bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis and characterization of novel thermoresponsive‐co‐biodegradable hydrogels composed of N‐isopropylacrylamide, poly(L‐lactic acid), and dextran
Authors: Huang Xiao , Nayak Bishwa Ranjan , Lowe Tao Lu 
Published: September 2004

AbstractA series of novel multifunctional hydrogels that combined the merits of both thermoresponsive and biodegradable polymeric materials were designed, synthesized, and characterized. The hydrogels were copolymeric networks composed of N‐isopropylacrylamide (NIPAAM) as a thermoresponsive component, poly(L‐lactic acid) (PLLA) as a hydrolytically degradable and hydrophobic component, and dextran as an enzymatically degradable and hydrophilic component. The chemical structures of the hydrogels were characterized by an attenuated total reflection–Fourier transform infrared spectroscopy (ATR–FTIR) technique. The hydrogels were thermoresponsive, showing a lower critical solution temperature (LCST) at approximately 32 °C, and their swelling properties strongly depended on temperature changes, the balance of the hydrophilic/hydrophobic components, and the degradation of the PLLA component. The degradation of the hydrogels caused by hydrolytic cleavage of ester bonds in the PLLA component was faster at 25 °C below the LCST than at 37 °C above the LCST, determined by the ATR–FTIR technique. Due to their multifunctional properties, the designed hydrogels show great potential for biomedical applications, including drug delivery and tissue engineering. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5054–5066, 2004
Cationic copolymerization behavior of cyclic ether monomers with norbornene‐containing cyclic carbonate or spiro–orthoether structure
Authors: Hino Tetsuo , Inoue Naoto , Endo Takeshi 
Published: September 2004

AbstractCationic ring‐opening copolymerizations of various cyclic ether compounds with volume expanding monomers bearing norbornene backbones [norbornene‐spiro orthocarbonate (N‐SOC) and norbornene‐cyclic carbonate (N‐CC)] were carried out in the presence of a thermally latent initiator 1. The 10% weight loss decomposition temperatures (Td10) and the volume changes on the copolymerizations were measured for these resultant products. In the comparison between copolymerizations of bifunctional epoxide 2 with N‐SOC and with N‐CC, it was found that N‐CC served as a more useful volume controllable comonomer than N‐SOC. The copolymerizations with N‐CC yielded the products with a decrease in the volume change (volume shrinkage) and with an increase in the monomer feed ratio of N‐CC; Td10 was relatively similar to the homopolymer of epoxide 2 and was observed except when the proportion of N‐CC was more than 20% in the monomer feed ratio of N‐CC. In contrast, similar copolymerizations with N‐SOC did not exhibit such tendencies, probably because of the low efficiency of the copolymerization derived from the low miscibility of N‐SOC for the epoxide. The other copolymerization systems of other bi‐ and monocyclic ether compounds (3–6 and phenyl glycidyl ether) with N‐CC also indicated an almost similar tendency toward that of the copolymerization with epoxide 2. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5113–5120, 2004
Antimicrobial activity on the copolymers of 2,4‐dichlorophenyl methacrylate with methyl methacrylate: Synthesis and characterization
Authors: Patel Milan V. , Patel Samir A. , Ray Arabinda , Patel Rajni M. 
Published: September 2004

AbstractCopolymers of monomers 2,4‐dichlorophenyl methacrylate (2,4‐DMA) and methyl methacrylate (MMA) were synthesized with different monomer feed ratios using toluene as a solvent and 2,2′‐azobisisobutyronitrile (AIBN) as an initiator at 70 °C. The copolymers were characterized by IR‐spectroscopy, and copolymer composition was determined with UV‐spectroscopy. The linearization method of Fineman–Ross was employed to obtain the monomer reactivity ratios. The molecular weights and polydispersity indexes were determined by gel permeation chromatography (GPC). Thermogravimetric analyses of polymers were carried out in nitrogen atmosphere. The homo‐ and copolymers were tested for their antimicrobial properties against selected microorganisms. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5227–5234, 2004
Polyelectrolyte complexes. VII. Complex nanoparticles based on poly(sodium 2‐acrylamido‐2‐methylpropanesulfonate) tailored by the titrant addition rate
Authors: Dragan Ecaterina Stela , Schwarz Simona 
Published: September 2004

AbstractNonstoichiometric interpolyelectrolyte complexes (IPECs) as colloidal dispersions have been widely used for the past decade as reactive materials for flocculation and surface modification. In this context, some new aspects of the preparation and properties of IPEC nanoparticles based on NaPAMPS, in salt‐free aqueous solutions, are reported in this article. IPEC dispersions with different characteristics, z‐averaged particle sizes, polydispersity indices, and colloidal stabilities were tailored by the addition rate of the titrant, a less investigated factor in the synthesis of IPECs as nanoparticles. Poly(sodium 2‐acrylamido‐2‐methylpropanesulfonate) (NaPAMPS) and two polycations bearing positive charges in the backbone, poly(diallyldimethylammonium chloride) and a polycation containing 95 mol % N,N‐dimethyl‐2‐hydroxypropyleneammonium chloride units, were used for this purpose. The complex nanoparticle characteristics and storage stability were monitored via the optical density at 500 nm and dynamic light scattering. IPEC nanoparticles with z‐averaged particle sizes of 100–250 nm resulted from the same polyion pair and the same polyion concentrations when the addition rate of the titrant, either the polyanion or polycation, varied within the range of 0.1–1.5 mL/mL of the starting polyion × h. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5244–5252, 2004
The effect of salts on the conformation and microstructure of poly(N‐isopropylacrylamide) (PNIPA) in aqueous solution
Authors: Krasovitski Elena , Cohen Yachin , Bianco‐Peled Havazelet 
Published: September 2004

AbstractWe present an experimental investigation of the conformation and microstructure of Poly(N‐isopropylacrylamide) (PNIPA) in aqueous solution in the presence of salts. As a model, a strong salting–out salt (Na2SO4) and a strong salting–in salt (NaSCN) were chosen. Light scattering measurements show that Na2SO4 decreases the radius of gyration of PNIPA compared to its value in water, whereas NaSCN increases it. Moreover, the NaSCN solution was found to be a better solvent for PNIPA compared to water, whereas Na2SO4 solution is worse. Small‐angle neutron scattering measurements of semidilute PNIPA solutions, at temperatures well below the phase‐transition temperature, exhibit the behavior predicted by the model of dynamic concentration fluctuations characterized by a single correlation length. Excess scattering at low angles is observed in salt solutions at temperatures that are near, yet below, the phase‐transition temperature. This may indicate intrachain heterogeneities on the scale of 6–8 nm. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3713–3720, 2004
Influence of solvents on the formation of ultrathin uniform poly(vinyl pyrrolidone) nanofibers with electrospinning
Authors: Yang Qingbiao , Li Zhenyu , Hong Youliang , Zhao Yiyang , Qiu Shilun , Wang Ce , Wei Yen 
Published: September 2004

AbstractAlthough there have been many reports on the preparation and applications of various polymer nanofibers with the electrospinning technique, the understanding of synthetic parameters in electrospinning remains limited. In this article, we investigate experimentally the influence of solvents on the morphology of the poly(vinyl pyrrolidone) (PVP) micro/nanofibers prepared by electrospinning PVP solution in different solvents, including ethanol, dichloromethane (MC) and N,N‐dimethylformamide (DMF). Using 4 wt % PVP solutions, the PVP fibers prepared from MC and DMF solvents had a shape like a bead‐on‐a‐string. In contrast, smooth PVP nanofibers were obtained with ethanol as a solvent although the size distribution of the fibers was somewhat broadened. In an effort to prepare PVP nanofibers with small diameters and narrow size distributions, we developed a strategy of using mixed solvents. The experimental results showed that when the ratio of DMF to ethanol was 50:50 (w/w), regular cylindrical PVP nanofibers with a diameter of 20 nm were successfully prepared. The formation of these thinnest nanofibers could be attributed to the combined effects of ethanol and DMF solvents that optimize the solution viscosity and charge density of the polymer jet. In addition, an interesting helical‐shaped fiber was obtained from 20 wt % PVP solution in a 50:50 (w/w) mixed ethanol/DMF solvent. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3721–3726, 2004
Isothermal and nonisothermal crystallization kinetics of poly(propylene terephthalate)
Authors: Achilias Dimitris S. , Papageorgiou George Z. , Karayannidis George P. 
Published: September 2004

AbstractThe kinetics of crystallization of poly(propylene terephthalate) (PPT) samples of different molecular weights were studied under both isothermal and nonisothermal conditions. The Avrami and Lauritzen–Hoffmann treatments were applied to evaluate kinetic parameters of PPT isothermal crystallization. It was found that crystallization is faster for low‐molecular‐weight samples. The modified Avrami equation, and the combined Avrami–Ozawa method were found to successfully describe the nonisothermal crystallization process. Also, the analysis of Lauritzen–Hoffmmann was tested and it resulted in values close to those obtained with isothermal crystallization data. The nonisothermal kinetic data were corrected for the effect of the temperature lag and shifted alone with the isothermal kinetic data to obtain a single master curve, according to the method of Chan and Isayev, testifying to the consistency between the isothermal and corrected nonisothermal data. A new method for ranking of polymers, referring to the crystallization rates, was also introduced. This involved a new index that combines the maximum crystallization rate observed during cooling with the average crystallization rates over the temperature range of the crystallization peak. Furthermore, the effective energy barrier of the dynamic process was evaluated with the isoconversional methods of Flynn and Friedmann. It was found that the energy barrier is lower for the low‐molecular‐weight PPT. The effect of the catalyst remnants on the crystallization kinetics was also investigated and it was found that this is significant only for low‐molecular‐weight samples. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3775–3796, 2004
Electrically conductive, melt‐processed ternary blends of polyaniline/dodecylbenzene sulfonic acid, ethylene/vinyl acetate, and low‐density polyethylene
Authors: Zhang Qing‐Hua , Wang Xian‐Hong , Chen Da‐Jun , Jing Xia‐Bin 
Published: September 2004

AbstractAlthough polyaniline (PANI) has high conductivity and relatively good environmental and thermal stability and is easily synthesized, the intractability of this intrinsically conducting polymer with a melting procedure prevents extensive applications. This work was designed to process PANI with a melting blend method with current thermoplastic polymers. PANI in an emeraldine base form was plasticized and doped with dodecylbenzene sulfonic acid (DBSA) to prepare a conductive complex (PANI–DBSA). PANI–DBSA, low‐density polyethylene (LDPE), and an ethylene/vinyl acetate copolymer (EVA) were blended in a twin‐rotor mixer. The blending procedure was monitored, including the changes in the temperature, torque moment, and work. As expected, the conductivity of ternary PANI–DBSA/LDPE/EVA was higher by one order of magnitude than that of binary PANI–DBSA/LDPE, and this was attributed to the PANI–DBSA phase being preferentially located in the EVA phase. An investigation of the morphology of the polymer blends with high‐resolution optical microscopy indicated that PANI–DBSA formed a conducting network at a high concentration of PANI–DBSA. The thermal and crystalline properties of the polymer blends were measured with differential scanning calorimetry. The mechanical properties were also measured. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3750–3758, 2004
Metallocenic copolymers of ethylene and 5,7‐dimethylocta‐1,6‐diene: Structural characterization and mechanical behavior
Authors: Cerrada María L. , Benavente Rosario , Pérez Ernesto , Moniz‐Santos Jorge , Ribeiro M. Rosário 
Published: September 2004

AbstractThe relationship between the structure and mechanical properties has been established for several copolymers of ethylene and 5,7‐dimethylocta‐1,6‐diene synthesized with a metallocene catalyst. A dependence on the composition and polymerization temperature has been found. The branches cannot be incorporated into the orthorhombic crystal lattice, and consequently, structural parameters such as the crystallinity and crystal size are considerably affected as the 5,7‐dimethylocta‐1,6‐diene content increases in the copolymers. The viscoelastic relaxations have been analyzed and compared with those exhibited by high‐density polyethylene (HDPE). The β relaxation does not appear in HDPE and is exclusively seen in the copolymers. As the 5,7‐dimethylocta‐1,6‐diene content rises, the intensity of this process is increased, and its location is shifted to a lower temperature up to comonomer contents of approximately 6–8 mol % in the copolymers. On the other hand, the α mechanism associated with motion within the crystalline regions is also moved to a lower temperature and its intensity is diminished as the 5,7‐dimethylocta‐1,6‐diene molar fraction increases in the copolymers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3797–3808, 2004
Interfacial toughness in polymer‐layered laminar composites
Authors: Devasahayam Sheila 
Published: September 2004

AbstractThe investigation of the interfacial toughness of polymer layered laminar composites with two different approaches produced results differing by up to an order of magnitude and following opposite trends with respect to the strain rates. The flexural modulus and neutral axis of a constrained epoxy‐adhesive layer bound to a painted metal substrate varied with the thickness of the adhesive layer. The adhesion energy depended on the rate at which the force was transmitted to the adhesion bonds—not just on the strength of the adhesion bonds—and on the concomitant strain hardening at high strain rates. As the strain rate and thickness of the polymer layer increased, the transition from a cohesive mode to an adhesive–cohesive (polymer–polymer interface) mode of debonding led to the observed high adhesion energy. The high adhesion energy and increased strain hardening were attributed to the formation of organic–inorganic composites and nanocomposites within the polymer matrix, which evolved as a result of the interactions between the metal oxide pigments and fillers with the polymer matrix during curing. Scission of the polymer chains at the interface was proposed to be the predominant fracture mechanism; it was based on the high relaxation time (∼1017 s) and the high activation energy (∼175 kJ mol−1). © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3822–3835, 2004
Surface Analysis of Plasma‐Deposited Polymer Films, 2
Authors: Swaraj Sufal , Oran Umut , Lippitz Andreas , Schulze Rolf‐Dieter , Friedrich Jörg F. , Unger Wolfgang E. S. 
Published: September 2004

AbstractSummary: Chemical properties of plasma‐polymerized styrene films can be effectively controlled by the appropriate choice of external plasma parameters, such as duty cycle, power and monomer pressure. Chemical properties here are the regularity of the primary structure, the amount of long living radicals and branching or cross‐linking or both in plasma polymerized styrene films, which can be indirectly monitored by X‐ray photoelectron spectroscopy (XPS) and near edge X‐ray absorption fine structure (NEXAFS) spectroscopy. Principally, XPS and NEXAFS spectra of plasma‐polymerized styrene show all the spectroscopic fingerprints characteristic of atactic polystyrene indicating an inherent similarity of the respective primary chemical structures. There is an increase in irregularity and radical concentration for the plasma deposited films with increasing duty cycle or power. With an increase in monomer pressure, a decreased level of monomer fragmentation and, consequently, an increase in regularity must be concluded from the experimental data. The applied power regulates the fragmentation of the monomers as monitored by spectroscopic signals correlated to the aromatic rings. A trend in the extent of the post‐plasma oxygen incorporation according to the variation of the various external plasma parameters was deduced, which agrees with earlier ToF‐SIMS findings (Plasma Process. Polym., 2004, 1, 123).Total electron yield NEXAFS spectra of atactic polystyrene reference film (a) and a selected pulsed plasma‐polymerized styrene film (b).magnified imageTotal electron yield NEXAFS spectra of atactic polystyrene reference film (a) and a selected pulsed plasma‐polymerized styrene film (b).
PBS 180 – A New Standard in Plasma Technology
Authors: Preiß Gregor 
Published: September 2004

AbstractPlasma News: This section contains news of the plasma community all over the world. Articles about, for example, people, projects, and market trends are welcome. Suggestions should be sent to the editorial office of the Plasma Processes and Polymers, preferably by E‐mail to plasma@wiley‐vch.de. The editorial office decides which articles will be published.
Geophysical surveys designed to delineate the altitudinal limit of mountain permafrost: an example from Jotunheimen, Norway
Authors: Hauck Christian , Isaksen Ketil , Vonder Mühll Daniel , Sollid Johan Ludvig 
Published: September 2004

AbstractThree geophysical methods have been applied to delineate the altitudinal limit of permafrost at Juvvasshøe/Jotunheimen in southern Norway. By using each method in a complementary way according to its applicability, the permafrost distribution could be analysed on both large and small scales. In addition, temperature‐based methods such as the BTS method (bottom temperature of snow cover) were used to validate the results. On a large scale, electromagnetic induction profiling with the EM‐31 was used to detect the location of the transition area between frozen and unfrozen ground. Within this area direct‐current (DC) resistivity and refraction seismic tomography were also applied to further characterize and visualize the permafrost transition. The large scale surveys revealed a sharp increase in conductivity, indicating an increase in unfrozen water content, near 1400 m a.s.l., with a possible transition zone between 1500 m a.s.l. and 1380 m a.s.l. The small scale investigation delineated the altitudinal limit of permafrost between 1470 m a.s.l. and 1410 m a.s.l., with sporadic ground ice occurrences and temperatures near the freezing point. Copyright © 2004 John Wiley & Sons, Ltd.
Permafrost and Little Ice Age glacier relationships, Posets Massif, Central Pyrenees, Spain
Authors: Lugon Ralph , Delaloye Reynald , Serrano Enrique , Reynard Emmanuel , Lambiel Christophe , González‐Trueba Juan J. 
Published: September 2004

AbstractThis paper contributes to the study of permafrost in the Pyrenees by reporting geoelectrical investigations and thermal measurement on the Little Ice Age (LIA) forefields of two glaciers. The aim was to assess the internal composition of sedimentary bodies (debris rock glaciers and moraine deposits) located in this proglacial environment. Ground ice was prospected using two DC resistivity techniques: vertical electrical soundings and resistivity mapping at a fixed pseudo‐depth. Extreme specific resistivities ranging between 1 and 25 MΩ m were detected under a thin (1–2 m) unfrozen layer, indicating the presence of a massive ice layer, certainly buried glacier ice. This ice of glacial origin probably covers former permafrost bodies, i.e. a much thicker layer of perennially frozen sediments. Low subsurface temperatures measured on the deposits indicate that buried glacier ice could have been preserved on top of permafrost since the end of the LIA or earlier Holocene glacier advances. This stratigraphy demonstrates that glaciers and pre‐existing perennially frozen sediments (permafrost) were in contact during the LIA. Copyright © 2004 John Wiley & Sons, Ltd.
New insights into mountain permafrost occurrence and characteristics in glacier forefields at high altitude through the application of 2D resistivity imaging
Authors: Kneisel Chr. 
Published: September 2004

AbstractInvestigation of permafrost in glacier forefields at high altitude in the Upper Engadine has been undertaken during recent years (1996–1998) using one‐dimensional geoelectrical soundings as the standard geophysical technique to detect mountain permafrost. In summer 2002, two of the glacier forefields were revisited and two‐dimensional electrical resistivity tomography applied at the same survey locations. The findings based on the interpretation of one‐dimensional vertical geoelectrical soundings were confirmed by two‐dimensional resistivity imaging. Furthermore, the application of electrical resistivity tomography provides more detailed insights into the occurrence and characteristics of permafrost in recently deglaciated glacier forefields as compared to the results obtained by traditional one‐dimensional vertical soundings. Additionally, the more effective data acquisition enables new fields of application, which in turn will allow a more complete interpretation of the factors influencing the distribution of discontinuous and sporadic mountain permafrost. Copyright © 2004 John Wiley & Sons, Ltd.
The thermal regime of the active layer at the Murtèl rock glacier based on data from 2002
Authors: Hanson Susanne , Hoelzle Martin 
Published: September 2004

AbstractActive layer temperatures are presented from a rock glacier in the Swiss Alps. The data represent a full year (2002) covering parts of two very different winters. Winter/spring 2002 was very cold and dry; fall 2002 was characterized by an unusual amount of snow. Active layer temperatures are examined together with climate data and are used to discuss the processes which control the thermal regime of an active layer on a slope of a bouldery rock glacier surface. The development of the snow cover as well as the snow depth are shown to be essential, but the non‐linear heating of the bouldery material with increasing air temperatures and the micro‐topography of the rock glacier surface are also shown to have an influence on the thermal regime of the active layer. Furthermore, it is shown that the advective air movement within the blocky deposit has much less influence on the thermal regime than the vertical displacement of air masses. This is contradicts earlier literature on the subject. Copyright © 2004 John Wiley & Sons, Ltd.