bluuebunny/crossref_metadata_2025_split huggingface dataset:
Excimer fluorescence as a probe of miscibility in styrene copolymer blends
Authors: Haines David J. , Wilson Gerard J. , Ghiggino Kenneth P. , Hill David J. T. 
Published: April 2007

AbstractThe miscibility of styrene‐alt‐maleic anhydride (SMA) and a series of styrene‐acrylonitrile (SAN) copolymers in blends with either PMMA or PVC were examined by fluorescence and FTIR spectroscopic techniques. In the case of the alternating copolymer intra‐molecular excimer formation is precluded and changes in the excimer/monomer fluorescence intensity (IE/IM) reflect changes in the amount of inter‐chain excimer formation. The value of IE/IM in blends, therefore, provides a sensitive measure of phase separation (miscibility). In the case of the acrylonitrile copolymers the IE/IM of the blend had to be corrected to account for intra‐molecular excimers formed between adjacent chromophores in the SAN. These results compared favourably with observed frequency shifts in the phenyl C—H out‐of‐plane bend (∼700 cm−1).
Effects of mastication on the distribution of molecular weights and on the mechanical properties of native and commercial dental gutta percha (trans‐polyisoprene)
Authors: Arvanitoyannis Ioannis , Blanshard John M. V. , Kolokuris Ioannis 
Published: April 2007

AbstractMastication of gutta percha (trans‐polyisoprene) resulted in the selective scission of molecules, producing a narrower distribution of lower molecular weights. The mechanical properties of the samples also underwent a significant change due to mastication. The greater the content of incompatible substances (salts and oxides) in commercial gutta percha. the more substantial were these effects. The atmosphere (air, N2, O2) in which the experiments were conducted yielded significantly different results. The decrease in molecular weight was far greater in an O2 atmosphere than under a current of nitrogen or air, owing to the combination of double bonds with O2.
Surface activity of aqueous solutions of cellulose acetate with low degree of substitution
Authors: Kamide Kenji , Saito Masatoshi , Akedo Takaharu 
Published: April 2007

AbstractSurface activity of aqueous solutions of cellulose acetate (CA) with total degree of substitution (〈F〉) ranging from 0.58 to 0.80 was examined. Critical micelle concentration (CMC) of the aqueous CA solutions, determined from the polymer concentration dependence of surface tension (γ), is unequivocally determined by 〈F〉, and an increase in 〈F〉 of CA brings about a lowering of the CMC. From light scattering measurements on aqueous solutions of CA with 〈F〉 = 0.8 at 20°C, it was revealed that in the vicinity of the CMC the micelles in the solution consist of c. four CA molecules, which is very close to the value obtained by analysing the data obtained from the mass action model. The surface tension of aqueous solutions of CA (〈F〉 = 0.8) in the polymer concentration range above the CMC was c. 0.74 times that of pure water over the temperature range 0–80°C.
Studies on polymer latex films: III. Permeability of latex films to aqueous organic solutes
Authors: Roulstone B. J. , Wilkinson M. C. , Hearn J. 
Published: April 2007

AbstractThe transport of p‐nitrophenol across films formed from surfactant‐free poly(butyl methacrylate) latices has been investigated with a view to better understanding the morphology of, and morphological changes occurring in, such films. The importance of the temperature and time, both of film formation and of storage, are identified and related to the state of coalescence of the latex particles within the films. especially with respect to interparticle boundaries.
On the interactions and miscibility of PVC/PMMA blends
Authors: Li Weisheng , Shi Lianghe , Shen Deyan , Zheng Jun 
Published: April 2007

AbstractA DSC thermogram showed two separate glass transition temperatures in PVC/PMMA mixtures over the entire composition range; multiphase structures were observed in an optical microscope. FTIR spectra indicate that there are no strong specific interactions between these two polymers. The earlier studies on this blend system are briefly reviewed.
Apparent solubility parameters from photophysical investigation of copolymers with pendent naphthyl chromophores
Authors: McCormick C. L. , Hoyle C. E. , Clark M. D. , Schott T. A. 
Published: April 2007

AbstractThe effect of solvent on the formation of excimer from copolymers of 2‐(1‐naphthylacetyl)ethylacrylate (NAEA) with both acrylamide (AM) and N‐vinyl pyrollidone (VP) in dilute solution was investigated. A minimum in excimer intensity was observed for each of the copolymers at approximately 2.20 × 104 (J/m3)0.5. It is suggested that the relatively high content of NAEA in the copolymers (between 30 and 60%) governs the overall solubility parameter of the polymer.
Photoresponsive peptide and polypeptide systems: part II. Photochromism of poly(l‐ornithine) containing various azo‐contents in side chains
Authors: Yamamoto Hiroyuki , Ikeda Kengo , Nishida Ayako 
Published: April 2007

AbstractPoly(L‐ornithine)s having various azo‐contents in the side chains were synthesized by the water‐soluble carbodiimide procedure. The photochemical properties of the polypeptides poly[Nδ‐p‐(phenylazo)benzoyl‐L‐ornithine] (PPABLO) containing 3–77 mol% azobenzene were investigated by absorption and circular dichroism spectroscopy in hexafluoro‐2‐propanol (HFIP) or water, and in HFIP‐water or methanol‐water solvent mixtures. The photochromism of the dichroic bands of the PPABLOs containing 20–77 mol% azobenzene in the visible and ultraviolet wavelength regions was found to be mostly reversible as a function of irradiation time at different wavelengths due to the photostationary state (above 80% trans‐cis photoisomerization) of the azo aromatic moieties. The PPABLO containing 3.2 mol% azobenzene in water exhibited conformational changes from random coil to helix by the addition of methanol or sodium dodecyl sulphate (SDS). The photo‐induced conformational change was observed in HFIP‐water‐SDS solvent mixtures, while no conformational change was seen in water and HFIP‐water solvent mixtures.
Modelling of emulsion copolymer microstructure
Authors: van Doremaele G. H. J. , van Herk A. M. , German A. L. 
Published: April 2007

AbstractA model has been developed to describe stages II and III of batch emulsion copolymerization, and its predictive capabilities have been investigated by application to the system styrene‐methyl acrylate.The main reaction site is considered to be the monomer‐swollen polymer particle. Copolymerization rate and copolymer microstructure (molar‐mass‐chemical‐composition distribution and sequence distribution at the triad level) are controlled by the local concentrations of monomers and free radicals inside the particles. The model accounts for radical absorption and desorption processes, bimolecular termination within the particles, and transfer to monomer and chain transfer agent. Monomer partitioning is described using experimentally determined relations. The results include rate of (co)polymerization. composition drift and copolymer microstructure.It is demonstrated that ‘apparent’ reactivity ratios are generally incapable of describing the course of emulsion copolymerizations in an adequate manner.
Plasma surface modifications for improved biocompatibility of commercial polymers
Authors: Griesser Hans J. , Chatelier Ronald C. , Gengenbach Thomas R. , Vasic Zoran R. , Johnson Graham , Steele John G. 
Published: April 2007

AbstractThis report describes work using low pressure gas plasma techniques for the fabrication of surfaces designed for compatibility with biological tissue and fluids. The smoothness of the surfaces was investigated using scanning tunnelling microscopy (STM) and the wettability was assessed by measurement of air/water contact angles. Plasma surface treatment rendered fluorocarbon polymers wettable by polar liquids, but the wettability decreased with time during storage of the samples in air. Plasma polymerization, on the other hand, allowed the deposition of thin coatings which were more stable with time. STM of plasma polymers, which were coated with a sputtered film of platinum or gold, showed that these coatings were smooth and continuous. The attachment and growth of human umbilical artery endothelial cells was used to assess the biocompatibility of several plasma polymer surfaces. There was some correlation between the ability of a surface to grow cells and the wettability of that surface with polar liquids, but significant differences in cell growth on surfaces with very similar hydrophilicity indicated that other factors are at least as important.
Optical data storage by novel photoelectrochromic polymer
Authors: Nagamura Toshihiko , Isoda Yuji , Sakai Kenkichi 
Published: April 2007

AbstractA novel elastic polymer containing 4,4′‐bipyridinium salts with tetrakis[3,5‐bis(trifluoromethyl)phenyl]borate as part of the main chain was synthesized. The cast film showed persistent and reversible colour changes due to photoinduced electron transfer upon excitation of an ion‐pair charge‐transfer band (ex >365 nm) in vacuo. The lifetime of the coloured state markedly depended on temperature. The optically written data were stored without decay below 0°C and were erased thermally at elevated temperatures. The colour changes were reversibly repeatable for many times.
Asbestos replacement aspects: Modification of the fibre‐matrix interphase in lonomer based composites
Authors: Papaspyrides C. D. , Poulakis J. 
Published: April 2007

AbstractAsbestos fibres, of the chrysotile variety, and chopped carbon fibres were pretreated by an in‐situ polycondensation technique eventually resulting in a polyamide coating on the fibre surface. Ionomer based composites containing either carbon or asbestos fibres in random in plane fibre orientation were prepared, and the influence of this coating process on the tensile properties was investigated. It was found that for the asbestos‐filled composites the presence of the nylon 6,6 interlayer improves the tensile performance, especially at moderate polyamide depositions. This is not the case with the pretreated carbon‐filled composites for which carbon fibres with higher polyamide contents are preferred. Combinations of the treated asbestos fibres with carbon and/or aramid fibres may be used to reduce the asbestos content in asbestos‐only based engineering plastics.
Supercritical fluid extraction of polymer additives for use in biocompatibility testing
Authors: Braybrook Julian H. , Mackay Graham A. 
Published: April 2007

AbstractBiocompatibility is the ability of a material to perform with an appropriate host response in a specific application. This response is poorly understood and so there exist inconsistencies in test results both between different laboratories and within the same laboratory. Standard reference materials and test protocols are essential.Analytical‐scale supercritical fluid extraction (SFE) has been investigated as a potential standard test protocol for obtaining additives from polymer matrices. These extracts have been analysed for in‐vitro cytotoxicity using standard cell culture techniques whose clinical relevance has already been established.
Synthesis and characterization of poly(siloxane‐urethane)s
Authors: Chun Yong‐Chul , Kim Kong‐Soo , Shin Jae‐Sup , Kim Kyung‐Ho 
Published: April 2007

AbstractA series of polyurethane block copolymers based on hydroxy‐terminated polydimethylsiloxane and poly(propylene glycol) soft segments of molecular weights 1818 and 2000, respectively, were synthesized. The hard segments consisted of 4,4′‐diphenylnethane diisocyanate and 1,4‐butanediol as the chain extender. Samples with different molar ratios were prepared. We tried to synthesize polydimethylsiloxane‐based polyurethanes (PDMS‐PU) containing a hard block as major fraction and a soft block as minor fraction for preparing toughened rigid systems. After a study of the pure polydimethylsiloxane‐based polyurethane and poly(propylene glycol)‐based polyurethane (PPG‐PU), (mixed polyol)‐based block copolymers and blends of PDMS‐PU and PPG‐PU were synthesized, and characterized by means of differential scanning calorimetry, tensile testing and scanning electron microscopy. In (mixed polyol)‐based copolymers and lower hard‐segment content blends, macro‐phase separation occurred, but blends with higher hard‐segment contents showed significant reduction in amounts of phase separation.
Thermal stability of polypyrroles
Authors: Truong Van‐Tan , Ennis Brian C. , Turner Terrence G. , Jenden Charles M. 
Published: April 2007

AbstractThe effect of dopants and level of doping on the thermal stability of polypyrrole at 90, 120 and 150°C in dry air and nitrogen was investigated by monitoring the decay of conductivity. Polymers doped with aromatic anions (p‐toluene sulphonate and p‐chlorobenzene sulphonate) exhibit better stability than polymers doped with an aliphatic anion (dodecyl sulphate). The conductivity decay appears to follow diffusion controlled kinetics. After an initial decrease in conductivity, polypyrrole doped with p‐toluene sulphonate anion maintains a constant conductivity at 150°C in air for at least 4 weeks. Dedoping results in materials of lower conductivity but greater thermal stability. Differential scanning calorimetry (DSC) and thermogravimetry (TG) were found to be useful techniques to characterize and investigate thermal stability. Oxidation of polypyrrole films, monitored by DSC, shows diffusion controlled kinetics. Although both oxidation and conductivity decay show typical diffusion kinetics, oxidation is a necessary but not sufficient condition for the decay.
Characterisation of the surface of wool and hair using microscopical and fluorescence probe techniques
Authors: Jurdana Lucia E. , Leaver Ian H. 
Published: April 2007

AbstractFluorescence probing methods, in combination with light microscopy, were used to image and characterise the hydrophobic surfaces of wool and human hair fibres. When applied from an aqueous dispersion, uncharged lipophilic fluorescent probes displayed a selective affinity for the boundaries of the cuticle cells on the fibre surface. Adsorption generally occurred on the surface of the lower scale emerging from each cell junction. An indication of the fibre surface polarity was given by the fluorescence fine structure of adsorbed pyrene molecules.Treatment of hair with the lipid stain Nile Red produced an unusual diamondshaped pattern (each segment approximately 40 μm in length and 10 μm in width) in areas where the cuticle had been damaged. Cuticle cells isolated from hair fibres showed distinct geometrical features on their surfaces when examined using differential interference contrast microscopy. The results are interpreted to indicate the presence of a residue of lipid‐staining material adhering to the cuticle cells of hair, the residue possibly being derived from adhesive material produced at the areas of contact between presumptive cuticle cells during the early stages of cuticle shape differentiation.
Synthesis and Characterization of Poly (Acrylic Acid‐co‐Divinylbenzene) Microgels by Ultrasonic Degradation
Authors: Kim Young‐June , Kim Kong‐Soo , Park Myung‐Hwan 
Published: April 2007

AbstractThe preparation of pure microgels in high yield was investigated by a new method which restricts the intermolecular crosslinking reaction between second‐stage crosslinked products by steric hindrance of the first‐stage crosslinked products. This is followed by ultrasonic degradation of the first‐stage crosslinked products. The first‐stage crosslinked products were prepared by copolymerization of styrene and divinylbenzene monomer in dioxane. with α,α′‐azobisisobutyronitrile as initiator. The second‐stage crosslinked products were prepared by copolymerization of acrylic acid and divinylbenzene monomer in first‐stage crosslinked products highly swollen in dioxane, using α,α′‐azobisisobutyronitrile as initiator. Degradation of first‐ and second‐stage crosslinked products was carried out using an ultrasonic vibrator.The characteristics of the crosslinked products synthesized were investigated by gel permeation chromatography, dynamic laser light scattering and electron microscopy. It was found that the styrene‐divinylbenzene gel of high molecular weight was scissioned preferentially with increasing ultrasonic degradation time and that ultrasonic degradation of compact and small size crosslinked products was very difficult. The crosslinked poly(acrylic acid)s are small compact microgels having a very narrow size distribution of 20‐30 nm diameter.A pure microgel at nearly 100% conversion was obtained by the new preparation method suggested in this study.
Effect of Space Charge on Polarization Reversal Currents in a Vinylidene Fluoride/Trifluoroethylene Copolymer
Authors: Guy Ian L. , Das‐Gupta Dilip K. 
Published: April 2007

AbstractPolyvinylidene fluoride and its copolymers with trifluoroethylene and tetrafluoroethylene are ferroelectric. Reversal of polarization in these polymers is known to occur by a rotation of the polar molecular chains, in response to an externally applied electric field. Recent evidence suggests that the dynamics of polarization reversal can be affected by movement of space charges in the amorphous phase of the polymers. If a 75/25 mol.% vinylidene fluoride/trifluoro‐ethylene (VF2/VF3) copolymer is poled at elevated temperature, the subsequent polarization reversal currents show large asymmetry and significant shifts in successive reversals. The field required to reverse the polarization in such high‐temperature poled material is significantly larger than the normal coercive field. The asymmetry in the reversal currents is consistent with the presence of local fields within the polymer, generated by space charge which accumulates during the poling process. The subsequent movement of this space charge causes the shift in successive reversal currents. The variation of reversal current with temperature indicates that the movement of space charge within the copolymer is a thermally activated process.
Interaction between Poly(2‐ hydroxyethyl methacrylate) and High Energy Excimer Laser Radiation
Authors: Vernon Chris F. , Klauber Craig , van Saarloos Paul P. , Chirila Traian V. 
Published: April 2007

AbstractPoly(2‐hydroxyethyl methacrylate) was prepared by bulk polymerization and then exposed to ablation by 193‐nm pulsed radiation provided by an ArF excimer laser. The etch curve, i.e. ablation rate versus radiation fluence, presents two changes in the slope, which are consistent with a presumably characteristic behaviour of addition polymers with a strong tendency towards thermal depolymerization. Samples exposed to two fluences, each in the vicinity of one of the inflection points, were analysed by X‐ray photoelectron spectra (XPS) at two different take‐off angles. The results suggest that the ablation mechanism may vary when the fluence changes. At the higher fluence (280mJ/cm2), depolymerization is the dominant process and the material left after etching displays almost no change in the O/C atomic ratio. At the lower fluence (80mJ/cm2), cleavage of the pendant group is dominant and the O/C ratio decreases significantly, especially on the polymer surface.
Electroplasticity memory devices using conducting polymers and solid polymer electrolytes
Authors: Takashima Wataru , Sasano Kiyotaka , Asano Tanemasa , Kaneto Keiichi 
Published: April 2007

AbstractErasable memory devices are fabricated by the combination of a conducting polymer and solid polymer electrolyte. The former is used as a memory channel and the latter as an electrolyte medium. The channel conductivity can be controlled over 3‐4 orders of magnitude by electrochemical doping through a writing electrode. The response time, depending on the writing voltage, is several seconds. The characteristics of the memory device are discussed.
Factors influencing the rate of the electrochemical oxidation of heterocyclic monomers
Authors: John R. , Wallace G. G. 
Published: April 2007

AbstractThe influence of several variables on the rate of oxidation of heterocycles to form conductive, electroactive polymers has been considered. It has been shown that the extent to which variables such as electrode size, monomer/counterion concentrations and applied potential influence the rate depends on the monomer and counterion being employed.
Synthesis and characterization of novel liquid‐crystalline copolymers containing thermally stable photochromic groups
Authors: Liu Jui‐Hsiang , Yang Po‐Chih , Chiu Yi‐Hong , Suda Yasuo 
Published: April 2007

AbstractTo overcome the defects of the thermal instability of azobenzene, a series of novel photochromic, chiral, liquid‐crystalline monomers and polymers were synthesized from (+)‐camphor. The copolymerization of the photochromic monomers with comonomers was carried out. The synthesized monomers and polymers were identified with nuclear magnetic resonance, Fourier transform infrared, and elemental analysis. The composition of the copolymers was estimated with elemental analysis. The specific rotation of the chiral compounds and polymers was evaluated. The thermal stability and phases of the polymers during heating and cooling cycles were studied with differential scanning calorimetry and thermogravimetric analysis. The phases of the polymers were identified with polarized optical microscopy textures and X‐ray diffraction analysis. The distance between the layers of smectic liquid crystals was estimated from the diffraction angles. Photoisomerization of the configurational E/Z structures was investigated with an ultraviolet–visible spectrophotometer with 300‐nm ultraviolet irradiation. The thermal stability of the Z‐structural segment in the polymers was confirmed through the heating of the polymer at 70 °C for over 10 h. The photoisomerization and thermal stability of the CC bond in the polymeric materials were demonstrated through a series of novel chiral polymers synthesized in this investigation. Both the polarity of the center part and the molecular length at the ends of the molecules were found to be necessary factors for the formation of liquid‐crystalline molecules. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2026–2037, 2007
Synthesis and optical properties of light‐emitting π‐conjugated polymers containing biphenyl and dithienosilole
Authors: Liao Liang , Cirpan Ali , Chu Qinghui , Karasz Frank E. , Pang Yi 
Published: April 2007

AbstractCopolymers containing oligo(phenylene vinylene) (2.5), fluorene, and 4,4‐dihexyldithienosilole (DTS) units were synthesized and characterized. The π‐conjugated monomers were joined with the palladium(0)‐catalyzed Suzuki–Miyaura coupling reaction, thus forming either biphenyl– or phenyl–thiophene linkages. These polymers were photoluminescent, with the fluorescent quantum efficiency between 54 and 63% and with λmaxfor fluorescence at ∼448 nm in tetrahydrofuran. The presence of 5% DTS in the copolymers had little influence on the optical absorption and emission wavelengths. Double‐layer light‐emitting‐diode devices using these polymers as emissive layers had low turn‐on voltages (3.5–4 V) and moderate external quantum efficiencies (0.14–0.30%). The results show that DTS plays a positive role in improving the charge‐injection characteristics of poly(phenylene vinylene) materials. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2048–2058