bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of water on the physical aging of poly(ethylene terephtalate)
Authors: D'Aniello Concetta , Romano Gennaro , Russo Roberto , Vittoria Vittoria 
Published: March 2011

AbstractPhysical aging in polyethylene terephtalate (PET) has been studied on samples well characterized in terms of aging history and their content of water. This allows us to better understand the role played by water in the complex phenomenology of the physical aging in a hygroscopic material as PET. No appreciable changes in the thermal behavior in the sample aged in water at room temperature for one month were noted, while substantial changes were observed in samples aged in more severe conditions like 50°C under vacuum and 50°C in water for one month. The results are consistent with the formation of small regions in which segments of chains are closely packed.
Behavior of polymers at surfaces and interfaces as observed in simulated systems
Authors: Pakula Tadeusz 
Published: March 2011

AbstractCooperative motion algorithm (CMA) is used to simulate polymer chains in three types of dense systems reflecting special cases of polymer behavior at surfaces and interfaces: polymer brushes with variable grafting density in the range 0–1, both in a neutral solvent and in a polymer melt, layers of end‐functionalized polymers between parallel end‐adsorbing walls, and copolymers of various distributions of comonomer units (random, block and gradient copolymers) at interfaces with noncompatible polymers.
Polysoaps and biopolymers: The effect of secondary structure on the extension elasticity
Authors: Borisov Oleg V. , Halperin Avraham 
Published: March 2011

AbstractExtension of DNA and the protein titin reveals a plateau in the force vs. end‐to‐end distance diagram. A similar feature is predicted for the stretching elasticity of long polysoaps. These are linear hydrophilic chains that incorporate, at intervals, covalently bound amphiphilic monomers. In water, the amphiphilic monomers self‐assemble into intrachain micelles thus endowing the chain with a secondary structure. The similarity in the force laws is traceable to the equilibration of the secondary structure. For polysoaps forming a linear string of micelles, the plateau is associated with a coexistence of weakly perturbed micelles and fully dissociated amphiphiles. Similar scenarios can be invoked to explain the behaviour of DNA and titin. The resulting functional form seems to depend only weakly on the precise nature of the system.
Unusual adsorption behavior of polymers in layered structures
Authors: Sommer Jens‐Uwe , Blumen Alexander 
Published: March 2011

AbstractWe studied the conformations of polymer chains embedded in regular lamellar matrices such as microphase‐separated block copolymer melts or lipid/water systems. In such quasi‐one‐dimensional systems, the host plays the role of a nearly‐periodic external potential. A probe chain can get trapped with the localization length L at isolated defects, when its degree of polymerization N exceeds a cross‐over value NL. Interestingly, the radius of gyration, Rg, of the chain displays a minimum as a function of the defect density, ρ, the minimum being estimated by ρcL ≃ NL/N. Using Monte Carlo simulation, we underline the non‐monotonic behavior of Rg and calculate Green's function for various defect densities. On the same vein, the mean square displacement of the monomer units at large times shows a pronounced minimum as a function of the defect density, ρ.
Unique properties of high viscosity gums
Authors: Hoppe Craig A. , Goswami Animesh 
Published: March 2011

AbstractGuar gum, a galactomannan from the seed endosperm of the legume, Cyamopsis tetragonolobus, is an important food stabilizer used in a variety of food products ranging from sauces to ice cream. Two guars having viscosities 13‐250% higher than conventional guars were studied. Viscosity, effect of shear rate on viscosity, synergy with xanthan gum, granulation, galactomannan content, molecular weight, and scanning electron microscopy of the guar types were evaluated. At equal usage levels of guar, the high viscosity type showed a higher viscosity alone and in combination with xanthan gum under all conditions tested. The high viscosity products have electron microscopic morphology that is more elongated and molecular weights which are greater than normal guars. These factors are discussed in light of the viscosity differences which exist between these products.
Physical properties of xanthan, galactomannan and their mixtures in aqueous solutions
Authors: Rinaudo M. , Milas M. , Bresolin T. , Ganter J. 
Published: March 2011

AbstractSome new information on the conformation of xanthan in aqueous solutions is given. A single helical chain conformation characterizes xanthan in the native state. When heated over the critical temperature for conformational change ( helixŕ coil), the xanthan is denatured and renatured when it is cooled down in a localy double helical structure. A galactomannan was also characterized and its persistence length was obtained (Lp ≈︁ 90A°). Then mixtures of the galactomannan and xanthan were investigated to propose a mechanism for the specific gelation. From the results of microcalorimetry and circular dichroism, it is concluded that a complex is formed between one disordered xanthan chain and one galactomannan chain and that an ordered conformation is stabilized at temperatures lower than 25°C when the galactomannan has a M/G ratio of ≈︁ 3. This temperature corresponds to the sol‐gel transition. This is the first time that a structure of the crosslink points is demonstrated.
Rheology of carboxymethylcellulose made from bacterial cellulose
Authors: Cheng H. N. , Takai Mitsuo , Ekong Ekong A. 
Published: March 2011

AbstractPartly as a result of the high solution viscosity of bacterial cellulose, carboxymethylcellulose (CMC) derived from this material exhibits shear‐thinning and thixotropic properties. With suitable sample treatment, the CMC solution shows gel‐like rheology suggesting the presence of a three‐dimensional network. This behavior is consistent with heterogeneous substitution of the carboxymethyl functionality on the polymer chains. For comparison, bacterial cellulose is also degraded by either acid or ultrasound to reduce its molecular weight and converted to CMC. The flow behavior of the resulting CMC solutions is nearly Newtonian with slight shear thinning but no thixotropy, suggesting that the carboxymethylation reaction is almost random.
The measurement of mass and size distributions, conformation, and branching of important food polymers by mals following sample fractionation
Authors: Chen Michelle Hong , Wyatt Philip J. 
Published: March 2011

AbstractThree distinctive food polymers (ultra high molar mass amylopectin, guar gum, and hemi‐cellulose) were chosen as model samples to illustrate the use of multi angle light scattering (MALS) detection in conjunction with size exclusion chromatography (SEC) separations for the characterization of such macromolecules. By combining SEC and MALS, absolute molar mass, rms radius and their distributions can be measured readily without reference to any molar mass standards and without the need to make structural assumptions. In addition, the conformation and branching of those polymers can be derived also.
NMR of casein hydration and activity in solutions with ions
Authors: Mora‐Gutierrez Adela , Farrell Harold M. , Kumosinski Thomas F. 
Published: March 2011

AbstractOxygen‐17 NMR studies of caseins isolated from fresh milk of several species were carried out in concentrated electrolyte solutions as a function of both protein and electrolyte concentration. Molecular dynamics simulations of ion and water binding to caseins are compared with the experimental observations by 0–17 NMR of caseins in solutions with ions. Protein activities are also determined by utilizing Wyman's theory of linked functions with a detailed model of ion binding to casein.
Thermodynamic linkage of ion binding and hydration in myofibrillar protein solutions determined from multinuclear spin relaxation studies
Authors: Baianu Ion C. , Kumosinski Thomas F. , Mora‐Gutierrez Adela , Ozu Eiichi M. , Lioutas T. S. , Bechtel P. J. 
Published: March 2011

AbstractThe 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 concentration. Markedly nonlinear dependeces of the 17O and 23Na NMR transverse relaxation rates on salt concentration were analyzed with a thermodynamic linkage model of salt‐dependent solubility and hydration (ligand‐induced association model), according to Wyman's theory of linked functions. Nonlinear regression analysis of both 17O and 23Na NMR data suggested cooperative, reversible binding of hydrated ions to myofibrillar proteins. Both ions and water were found to exchange fast, on the NMR timescale, between the binding sites of the myofibrillar proteins and the aqueous solution. At sodium chloride concentrations higher than about 0.1 grams salt/gram water, ion activities have marked effects upon the NMR relaxation rates of both ions and water. A salt activity model allowed quantitative fitting of the NMR data at high salt concentrations. The effect of neglecting the ion activity in solutions of myofibrillar proteins was also estimated and compared with the ligand‐induced, cooperative association model for myofibrillar proteins. The comparison between the 17O and 23Na results strongly suggests that water is exchanged as the hydrated ion species between the myofibrillar protein binding sites and the bulk, aqueous solution.
Segmental orientation and chain relaxation of polymers by fourier transform infrared dichroism
Authors: Lachenal Gilbert , Ozaki Yukihiro 
Published: March 2011

AbstractFourier transform infrared dichroism has been used to investigate molecular orientation in polymeric materials. It is first applied to characterize network behavior in some elastomeric systems such as model networks of poly(dimethylsiloxane). The strain dependence of segmental orientation is analyzed through networks of known degree of cross‐linking and experimental results are compared with calculation predictions based on the rotational isomeric state formalism. Infrared dichroism spectroscopy has also been used to analyze orientational relaxation in binary blends of long and short polystyrene chains. The effect of short deuterated chains (Mw = 3000 to 72000) on the orientational relaxation of long entangled chains (Mw = 2 000 000) is examined in the bidisperse melts uniaxially deformed above the glass transition temperature. While the long chain relaxation is found to be dependent on the short‐chain concentration, the local orientational order of the latter is molecular weight dependent in agreement with the classical relaxation theories.
Structural changes in solvent‐induced crystallization of syndiotactic polystyrene viewed from the time‐resolved measurements of infrared/Raman spectra and X‐ray diffraction
Authors: Tashiro Kohji , Ueno Yoko , Yoshioka Akiko , Kaneko Fumitoshi , Kobayashi Masamichi 
Published: March 2011

AbstractSolvent‐induced crystallization behaviour has been investigated for the glass sample of syndiotactic polystyrene. The time‐resolved measurements of the Fourier‐transform infrared and Raman spectra and the X‐ray diffraction profile revealed the molecular and crystal structural change during the ordering process of polymer chains. On the basis of the idea of critical sequence length, the structural change in the conformational ordering process could be deduced. The crystallization rate was found to be affected remarkably by the kind of solvent: chloroform gave higher crystallization rate than benzene and toluene. This tendency was in contrast to that observed for the gelation process from the dilute solution: the gelation rate was chloroform «benzene. This high contrast between the crystallization and gelation rates could be interpreted qualitatively in terms of the difference in the solubility of polymer in these solvents.
Gel‐state NMR investigation of crosslinked poly(methy1 methacrylate) incorporating 13C labeled ethylene glycol dimethacrylate
Authors: Mathias Lon J. , Steadman Scott , Anderson Kelly , Davis Rick , Jarrett William , Redfearn Richard D. , Bunn Alan 
Published: March 2011

Abstract13C labeled ethylene glycol dimethacrylate (EGDMA) was used to form labeled crosslinked PMMA and model 13C labeled pendant double bond copolymers. Solution NMR was possible on solvent‐swollen samples containing less than 0.5% by weight EGDMA. Spectra confirm significant amounts of singly reacted EGDMA in fully polymerized networks. Peaks arising from the two most likely stereochemical triads (syndi‐ and heterotactic) were identified but no evidence of cyclic species was observed. Labeled EGDMA allowed observation of the crosslink site at concentrations as low as 0.02 wt‐% EGDMA.
Vibrational spectroscopic characterization of ethylene‐Co‐vinyl cinnamate copolymers before and after UV exposure
Authors: Coleman Michael M. , Hu Yin , Sobkowiak Maria , Painter Paul C. 
Published: March 2011

AbstractVibrational spectroscopic studies of a series of ethylene‐co‐vinyl cinnamate (EVCIN) copolymers, before and after exposure to UV radiation, are reported. The purpose of these studies is to determine whether or not significant reaction (photo‐crosslinking) of the cinnamate groups in EVCIN copolymers occurs upon UV exposure in the solid state as the concentration (fraction) of cinnamate groups is systematically reduced. By increasing the ethylene concentration in the EVCIN copolymers the cinnamate groups are “diluted” and progressively spaced apart in the copolymer. Somewhat surprisingly, we find that an EVCIN copolymer containing only 5 mole % vinyl cinnamate still undergoes a facile crosslinking in the solid state upon UV exposure.
The effect of branching on chain diffusion in ultralong N‐alkane crystals observed by 13C NMR
Authors: Driver Martin A. N. , Klein Philip G. 
Published: March 2011

Abstract13C NMR progressive saturation measurements are used to investigate solid state chain diffusion in semicrystalline alkanes. Monodisperse, ultralong n‐alkanes, of 198 and 191 carbon atoms in length, are characterized and prepared in such a way that they comprise crystals containing chains which are exclusively of once‐folded conformation. This preparation is confirmed with DSC and SAXS. The progressive saturation experiments show that the longitudinal relaxation of magnetisation is consistent with a solid state chain diffusion process. Reptation and one‐dimensional diffusion models are demonstrated to satisfactorily represent the data. The addition of branches to the alkane chains is shown to result in a decrease in the diffusion coefficient. The obtained diffusion coefficients range from 0.0918 nm2s−1 for the linear chain to 0.016 nm2s−1 for a chain with a branch 4 carbons in length. These diffusion coefficients are consistent with those previously obtained for polyethylenes.
Effect of molecular orientation on the biodegradability of aliphatic polyester
Authors: Yoo Eui Sang , Im Seung Soon 
Published: March 2011

AbstractThe effect of morphological microstructure on the biodegradability of aliphatic polyester, poly(ϵ ‐caprolactone) (PCL) was studied in terms of crystallite size, crystallinity and amorphous and crystalline orientation factors. Microstructural changes during hydrolysis/biodegradation of the drawn PCL films were investigated by the conventional small and wide angle X‐ray scattering methods. The lower was the draw ratio, the higher the hydrolytic degradability or biodegradability. With the increase of the hydrolysis time, the long period, at earlier stage, decreased; then slightly recovered and the crystallinity increased while the lamellar thickness remained unchanged. The amorphous orientation factors start to decrease at earlier stage and gradually go down to zero before the end of hydrolysis. In the case of crystalline orientation factor, although the values decrease with increasing hydrolysis time, they do not reach zero point. After the biodegradation for 60 days, crystallinity, crystal lateral size and lamellar thickness in all drawn PCL films decreased, and then it was confirmed that even crystalline regions were degraded for long term biodegradation test.
Synthesis and second harmonic generation studies of nlo‐functionalized polyimides
Authors: Shim Hong‐Ku , Yoon Chong‐Bok , Woo Han Young 
Published: March 2011

AbstractSeveral NLO‐functionalized polyimides were synthesized through novel synthetic pathways and their NLO properties were characterized. For preventing the disadvantage in poly(amic acid) precursor route, the Mitsunobu reaction and alternative synthetic route for NLO polyimides were chosen. The second‐order NLO coefficients (χ(2)) of the synthesized polyimides were between 48pm/V and 122pm/V. The thermal stability of nonlinearity characterized showed that all polyimide films retain their NLO activities at temperatures below 100°C.
Photoacid‐generating sulfonyloxymaleimide polymers and their application to photoimaging
Authors: Ahn Kwang‐Duk , Chung Chan‐Moon 
Published: March 2011

AbstractSynthesis and properties of photoacid generating polymers based on four sulfonyloxymaleimides (RsOMI), N‐(tosyloxy)maleimide (TsOMI), N‐(methanesulfonyloxy)maleimide (MsOMI), N‐(trifluoromethanesulfonyloxy)maleimide (TfOMI), and N‐(10‐camphorsulfonyloxy)maleimide (CsOMI) are described. The RsOMI polymers photochemically produce corresponding sulfonic acids (RsOH), TsOH, MsOH, TfOH and 10‐camphorsulfonic acid (CSA) which can catalyze deprotection of the acid‐labile t‐BOC groups in the same polymer chains via a chemical amplification process. The photoacid generating polymers with concurrent acid‐labile groups offer great potential for applications in functional transformation and photoimaging.
Complexation behaviour of polymers with pendant cyclodextrin side groups
Authors: Adams Jörg , Hollas Markus , Chung Myung‐Ae , Park Joon Woo , Hong Ji Hyun , Park Kwanghee Koh 
Published: March 2011

AbstractThe influence of the chain conformation on the formation of polymeric supramolecular complexes as well as the influence of the complexation on the conformation of the polymer chain has been studied. The complexation of pyrene into the cavity of β‐cyclodextrin (β‐CD) was investigated in aqueous solutions of β‐CD substituted poly(allylamine) (PAA) under variation of external parameters, i.e. temperature, pH, ionic strength and addition of urea. The observed changes of the complexation constant K for the formation of the 2:1 β‐CD/pyrene complex can be explained by a change of the chain flexibility which leads to a variation of the mean distance between neighbouring β‐CD‐moieties along the polymer chain. The intra‐chain association of the decyl group with β‐CD in PAA with co‐pendant decyl and β‐CD is disrupted by the addition of 1‐adamantanamine HCl resulting in a more extended structure of the polymer. The β‐CD moiety in PAA‐CD shows one order of magnitude greater affinity to 2‐(p‐toluidyl)naphthalene‐6‐sulfonate than the native β‐CD and the affinity increases further by the presence of decyl side groups.
Highly efficient template‐based preparation of shape‐persistent macrocyclics
Authors: Höger S. 
Published: March 2011

AbstractThe synthesis of shape‐persistent macrocycles via oxidative dimerization or trimerization of rigid bisacetylenes (via Glaser coupling) is described. To enhance the yield of the desired target structures, the precursors are temporarily covalently bound to a template resulting in an intramolecular coupling instead of an intermolecular coupling. As a result, product yields up to over 90 % are observed.
Temperature dependence of radiation effects on polymers
Authors: Tabata Yoneho , Oshima Akihiro 
Published: March 2011

AbstractTemperature dependence of radiation effect on various polymers including hydrocarbon and fluorocarbon polymers was investigated. Gas evolution and mechanical properties were measured in a wide range of temperatures. G‐values of chain scission and crosslinking were estimated. It has been made clear from those experimental results that radiation effect be profoundly affected by temperature. Particularly, significant changes of radiation effect in the melting region were found out.
Inorganic‐organic polymers as a route to biodegradable materials
Authors: Allcock Hairy R. 
Published: March 2011

AbstractThe polyphosphazene platform allows the design and synthesis of a broad range of different polymers, some of which have special properties as biodegradable materials. Different polyphosphazenes are produced mainly by means of macromolecular substitution reactions carried out on a reactive polymeric intermediate, poly(dichlorophosphazene), (NPCl2)n. Organic side groups such as amino acid esters, glucosyl, glyceryl, glycolate, lactate, or imidazolyl sensitize the polymers to hydrolysis to benign materials such as phosphate, ammonia, and the free side unit. Other polymers are of interest as the basis for hydrogels and microencapsulation materials.
Degradable plastic films for agricultural applications in Taiwan
Authors: Yang Shaw‐Rong , Wu Chin‐Hsiang 
Published: March 2011

AbstractTainan District Agricultural Improvement Station began in February 1991 to evaluate the feasibility of using degradable plastic films for horticultural crops production. Products from China, Korea, Israel, Germany, U.S.A. and Taiwan were used for comparison. Results are summarized as follows: Macro‐and micro‐environmental changes in different seasons affected the degradation time of the tested degradable plastic films. The silver/black bio/photo‐degradable PE films containing 20% starch from USI Far East Corporation degraded after 56, 83, 38, and 33 days when they were mulched in fall(October, 1991), winter(December, 1991), spring(April, 1992) and summer (August, 1992), respectively. The more starch incorporated, the faster the films degraded. No difference was observed in size, weight, yield, total soluble solids and heavy metal contents of the fruits of cantaloupe and watermelon grown on the beds mulched with various kinds of degradable PE films or traditional PE film. No difference was observed in yield as well as the heavy metal (Fe, Pb, Ni, Cu, Cd and Cr) contents in the edible part of the crops of cabbage mustard and head lettuce that were grown in the soil without or incorporated with debris of degradable PE films in 6 consecutive years. The same results were also obtained in another trial on cantaloupe and paddy rice for 4 consecutive years. Various amounts(0, 4, 8, 16, 32 and 64g) of used degradable PE films were seperately mixed with field soil. The mixed soil were used to grow paddy rice in clay pots. No difference was observed in plant height, length and weight of the spike, 1,000‐seed weight and the kernel per spike among the treatments at harvesting. Six pieces (each 10cm□10cm) of Bioplastics, Bioflex and Green choice biodegradable films were buried in a 8‐inch clay pot. Then head lettuce were planted in the pots. No difference was observed in head weight and qualities(vitamin C. total soluble solids and crude fiber)either among the treatments or the control. The weight losses for Bioflex, Bioplastics and Green choice were 58.4%,47.9% and 11.3%, respectively after 40 days.
Accelerated chemical degradation of polyacrylamide
Authors: Gao Jianping , Lin Tong , Wang Wei , Yu Jiugao , Yuan Shaojun , Wang Shaomin 
Published: March 2011

AbstractThe chemical degradation of polyacrylamide(PAM) at low temperature in aqueous medium was initiated by peroxides. The degradation degree of the polymer rose with the reaction time. The degradation degree of PAM depended not only on peroxide characteristic but also on the concentration of polyacrylamide and potassium persulfate, degradation temperature and original molecular weight of PAM. The results showed that the order of degradation degree of PAM in three peroxides is K2S2O8 > K2S2O8 — Na2S2O3 > H2O2. The degradation degree of PAM grew as reaction temperature, molecular weight of PAM, concentration of potassium persulfate and PAM increased.