haidar Bassel , Vidal Alain
Published: August 2014

The adsorption on carbon black (CB) of a series of monodisperse polybutadienes (PBs) with different molecular weights (Mn in the range of 3000 to 120 000) but identical microstructure (1,2-PB content ≈ 80%) was studied in the bulk for different polymer/CB ratios (τ, in the range of 2 to 10 g/g). In this respect we particularly studied the evolution of the amount of polymer, which cannot be extracted from the polymer/filler system upon blending, the so-called bound polymer, and attempted to investigate the conformation of the resulting adsorbed molecules as well as the conditions that control the formation of the polymer/filler network. The conformational transition turned out to depend exclusively on molecular weight, and the networking transition to occur at constant Mn1/2/τ, essentially through an entanglement process of the adsorbed chains.
Glutaraldehyde-crosslinked poly(glycidol-block-ethylene oxide-block-glycidol) networks with temperatureresponsive swelling behaviour
Authors: Christova Darinka , Ivanova Sijka , Trzebicka Barbara , Walach Wojciech , Velichkova Rumiana , Dworak Andrzej
Published: August 2014

In order to obtain temperature-responsive hydrogel networks, poly- (glycidol-block-ethylene oxide-block-glycidol) copolymers were chemically crosslinked by using glutaraldehyde and tetraethoxysilane in a sol-gel reaction. The crystallinity of copolymer networks prepared has been estimated by differential scanning calorimetry. Thermo-responsive properties were evaluated by measuring the equilibrium swelling degree for a series of copolymer hydrogels as a function of temperature.
Synthesis and properties of poly(4-vinylpyridine)/ montmorillonite nanocomposites
Authors: Sen Sinan , Nugay Nihan , Nugay Turgut
Published: August 2014

4-Vinylpyridine monomer was mixed with organically modified montmorillonite (MMT) and polymerized in the presence of 2,2’-azoisobutyronitrile as radical initiator. Organophilic montmorillonite was obtained by using a block copolymer of poly(methyl methacrylate) and quaternized poly(4-vinylpyridine) (P4VP) in different compositions. X-ray diffraction (XRD) and thermogravimetric analysis confirmed that the block copolymer is inserted between MMT layers while the interlayer distance is expanded. The P4VP nanocomposites obtained from the block copolymer with the longer P4VP block exhibited no XRD peak, suggesting an exfoliated structure. These composites showed increased storage modulus and thermal stability at a very low loading of 1 - 2 wt.-%, compared to neat P4VP. Scanning electron microscopy and atomic force microscopy analyses were also conducted for selected nanocomposites.
Metallo-celluloses, 1 Synthesis and solution properties of 4-ferrocenylbutylsubstituted cellulose derivatives
Authors: Laube Bettina , Radke Wolfgang , Rehahn Matthias , Wunderlich Winfried
Published: August 2014

An efficient method is described for the simultaneous introduction of 4-ferrocenylbutyl and n-hexyl side groups into cellulose. For this purpose, cellulose triacetate is treated in dimethyl sulfoxide/NaOH solution with mixtures of 4-bromobutylferrocene and n-hexyl bromide. An almost quantitative conversion of the cellulose hydroxyl groups was reached when less than one ferrocene substituent was attached to the cellulose repeating units on average. At higher degrees of ferrocene substitution, some of the cellulose hydroxyl groups seem to remain unsubstituted. This conclusion has been drawn on the basis of size exclusion chromatography (SEC) with online light-scattering detector where coil contraction was observed with increasing ferrocene content in the cellulose sample. This finding was further supported by IR spectroscopy, viscometry, and conventional SEC investigations. We assume that steric hindrance of the bulky side groups is responsible for incomplete conversion.
Synthesis and characterization of unsaturated polyester resins cured by frontal polymerization
Authors: Fiori Stefano , Mariani Alberto , Bidali Simone , Malucelli Giulio
Published: August 2014

Various crosslinking agents have been used to frontally cure the unsaturated polyester derived by the reaction of maleic anhydride and 1,2-propanediol. The effect of composition of the curing mixture on the front velocity and its maximum temperature, as well as on the thermal properties of the obtained materials, is described.
Nucleation versus melting point depression of the polycaprolactone phase in polypropylene/polycaprolactone blends
Authors: Balsamo Vittoria , Gouveia Laura
Published: August 2014

Polypropylene/poly(ε-caprolactone) (PP/PCL) blends were prepared by melt mixing. The thermal behaviour of the blends was investigated using differential scanning calorimetry (DSC) and dynamical rheology in the solid state (RSA). Both non-isothermal and isothermal crystallizations were performed. The Avrami equation was applied to the latter case. DSC and RSA results demonstrated in agreement with morphological observations that PP/PCL blends are immiscible in the whole composition range. PP acts as a nucleating agent for PCL, and when PP forms the disperse phase, it crystallizes in a fractionated fashion. When PCL is the disperse phase, it exhibits an unexpected melting point depression after cooling at 10 °C/min. Such depression was not observed after isothermal crystallizations, indicating that under non-isothermal crystallization kinetic problems show up. Thus, global crystallization is governed by a competition between nucleation and diffusion, which depends on crystallization conditions and composition.
Polymer/organoclay nanocomposites with biodegradable aliphatic polyester and its blends: preparation and characterization
Authors: Lim Sung Taek , Lee Chung Ho , Kim Hee Bong , Choi Hyoung Jin , Jhon Myung Sik
Published: August 2014

Synthetic biodegradable aliphatic polyester (BAP) and its blends with polyepichlorohydrin (PECH) were processed with organophilic montmorillonite (OMMT) to make polymer/organoclay nanocomposites via a solvent casting method. Interlayer spacings of each system, measured by X-ray diffraction analysis, suggested that BAP had better affinity to clay than PECH in a competitive intercalation mechanism. The internal structures were visualized using transmission electron microscopy and were discussed in conjunction with the result of other experimental studies, such as thermogravimetric analysis and rheometry. In rheological measurements, the degree of shear-thinning increased drastically with OMMT loading, and both the storage modulus and loss modulus were found to increase with OMMT loading at all frequencies. Throughout this study, we compared the behaviours of polymer/clay nanocomposites in homo and blend systems, and examined the role of various parameters on the material characteristics of polymer/clay nanocomposites.
Scale-free power-law distribution of nonlinear polymers formed in a homeostatic system
Authors: Tobita Hidetaka
Published: August 2014

A power-law distribution of molecular weight is found for low-density polyethylene formed in a one-zone autoclave reactor. This reactor could be modelled as a continuously stirred tank reactor (CSTR) operated under homeostatic conditions where the concentration of each component as well as temperature and pressure are kept constant. A simple stochastic model is used to investigate the molecular weight distribution (MWD) formed in free-radical polymerization involving chain transfer to polymer. The MWD profiles are dominated by the Pb value, which represents the probability that the chain end is connected to a backbone chain. By increasing Pb, MWD changes from an exponential to a powerlaw distribution. A scale-free power-law distribution is found for Pb > 0.5. Because the power of the weight fraction distribution, W(M) ~ M -γ, is 1 < γ < 2, the number average molecular weight will reach a stationary-state value but the weightaverage may continue to increase unlimitedly under ideal CSTR conditions.
New materials from degraded styrene-acrylonitrile and ethylene-propylene-diene copolymers
Authors: Vugrinec Jasminka , Kratofil Ljerka , Hrnjak-Murgić Zlata , Jelenčić Jasenka
Published: August 2014

Polymer blends of styrene-acrylonitrile (SAN) and ethylene-propylenediene copolymer (EPDM) were prepared by casting films from chloroform solution. Their compositions were 95/5, 90/10 and 80/20, respectively. To simulate ageing, SAN/EPDM blends were degraded at 140°C for several different time intervals and the degree of degradation was followed by IR spectroscopy and by determination of molar masses. To recover thermally degraded SAN/EPDM blends, in situ polymerization by addition of styrene monomer was applied. Characterization of SAN and EPDM, graft copolymer and gel was carried out in order to reveal the polymerization process. Extractions of the polymers were made using solvents in a Soxhlet equipment: SAN in a mixture of acetone/ methanol, EPDM in hexane, graft copolymer in tetrahydrofuran, while the remaining part was considered as gel. Identification of extracted polymers has been conducted by IR spectroscopy. The presence of graft copolymer in the polymerization mixture proved the grafting reaction of polymer radicals. The highest content of graft copolymer was obtained for SAN/EPDM polymer blends that were exposed to thermal treatment for the longest time interval of 90 h.
Novel pattern formation in blends of asymmetric ABC triblock terpolymers
Authors: Abetz Volker , Jiang Shimei , Göpfert Astrid
Published: August 2014

A series of polystyrene-block-poly(1,2-butadiene)-block-poly(2-vinylpyridine) (SBV) triblock terpolymers were used to prepare blends with symmetric polystyrene-block-poly(2-vinylpyridine) (SV) and poly(2-vinylpyridine)-block-poly- (cyclohexyl methacrylate) (VC) diblock copolymers. Morphological characterization was carried out by transmission electron microscopy. These triblock terpolymers self-assemble into various core-shell type or lamellar morphologies. In the SBV/SV blends, macrophase separation between the two block copolymers, continuous centrosymmetric lamellae and stacks of non-centrosymmetric lamellae with antiparallel orientation were found. In the blends of SBV/VC, macrophase separation was never observed, what is due to the specific interactions between S and C domains. These systems showed among other morphologies also a cylindrical morphology in which rings surround the cylinders.
Dielectric and hydration properties of segmental polyurethanes
Authors: Raftopoulos Konstantinos , Zegkinoglou Ioannis , Kanapitsas Athanasios , Kripotou Sotiria , Christakis Iraklis , Vassilikou-Dova Aglaia , Pissis Polycarpos , Savelyev Yuri
Published: August 2014

Novel polyurethanes (PUs), based on oligo(oxytetramethylene glycol), 4,4’-diphenylmethanediisocyanate and 1,1-dimethylhydrazine as chain extender, were prepared in a two-step process. The ratio prepolymer (PP) to chain extender (CE) was systematically varied in extreme ranges, from 1:1 to 10:1. Dielectric relaxation spectroscopy and thermally stimulated depolarization currents (TSDC) techniques were employed to investigate molecular dynamics and to conclude on microphase separation (MS). In that respect TSDC was proven to be very powerful, in particular as far as the investigation of the interfacial Maxwell-Wagner-Sillars polarization is concerned. Additional information on micromorphology is obtained from water sorption/diffusion measurements. A part of the results suggest that MS improves with increasing the PP:CE ratio. The whole body of results can be explained if, at the same time, it is assumed that a branched structure is developed for samples out of stoichiometry and branching increases with increasing the PP:CE ratio. Preliminary experiments with solutions of the PUs in organic solvents provide support for that assumption.
Some experimental results for the end-linked polydimethylsiloxane network system
Authors: Ladegaard Larsen Anne , Sommer-Larsen Peter , Hassager Ole
Published: August 2014

Small-strain equilibrium modulus data of polydimethylsiloxane (PDMS) networks are reviewed. 58 different articles in the literature with values of the modulus of end-linked PDMS networks were found [1-58] including more than 250 values of the small-strain equilibrium modulus as function of variables in the crosslinking system. The dominating variable is shown to be the molecular weight of PDMS as expected, whereas the functionality of the crosslinker methylhydrosiloxane/ dimethylsiloxane copolymer is shown to be less important in good agreement with the phantom model. The data collected was fitted to the phenomenological model of Langley and Graessley including an entanglement contribution. The fitted entanglement plateau (0.16 MPa) is in good agreement with literature values and with the theoretical prediction of the tube model. Experimental data for the Mooney-Rivlin constants was found and it was shown that C2 is constant with increasing functionality. Furthermore it was found that trapped entanglements can be split into two categories, viz. locked entanglements contributing to the C1 term and traditionally trapped entanglements contributing to C2.
Modified chitosan, 7 Graft copolymerization of methacrylonitrile onto chitosan using ammonium persulfate initiator
Authors: Pourjavadi Ali , Barzegar Shahram , Mahdavinia Gholam Reza
Published: August 2014

Graft copolymerization of methacrylonitrile (MAN) onto chitosan using ammonium persulfate (APS) as an initiator was studied. The reactions were carried out under argon atmosphere in a homogenous aqueous phase containing a small portion of acetic acid (AcOH). Evidence of graft copolymerization was obtained by FTIR spectroscopy, e.g., the appearance of nitrile in the spectrum of chitosan-graftpolymethacrylonitrile. The synthetic conditions were systematically optimized through studying the influential factors including temperature, as well as concentrations of initiator, MAN, AcOH, sodium dodecyl sulfate surfactant (SDS) and chitosan. The effects of individual factors were investigated by calculating and monitoring the variation of the grafting parameters, i.e., grafting ratio, grafting efficiency, add-on value, homopolymer content, and total conversion. The optimum condition was achieved at APS 0.0108 mol/L, MAN 0.201 mol/L, 80°C, SDS 0.0016 mol/L, chitosan 0.5 g, AcOH 0.0086 mol/L. The overall activation energy for the graft copolymerization was determined to be 7.3 kJ/mol.
Surface modification of polyamides by direct fluorination
Authors: Solomun Tihomir , Schimanski Arnd , Sturm Heinz , Mix Renate , Illenberger Eugen
Published: August 2014

Bulk samples and thin films of polyamides (PA6 and PA12) were exposed to fluorine (1 - 10 vol.-% F2 in N2) and analysed with photoelectron (XPS) and infrared spectroscopy. Fluorination affects both, the amide and the hydrocarbon parts of the polymers. However, only the carbon atom next to the carbonyl is readily fluorinated. Chemical modification of the amide group is apparent in a large binding energy shift (+5 eV) of the N1s level and the appearance of a νCO band at 1734 cm-1. It is concluded that the amide C-N bond is cleaved in the fluorination process and that COOH and NF2 end groups are formed. This conclusion is corroborated by the appearance of ester oxygen in the XPS and by the 19F NMR spectra of the volatile products that show fluorine signals chemically shifted about 200 ppm towards lower field as compared with the CHF environment.
Electrodeposition of mixed adherent thin films of poly(ethyl acrylate) and polyacrylonitrile onto nickel
Authors: Baute Noëlle , Geskin Victor M. , Lazzaroni Roberto , Brédas Jean-Luc , Arys Xavier , Jonas Alain M. , Legras Roger , Poleunis Claude , Bertrand Patrick , Jérôme Robert , Jérôme Christine
Published: August 2014

Adherent thin polymer films have been prepared by sequential electrodeposition of ethyl acrylate (EA) and acrylonitrile (AN) onto nickel. Their composition has been studied by IR spectroscopy and time of flight - secondary ion mass spectrometry. Morphology and thickness have been analyzed by atomic force microscopy and ellipsometry, respectively, and compared to single component films of PEA and PAN. No microphase separation was detected in the mixed PEA/ PAN films. These show a granular morphology comparable to that of PAN films. The grains contain the two constitutive polymers, as confirmed by the selective thermal degradation of PEA.
Morphology and phase behaviour of poly(propylene oxide) containing copoly(ether ester)s
Authors: Lange Ronald F. M. , Gabrielse Wouter
Published: August 2014

The morphology and phase behaviour of six different copoly(ether ester) elastomers, based on poly(butylene terephthalate) (PBT) hard blocks and poly- (ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (PEO-b- PPO-b-PEO) soft blocks, differing in soft-block content and molecular weight of the soft block, have been investigated using various analytical techniques such as DSC, dynamic mechanical thermal analysis, dielectric spectroscopy, 13C CP-MAS NMR, AFM, TEM, and optical microscopy. The PBT blocks were found to crystallize in lamellar structures that form a continuous highly interconnected architecture. No crystalline regions for the PEO-b-PPO-b-PEO triblock could be observed, whereas no indications of a separate pure amorphous PBT phase were found. It is further shown that the amorphous phase is not a homogeneous mixture of amorphous PBT and soft segments. Based on the combined results of the analytical techniques used it is concluded that the PPO segments form an almost pure amorphous phase, whereas the PEO segments form a mixed phase with amorphous PBT. It is believed that the presence of this pure amorphous PPO phase provides the PEO-b-PPO-b-PEO containing copoly(ether ester)s with their excellent coldtemperature properties.
Fractionation and ammonolytic degradation of poly(hexamethylene carbonate) in (supercritical) ammonia
Authors: Mormann Werner , Spitzer David
Published: August 2014

Solubility, fractionation by extraction as a function of temperature, and ammonolysis of α-hydro-ω-hydroxy-poly(oxycarbonyloxyhexane-1,6-diyl) in liquid and supercritical ammonia have been studied. Up to 120°C, the solubility of poly- (hexamethylene carbonate) increases with temperature without significant ammonolytic cleavage. Above the critical temperature of ammonia, solubility and molar mass of the solute decrease as ammonolysis becomes more and more important. The molar mass of the extracted and residual polymer decreases with temperature under supercritical conditions. Adjusting residence time and reactivity through temperature and flow rate enables controlled ammonolysis to constant molar mass. Kinetics of dihexyl carbonate and hexyl carbamate shows that ammonolysis of the carbamate is much faster than of dihexyl carbonate.
Influence of the structure of new poly(amide-imide)s on their optical properties
Authors: Sęk Danuta , Grabiec Eugenia , Sobolewska Anna , Miniewicz Andrzej
Published: August 2014

Two classes of poly(amide-imide)s with mono- and bisazoaromatic chromophores in the side chain have been synthesized using one-step hightemperature polycondensation. The influence of the structures of the macromolecules on their properties was investigated. Preliminary results of the kinetics of holographic grating recording using 514.5 nm Ar+ laser light for chosen poly(amideimide) films are presented. The gratings were recorded using two linearly polarized beams with s-s or s-p configurations. For comparative purposes all experimental conditions (light intensity, two-beams intersection angle) were kept unchanged. It was found that time constants of grating build-up were significantly larger for polymers containing a chromophore with two azo groups when compared with the same polymers having a single azo group. On the other hand diffraction efficiencies were lower for polymers containing a chromophore with two azo groups than with a single azo group.
Scale-free power-law distribution of branched polymers formed in a continuously stirred tank reactor: Simple relationship for the exponent
Authors: Tobita Hidetaka
Published: August 2014

The high-molecular-weight tail of the molecular weight distribution (MWD) of branched polymers formed via free-radical polymerization involving polymer transfer reactions conducted in a continuously stirred tank reactor (CSTR) follows a power-law distribution. The exponent, α, of the weight fraction distribution W(M) ~ M-α is determined by the Pb value, which represents the probability that the chain end is connected to a backbone chain, with the simple relationship, α = 1/Pb. Since α > 1, the number-average molecular weight will always reach a stationary-state value but the weight-average and higher-order averages of molecular weights may continue to increase without limit under ideal CSTR conditions. Because it takes an infinitely long time for the second or a higher moment of the MWD to go to infinity, the kinetic behaviour is significantly different from usual gelation phenomena. The i-th moment of the MWD goes to infinity for Pb ≥ 1/i.