bluuebunny/crossref_metadata_2025 huggingface dataset:
Physical processes in azobenzene polymers on irradiation with polarized light
Authors: Holme N. C. R. , Nikolova L. , Norris T. B. , Hvilsted S. , Pedersen M. , Berg R. H. , Rasmussen P. H. , Ramanujam P. S.
Published: March 2011

Azobenzenes can serve as model compounds for the study of transcis isomerization in more complex molecules. We have performed time‐resolved spectroscopy in solutions containing free azobenzene chromophores and diols with a view to obtaining the energy levels and lifetimes of the excited states. A transition route based on experimental results for the theoretically calculated energy level scheme is proposed. Physical observations of surface relief in thin films of azobenzene polymers when irradiated with polarized light are reported. These include two beam polarization holographic observations and single beam transmission measurements through a mask, followed by atomic force microscope and profiler investigations. It is concluded that none of the prevalent theories can explain all the observed facts.
Water vapor sorption and diffusion in glassy polymers
Authors: Paul D. R.
Published: March 2011

By establishing relationships between polymer structure and gas permeation behavior, significant advances have been made in designing materials for membrane separation of gas mixtures. However, the situation is not so well understood when water vapor is one of the components since water molecules may interact with the polymer (plasticization) or each other (clustering) in ways that complicate the structure‐property relationships. In addition, accurate measurement of water sorption, diffusion, and permeation is more complicated than for gases because of the unique hydrogen bonding capability of water, e.g., its tendency to strongly adsorb on high‐energy surfaces and high heat of vaporization. A progress report on a broad program to understand water sorption and diffusion in glassy polymers that may be of interest for membrane applications is outlined; specific strategies include studies of structurally related polymers and miscible blends of hydrophobic/hydrophilic polymer pairs.
The surface tension of polymer liquids
Authors: Dee Gregory T. , Sauer Bryan B.
Published: March 2011

A brief review of the surface tension of polymer liquids is presented. A strong emphasis is placed on recent measurements of surface tensions of homologous liquid series up to high‐molecular‐weight polymers, and the thermodynamic liquid properties of these same homologous series obtained from sources such as pressure‐volume‐temperature (PVT) data. The accuracy and limitations of the thermodynamic information which are used as input to many of the theories applied to the surface properties of polymer molecules are discussed. By scaling the surface tension data using a true measure of the cohesive energy density of the liquid state, we can clearly observe the entropic contribution to the surface tension caused by the conformational restriction of a large molecule at the liquid‐vapor interface. The scaling implies the existence of a corresponding states principle for both polymer liquids and for low‐molecular‐weight liquids. The ramifications of the existence of a corresponding states principle for the surface tension of polymer melts are discussed. One consequence of the corresponding states principle is that it allows us to use surface tension measurements to compute the cohesive energy density of polymer melts using PVT data.
X‐ray and molecular modeling studies on the structure‐function correlations of polysaccharides
Authors: Chandrasekaran Rengaswami
Published: March 2011

X‐Ray fiber diffraction analysis and computer molecular modeling have revealed the three‐dimensional structures of several important industrially useful polysaccharides such as algin, carrageenan, galactomannan, gellan, pectin, welan, xanthan and xanthan:guaran complex. Consistent with their chemical structures, their molecular morphologies, which include single and double helices, are quite distinct. The helix‐helix associations are promoted by cations and/or water molecules and the patterns are not always the same. The polymer‐dependent structural details can be correlated with, and used to understand the molecular basis of, the observed physical properties.
Targeting of an appropriate amylose type starch for specific product applications
Authors: Friedman Robert B. , Deboer Edward D. , Delgado Gregory A. , Furcsik Susan L. , Qvyjt Fernando , Tenbarge Frank L.
Published: March 2011

Some varieties of maize are known to produce starches with different chemical and physical properties. These characteristics have been recognized over the years to provide different functional properties. Amylose, in particular, has been used to provide unique functionality in numerous applications where gel strength and rigidity, as well as film forming capability, have been desired qualities. In recent years, researchers have begun to recognize that amylose is not a single chemical substance, but rather a diverse group of glucans differing in molecular size, and branching characteristics. The main shared attribute of all “amylose” polymers is their common ability to bind iodine. This binding ability is still the basis for most routine amylose determination assays. We have shown that there are uniquely different amylose polymers, and our laboratory has reported on some of the differences in physical properties. This paper reports how these unique physical properties can be applied effectively to practical applications.
Branching ratios of starch via proton nuclear magnetic resonance and their use in determining amylose/amylopectin content: Evidence for three types of amylopectin
Authors: Dunn Larson B. , Krueger William J.
Published: March 2011

The branching (α‐1,4)/(α‐1,6) ratio of starch from a number of sources can be quickly and accurately determined by proton nuclear magnetic resonance (NMR). This NMR ratio, with standard ratios for isolated amylose and amylopectin, can then be used to determine the amylose/amylopectin content of starches. In the course of determining the amylose/amylopectin content of various starches, it was discovered that two different types of amylopectin standards were required to obtain results comparable to those obtained from iodine‐binding amylose determinations. These two types were a waxy amylopectin, with a high level of branching, and a potato amylopectin, with a lower level of branching. A third type of amylopectin, with a still lower level of branching, is apparently present in high amylose cornstarches, leading to the conclusion that starches with higher amylose contents generally contain amylopectin with a lower level of branching. The three amylopectin types are referred to as amylopectin I, II and III, with the higher numeral coinciding with higher branching (α‐1,4)/(α‐1,6) ratio, or less branching.
Latex film formation and dissolution: A fluorescence study
Authors: Pekcan Önder , Ugur Saziye
Published: March 2011

A new technique based on steady state fluorescence (SSF) measurements is introduced for studying dissolution of polymer films. These films are formed from naphthalene (N) and pyrene (P) labeled poly(methyl methacrylate) (PMMA) latex particles, sterically stabilized by polyisobutylene (PIB). Annealing was performed above Tg at elevated temperatures for 30 min time intervals for film formation. Film formation from these latexes is monitored by the extent of energy transfer from N to P using SSF and by the transmitted photon intensity from these films using UV visible (UVV) methods. Desorption of P labeled PMMA chains was monitored in real‐time by the change of pyrene fluorescence intensity. Dissolution experiments were performed in various solvents with different solubility parameters, δ, at room temperature. Diffusion coefficients, D, in various solvents were measured and found to be around 10−10 cm2/s. Strong relationships between D and δ were observed. Diffusion activation energy was measured by performing dissolution experiments in toluene‐heptane mixtures at elevated temperatures and determined to be 24.4 kcal mol−1.
Synthesis and solution properties of rodlike polyelectrolytes
Authors: Wittemann Matthias , Kelch Steffen , Blaul Jürgen , Hickl Peter , Guilleaume Birgit , Brodowski Gisela , Horvath Andreas , Ballauff Matthias , Rehahn Matthias
Published: March 2011

The synthesis and the solution behavior of rigid, rodlike cationic polyelectrolytes having (i) poly(p‐phenylene) backbones and (ii) main chains composed of 4,4“‐bis(2,2′:6′,2”‐terpyridine)2′,5′‐dihexyl‐p‐terphenyl moieties and ruthenium(II) centers are presented. All these polymers are shown to have a homogeneous constitution and degrees of polymerization of up to Pn ≈ 70. Their solution properties were analyzed using viscosimetry, small‐angle X‐ray scattering (SAXS) and osmometry. Pronounced polyelectrolyte effects were found in salt‐free solutions using viscosimetry. Small‐angle X‐ray scattering demonstrated directly the strong correlation of the counterions and the macroions. The osmotic coefficients measured in salt‐free solution as function of polyelectrolyte concentration were found to be lower than predicted by the cell model.
Synthesis and properties of new aromatic polyimides — Polymeric materials for light‐emitting and liquid‐crystal displays
Authors: Ree Moonhor , Kim Sang Il , Pyo Seung Moon , Shin Tae Joo , Park Hong Ki , Jung Jin Chul
Published: March 2011

New aromatic diamines containing π‐conjugated heterocyclic rings were synthesized, which emit blue light in the photoluminescence. Using these new monomers, soluble poly(amic acid)s were prepared by the polycondensations with pyromellitamic dianhydride, and thermally converted to the polyimides in films which emit intense blue‐light. These polyimides are considered as potential candidate materials for fabricating optoelectronic devices which emit blue light. In addition, new poly(m‐phenylene 4,4′‐oxydiphthalimide)s containing various side chains were synthesized. For these polyimides, thermal properties were investigated with considering the chain flexibility of polymer backbone as well as the spacer and biphenyl mesogen end group in the side chains. In particular, these polyimides exhibited excellent performance in the rubbing process and the controlling of both the alignment and the pretilt of liquid‐crystal (LC) molecules in the LC cell. This might be attributed mainly to a strong interaction between the biphenyl mesogen end group in the side chains and the mesogen unit of LC molecules.
Fluorinated heteroaromatic polyethers for low dielectric constant / high temperature applications
Authors: Maier Gerhard , Haußmann Jörg , Dietlmeier Marcus , Banerjee Susanta
Published: March 2011

Several series of poly(arylene ether)s with trifluoromethyl substituents were prepared and characterized. These materials are potential candidates for the use as low dielectric constant insulators (intermetal dielectrics, IMD, and interlayer dielectrics, ILD) on microchips. Thermal stability up to 450 °C and a dielectric constant below 3 preferably below 2.5) is required for this application. The thermal stability of the poly(arylene ether)s was increased from 320°C to more than 500 °C by optimization of the structure of the repeating unit. The dielectric constant of one of the most promising structures was determined to be 2.8. In addition, plasma polymerized thin films from hexafluorobenzene, tetrafluorobenzene, perfluorotoluene and perfluorodecaline were prepared and characterized with respect to solubility, dielectric constant, adhesion, and thermal stability.
Photocrosslinking of thin polymer films – materials for sensors and actuators
Authors: Kuckling Dirk , Adler Hans‐Jürgen , Arndt Karl‐Friedrich , Wolff Thomas , Hoffmann Jan , Fischer Wolf‐Joachim
Published: March 2011

Polymers with temperature dependent degrees of swelling, especially polymers which exhibit lower critical solution temperature (LCST) behaviour in aqueous solutions, are of interest for applications in microsystems. For these applications it is necessary to form and pattern thin films in the μm‐range. This has been achieved through photocrosslinking of linear prepolymers. Copolymers based on N‐isopropylacrylamide (NIPAAm) were modified with a stilbazolium salt chromophore to yield photocrosslinkable temperature sensitive polymers. The chromophore reacts via a [2+2]‐cycloaddition under irradiation, this can be used to crosslink the polymer. The photocrosslinking properties were studied by UV irradiation of thin films and measuring the changes in UV absorption spectra. Through irradiation of thin films through a mask it was possible to obtain patterned networks in the μm‐range (20 μm space width and > 50 μm line width). The polymers exhibited LCST behaviour, which was measured using DSC. The resulting patterned networks had temperature dependent swelling properties in aqueous media.
Soluble polyimides containing alicyclic structures
Authors: Choi Kil‐Yeong , Yi Mi Hie
Published: March 2011

A series of novel aromatic diamines containing kinked cycloalkane structures between two phenyl rings were synthesized by HCl‐catalyzed condensation reaction of excess aniline and corresponding cycloalkanone derivatives. The structures of the diamines were indentified by 1H NMR, 13C NMR, FT‐IR spectroscopy and elemental analysis. The polyimides were synthesized from the obtained diamines with various aromatic dianhydrides by one‐step polymerization in m‐cresol. The polymerization was conducted for 6∼8 h with refluxing, which was enough to obtain the polymers with high molecular weight. The inherent viscosities of the resulting polyimides were in the range of 0.37∼1.66 dl/g. All polymers were readily soluble in common organic solvents such as chloroform, tetrachloroethane, dimethylacetamide, etc. and the glass transition temperatures were observed at 290 to 372°C. UV‐visible spectra were obtained to measure the transparency of polymer films. Most of the polymers showed high transmission above 90 % in the wavelength of 450 ∼ 600 nm.
Preparation and photophysics of polyimide/silica organic/inorganic hybrid composites
Authors: Ha Chang‐Sik , Cho Won‐Jei
Published: March 2011

In this work, polyimide/silica hybrid composites were prepared by the sol‐gel reaction of tetraethoxysilane(TEOS) and the thermal imidization of poly(amic acid) from 3,3′,4,4′‐biphenyltetracarboxylic dianhydride(BPDA) and 4,4′‐oxydianiline(ODA), and their photophysical properties were investigated using a fluorescence spectroscopy. It was found that the intrinsic fluorescence of poly(4,4′‐oxydiphenylene‐3,3′4,4′‐biphenyltetracarboximide)(BPDA‐ODA) such as emission intensity and emission wavelength depends strongly on the changes in the molecular conformations during the sol‐gel reaction and the thermal imidization. In conclusion, we found that the fluorescence spectroscopy can provide an insight into how the intermolecular or intramolecular interaction of polyimide in the hybrid composite system is affected by the silica contents, depending on the sample states.
Photooxidative degradation of polyether‐based polymers
Authors: Gardette Jean‐Luc , Mailhot Bénédicte , Posada Fabrice , Rivaton Agnès , Wilhelm Catherine
Published: March 2011

The mechanisms of photooxidation of several polyether based polymers were compared in order to give general rules of orientation of the oxidative reactions. These polymers were a poly(ether‐ester) and two poly(ether‐urethane)s. The behavior of the polyether component as homopolymer was also studied. This study was extended to copolymers of fluorinated olefins and allyl or vinyl ethers, and the non fluorinated homologues. The elucidation of the photooxidation mechanisms was based on the identification of the photoproducts by analysis of both the solid polymeric matrix and the gaz phase formed on irradiation. It was shown that the photochemical sensitivity of the polyether component was responsible for the rapid oxidation of the copolymers. However, in the case of the fluorinated compounds, different behaviors were observed. It was shown that the presence of the fluorine atoms strongly influenced the orientation of the reaction and modified the oxidation kinetics. The reactivity of the methylene groups in α‐position of the oxygen atom of the ether groups were not found to be equivalent regarding oxidation and the secondary was more oxidizable than the tertiary one.
Chain transfer to polymer in emulsion polymerization
Authors: Ahmad Nasir M. , Heatley Frank , Britton David , Lovell Peter A.
Published: March 2011

Chain transfer to polymer in emulsion polymerizations of acrylate monomers and vinyl acetate has been studied using 13C NMR spectroscopy to elucidate the chemistry by which chain transfer occurs and to quantify the mol% branches resulting from the reaction. In emulsion polymerizations of n‐butyl acrylate, ethyl acrylate and methyl acrylate, chain transfer to polymer proceeds via abstraction of hydrogen atoms from backbone tertiary C‐H bonds and typically gives rise to 2‐4 mol% branches in the polymers obtained at complete conversion, the level of branching increasing with reaction temperature. For these acrylates, there is no evidence for a significant difference between the extent of chain transfer to polymer. In emulsion polymerizations of vinyl acetate, chain transfer to polymer proceeds mainly via H‐abstraction from methyl side‐groups, though there is a small contribution from abstraction at backbone tertiary C‐H bonds. The levels of branching that result are substantially lower than in acrylate emulsion polymerizations, typically being in the range 0.6‐0.8 mol% in the polymers obtained at complete conversion. The level of branching increases with temperature and as the degree of monomer starving (and hence instantaneous conversion) increases. Emulsion copolymerization of vinyl acetate with a small amount (5‐20 wt%) of n‐butyl acrylate gives rise to a significant increase in the level of branching (to values around 1.3‐1.6 mol%), which results predominantly from H‐abstraction of backbone tertiary C‐H bonds in n‐butyl acrylate repeat units by propagating radicals with vinyl acetate end units.
Biodegradability of scott‐gelead photodegradable polyethylene and polyethylene wax by microorganisms
Authors: Kawai F. , Shibata M. , Yokoyama S. , Maeda S. , Tada K. , Hayashi S.
Published: March 2011

This paper describes the biodegradability of photodegraded polyethylene (PE) and commercial PEwax and molecular size limits of PE for biodegradation. Photodegradation was accelerated by Scott‐Gelead System. Photofragmented PE and commercial PEwax were used as a sole carbon and energy source for soil microorganisms, respectively. Biodegradation by microbial consortia was confirmed by the increase of viable cell numbers and GPC analysis of PE added. Significant weigh decrease of PE samples added was also observed. Both photofragmented PE and PEwax were suggested to be biodegradable up to Mw 5,000 or more: Mw lower than 500 was degraded by more than 40%. Mw 500–2,000 was by more than 10%. Mw higher than 2,000 was only by a few %. Logarithms of biodegradation ratio (%) and Mw were correlated to show linearity and to suggest the biodegradability limit close to Mw 10,000.
Antioxidant control of polymer biodegradation
Authors: Scott Gerald
Published: March 2011

Hydrocarbon‐based synthetic polymers are versatile and cost‐effective materials in packaging and agriculture. Unstabilised polyolefins are known to biodegrade through peroxidation initiated by both abiotic and biotic and mechanisms. Both abiotic and biotic peroxidation can be accelerated and controlled by specially designed antioxidants and this has resulted in their commercial use in packaging, mulching films and baler twines. They are currently being evaluated in controlled release fertilisers.
Characterization of polymer soil burial degradation by thermal analysis and mechanical spectroscopy
Authors: Contat‐Rodrigo Laura , Ribes‐Greus Amparo
Published: March 2011

Polypropylene (PP) and High density polyethylene (HDPE) / Polypropylene (PP) blend with different biodegradable additives (Granular starch/iron oxide mixture, Bioefect 72000 and Mater‐Bi AF05H) were selected for degradation experiments. All the samples, processed by injection as seedboxes, have been subjected to an outdoor soil burial test and removed at different periods of time between 0 and 21 months. Their chemical structure and morphology have been analysed. Studies of dynamic‐mechanical relaxation spectra of the samples before and after each exposure time have been carried out. The three characteristic relaxation zones α, β and γ, in order of decreasing temperature, have been obtained. It has been observed that due to the degradation process both, the HDPE/PP blend and the PP matrix, become more brittle than the undegraded ones regardless of the additive used. Degradation seems to start from the molecular chains of the amorphous phase or interfacial region. However the analysis of the mechanical behaviour manifested that the crystalline zone is also been affected by the exposure time.
Viscosity, sorption of water and biodegradation of starch/copolyamide blends
Authors: Suvorova Anna I. , Tujkova Irina S. , Trufanova Elena I.
Published: March 2011

Compatibility of the components, shear viscosity, sorption properties in liquid and vapor water were determined for the mixture of ternary copolyamides (types 6/66/610 and 6/12/66) and amilose starch. This system was shown to be suitable for creation of biodegradable materials.
Dextran as antioxidant's activity carrier
Authors: Domnina Nina , Aref'ev Denis , Komarova Elena , Bilibin Alexander
Published: March 2011

Two series of conjugates of dextran and antioxidants from the class of sterically hindered phenols were prepared. The conjugates were characterized by the substitution degree of glycoside units, solubility in different solvents, intrinsic viscosity. The investigation of radical scavenging activity (RSA) of conjugates was carried out in their reactions with two free radicals — 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) and sodium salt of 2,2‐diphenyl‐1‐picrylhydrazyl sulfonic acid (DPPH‐salt). The usage of water soluble DPPH‐salt enabled to estimate the RSA of the conjugates in water. It was shown that the rate constants of interaction of the DPPH‐salt and the conjugates were 10–30 times higher than this value for low‐molecular analogue of phenoxan. High RSA of the conjugates in water can be explained by large solvation shell formed due to high content of hydroxy groups in dextran.
Biodegradable composite films based on waste gelatin
Authors: Kenawy El‐Refaie , Cinelli Patrizia , Corti Andrea , Miertus Stanislav , Chiellini Emo
Published: March 2011

Gelatin, a naturally occurring polymer, is currently used in various applications comprising manufacturing of pharmaceutical products, x‐ray and photographic films development and food processing. However, gelatin scraps generated in the different manufacturing processes may constitute a concern for the environment. Basically speaking, waste disposal deriving from plastics based on synthetic as well as semisynthetic polymeric materials, is becoming an increasingly difficult problem for their unfavorable volume‐to‐weight ratio and extremely wide variability of type, shape and composition of post consume plastic items that hinder the way to a general unique option for a simple and economically feasible management.

As a partial solution to the global issue of plastic waste, in recent years much interest has been devoted to the formulation of environmentally degradable plastic items.

Biodegradable mulching films were formulated from blends and composites based on waste gelatin and other natural waste such as sugarcane bagasse or synthetic materials such as PVA. Also, crosslinked films were produced using external or inherent crosslinker. The films were produced either by casting method or spraying on soil surface. The composites were submitted to biodegradation trials. The results showed that the films were biodegradable and the crosslinking could delay and predeterminate their biodegradation rate and extent.
Production of PHAs from agricultural waste material
Authors: Braunegg Gerhart , Genser Klaus , Bona Rodolfo , Haage Gudrun , Schellauf Florian , Winkler Elisabeth
Published: March 2011

Polyhydroxyalkanoates (PHAs) are biodegradable substitutes to fossil fuel plastics that can be produced from renewable raw materials such as saccharides, alcohols and low‐molecular‐weight fatty acids. They are completely degradable to carbon dioxide and water through natural microbiological mineralization. Consequently, neither their production nor their use or degradation have a negative ecological impact. By keeping closed the cycle of production and re‐use, PHAs can enable at least part of the polymer‐producing industry to switch from ecologically harmful end‐of‐the‐pipe production methods towards sounder technologies. Up to now such polyesters have been produced biotechnologically from refined raw materials (e.g. glucose and sodium propionate), but they can as well be produced much cheaper from agricultural waste materials (e.g. molasses, maltose, glycerol phase from biodiesel production, whey), as long as these materials have a known composition and are available in appropriate quantities. Yield factors and specific rates for growth and PHA accumulation are shown for 3 strains of Alcaligenes latus for different agricultural waste carbon sources.
Characterisation and morphology of biodegradable chitosan / synthetic polymer blends
Authors: Mucha Maria , Piekielna Joanna , Wieczorek Anna
Published: March 2011

Chitosan has been used to form miscible, biodegradable blends with hydrophilic synthetic polymers as PVA and PEO. Characterisation of the blends by DSC, IR and microscopy analysis was made giving much attention to possible interactions of molecular polar group in the polymer chains. PVA/chitosan are found to be amorphous in the whole range of composition having one glass transition temperature. Molecular interactions in the pair of polymers are connected with amide group of chitosan and hydroxyl groups of PVA. PEO/chitosan blends stay amorphous up to 0.2 weight fraction of PEO. For a higher amount of PEO that polymer crystallises forming a spherulite crystalline structure. We correlate the overall kinetics of crystallisation and melting behaviour of solid, semicrystalline blends PEO/chitosan in the form of thin films for a set of PEO species of different blend composition with a morphological structure of the blends. Negative values of the Flory‐Huggins interaction parameter due to specific interactions by hydrogen bonding through ether group of PEO and hydroxyl group of chitosan were evaluated. Amide groups do not participate in the molecular interaction between PEO and chitosan molecules. Avrami equation was applied to describe kinetics of crystallisation of pure PEO and PEO/chitosan blends of various compositions.
Evaluation of the transport properties of Poly(3‐hydroxybutyrate) and its 3‐hydroxyvalerate copolymers for packaging applications
Authors: Miguel Oscar , Iruin Juan José
Published: March 2011

Poly(3‐hydroxybutyrate) (PHB) and ist 3‐hydroxyvalerate containing copolymers form a family of fully biodegradable polyesters with many potential applications. In this work, the results obtained in our laboratory concerning carbon dioxide, water and organic solvent transport through PHB and three low 3‐hydroxyvalerate copolymers are reviewed. Comparison established between the former results and some data taken from the literature, have revealed that PHB and the above mentioned copolymers show transport properties similar to other common thermoplastics such as PVC and PET, particularly in the case of carbon dioxide and water. Consequently, PHB and copolymers can be catalogued as good barrier materials against these penetrants. On the other hand, these biopolymers show a low barrier character against organic compound permeation. All these features conform a good balance of physicochemical properties for these polyhydroxyalkanoates, which may take them suitable for several applications, including its use in biodegradable packaging materials.
Investigation of the adsorption of surfactants on the poly(styrene) latex particles by small‐angle X‐ray scattering
Authors: Seelenmeyer S. , Ballauff M.
Published: March 2011

We present the study of the adsorption of a non‐ionic surfactant onto latex particles by small‐angle X‐ray scattering (SAXS). The analysis of the process of adsorption by SAXS is discussed in detail. It is demonstrated that SAXS allows to monitor the gradual built‐up of the surface layer with increasing amount of added surfactant. SAXS also allows to obtain the radial volume fraction of the hydrophilic tails of the surfactant. Possible limitations of this analysis are discussed.
Investigation of swelling and diffusion in polymers by NMR imaging
Authors: Knörgen Manfred , Heuert Uwe , Schneider Horst , Kuckling Dirk , Richter Sven , Arndt Karl‐Friedrich
Published: March 2011

The kinetics of diffusion in polymers ranges from simple Fickian diffusion to higher order diffusion, such as Case II diffusion1‐2). The conventional method for determining the characteristics of solvents into polymer matrices is by measuring the mass uptake of the polymer as the solvent penetrates the matrix. However, since such measurements perform observations at a macroscopic level, little information has been obtained relating to the nature of the solvent in the polymer matrix and the mechanisms of the processes that control the diffusion. Nuclear magnetic resonance (NMR) imaging (‘MRI’) has been used to observe the penetration of solvents into solid systems in realtime. The method provides a one‐ or more‐dimensional image of the density and the mobility of the solvent in a material or of the network changes of the material itself due to the softening influence of the solvent. The first (imaging of the solvent) can be used for a quantitative measurement of the diffusion whereas the observation of the network gives information about the changing of the network (mobility, de‐crystallization…) during the swelling process. For example the diffusion of organic solvents in some polymeric materials (natural rubber, water gels (PNIPAAm), and nematic diblock‐copolymers) are investigated.
Neutral and charged polymer brushes at solid surfaces
Authors: Biesalski Markus , Johannsmann Diethelm , Rühe Jürge N.
Published: March 2011

Neutral and charged polymer brushes covalently attached to planar solid surfaces were generated by using self‐assembled monolayers of an azo initiator and radical chain polymerization in situ. The brushes were characterized by FTIR‐spectroscopy, optical waveguide‐spectroscopy and Ellipsometry. Especially the film thicknesses of surface bound polyelectrolyte (PEL) monolayers were measured by optical waveguide spectroscopy (OWS) as a function of the humidity of the environment. The PEL brushes show strong increases in thickness as well as strong decrease of the refractive index of the surface attached layer due to water incorporation caused by the exposure to the humid environment. Additionally the behavior of neutral as well as charged brushes in contact with solvent was investigated by using multiple‐angular‐scans of ellipsometry in a total internal reflectance setup. The scaling behavior of the brush height as a function of the graft density of the attached polymer molecules was investigated for the neutral brush as well as for the PEL brush system.
NMR and vibrational spectroscopic study of the order and mobility in polycarbonate and polycarbonate — poly(ethylene oxide) blends
Authors: Dybal Jiří , Brus Jiří , Schmidt Pavel
Published: March 2011

Time dependence of the gel formation in toluene solutions of polycarbonate (PC) was investigated by two‐dimensional Fourier‐transform infrared (2D FT‐IR) correlation spectroscopy. The 2D correlation approach reveals that there are at least three bands in the C=O stretching region. The intensity increase of the band at 1771 cm−1 occurs later compared with the onset of the intensity changes of the bands at 1778 and 1765 cm−1 corresponding to amorphous and crystalline‐like domains, respectively. The band at 1771 cm−1 is assigned to the chain conformations occurring in the partial‐order regions accompanying crystalline‐like domains. Splitting of the signals of aromatic carbons in the solid‐state 13C CP/MAS NMR spectra of semicrystalline PC and PC‐PEO blends indicates restricted mobility resulting from the fixed ordering due to partial crystallinity of PC itself and from blending of PC with PEO. The decreasing mobility of PC with the increasing content of highly mobile PEO in the blends was proved by the dipolar dephasing rates obtained in the 1H‐1H CRAMPS (combined rotation and multi‐pulse spectroscopy) NMR experiments.
Comparative analysis of structure and temperature behaviour of two copolyamides ‐ regular KEVLAR and statistical ARMOS
Authors: Levchenko Andrei A. , Antipov Evgueni M. , Plate' Nikolaj A. , Stamm Manfred
Published: March 2011

In the present investigation X‐ray diffraction techniques, DSC and dynamic mechanical relaxation (DMR) methods have been employed to compare the structure and thermal behaviour of Kevlar (“DuPont”, USA) and Armos (Russia) fibers. Our recent studies have indicated that the non‐crystalline phase of copolyesters always contains LC smectic structure in addition to some part of the nematic LC mesophase. It turned out that the copolyamides also possess this interesting feature. Moreover, on heating of a semicrystalline copolyester always the second order phase transition from the crystalline state to condis mesophase has been observed, whereas in the case of copolyamides such a transition has the «virtual» character. As was established by other authors both polymers under study reveal the moisture content. The changes in wide angle X‐ray scattering of copolyamides under heat treatment were interpreted in terms of desorption of bound water and structural rearrangement in the plane perpendicular to the chain axis involving of the hydrogen bonding between neighboring macromolecules.
Mechanical behavior of polymer microlayers
Authors: Kerns Julia , Hsieh Alex , Hiltner Anne , Baer Eric
Published: March 2011

The mechanical behavior of polycarbonate (PC) coextruded as microlayers with a brittle polymer, either poly(styrene‐co‐acrylonitrile) (SAN) or poly(methyl methacrylate) (PMMA), was examined. Adhesion between layers was measured with the T‐peel method. The much higher interfacial toughness of PC/PMMA microlayers compared to PC/SAN was attributed to partial miscibility. Comparison of the microdeformation behavior of 32‐layer PC/SAN and PC/PMMA microlayers revealed that very good adhesion between PC and PMMA constrained yielding of the PC. This was seen in the tensile stress‐strain curves as a broader stress drop at the yield point and a lower fracture strain. Decreasing the layer thickness by increasing the number of layers enhanced the ductility of both PC/SAN and PC/PMMA microlayers. A PC/PMMA microlayer with 4096 layers and a composition of 80% PC achieved the ballistic performance of polycarbonate.
Study of the structural changes in urea‐formaldehyde condensates during synthesis
Authors: Siimer Kadri , Pehk Tõnis , Christjanson Peep
Published: March 2011

Chemical constitution of urea‐formaldehyde resins in synthesis and in storage was determined using 13C NMR spectroscopy. Methylolation, methylene and dimethylene ether bond‐forming reactions were discussed. The changes in the content of structural elements with secondary and tertiary amino groups of urea at various stages were followed. The resin synthesis technology was used, which considers the requirement in low free formaldehyde content, connected with somewhat smaller storage stability of resins.
The effect of prepolymer composition of amino‐hardened liquid crystalline epoxy resins on physical properties of cured thermoset
Authors: Carfagna Cosimo , Amendola Eugenio , Giamberini Marta , D'Amore Alberto , Priola Aldo , Malucelli Giulio
Published: March 2011

Diglycidyl terminated 4,4'‐oxydiphenyl cured with an aromatic diamine exhibits liquid crystalline properties, even if the amount of hardener is used in defect with respect to the stoichiometric amount. Physical properties of the resin, hardened with different quantities of amine are presented and discussed. In particular the high values of fracture toughness of this class of thermoset has been explained on the basis of the biphasic nature of the crosslinked resin. The differences in mechanical properties are analyzed taking into account the different crosslink densities.
Characterization of poly(methylphenylsilane) prepared by plasma polymerization
Authors: Cech Vladimir , Horvath Pavel , Jancar Josef , Schauer Frantisek , Nespurek Stanislav
Published: March 2011

Poly(methylphenylsilane) plasma polymer layers of the thickness ranging from 10−2 to 100 μm intended to engineer interphases in glass fibre reinforced polymer composites and light‐emitting displays were prepared by r.f. glow discharge technique. The films synthesized from a mixture of dichloro(methyl)phenylsilane vapor and gaseous hydrogen were deposited on flat glass and silicon substrates and glass fibres as well. Deposition conditions were optimized to obtain required thickness, mechanical and electrical properties of interphases. Prepared layers were amorphous, relatively rigid and transparent at room temperature with excellent adhesion to substrates. The surface of plasma polymer is rough with isolated (silicon substrate) and conglomerate (glass substrate) grains. FTIR and XPS spectra revealed a great amount of atomic oxygen bound to silicon atoms and enabled to determine the atomic concentrations. The structure model is proposed assuming a carbosiloxane network with not‐crosslinked methyl and phenyl groups.
Processing, properties and morphology of polypropylene‐epdm blends
Authors: López‐Manchado Miguel A. , Biagiotti Jerico , Arroyo Miguel , Kenny José M.
Published: March 2011

Blends of polypropylene and an elastomer (ethylene propylene diene terpolymer, EPDM) are systematically investigated to determine the effect of the rubber on the polymer properties. Five compositions on the complete range of blend compositions are analyzed. The study reported here is a first of a series which main objective is to analyze in a systematic way the influence of the different factors that determine the effectiveness of EPDM as an impact modifier for PP. In this first part of the study, the processing behavior of the PP‐EPDM blends are analyzed and the mechanical properties of the processed blends (tensile, flexural and impact resistance) are examined. Halpin‐Tsai and porosity models successfully represent the mechanical behavior of the blends. The model results allow a physical interpretation of the role of the dispersed phase in terms of the aspect ratio and of the stress concentration factors associated to the dispersed particles. Moreover, the mechanical properties are correlated with the morphology of the blends studied by scanning electron microscopy, where two phases are clearly observed in the complete range of compositions. The results show that PP‐EPDM blends with at low rubber content present a good processability, without significant deterioration with respect to neat PP and with a considerable improvement of the room and low temperature performance.
Qualitative and quantitative skeletal muscle ultrasound in late‐onset acid maltase deficiency
Authors: Zaidman Craig M. , Malkus Elizabeth C. , Siener Catherine , Florence Julaine , Pestronk Alan , Al‐Lozi Muhammad
Published: March 2011

Introduction: Acid maltase deficiency (AMD, or Pompe disease) is an inherited myopathic disorder of glycogen degradation. Diagnosis is often delayed. Muscle ultrasound could improve diagnosis. Methods: We compared skeletal muscle ultrasound images from adults with AMD (n = 10) to other myopathies (n = 81) and, in AMD, compared qualitative (Heckmatt) and quantitative (backscatter) ultrasound measurements with strength and function. Results: Qualitative ultrasound was abnormal in at least one muscle in all AMD subjects. Ultrasound patterns specific for AMD were: normal triceps brachii despite abnormalities in elbow flexors (89% vs. 17%, P < 0.0001); focal abnormalities affecting deep more than superficial biceps brachii (40% vs. 4%, P = 0.002); and more severe involvement of vastus intermedius than rectus femoris (40 vs. 11%, P = 0.03). In AMD, both qualitative (Heckmatt) and quantitative (backscatter) ultrasound measures increased with decreasing strength and function. Conclusions: Muscle ultrasound identifies the presence and specific patterns of AMD pathology, measures disease severity, and can help in the diagnosis of AMD. Muscle Nerve 44: 418–423, 2011
Genomic evidence of pre‐invasive clonal expansion, dispersal and progression in bronchial dysplasia
Authors: McCaughan Frank , Pipinikas Christodoulos P , Janes Sam M , George P Jeremy , Rabbitts Pamela H , Dear Paul H
Published: March 2011

The term ‘field cancerization’ is used to describe an epithelial surface that has a propensity to develop cancerous lesions, and in the case of the aerodigestive tract this is often as a result of chronic exposure to carcinogens in cigarette smoke 1, 2. The clinical endpoint is the development of multiple tumours, either simultaneously or sequentially in the same epithelial surface. The mechanisms underlying this process remain unclear; one possible explanation is that the epithelium is colonized by a clonal population of cells that are at increased risk of progression to cancer. We now address this possibility in a short case series, using individual genomic events as molecular biomarkers of clonality. In squamous lung cancer the most common genomic aberration is 3q amplification. We use a digital PCR technique to assess the clonal relationships between multiple biopsies in a longitudinal bronchoscopic study, using amplicon boundaries as markers of clonality. We demonstrate that clonality can readily be defined by these analyses and confirm that field cancerization occurs at a pre‐invasive stage and that pre‐invasive lesions and subsequent cancers are clonally related. We show that while the amplicon boundaries can be shared between different biopsies, the degree of 3q amplification and the internal structure of the 3q amplicon varies from lesion to lesion. Finally, in this small cohort, the degree of 3q amplification corresponds to clinical progression. Copyright © 2011 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Increased production of sonic hedgehog by ballooned hepatocytes
Authors: Rangwala Fatima , Guy Cynthia D , Lu Jiuyi , Suzuki Ayako , Burchette James L , Abdelmalek Manal F , Chen Wei , Diehl Anna Mae
Published: March 2011

Ballooned hepatocytes distinguish non‐alcoholic steatohepatitis (NASH) from steatosis. Such cells contain dilated endoplasmic reticulum and ubiquitin aggregates, characteristics of endoplasmic reticulum stress. Hepatocyte ballooning increases the risk for fibrosis in NASH, suggesting that ballooned hepatocytes release pro‐fibrogenic factors. Hedgehog ligands function as pro‐fibrogenic factors in liver diseases, but mechanisms for hedgehog ligand production remain poorly understood. We evaluated the hypothesis that endoplasmic reticulum stress induces hepatocyte production of hedgehog ligands that provide paracrine pro‐fibrogenic signals to neighbouring cells. In livers from NASH patients, keratin 8/18 and ubiquitin staining demonstrated enlarged, keratin 8/18‐negative/ubiquitin‐positive hepatocytes (ballooned hepatocytes) that were positive for Sonic hedgehog. In order to model endoplasmic reticulum stress in vitro, primary mouse hepatocytes were treated with tunicamycin. Compared to vehicle, tunicamycin significantly increased Sonic hedgehog and Indian hedgehog expression. Furthermore, conditioned medium from tunicamycin‐treated hepatocytes increased Gli‐luciferase reporter activity 14‐fold more than conditioned medium from vehicle‐treated hepatocytes. Cyclopamine (hedgehog signalling inhibitor) abrogated the effect of conditioned medium from tunicamycin‐treated hepatocytes, verifying that soluble hepatocyte‐derived factors activate hedgehog signalling. Ballooned hepatocytes in NASH patients did not express the hedgehog target gene, Gli2, α‐smooth muscle actin or vimentin, but were surrounded by Gli2‐positive stromal cells expressing these myofibroblast markers. Trichrome staining demonstrated the accumulation of ballooned hepatocytes in areas of matrix deposition, and numbers of Sonic hedgehog‐positive hepatocytes correlated with the degree of ballooning and fibrosis stage. Hepatocytes undergoing endoplasmic reticiulum stress generate hedgehog ligands which act as paracrine pro‐fibrogenic factors for hedgehog‐responsive stromal cells. These results help to explain why fibrosis stage correlates with hepatocyte ballooning in NASH. Copyright © 2011 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Usefulness of the hematopoietic cell transplantation‐specific comorbidity index (HCT‐CI) in predicting outcomes for adolescents and young adults with hematologic malignancies undergoing allogeneic stem cell transplant
Authors: Wood William , Deal Allison , Whitley Julia , Sharf Andrew , Serody Jonathan , Gabriel Donald , Shea Thomas
Published: March 2011

Background

The HCT‐CI helps to predict non‐relapse mortality (NRM) and overall survival (OS) in allogeneic hematopoietic cell transplantation (HCT) recipients. The usefulness of this index in a younger, adolescent and young adult (AYA) population is unclear.

Procedure

We tested the validity of the HCT‐CI as a predictor of mortality in a retrospective cohort of 56 AYA recipients between the ages of 16 and 39, using chart abstraction followed by univariable and multivariate analysis.

Results

Only pulmonary dysfunction (46%), hepatic dysfunction (27%), infection (20%), and psychiatric disturbance (11%) had frequencies greater than 5% in this population. HCT‐CI scores of 0–2 were present in 54%, and scores of >3 in 46%. The cumulative incidence of NRM at 2 years was 32%, with an OS of 46%; the NRM and OS for patients with an HCT‐CI of 0–2 were 24% and 62%, whereas the NRM and OS for patients with an HCT‐CI >3 were 38% and 28%. Patients with pulmonary dysfunction prior to transplant had a 29% OS at 2 years, compared to a 61% OS among patients without (P = 0.001). There was no statistically significant difference for patients and a worse NRM (P = 0.08). In multivariable analysis, both an HCT‐CI score of >3 and any pulmonary dysfunction remained associated with OS (P = 0.01, P = 0.03), but neither with NRM.

Conclusions

The HCT‐CI appears useful in predicting OS in AYAs, though higher scores may reflect prior treatment, with pulmonary dysfunction particularly prevalent. Prospective studies to further validate and explain these findings are warranted. Pediatr Blood Cancer 2011; 57: 499–505. © 2011 Wiley‐Liss, Inc.
Properties of microinjection molding of polymer multiwalled carbon nanotube conducting composites
Authors: Abbasi Samaneh , Derdouri Abdessalem , Carreau Pierre J.
Published: March 2011

The effects of processing conditions on the microstructure and properties of polypropylene/multiwalled carbon nanotube (PP/MWCNT) and polycarbonate/multiwalled carbon nanotube (PC/MWCNT) composites were studied. Samples of various MWCNT loadings were prepared by diluting commercial masterbatches. Different processing conditions were then used to systematically change the degree of nanotube alignment, from random to highly aligned. The crystallinity of the PP/MWCNT nanocomposites was found to go through a maximum as a function of nanotube content while the overall rate of crystallization increased. For the highly sheared microinjected PP/MWCNT samples well oriented crystals were formed. Electrical conductivity of the nanocomposites was improved by the presence of the crystalline structure; however, the high degree of nanotube alignment in the microparts resulted in a significant increase in the electrical percolation threshold. The PP nanocomposites exhibited mechanical properties significantly enhanced by nanotube loading; this effect was small in the case of the PC nanocomposites. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers