bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structural and hydration studies of waxy and mealy potato starch cultivars by deuterium, carbon‐13 CP‐MAS/MASS NMR, and electron microscopy
Authors: Baianu I. C. , Yakubu P. I. , Ozu E. 
Published: March 2011

AbstractProton and deuterium pulsed Nuclear Magnetic Resonance (NMR) techniques were employed to investigate the hydration properties of raw and cooked (steamed, oven baked and microwave baked) waxy (LaSoda and Pontiac) and mealy (Russet Burbank and Norchip) potato cultivars and starches. Three water components (T2Q internal, T2A medium and T2B long component) were resolved in potato cultivars and starches. The first water component T2Q is assigned to the anisotropically bound water within the potato starch granule structure. The T2A corresponds to trapped water, whereas, the T2B‐long component is assigned to the average between weakly bound and free water populations. The anisotropically bound water (T2Q internal) in potato cultivars and starches does not seem to be in fast chemical exchange with free and weakly bound water populations. Well defined powder patterns with a residual deuterium quadrupole splitting of about 1 kHz were observed at 22°C for raw potato cultivars and starches (17%, w/w). The quadrupole splitting, however, disappeared after cooking as a result of heat induced structural changes, and only rapidly, isotropically reorienting water remained. The T2A and T2B values were also significantly affected by the cooking method. The T2B values of cooked potatoes were shorter than those of raw potatoes. Heat induced structural changes were reflected in the shorter T2B value of the cooked and crushed potatoes. Lower average 1H NMR transverse relaxation rates were observed in cooked waxy (LaSoda) in comparison with those of other potatoes.
Molecular dynamics and NMR studies of proteins in ionic solutions
Authors: Baianu I. C. , Kumosinski T. F. , Wei T. C. 
Published: March 2011

AbstractThe molecular dynamics of water and selected ions was studied in concentrated electrolyte solutions with, or without, proteins added. Our experimental results by multinuclear spin relaxation techniques were then compared with molecular dynamics computations for water and ions in concentrated electrolyte solutions. The mechanisms for the anionic and cationic interactions with myofibrillar proteins in aqueous solutions were investigated by nuclear magnetic resonance over a wide range of salt concentrations. The multinuclear spin relaxation data were analyzed with a thermodynamic linkage model of hydrated ion clusters of various sizes and composition. Protein amide groups were found to bind to anions with strengths in the order of the lyotropic series.
An infrared spectroscopic study of a hyperbranched, dendrimer‐like, polyester and its blends with poly(4‐vinyl phenol)
Authors: Painter Paul C. , Pruthtikul Rittirong , Coleman Michael M. , Tan Beck Nora 
Published: March 2011

AbstractA dendrimer‐like hyperbranched polyester is characterized by infrared spectroscopy. By converting and labeling the terminal groups by acetylation with 13C acetic anhydride, the relative accessibility of core and terminal functional groups to solvents and linear polymers can be measured by counting the number of hydrogen bonds formed between the complementary functional groups found in these materials. The terminal groups form hydrogen bonds as readily as the same groups in linear polymers, but the core groups are highly screened. These results suggest that in these mixtures the dendrimer is extended, with the terminal groups located near the periphery of the molecule.
Raman spectroscopy for polymer characterization in an industrial environment
Authors: Everall Neil , King Bert 
Published: March 2011

AbstractIn this paper we discuss the use of Raman spectroscopy for characterising polymers both in the laboratory and also in‐situ at the production line. We show how polymer crystallinity can be followed during extrusion and drawing, and describe the compositional analysis of cross‐linked acrylic terpolymers in a polymerisation reactor. We also discuss problems which can arise such as sample fluorescence from moving polymers, distortion of relative band intensities due to chromatic aberration, and sampling difficulties with turbid solutions.
Fiber‐optic evanescent wave fourier transform infrared (FEW‐FTIR) spectroscopy of polymer surfaces and living tissue
Authors: Afanasyeva Natalia I. 
Published: March 2011

AbstractThe new method of fiber‐optic evanescent wave Fourier transform infrared (FEW‐FTIR) spectroscopy has been applied to studies of polymer surfaces and the diagnostics of normal, precancerous and cancerous tissue. This technique using optical fibers and fiber‐optic sensors operating in the attenuated total reflection (ATR) mode in the mid‐infrared (IR) region of the spectrum (850 – 1850 cm−1) has found recently application in the area of tissue diagnostics. The method is suitable for noninvasive and rapid (seconds) direct measurements of the spectra of normal and pathological tissues in vitro, ex vivo, and in vivo.The FEW‐FTIR technique is an ideal diagnostic tool for different types of soft, porous, foam, and rough polymer surfaces. Inhomogeneous coatings and defects on polymer surfaces as well as layer structures have also been detected by this method. It is convenient to apply this method to analyze large pieces of soft plastics and/or surfaces covered by plastics, since these types of surfaces are comparatively hard to analyze by traditional absorption spectroscopy. The FEW‐FTIR technique is non‐destructive, fast (15 seconds), and remote (up to a fiber length of 3m). In addition, it is sensitive enough to detect any changes in the vibrational spectra of a polymer surface, without heating and damaging it. The surfaces of polyethylene crumpled bags and rumpled films have been investigated in the range of 2000 – 1000 cm−1. The distinct spectra of these surfaces as well as spectra of polytetrafluoroethylene have been recorded. The spectra of white and colored foams and different plastics have also been studied. Weak but distinct spectra have been recorded for carbon fibers (black, narrow fibers with a diameter of about 10 μm). Using the FEW‐FTIR technique, measurements can be taken without preparing the sample. High quality spectra have also been obtained for the bulk and surfaces of apple, banana, grapefruit, and other food products. The method is expected to be further developed for geological and microelectronic applications.
Infrared reflectance as a tool to reveal preferential molecular orientation of polymers adsorbed onto flat substrates
Authors: Brogly M. , Bistac S. , Schultz J. 
Published: March 2011

AbstractFTIR‐Reflectance experiments have been made on thin ethylene‐vinyl acetate (EVA) copolymer layers deposited on aluminum mirrors in order to determine orientation of polymer functional groups at the interface. This was accomplished by using various reflection angles under p polarization state of the incident IR beam. Film thicknesses were estimated by ellipsometric experiments. Kramers‐Kronig analysis is first applied to the external infrared reflection spectrum from a single copolymer surface measured near the normal incidence angle. Absorption spectra, k(v), are then deduced and used to calculate specular reflectance intensities of the functional groups of interest as a function of incidence angle, polarization state and film thickness. The calculated values are compared to those observed. A layer model is developed, which allows the molecular orientation of both EVA carbonyl groups and the main chain axis at the interface to be determined. Only carbonyl groups involved in specific electron donor‐electron acceptor interactions at the interface appear to be subject to specific orientation. A persistence thickness of the preferential orientation in the film is determined, also from which it is concluded that even in nanofilms, preferential molecular orientation induced by an hydroxylated substrate does not persist throughout the film thickness. It is localized at a near interfacial region, the thickness of which depends on the ability of the comonomer to undergo conformational changes.
Analysis of the hydrogen bonding in (2‐hydroxypropyl)cellulose‐poly(acrylic acid) composites by Raman spectroscopy
Authors: Kozanecki Marcin , Ulański Jacek , Wojciechowski Piotr , Kryszewski Marian , Boudeulle Micheline , Duval Eugen 
Published: March 2011

AbstractNovel anisotropic polymer composites obtained by the photopolymerisation of acrylic acid (AA) in lyotropic solutions of (2‐hydroxypropyl)cellulose (HPC) were investigated. Raman spectroscopy was used in the study of hydrogen bonding formed by carboxylic groups of poly(acrylic acid) (pAA) between themselves and with the hydroxyl groups of HPC macromolecules. These investigations show that the supramolecular structure of pAA obtained by photopolymerisation contains mainly inner oligomeric forms and cyclic dimer forms, as a consequence of the “matrix polymerisation” of AA. The presence of HPC affects the process of the photopolymerisation of AA, by a redistribution of hydrogen bonding within the system, leading to a different supramolecular structure of pAA. With increasing amounts of HPC the inner oligomeric forms characteristic of bulk pAA disappear. In the composites, the pAA chains probably form the terminal oligomeric structure, with some free COOH groups, as well as hydrogen bonds with HPC.
Hydrogen bond network formation
Authors: Chase D. B. , Ikeda R. M. 
Published: March 2011

AbstractThe signs of the dynamic dichroism of the NH stretch and the amide I bands in nylons were found to be counterintuitive. Experiments show that polymer chains tend to align in the direction of an applied tensile strain. The CH stretching bands in nylons exhibit the expected negative dynamic dichroism indicating chain alignment in the strain direction. The ΔA′ peaks for the NH and amide I bands are positive. The ΔA′ peak for the NH band is also unusual in that it has a derivative shape. This can be explained by band shifts brought about by anisotropic changes in the intermolecular spacing in the glassy polymer. Above Tg the derivative shape disappears but the ΔA′ peak for both the NH and amide I absorption remain positive. We postulate that the positive ΔA′ peaks of the NH and amide I bands result from a hydrogen bonding network where stress is transmitted through a network consisting of covalent chains connected by hydrogen bonds.
Fluorescence to study aggregation of amphiphilic copolymers in aqueous media
Authors: Frochot Céline , Brembilla Alain , Lochon Pierre , Viriot Marie‐Laure 
Published: March 2011

AbstractRandom copolymers of 3‐hexadecyl‐1‐vinylimidazolium bromide and N‐vinyl‐2‐pyrrolidinone were synthesized by free radical copolymerization at various feed compositions. These copolymers, whose structure was determined by 13C NMR spectrometry, self‐aggregate in aqueous media. The formation of the resulting hydrophobic microdomains was analyzed by spectrofluorimetry, using pyrene and a molecular rotor as fluorescent tracers. The results are discussed in relation to the molecular structure of the copolymers, particularly for the case of the micro cohesion sensed by the molecular rotor.
The effect of spacer length on the polymerization of diacetylenes in sams on gold surfaces
Authors: Menzel Henning , Mowery Mark D. , Cai Mei , Evans Christine E. 
Published: March 2011

AbstractThe influence of the molecular architecture of diacetylene disulfides on the structure and polymerizability of self assembled monolayers on gold was investigated. The position of the diacetylene group was varied systematically by adjusting the length of the tail and the spacer. For the structures studied, the longer the tail, the higher the akyl chain crystallinity as sensed by IR spectroscopy, and the higher the polymerization efficiency as probed by resonance Raman spectroscopy. The influence of the spacer on the polymerizability is more complicated. It is conjectured that the spacer reduces the lattice strain due to the misfit of the arrangement of the anchor groups and the arrangement of the diacetylene units and the polydiacetylene backbone, respectively. Simple modeling reveals that the number of the methylene units (odd or even) and the overall length both influence the arrangement. The highest polymerization efficiency is found for the longest, odd numbered spacer.
Self‐assembled multilayers of photochromic bola‐amphiphile and ionene‐type oligomer: Relation of aggregate state and photoisomerization
Authors: Park Ae‐Li , Hong Jong‐Dai 
Published: March 2011

AbstractPhotoisomerization process of azobenzene has been studied in the multilayer assemblies of poly(vinylsulfate, potassium salt) and two different layer‐elements; 4,4′‐azobenzene‐bis(12‐trimethylammonium‐N‐yl dodecyloxy) dibromide (BA‐12, 1) and an ionene oligomer, poly(4,4′‐azobenzene‐bis(12‐dimethyl‐ammonium‐N‐yl dodecyloxy) bromide) (PAZ‐12, 2). The change of the photoactive layers from BA‐12 to PAZ‐12 was found to dramatically influence the photoisomerization characteristics of the azobenzene in the multilayer. Surprisingly, we have observed that the chromophore interaction in PAZ‐12 is stronger than that in BA‐12 in self‐assembled (SA) film (λmax = 320 nm compared to 341 nm), although the aggregate formation is considered to be hindered by the strains of the polymer chains. For BA‐12/PVS and PAZ‐12/PVS multilayers, the steady state between cis and trans isomers reached after ca 20 min. and 48 min. of UV irradiation, respectively. It was also found that after first one trans‐cis‐trans cycle of the photoisomerization, the trans to cis isomerization was completed in 30 sec of irradiation in the following 10 cycles without appearance of any fatigue in the multilayer film.
The volume transition in thermosensitive core‐shell latex particles investigated by small‐angle x‐ray scattering and dynamic light scattering
Authors: Kim J. , Deike I. , Dingenouts N. , Norhausen C. H. , Ballauff M. 
Published: March 2011

AbstractWe present a survey over recent studies of the volume transition in colloidal core‐shell particles composed of a solid poly(styrene) core and a shell of a thermosensitive crosslinked polymer chains. The thermosensitive shell is built up from poly(N‐isopropylacrylamide) chains (PNIPA) crosslinked by N,N′‐methylenbisacrylamide (BIS). In addition, particles containing acrylic acid (AA) as comonomer have been synthesized and investigated. The volume transition of these particles have been studied by dynamic light scattering (DLS) and by small‐angle X‐ray scattering (SAXS). In all cases analyzed so far the volume transition was found to be continuous. This finding shows that the core‐shell microgels behave in a distinctively different manner than ordinary thermosensitive gels: The crosslinked chains in the shell are bound to a solid boundary independent of temperature. The spatial constraint by this boundary decreases the maximum degree of swelling but also prevents a full collapse of the network above the volume transition.
Crystalline polymers in real space
Authors: Bassett David C. 
Published: March 2011

AbstractRecent work has resolved uncertainties as to how polymers develop their melt‐crystallized textures and brought a unified context to the subject. Spherulites form because of the long molecular length not because of its polydispersity. When a molecule is only partly attached to a growing lamella the unattached portions will occupy adjacent space and exert a short‐range repulsive pressure on any neighbouring lamella at a branch point. This is confirmed by monodisperse long n‐alkanes forming spherulites only with chainfolded lamellae not when crystallizing as extended chains. An additional textural element, cellulation, is superposed on regular spherulitic growth beyond a certain radius (in linear‐low‐density polyethylenes) when there is sufficient fractional crystallization of segregated species which lower the local equilibrium melting temperature and thence the isothermal supercooling and growth rate, the last declining continuously to an asymptotic limit. First results show that both the radius to cellulation and the cell width are effectively independent of growth velocity; neither scales with the diffusion length. A possible explanation is proposed for this novel situation which has no precedent in either polymeric or non‐polymeric systems.
Bulk and surface modification of elastomers by electron beam irradation: Structure‐property relationship
Authors: Bhowmick Anil K. , Majumder Papiya Sen , Banik Indranil 
Published: March 2011

AbstractBulk and surface modification of ethylene propylene diene monomer (EPDM) and fluoroelastomer by electron beam irradiation was investigated. The structure of the modified elastomers was analysed with the help of Infrared (IR) spectroscopy, Electron Spectroscopy for Chemical Analysis (ESCA) and gel content. Mechanical and dynamic mechanical properties of bulk modified fluoroelastomers and surface energy and frictional coefficient of the surface modified EPDMs were measured. The properties were correlated with the structure developed.
Recent developments in photoinitiated radical polymerization
Authors: Decker Christian 
Published: March 2011

AbstractThis article presents the progress made in the development of high‐speed photocurable resins and reports the performance of some novel radical‐type photoinitiators, acrylate monomers and telechelic oligomers. The polymerization kinetics has been studied by real‐time infrared spectroscopy, which records conversion versus time curves for reactions occurring in a fraction of a second. Phosphine oxides are among the most efficient photoinitiators and proved to be particularly well suited for the photocuring of pigmented systems and for solar‐assisted polymerization. Acrylate monomers containing a heterocyclic oxygen in their structural unit exhibit an unexpectedly high reactivity. The introduction of an amino group in the chain of a telechelic acrylate‐polyester causes a substantial acceleration of the polymerization process. In both cases, the increase in reactivity was attributed to the presence of labile hydrogen atoms which favor chain transfer reactions. The copolymerization of donor‐acceptor monomer systems, like vinyl ether‐maleate or vinyl ether maleimide, was shown to proceed readily upon UV irradiation, even in the absence of added photoinitiator. Light‐induced polymerization was also used to crosslink rapidly polymers functionalized with acrylate or vinyl double bonds, namely acrylated polyisoprene and a styrene‐butadiene block copolymer. The addition in small amounts (1 wt%) of a trifunctional thiol was found to speed up drastically the crosslinking polymerization, causing insolubilization of the thermoplastic elastomer to occur after a 0.1 s exposure.
Advanced research work on radiation cross‐linking of polymers in CIAC
Authors: Jiazheng Sun , Xiaoguang Zhong 
Published: March 2011

AbstractRecent research carried out at the Chinese Institute of Applied Chemistry has contributed significantly to the understanding of the radiation chemistry of polymers. High energy radiation has been successfully used to cross‐link fluoropolymers and polyimides. Here chain flexibility has been shown to play an important role, and T‐type structures were found to exist in the cross‐linked fluoropolymers. A modified Charlesby‐Pinner equation, based upon the importance of chain flexibility, was developed to account for the solradiation dose relationship in systems of this type. An XPS method has been developed to measure the cross‐linking yields in aromatic polymers and fluoropolymers, based upon the dose dependence of the aromatic shake‐up peaks and the F/C ratios, respectively. Methods for radiation cross‐linking degrading polymers in polymer blends have also been developed, as have methods for improving the radiation resistance of polymers through radiation cross‐linking.
Dependence of the fracture and fatigue performance of polyolefins and related blends and composites on microstructural and molecular characteristics
Authors: Karger‐Kocsis József 
Published: March 2011

AbstractThis article surveys the influence of microstructural, morphological and molecular variables on the fracture and fatigue behavior of polyolefins, related blends and composites. The effects of major parameters of the structural hierarchy on the fracture mechanics (FM) response were considered and the related model descriptions reviewed. Emphasis was put on how important is to select the right FM approach for the toughness determination. It was pointed out that a clear distinction between crack initiation and growth is the essential prerequisite to differentiate between effects of the initial structure and its alteration due to mechanical loading. Although the microstructural dependence of the fracture and fatigue properties in reinforced, filled and impact modified polyolefins is quite well explored, this information is still missing for the neat polymers. This is due to a strong interlinking among molecular and morphological variables in neat polyolefins. Recommendations were given how to overcome this difficulty.
Electroluminescence in alternating copolymers with the acetylene unit
Authors: Kim Dong Young , Hong Jae Min , Kim Jai Kyeong , Cho Hyun Nam , Kim Chung Yup 
Published: March 2011

Abstract2,7‐diethynyl‐9,9î‐di‐n‐hexylfluorene and 2,7‐dibromo‐9,9î‐di‐n‐hexylfluorene were alternately bonded with each other by a Heck reaction to produce poly(9,9î‐di‐n‐hexyl‐2,7‐fluorenyleneethynylene). The alternating copolymer emitted blue color with the peak maximum at 475 nm on excitation either at 340, 365 or 400 nm. The principal emission maximum shifted to 425 nm on excitation at 340 nm when the polymer was blended with polyvinylcarbazole(PVK). Light‐emitting diodes (LEDs) fabricated with the alternating copolymer sandwiched between indium‐tin oxide glass and Al emitted a light with the peak maximum at 550 nm. The peak maximum shifted to 425 nm when the copolymer was blended with PVK with the blending ratios between 5 to 20% of the emissive copolymer.
Flash hydrolysis deinking of laser print using degradable toner resin
Authors: Debzi El‐Medhi , Marchessault Robert H. , Excoffier Gérard , Chanzy Henri 
Published: March 2011

AbstractThe choice of vinyl polymers as the plastic matrix for the pigment in xerographic toner did not anticipate the deinking thrust which has swept the paper industry. The hydrolytic stability of the carbon‐carbon bond in vinyl and diene copolymers has prevented the use of a plastic degradation strategy for toner removal. New toner resins based on alkali degradable plastics have been shown to allow up to 97% toner removal. Based on polyimide and polyesterimide toners (either magnetic or non‐magnetic) developed by Xerox, this study uses flash hydrolysis in the presence of 0.5% alkali to repulp. The process operates on 200‐300 second batches at 190−210°C. The best results were obtained using alkaline repulping and magnetic deinking coupled with washing. The alkali also inhibits the hydrolytic degradation of cellulose although it negatively impacts the brightness. Thus the use of a polymer resin containing a chemically sensitive function allows conversion of the toner to pigment fragments and water soluble oligomers. The former is best separated by magnetic deinking while the latter is removed by washing.
New (Co)polymers by atom transfer radical polymerization
Authors: Matyjaszewski Krzysztof 
Published: March 2011

AbstractThe fundamentals of atom transfer radical polymerization (ATRP) are presented. This includes the mechanistic considerations including structure of active and dormant species and structural features of the catalyst and reaction conditions as well as the nature of initiation and propagation steps. Extension of homogeneous polymerization to heterogeneous systems including emulsion polymerization is presented. Synthesis of (co)polymers with predefined molecular weights and low polydispersites as well as with controlled compositions, functionalities and architectures is reviewed.