bluuebunny/crossref_metadata_2025 huggingface dataset:
Photochemical synthesis of colloidal metals
Authors: Loginov Anatol V. , Boitsova Tatiana B. , Gorbunova Valentina V.
Published: March 2011

New photochemical method for preparation of colloidal metal particles (Cu, Ag, Au) as a films on the quartz surface and colloidal dispersion in different matrixes has been devised. Possibilities to control the properties of photogenerated colloidal metal particles are discussed.
Synthesis and polymerization of the 16‐(methacryloyloxy)‐hexadecanoic acid and phospholipid in monolayers
Authors: Baryshnikova Elena A. , Sergeeva Tatjana I. , Novikova Olga S. , Zubov Vitaly P. , Zaitsev Sergei Yu.
Published: March 2011

Two surface‐active monomers with methacrylic group at the end of hydrophobic tail: 16‐(methacryloyloxy)hexadecanoic acid (16‐MAHDA) and bis[16‐(methacryloyloxy)hexadecanoil]‐phosphatidylcholine (16‐MAHDPC) have been synthesized and investigated. The monomers form stable monolayers at the liquid/gas interfaces with liquid‐expanded and liquid‐condensed states at low and high surface pressures, respectively. These monomers have been polymerized in the monolayers by low intensity UV‐irradiation (254 nm). Dependences of polymerization rate vs. surface pressure for both monomers have maxima (3.4. 10−4 s−1 for 16‐MAHDA and 5.5.10−4 s−1 for 16‐MAHDPC) at about 12 mN/m. The higher rate of 16‐MAHDPC polymerization as compared to 16‐MAHDA is due to the two polymerizable group in the molecule of lipid as compared to the only one in the molecule of acid. The collapse pressures increase after monomer polymerization that evidences an increase of the monolayer stability in the case of polymer as compared to monomer.
Research of properties of polyfunctional polymeric films
Authors: Ostrovidova G. U. , Makeev A. V. , Zamyslov E. V. , Richter A. , Terukov E. I.
Published: March 2011

At present the problem of creating materials for medical application, which possess surface thromboresistant and antiseptic properties is of the great importance. The method of creating hydrogel films, containing anticoagulants, biologically active and antiseptic substances on the surface of well‐known polymers of medical purity allows to give their surface special functions and properties and to retain the good mechanical properties [1,2]. In the majority of cases, the methods which are used for the creation of such films have a limitations which impede their wide application as they do not allow to obtain surface layers, possessing different medico‐biological and physic‐chemical properties.

The aim of our research was the electroformation of biocompatible, polyfunctional poly(vinyl alcohol) (PVA) films with immobilizied anticoagulant, enzyme and antibiotic on the surface of a composite material on the base of polysiloxane of medical purity [3,4].
Driving dendrimers with light: Dendrimers with azobenzene central linkers
Authors: McGrath Dominic V. , Junge Denise M.
Published: March 2011

Several new classes of azobenzene‐containing dendrimers have been prepared and characterized. Three central linker azobenzenes, p‐(pî‐hydroxyphenylazo)phenol (A), aniline p‐(p'‐chlorocarbonylphenylazo)benzoyl chloride (B), and p‐(pî‐aminophenylazo) (C) were reacted with the appropriate dendritic fragment ([Gn]Br for A and C; [Gn]OH for B) to yield dendrimers 1–3 of varying generational size. The photoresponsive characterization of these dendrimers illustrates the insensitivity of the photoresponsive behavior of the azobenzene with respect to the nature of the attached dendritic fragment.
Photosensitive chiral polyisocyanates
Authors: Mayer Sabine , Maxein Georg , Zentel Rudolf
Published: March 2011

The dynamic polyisocyanate helix amplifies changes in the conformation of its side groups. Thereby it acts like a fast responding switch for optical properties. Here we show how the photoisomerization of chiral azo side groups can be used to induce large changes of chirooptical properties. These changes can be detected by CD measurements or by ORD measurements far from the absorption region. Large changes of the optical rotation can be induced reversibly in a multicycle process.
All‐optical manipulation of azo‐dye molecules
Authors: Fiorini Céline , Prudhomme Nicolas , Etilé Anne‐Catherine , Lefin Philippe , Raimond Paul , Nunzi Jean‐Michel
Published: March 2011

A challenging issue in the field of the design of devices for photonic applications is to achieve complete manipulation of the molecular order. Azo‐dye aromatic polymers have been shown to offer interesting prospects for material engineering using light matter interactions. Dual‐frequency irradiation using appropriate combinations of circular beams polarizations are demonstrated to enable full control of the molecular polar rotation. More recent results on photoinduced surface‐relief gratings have also opened the way of molecular translation control using optical fields. Understanding of the relevant parameters of molecular translation processes is a key issue for optimization of such an optomechanical effect: a simple model accounting qualitatively for the essential features of photoinduced surface‐relief gratings will be presented.
Thermally stable photoaligned p‐cyanoazobenzene moieties in polymer thin films
Authors: Ichimura Kunihiro , Kidowaki Masatoshi , Fujiwara Takenori
Published: March 2011

Poly(4‐cyano‐4î‐methacryloyloxyazobenzene) displayed a slow E‐to‐Z photoisomerization rate and a low Z‐isomer content at a photostationary state in a film. Linearly polarized 436 nm light irradiation resulted in the gradual generation of dichroism due to the reorientation of the azobenzene chromophores. The photodichroism was enhanced markedly by heating the film and not deteriorated even at 240 °C. Discussion was made on the thermally enhanced photodichroism of the polymer with p‐cyanoazobenzene side chains in respect to its semi‐crystallinity.
Dynamics of photoinduced orientational order of azo‐dyes in polymer films
Authors: El Osman Ahmad , Dumont Michel
Published: March 2011

Dynamical and spectral behavior of photoassisted electrical poling and photoinduced anisotropy are studied in films of DR1‐doped PMMA, DR1‐PMMA copolymer and new DR1‐Polyimide copolymer. The orientational mobility of DR1 is characterized both in ordering processes (angularly selective trans‐cis photoisomerization) and in disordering relaxation processes. Mobility is increased by the photoisomerization and decreases slowly with time, after the end of optical pumping. The transient dichroism recorded simultaneously on six probe wavelengths shows a spectral inhomogeneity of the absorption band of DR1 and of the photoinduced anisotropy (particularly in polyimide films).
Polarized light‐induced anisotropy depending on polymer matrices studied by polarized ftir spectroscopy
Authors: Tawa Keiko , Kamada Kenji , Sakaguchi Toru , Ohta Koji
Published: March 2011

Polarized‐light induced anisotropy of Disperse Orange 3 (DO3) depending on the polymer matrices was investigated by polarized FTIR spectroscopy. The dynamic behavior of the azo dyes doped in a series of methacrylate polymers was analyzed in terms of the orientation factors. Two factors, the free volume and the local polarity of matrices, are found to govern the dynamic behavior of DO3. It was found that induced anisotropy for trans and cis isomers varies depending on Tg of polymer matrix. Further, the thermal isomerization rate depend on the isomerization mode which is governed by the matrix polarity. The branched‐alkyl chains are considered to block the interaction between ester groups and DO3 and introduce the DO3 molecules into the less polar environment.
Modelling of molecular interactions and inclusion phenomena in substituted β‐cyclodextrin: From simple probes to proteins
Authors: Miertus S. , Chiellini E. , Chiellini F. , Kona J. , Tomasi J. , Solaro R.
Published: March 2011

The ability of β‐cyclodextrin (βCD) to form stable complexes with α‐interferon was investigated. By using simple molecular mechanics approach interaction energy profiles of simple probes passing the center of βCD ring cavity along the main molecular symmetry axis were evaluated first. A computational study of host‐guest inclusion complexes between βCD and L‐α‐aminoacids and some selected pentapeptides was also carried out and aimed at understanding the nature of the driving forces and mechanism, leading to their formation. Relative complexation energies for the complexes and the solvation Gibbs free energies for single L‐α‐aminoacids were calculated. Both the aminoacid residue inside the βCD cavity and neighbouring residues were found to contribute to the stabilization of βCD complexes with the side‐chain of aminoacids present on the surface of α‐interferon. The most appropriate number of host βCD molecules for the encapsulation in the first shell of one α‐interferon molecule resulted to be 25.
Crystal structure of poly(ethylene‐oxide) supramolecular assemblies
Authors: Damman Pascal , Paternostre Laurent , Moulin Jean‐François , Dosière Marcel
Published: March 2011

The formation of poly(ethylene oxide) (PEO) supramolecular complexes is discussed in terms of intermolecular interactions and molecular packing. On the basis of the different known crystal structures, several mechanisms are proposed. First, the PEO complexes can be formed by an Intercalation or Inclusion process, guest molecules diffusing into the PEO unit cell. On the other hand, molecular complexes based on hydrogen bonding cannot be obtained by such a way, their formation requires the complete removal of the initial PEO structure either by melting or dissolution. Finally the relations between the crystal lamellar morphology, the host‐guest interactions and the PEO chain mobility are discussed.
Water sorption and protonic conductivity in a filled/unfilled thermostable ionomer for proton exchange membrane fuel cell
Authors: Baradie B. , Poinsignon C. , Sanchez J. Y. , Piffard Y.
Published: March 2011

A filled ionomeric membrane is achieved by dispersing several % in weight of the phosphatoantimonic acid H3Sb3P2O14, xH2O (H3), in a Sulfonated PolySulfone (SPS) solution1). Water up‐take of pristine and filled SPS of different cation exchange capacity (cec) was measured at 25°C and 80°C: It is higher for filled than unfilled membrane. Comparatively, protonic conductivity measurements performed on the same samples show a higher conductivity for the filled samples than for the unfilled. The conductivity value is higher than that expected from the overall calculated concentration in charge carriers: A conductivity value of 0.06 S.cm−1 is gained at 80°C under 100% Relative Humidity (HR) for a 1.4 meq.g−1 cec SPS filled with 8% in H3.
Development and characterization of PPO composite membranes for gas separation
Authors: Bove Lucia , Clarizia Gabriele , Golemme Giovanni , Drioli Enrico
Published: March 2011

Poly(phenylene oxide) (PPO) composite membranes have been prepared on a polysulfone (PSf) ultrafiltration support, which was previously coated with highly permeable polydimethylsiloxane (PDMS). The PDMS gutter layer was used in order to: Plug the pores of the support; minimise the thickness of the separating PPO deposit; and reduce the tortuosity of the path of the gas molecules to the pores of the support.

Composite membranes with high fluxes and good selectivities for gas separations have been obtained with an amorphous and cross‐linkable phenylene oxide co‐polymer.
Compound formation and solvent (dis)ordering in syndiotactic polystyrene/benzylmethacrylate systems
Authors: Goossens Han , Rastogi Sanjay , Lemstra Piet
Published: March 2011

In‐situ small‐ and wide‐angle X‐ray scattering (SAXS and WAXS) experiments combined with Raman spectroscopy have been performed to study the phase behaviour of syndiotactic polystyrene (sPS) and benzylmethacrylate (BzMA). In the quenched gels, sPS adopts a helical conformation which is stabilised by the solvent molecules, in fact compound formation occurs. From the combined experimental data it was concluded that two different structural modifications exist within the solvent‐included helical δ‐phase, respectively the δ' phase in which the solvent molecules are intercalated and ordered between the phenyl rings of sPS and a δ” phase where this solvent ordering is lost.
A Study on the ordering of intercalated solvents in poly‐benzyl‐l‐glutamate; In‐situ raman and X‐ray scattering investigations
Authors: Corstjens Tosca , Rastogi Sanjay , Lemstra Piet
Published: March 2011

A polymer/solvent system can form a gel due to specific interactions between the polymer and the solvent. For poly‐benzyl‐L‐glutamate/solvent systems, gelation can be based on carbonyl or phenyl ring interactions, depending on the solvent. The present paper describes X‐ray scattering and Raman investigations on cast films of poly‐benzyl‐L‐glutamate (PBLG) and benzylmethacrylate (BzMA). The studies indicate that in the cast samples separate zones of PBLG and BzMA are present. Upon heating, the system homogenises and the PBLG molecules pack in a pseudo hexagonal lattice. At approximately 150°C a new reflection at 11.4 Å in the WAXS pattern arises. This reflection is attributed to structural ordering of the solvent, due to intercalation of the solvent molecules within the helices of PBLG. The observed changes in the WAXS pattern upon heating are supported by Raman experiments.
Polymer‐solvent interactions in thermoreversible gels of isotactic poly(methyl methacrylate) as studied by measurement of 1h NMR relaxation of the solvent
Authors: Spêváček Jiři , Brus Jiři
Published: March 2011

Dynamic structure and polymer‐solvent interactions in solutions and gels of isotactic (i) poly(methyl methacrylate) (PMMA) in butyl acetate (BAC) were characterized by measurements of nonselective and selective 1H NMR spin‐lattice relaxation times of the solvent. In thermoreversible gels, the existence of i‐PMMA‐BAC complex, where the life‐time of the bound solvent is − 100 ms or shorter, was confirmed. Although the correlation time of the solvent bound in i‐PMMA‐BAC complex is 5‐10 times longer than for the free solvent, there is still a relative motional freedom for complexed solvent molecules. The same behaviour observed recently for thermoreversible gels of syndiotactic PMMA indicates the same character of polymer‐solvent complexes in gels of both stereoregular forms of PMMA.
Scattering properties of agarose gels
Authors: Rochas Cyrille , Hecht Anne‐Marie , Geissler Erik
Published: March 2011

Static light scattering and small angle neutron scattering measurements are reported for agarose hydrogels prepared under various conditions of concentration and temperature. For the wide range of transfer wave vector explored, these measurements show that the gels do not display fractal behaviour. Their structure is better described by a stretched exponential form, in which the value of the exponent is n = 0.2.

As found by other authors, a maximum in the scattering intensity is observed in the light scattering spectra. The position of the maximum, qmax, depends on the concentration and on the thermal history of the sample. The inverse length 1/qmax is in good agreement with published measurements of the pore size D in this system.

Preliminary measurements by small angle scattering indicate that the sol‐gel transition is not of spinodal type.
Structural and thermodynamic features of the polyhydroxybutyrate physical gels
Authors: Cesàro Attilio , Fabri Deborah , Sussich Fabiana , Paradossi Gaio
Published: March 2011

The structural and thermal properties of polyhydroxybutyrate (PHB) gels in dimethylformamide (DMF) are presented and discussed. The dilute and semi‐dilute mixed PHB/DMF system undergoes a phase separation on cooling at a temperature Tgel, producing a gel in which the crystalline fraction is of the order of 50‐60% and the diffraction pattern is that of disperse nano‐crystals, with the same unit cell of the pure crystalline PHB. Upon heating, two melting peaks are normally observed at Tm1 and Tm2 (always higher than Tgel). Shapes of the peaks, temperatures and enthalpies of melting depend slightly on scanning rate on heating but on the procedure of gel preparation. Reproducibility and reversibility have always been found with repeated thermal cycles. A thermodynamic phase diagram is therefore constructed and discussed, although the morphology of the system may be subject to the experimental conditions under which the gel is prepared.
The mutual effect of absorption of biologically active substances and microstructure of native cellulose matrix on the properties of resulting compounds
Authors: Kotelnikova N. E. , Panarin E. F. , Serimaa R. , Paakkari T. , Wegener G. , Windeisen E.
Published: March 2011

In order to obtain multicomponent polymer systems exhibiting biological activity microcrystalline cellulose was used as a matrix for biologically active compounds, such as dimethylbenzylalkylammonium chloride, poly‐N‐vinylpyrrolidone, copolymer of N‐vinylpyrrolidone and crotonic acid, and complex of dimethylbenzylalkylammonium chloride with copolymer of N‐vinylpyrrolidone and crotonic acid. Adsorption interaction of microcrystalline cellulose with these was studied under various conditions. Adsorption isotherms of compounds of polymer nature are of similar character and are described by the Freundlich equation. The isotherms of dimethylbenzylalkylammonium chloride are described by the Langmuir equation. Characteristics of the resulting compounds were obtained using XPS and IR Fourier spectroscopy, WAXS, and SEM. Chemical interaction between microcrystalline cellulose and dimethylbenzylalkylammonium chloride takes place. This interaction leads to a new labile morphological cellulose structure accessible to penetration, which is confirmed at a morphological level by SEM.
Correlations between mark‐houwink‐sakurada parameters for linear and star‐like polymers
Authors: Ioan Catalina , Ioan Silvia , Simionescu Bogdan C.
Published: March 2011

The influence of the excluded volume on the intrinsic viscosity of linear and star‐like polymers in dilute solution is reflected on the Mark‐Houwink‐Sakurada (MHS) parameters k and “a”. A correlation between these parameters and the number of arms for star‐like polybutadiene in different solvents is proposed. Also, for various linear polymers, a relation describing the decrease of parameter k with increasing “a”, the proportionality coefficient being the unperturbed parameter kθ, is established.
Short‐and long‐range interaction parameters for polydimethylsiloxanes with different terminal groups
Authors: Grigorescu Gabriela , Ioan Silvia , Simionescu Bogdan C.
Published: March 2011

The paper discusses the behaviour of polydimethylsiloxanes with different terminal groups as induced by polymer molecular weight and solvent mixture composition in dilute solution.
Structural study of hyaluronic acid oligomers and their complexes with copper in water by NMR and IR and molecular dynamics calculations
Authors: Marchettini Nadia , Barbucci Rolando , Bonechi Claudia , Donati Alessandro , Magnani Agnese , Niccolucci Valentina , Tiezzi Enzo
Published: March 2011

The hexasaccharide (trimer) and tetrasaccharide (dimer) oligomers of hyaluronic acid were investigated by 1H and 13C high resolution Nuclear Magnetic Resonance. The dynamic behavior of the molecules and their complexation with copper(II) were analysed by 1H NMR relaxation studies. A specific site for the complexation of the tetrasaccharide with Cu2+ was demonstrated by analysis of the paramagnetic effect of the metal on non‐selective proton relaxation rates. A model for the complex involving two molecules of the tetrasaccharide is proposed.
Studies of the γ ← α transition in syndiotactic polystyrene
Authors: Naddeo Carlo , Guadagno Liberata , Acierno Domenico , Vittoria Vittoria
Published: March 2011

In this work we compare calorimetric and X‐ray diffraction experiments realized on annealed sPS in helical γ forms resulting by different treatements: From clathrate δ form and from interaction of amorphous sample with acetone. The experimental results show that the γ form obtained by acetone converts into the more ordered final α” form modification; while the γ form, obtained by thermal treatments of δ form, transforms into the poorly ordered final α' form.
The rate of solvent diffusion in amorphous polymers
Authors: Vesely D.
Published: March 2011

The present work is a contribution to our understanding of one aspect of the diffusion process, the diffusion rate. It attempts to show that all diffusion theories must satisfy the following:

1) the rate of diffusion at the initial stages of the process must be finite

2) the rate of diffusion must have square root time dependence at longer diffusion distances.

Deviations of experimental data from these rules usually result from experimental inaccuracies. Whereas Fickian approach satisfies the second but not the first rule and Case II sorption the opposite, their combination satisfies neither. Two alternative explanations, which provide a very good correlation with the experimental data, are suggested: Limited diffusion rate and sorption kinetics.
Functionalization of a polyaspartamide with glycidyl methacrylate: A useful method to prepare hydrogels through gamma irradiation
Authors: Giammona Gaetano , Pitarresi Giovanna , Cavallaro Gennara , Spadaro Giuseppe
Published: March 2011

α,β‐Poly(N‐2‐hydroxyethyl)‐DL‐aspartamide (PHEA) was derivatized with glycidyl methacrylate (GMA). Aqueous solutions of the obtained copolymer PHEA‐GMA (PHG) were irradiated by gamma rays with a dose rate of 0.5 KGy/h and at zero°C in the presence or in the absence of N, N'‐methylenebisacrylamide (BIS). New hydrogel systems were obtained and characterized by FT‐IR analyses and swelling measurements in aqueous medium at different pH values.
Transport properties of an hydrophobic‐hydrophilic copolymer
Authors: Gorrasi G. , Vittoria V.
Published: March 2011

Sorption and diffusion properties of a copolymer composed by hydrophilic and hydrophobic blocks have been analyzed. The material, obtained as a film by moulding the powders under pressure, was submitted to thermal treatments, and the structural organization of the samples was investigated using water vapour and dichloromethane as permeants. The polar solvent (water) has been useful to investigate the hydrophilic amorphous regions, while the apolar one (methylene chloride) gave information about the organization of the hydrophobic amorphous phases.
Interfacial phenomena, adhesion and macroscopic properties in polymer composites
Authors: Pegoraro M. , Di Landro L. , Severini F.
Published: March 2011

The microfragmentation or the single‐fiber composite method for the evaluation of fiber‐matrix adhesion in polymer composites is presented emphasizing advantages and drawbacks. The improvements of the methods introduced in recent years (laser Raman spectroscopy, optical examination of interfacial region, estimation of the stress state at the interface, consideration of viscoelastic properties of the matrix) to obtain more detailed information on the interface failure mechanisms are described. A modified method with a coaxial geometry, which extends the applicability of the test to brittle matrices, is shown. A number of experimental results obtained both with thermoplastic and thermoset matrices containing carbon and glass fibers is reported. Chemical modifications of carbon fiber surfaces were carried out, which effectively changed the adhesion to the high‐performance bismaleimide matrix. In particular, the treatment with ammonia is shown to be promising for improvement of adhesion in graphite/bismaleimide composites.
Collective dynamics of terminally anchored polymer chains
Authors: Anastasiadis Spiros H.
Published: March 2011

Thermal fluctuations of the segment density profile of a polymer brush were probed by dynamic light scattering in the evanescent wave configuration; the time correlation functions of concentration fluctuations with wavevector q were measured. It is found that there is a preferred wavelength of the order of the brush thickness, L0, of these fluctuations with a concurrent slowing down of their thermal decay rate. A theory is presented for the small‐amplitude deformation of the free surface of a parabolic brush in solution; a maximum in the respective structure factor of the concentration fluctuations is predicted at q* L0 ∼ O(1), in agreement with the experiment.
Wetting reversal transition in phase‐separated polymer mixtures
Authors: Genzer Jan , Heier Jakob , Kramer Edward J.
Published: March 2011

We investigate a wetting reversal transition in thin films of two‐phase mixtures of poly(ethylene‐propylene) (PEP) and its deuterated analogue (dPEP) on a substrate covered by a self‐assembled monolayer (SAM) whose surface energy, γSAM, is tuned by varying the SAM composition. As γSAM increases from 21 to 24 mJ/m2, a transition from a three‐layer (air/dPEP/PEP/dPEP/SAM) to a two‐layer (air/dPEP/PEP/SAM) structure occurs at increasing Tc ‐ T, where Tc and T are the critical and transition temperatures, respectively. As the system structure changes from three‐layer to two‐layer, the thicknesses of the dPEP‐rich wetting layers at the air/mixture and mixture/SAM interfaces are found to smoothly increase and decrease, respectively, while the thickness of the PEP‐rich layer (ca. one half of the total film thickness) does not change. The dependence of the transition temperature on γSAM is predicted by a simple model using the experimental data on the surface energies of PEP/dPEP and estimates of the interfacial energy between PEP and dPEP.
Interfacial tension between polymer‐containing liquids — Predictability and influences of additives
Authors: Wolf B. A.
Published: March 2011

The first part of the contribution deals with the interfacial tension, σ, of phase‐separated polymer solutions in single or mixed solvents and of binary polymer blends as a function of the relative distance to the critical temperature of the system, special attention being paid to the possibilities of theoretical prediction. Two methods are discussed in more detail. One is based on a realistic description of the Gibbs energy of mixing as a function of composition, the second correlates σ with the length of the measured tie line. The second part is devoted to another aspect, namely the effects of additives on the interfacial tension between the coexisting phases of demixed polymer solutions and between highly incompatible polymers. In the former case, it is demonstrated that an addition of a thermodynamically good solvent is normally associated with a reduction in σ; however, adding a high‐molecular‐weight compound which is incompatible with the dissolved polymer leads to an increase in σ. The interfacial tension between incompatible homopolymers is efficiently reduced by block copolymers consisting of monomeric units which are either identical with or different from those of the homopolymers; in contrast to theoretical expectation, the molecular architecture of the additives seems to be of minor importance only. Random copolymers which are insoluble in the homopolymers can also efficiently reduce the interfacial tension.
Silane treatment in polypropylene composites: Adsorption and coupling
Authors: Pukánszky Béla , Demjén Zoltán
Published: March 2011

The study of the effect of eight silane coupling agents on mechanical properties of PP/CaCO3 composites showed that the application of certain compounds leads to the reactive coupling of the components. The adsorption of the silanes on the surface of the filler was studied by a dissolution method, while the structure of the adsorbed layer was determined by FTIR spectroscopy and GPC measurements. Model reactions and an FTIR study were carried out to reveal possible coupling reactions of PP and the active silanes. The results showed that amino‐functional silane coupling agents adsorb on the surface of the filler, polycondensation taking place and a polysiloxane layer of high molecular weight forms as a result. The model reactions indicated that during processing, PP oxidizes even in the presence of stabilizers and oxygen‐containing functional groups form on the polymer chains. These easily react with the amino functionality of the silane coupling agents strongly bonding the polymer to the treated filler.
Expolysaccharides from lactic acid bacteria: Technological bottlenecks and practical solutions
Authors: De Vuyst Luc , Degeest Bart
Published: March 2011

Microbial exopolysaccharides are added to or occur in a wide variety of food products, where they serve as viscosifying or gelling agents. Exopolysaccharides with different composition, size and structure are synthesized by several strains of lactic acid bacteria. Structural analyses combined with rheological studies reveal that there is considerable variation among the different exopolysaccharides; some of them exhibit remarkable thickening and shear‐thinning properties and display high intrinsic viscosities. Hence, several slime‐producing lactic acid bacterium strains and their biopolymers have interesting functional and technological properties, which may be exploited towards different products. However, the production of exopolysaccharides from lactic acid bacteria is low and often unstable, and their downstream processing is difficult. Strain improvement, enhanced productivities and advanced modification and production processes (both enzyme and fermentation technology) may contribute to their economic soundness.
Process characteristics of exopolysaccharide production by streptococcus thermophilus
Authors: Degeest Bart , van De Ven Sven , De Vuyst Luc
Published: March 2011

The kinetics of growth and exopolysaccharide (EPS) production from Streptococcus thermophilus were studied and optimized for different physical (temperature, pH, aeration rate) and chemical (carbon/nitrogen ratio) factors in milk medium. From these experiments, it was clear that EPS production displays primary metabolite kinetics. Using the optimized conditions, EPS production could also be established in de Man Rogosa Sharpe medium. Growth‐associated EPS production, bacterial growth and other fermentation data were translated into a mathematical model.
The “food polymer science” approach to flour functionality and ingredient technology in biscuit baking
Authors: Levine Harry , Slade Louise
Published: March 2011

An overview is made on the “food polymer science” approach developed by the authors. The quality and performance of flours for the production of cookies and crackers have been shown to depend upon the major functional polymeric components of flour: gluten protein, damaged starch, and pentosans. Of these, damaged starch and soluble pentosans in soft‐wheat flours are detrimental to the commercial production of low‐moisture cookies and crackers. The detrimental effects of soluble pentosans in flours can be eliminated through the use of pentosanase enzyme in cookie and cracker doughs. Three commercialized applications of this industrial enzyme technology have been patented by Nabisco. The “food polymer science” approach to baking technology has also been used to study finished‐product attributes such as texture, in the context of the thermomechanical properties (e.g. modulus) of glassy solid and rubbery liquid matrices. Results of various studies have clearly demonstrated that products in a glassy solid physical state (at T < Tg) are hard and crisp in texture, but upon increasing plasticization by water (such that Tg is depressed below the observation T), are transformed to a rubbery or viscous liquid state, wherein textural hardness (and mechanical modulus) and crispness are dramatically reduced.
Pectin‐based biodegradable water insoluble films
Authors: Pavlath Attila E. , Voisin Alexandre , Robertson George H.
Published: March 2011

Aqueous solutions of pectin, an acidic polysaccharide which occurs in various natural products, was cast into clear films. While the films were flexible enough to be used as wrapping materials, their strength and resistance to water were inferior to presently used commercial films. However, precast films immersed into aqueous solutions of multivalent cations became insoluble in water and depending on the ions became stronger in tension. Tensile strength increased to levels comparable to, or in the case of calcium, copper(II) and zinc, greater than those of some commercial wrapping materials
Effect of genetic polymorphism on the gelation of β‐lactoglobulin
Authors: Foegeding E. Allen , Lowe Ruth , Boland Mike J. , Hill Jeremy P.
Published: March 2011

The rheological properties of heat‐induced gels made from β‐lactoglobulin variants A, B and C were compared. The relative G' values (elastic moduli) for gels formed in 90 mM NaCl solutions were A = B > C. Conversely, in 30 mM CaCl2 the relative G' values were C > A = B. The differences in rheological properties were due to A and B variants forming less rigid gels in CaCl2 (∼ 7 kPa) than NaCl (∼ 20 kPa), and variant C forming gels of similar rigidity in both salt solutions. It was concluded that genetic variation in β‐lactoglobulin changes the effect of salts on gelation but does not cause a universal increase or decrease in gel forming ability.
Compositional heterogeneity in pectic polysaccharides: NMR studies and statistical analysis
Authors: Neiss Thomas G. , Cheng H. N. , Daas Piet J. H. , Schols Henk A.
Published: March 2011

Pectins are a class of heterogeneous polysaccharides used in the food industry as a result of their ability to form gels. They are primarily composed of a (1ŕ4)‐α‐D‐galactopyranosyluronic acid backbone where the carboxylic acid group is methyl esterified at a level which depends on the source of the pectin and processing conditions used to isolate the material. Of considerable interest is the distribution of the free acid and methyl ester groups along this polymer chain. NMR spectroscopy, coupled with statistical analysis, is a powerful technique for the study of sequence distribution of monomers. Experimental conditions (temperature, pD) are reported which are appropriate for the analysis of pectic polysaccharides. Results are presented from a study of sequence distribution in native, modified, and fractionated pectins using 1H and 13C solution NMR methods. The triad sequence information was examined using Bernoullian and Markovian probability models in conjunction with continuous Gaussian distribution and discrete models. Intermolecular heterogeneity in pectins results in triad frequencies which reflect the distribution of acid and ester monomers for native and base saponified pectins. Fractionation of pectin through physicochemical methods and subsequent spectroscopic analysis provide insight into this heterogeneity. Segregation into discrete polymer populations shows a structural diversity best approximated by a 3‐component statistical model.
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

Proton 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

The 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

A 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

In 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

The 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

FTIR‐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

Novel 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

The 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

Random 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

The 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

Photoisomerization 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.