bluuebunny/crossref_metadata_2025 huggingface dataset:
The volume transition in thermosensitive core‐shell latex particles investigated by small‐angle x‐ray scattering and dynamic light scattering
Authors: Kim J. , Deike I. , Dingenouts N. , Norhausen C. H. , Ballauff M.
Published: March 2011

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

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

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

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

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

This article surveys the influence of microstructural, morphological and molecular variables on the fracture and fatigue behavior of polyolefins, related blends and composites. The effects of major parameters of the structural hierarchy on the fracture mechanics (FM) response were considered and the related model descriptions reviewed. Emphasis was put on how important is to select the right FM approach for the toughness determination. It was pointed out that a clear distinction between crack initiation and growth is the essential prerequisite to differentiate between effects of the initial structure and its alteration due to mechanical loading. Although the microstructural dependence of the fracture and fatigue properties in reinforced, filled and impact modified polyolefins is quite well explored, this information is still missing for the neat polymers. This is due to a strong interlinking among molecular and morphological variables in neat polyolefins. Recommendations were given how to overcome this difficulty.
Self‐assemblies in ion‐containing polymers
Authors: Khokhlov Alexei R.
Published: March 2011

Recent interest in ion‐containing polymers is connected with the general shift of the main emphasis of polymer industry to functional polymer systems. The review of the main properties of ion‐containing polymers making them suitable for the use for functional purposes is presented and illustrated by recent experimental and theoretical findings.
Electroluminescence in alternating copolymers with the acetylene unit
Authors: Kim Dong Young , Hong Jae Min , Kim Jai Kyeong , Cho Hyun Nam , Kim Chung Yup
Published: March 2011

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

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

The fundamentals of atom transfer radical polymerization (ATRP) are presented. This includes the mechanistic considerations including structure of active and dormant species and structural features of the catalyst and reaction conditions as well as the nature of initiation and propagation steps. Extension of homogeneous polymerization to heterogeneous systems including emulsion polymerization is presented. Synthesis of (co)polymers with predefined molecular weights and low polydispersites as well as with controlled compositions, functionalities and architectures is reviewed.
Tailored polymers by free radical processes
Authors: Rizzardo Ezio , Chiefari John , Chong Bill Y.K. , Ercole Frances , Krstina Julia , Jeffery Justine , Le Tam P.T. , Mayadunne Roshan T.A. , Meijs Gordon F. , Moad Catherine L. , Moad Graeme , Thang San H.
Published: March 2011

This paper describes a versatile and effective method for the control of free radical polymerization and its use in the preparation of narrow polydispersity polymers of various architectures. Living character is conferred to conventional free radical polymerization by the addition of a thiocarbonylthio compound of general structure S=C(Z)SR, for example, S=C(Ph)SC(CH3)2Ph. The mechanism involves Reversible Addition‐Fragmentation chain Transfer and, for convenience of referral, we have designated it the RAFT polymerization. The process is compatible with a very wide range of monomers including functional monomers such as acrylic acid, hydroxyethyl methacrylate, and dimethylaminoethyl methacrylate. Examples of narrow polydispersity (≤1.2) homopolymers, copolymers, gradient copolymers, end‐functional polymers, star polymers, A‐B diblock and A‐B‐A triblock copolymers are presented.
Fluorescence of polymers: A probe of polymer assemblies
Authors: Webber S. E.
Published: March 2011

In this paper we discuss some general aspects of the use of fluorescence spectroscopy in the characterization of polymers and processes involving polymers. In particular we focus on the use of probes to detect formation of hydrophobic domains or to detect environmental changes because of solvation or pH changes, fluorescence quenching to determine the accessibility of the probe to solution phase small molecules, the use of fluorescence depolarization to characterize segmental motions and the use of energy transfer to characterize morphologies on the length scale of 1‐5 nm. We also will compare direct energy transfer (DET) with down‐chain electronic energy transfer (EET).
Dynamics in prediction of life‐time of environmental adaptable polymers
Authors: Albertsson Ann‐Christine , Karlsson Sigbritt
Published: March 2011

Environmentally adaptable polymers are materials with well‐defined life times made by tailoring the synthesis and creating a molecular architecture with precise functionality and morphology. Synthesis of such materials develops initiators/catalysts systems and enzymatic polymerisation while processing need to be adopted to the labile repeating units. The secondary structure of the environmentally adaptable polymers is susceptible to traditional processing introducing e.g. changes in the atomic positions of oxygen of poly(3‐hydroxy‐co‐3‐hydroxyvalerate). (Bio‐) degradation of these materials is complex and difficult to predict. Modelling test‐environments require an understanding of the many biological processes possible in nature. Many biodegradations require e.g. the co‐operation of more than one microbial specium, which sometimes render standard biodegradation tests inadequate. The nonabsolute specificity of enzymes are probably responsible for the transformation of many of the novel molecules created in recent times, but it is wishful thinking to expect that every new compound has an enzyme able to catalyse its alteration.
New alternating poly(amide‐ester)S: Synthesis and properties
Authors: Keul Helmut , Robertz Bernd , Höcker Hartwig
Published: March 2011

New alternating poly(amide‐ester)s derived from β‐hydroxy acids and α‐amino acids 3a,b or ϵ‐aminocaproic acid 4a‐c were prepared. Two approaches were considered: (i) polycondensation of N‐(β‐hydroxyacyl)‐amino acids 1a,b and 2b,c and (ii) ring‐opening polymerization of cyclic amide‐esters 5a‐c and 6a‐c. For all the linear precursors polycondensation reactions result in oligomers with number average molecular weights lower than 5000. The ring‐opening polymerization of the cyclic precursors is substrate specific and is sensitive to changes in the polymerization conditions. For N‐(3‐hydroxybutyroyl)‐ϵ‐aminocaproic acid lactone [c(3HB‐ϵAC); 5b] (IUPAC nomenclature: 2‐methyl‐5‐aza‐1‐oxa‐cycloundecan‐4,11‐dione) bulk and solution polymerizations result in oligomers with an alternating ester amide microstructure. Polymerization of N‐(3‐hydroxypropionyl)‐ϵ‐aminocaproic acid lactone [c(3HP‐ϵAC); 5a] (IUPAC nomenclature: 5‐aza‐1‐oxa‐cycloundecan‐4‐11‐dione) in dimethylformamide solution and with Bu2Sn(OMe)2 as initiator high molecular weight linear, semi‐crystalline polymers were obtained (Tm = 145.9°C). Polymerization of N‐(hydroxypivaloyl)‐ϵ‐aminocaproic acid lactone [c(HPv‐ϵAC); 5c] (IUPAC nomenclature: 3,3‐dimethyl‐5‐aza‐1‐oxa‐cycloundecan‐4‐11‐dione) in bulk results in amorphous alternating poly(amide‐ester)s with cyclic structure (Tg = 6.8°C). The fourteen membered cyclo(diamide‐diester)s 6a‐c (IUPAC nomenclatures:: 4,11‐diaza‐1,8‐dioxa‐cyclotetradecan‐2,5,9,12‐tetraone (6a), 7,14 dimethyl‐4,11‐diaza‐1,8‐dioxa‐cyclotetradecan‐2,5,9,12‐tetraone (6b), 3,10‐dimethyl‐4,11‐diaza‐1,8‐dioxa‐cyclotetradecan‐2,5,9,12‐tetraone (6c) based on β‐hydroxy acids and α‐aminoacids could not be polymerized.
Advances in properties and biodegradability of co‐continuous, immicisible, biodegradable, polymer blends
Authors: Mccarthy Stephen P. , Ranganthan Anadakumar , Ma Wenguang
Published: March 2011

A series of blends consisting of polylactic acid (PLA) and aliphatic succinate polyester (Bionolle#3000) have been prepared. The results of the mechanical property investigation have shown that using more than 20 wt % Bionolle#3000 can significantly increase the toughness of the PLA, increase the elongation at break (more than 200%) and increase the impact strength (more than 70 J/m). These properties were not significantly affected by the aging behavior of PLA for more than two months. DMA results show that Bio#3000 reduces the elastic modulus of the blends between −15°C and 60°C.

Soil degradation rates of the PLA/Bio#3000 blends also increase with increasing Bio#3000 content. However, for the blends with less than 30 wt % of Bio#3000, the degradation rates do not significantly increase. Enzymatic degradation rates of the blends are higher than for those of the two polymers, and these rates increase with increasing PLA content. Composting biodegradation rates increase with increasing Bio#3000 content.
Degradation by micro‐organisms of polymers and model compounds containing ester, amide or urethane groups: Kinetic and mechanistics aspects
Authors: David C. , Dupret I. , Lefèvre C.
Published: March 2011

This work has been performed using two pure strains of gram positive bacteria isolated from an industrial compost for household refuse and garden soil. These microorganisms have a stable phenotype, are easy to grow and were shown to be efficient degraders of various organic structures. It has been possible to get an insight both into fundamental mechanistic aspects of the degradation and into the fate of the studied derivatives in composts. Among others, measurement of oxygen consumption as a function of incubation time together with isolation and identification of degradation intermediates and residues has shown that short diester‐amides derived from phenylalanine are assimilated without prior hydrolysis. Also the mineralization of typical polyesteramides are limited by the assimilation of the fragments resulting from the ester groups hydrolysis.
Influence of metal ion on the degradation of LDPE at the composting temperatures
Authors: Yu Jiugao , Li Hansheng , Chen Songzhe , Gao Jianping , Lin Tong
Published: March 2011

Low Density Polyethylene(LDPE) films with additives that contain metal ions were subjected to accelerated degradation at simulated composting temperatures. The mechanical properties and viscosity‐average molecular weight of the samples, during the degradation, were determined and the degradation mechanism was studied. The results show that the samples containing metal ion show considerable decreases. Percentage crystallinity of LDPE in the samples has changed obviously during the degradation. [POOH] increases during the early stage of degradation followed by a more or less flat maximum before it starts to decrease, but carbonyl index shows a polynomial increase during the degradation.
Precision enzymatic polymerization to polyesters with lipase catalysts
Authors: Kobayashi Shiro , Uyama Hiroshi
Published: March 2011

Ring‐opening polymerization of lactones with different ring‐size has been achieved via lipase catalysis. Small‐size (4‐membered) and medium‐size lactones (6‐ and 7‐membered) as well as macrolides (12‐, 13‐, 16‐, and 17‐membered) were subjected to the lipase‐catalyzed polymerization. The polymerization behaviors strongly depended on the lipase origin and the ring‐size of the lactones. In using Pseudomonas family lipases as catalyst, the polymerization of macrolides showing much lower anionic polymerizability proceeded much faster than that of ϵ‐caprolactone. The enzymatic polymerizability of the lactones was evaluated by Michaelis‐Menten kinetics. Vmax increased as a function of the ring‐size, whereas Km values were not so different with each other. The granular immobilized lipase derived from Candida antarctica. showed the extremely efficient catalysis in the polymerization of ϵ‐caprolactone. Single‐step synthesis of methacryl‐ and ω‐alkenyl‐type polyester macromonomers was achieved by the lipase‐catalyzed polymerization of 13‐membered lactone in the presence of vinyl esters acting as terminator. Lipase also catalyzed a polycondensation of dicarboxylic acid and glycol in the aqueous medium, in which the dehydration took place in water.
Synthesis of aliphatic polyesters by controlled ring‐opening polymerization of cyclic esters. Characterization, properties, transesterification reactions
Authors: Spassky Nicolas , Simic Vesna , Hubert‐Pfalzgraf Liliane G. , Montaudo Maurizio S.
Published: March 2011

The polymerization of (D,L)‐Lactide at room temperature in solution using Y(OCH2CH2OiPr)3 and Ln5(μ‐O)(OiPr)13 with Ln = La, Sm, Y, Yb as initiators was studied. According to kinetic data, a controlled type polymerization is observed for most of the systems. La μ‐oxoisopropoxide is the most reactive initiator, but leads to a substantial broadening of molecular weight distribution at high conversions. The nature of transesterification reactions was studied by SEC, 13C NMR and MALDI‐TOF MS techniques. For Sm and Y‐μ‐oxo initiators only limited intermolecular ester exchange occurs, while with La μ‐oxoinitiator and with Y(OCH2CH2OiPr)3 initiator, but after a long time of the polymerization reaction, both inter and intramolecular transesterification occur with formation of cyclics.
Resorbable initiators for polymerizations of lactones
Authors: Kricheldorf Hans R. , Kreiser‐Saunders Ingrid , Damrau Dirk‐Olaf
Published: March 2011

Numerous salts were prepared from cations and anions belonging to the human metabolism, such as Na, K, Mg, Ca, Zn and Fe in combination with chloride, iodide, hydroxide, carbonate, acetate, stearate, glycolate, L‐lactate, D‐mandelate and various N‐substituted α‐amiono acids. All these salts were used as initiators for polymerizations of L‐lactide in bulk at 100–180°C. Furthermore, Grignard reagents, hemin and hematin were included in this study. Zn L‐lactate was found to be the most useful initiator in terms of reactivity, maximum molecular weight of the isolated poly(L‐lactide) and its optical purity. Zn L‐lactate initiated copolymerizations of L‐lactide and glycolide or ϵ‐caprolactone were also studied.
Kinetics and mechanism of glycolide and ethylenoxalate copolymerization. Characteristics of the copolymers formed and mechanism of the biodegradation
Authors: Ovchinnikova Tatjana , Zhuravleva Irina , Bush Ljudmila , Il'in Nicolay
Published: March 2011

The study of glycolide (GL) and ethylenoxalate (EO) copolymerization with the use of SnCl2 2 H2O as a catalyst was carried out by 1H NMR spectroscopy. Monomer reactivities are found to be close and equal to 1,1 and 1,11 for GL and 0,71 and 0,85 for EO at 150 and 170 °C, respectively. Kinetic data obtained show that the reaction proceeds without induction period up to entire consumption of every monomer. The detailed identification of 1H spectra enables to follow the polymer microstructure in the course of copolymerization. Thermal properties of copolymers and their biodegradation abilities have been studied. The biodegradation rate is shown to increase with growing EO proportion in the copolymer. The lactone biodegradation mechanism where the electrophility of carbon and nucleophility of OH group are playing the most important role, is suggested. The correlation between the biodegradation rate and the chemical shift in 13C NMR spectra of the carbon atom of the carbonyl group has been established.
Synthesis and thermal properties of cellulose‐based polycaprolactones
Authors: Hatakeyama Hyoe , Yoshida Takanori , Izuta Yoshinobu , Hirose Shigeo , Hatakeyama Tatsuko
Published: March 2011

Cellulose‐based polycaprolactone (CAPCL) sheets were prepared from cellulose acetate (CA) and ϵ‐caprolactone (CL). Thermal properties of the obtained CAPCL's were studied by differential scanning calorimetry (DSC), thermogravimetry (TG) and TG‐Fourier transform infrared spectrometry (TG‐FTIR). The glass transition temperatures (Tg 's) of CAPCL decreased with increasing CL/OH ratio, until CL/OH ratio reached 15 and then increased above that ratio. Melting of CAPCL was observed when CL/OH ratio was over 10. The thermal degradation temperatures (Td 's) of CAPCL increased from ca. 350 °C to 390 °C with increasing CL/OH ratio. The results obtained by TG‐FTIR analysis of CAPCL showed that gases with OH, CH, C=O, C‐O‐C groups evolved by thermal degradation.
Plasticization of corn gluten meal and characterization of the blends
Authors: Di Gioia Lodovico , Cuq Bernard , Guilbert Stéphane
Published: March 2011

Corn gluten meal has thermoplastic properties enhanced by it's high zein content. The addition of an efficient plasticizer is necessary to lower the glass transition temperature. Homogeneous blends of plasticizer and corn gluten meal can be obtained either by a wet mixing technique or by compounding the two substances in an heated batch mixer. The resulting raw material is suitable for “thermoplastic forming” of low cost biomaterials.
Development of a closed‐loop control system for production of medium‐chain‐length poly(3‐hydroxyalkanoates) (mcl‐PHAs) from bacteria
Authors: Kellerhals Michele B. , Kessler Birgit , Witholt Bernard
Published: March 2011

Large scale availability of bacterial polyhydroxyalkanoates (PHAs) is still limited to a few types of short‐chain‐length PHAs, namely poly(3‐hydroxybutyrate) (PHB) and its copolymer Biopol™, consisting of 3‐hydroxybutyrate and 3‐hydroxyvalerate repeating units. In order to increase the number of available medium‐chain‐length PHA (mcl‐PHA) copolymers a flexible high‐cell‐density fed‐batch process was developed. Continuous process monitoring and substrate control were achieved by coupling on‐line gaschromatography (on‐line GC) to a software‐based Proportional Integral (PI) substrate controller. System development time and continuous system upgrading were considerably shortened by using LABView™, a powerful graphical programming environment. The control of octanoic acid and 10‐undecenoic acid at 1.5 and 0.5 gL−1 respectively, enabled the production of high levels of biomass (30 gL−1) and mcl‐PHA (10.5 gL−1) by avoiding substrate limitations or toxicities. The resulting mcl‐PHA was an amorphous copolyester consisting of 37 mol% unsaturated monomers. The present system represents a valuable tool for the production of tailor‐made mcl‐PHAs, where the desired monomer composition is determined by the ratio of added cosubstrates.
Modification of chitosan for construction of efficient antioxidant biodegradable macromolecular systems
Authors: Alexandrova V. A. , Obukhova G. V. , Domnina N. S. , Topchiev D. A.
Published: March 2011

The chitosan derivatives containing antiradical fragments in the polymer side chain have been synthesized by interaction of the partially quaternized chitosan(QCH) with gallic acid (GA). The antioxidative activity of the chitosan derivatives — QCH‐GA was investigated by thiobarbituric method. Introduction of GA fragment in amount of 2. 0 mass % in the structure of QCH resulted in appearance of pronounced antioxidative activity of the polymeric system contrary to initial chitosan for which this activity was equal to zero. It was found that QCH‐GA was a markedly higher effective inhibitor in a peroxidase — catalyzed oxidation of the model amine than the low‐molecular antioxidant — GA. Targetted chitosan modification resulted in a substantial raize of the polymeric antimutagenic (at γ‐irradiation) efficiency, which for QCH‐GA was equal to 92% in comparison with the protective effect of the initial chitosan — 42% (plant test‐system, barley seeds, γ = 15 Gr).
Fluorocarbon modified chitin and chitosan I. Synthesis and characterization of perfluorocarbonyl chitin
Authors: Zhang Yun‐Xiang , Wang Tie‐Lin , Huang Wei‐Hong , Da Ai‐Hua
Published: March 2011

The esterification reaction of chitin with perflurocarboxylic acid was studied in methanic acid or perfluorocarboxylic acid as solvent. A series of substituted derivatives of trifluoroacyl. perfluorobutyric and perfluorooctanoyl chitin were synthesized. The properties of these chitin derivatives were investigated.
Degradation of polyolefines during various recovery processes
Authors: Teteris Gundars
Published: March 2011

The purpose of the presented research was the investigation of the stability and differences of degradation of polyolefines during various recycling processes. In modeling the recycling process during melting, extrusion with a one‐screw extruder was used. Recycling through selective dissolution was modulated by two different solvents (xylene and a definite mixture of n‐alkanes). Materials used for the investigations were polypropylene (PP), low‐density polyethylene (LDPE) and high‐density polyethylene (HDPE) (Ziegeler‐Natta technology with vanadium catalyst). Changes in the chemical structure of polymers were measured with infrared spectroscopy and differential scanning calorimetry (DSC). Flow properties were characterized by melt flow index, and mechanical characteristics by tension. Experimental results show that for PP and HDPE, utilizing all investigated recycling technologies, chain scission prevailed over branching. For the LDPE chain branching was obtained. By the same token, differences in crystallinity (and as follows, in molecular mass) between the same materials, recycled by extrusion and selective dissolution, was obtained. During selective dissolution changes of properties and morphology in dependence of the solvent used were observed with the trend being that the amount of the admixture of n‐alkane used in this investigation was more considerable with regard to the amount of material destruction as compared to xylene. Any reduction of the mechanical properties of any of the investigated polymers as a result of the various methods used was comparable.
Surface modification by polyelectrolytes: Studies on model systems
Authors: Oertel U. , Buchhammer H.‐M. , Müller M. , Nagel J. , Braun H.‐G. , Eichhorn K.‐J. , Sahre K.
Published: March 2011

An improved method for the preparation of uniform dispersions of non‐stoichiometric polyelectrolyte complexes on the basis of maleic acid copolymers and poly(diallyldimethylammonium chloride) was developed. The dispersed particles showed a narrow size distribution on the nm scale and were used as model systems for the investigation of their adsorption on different model surfaces. A combination of ATR‐FTIR, SPR, ellipsometry and SEM was useful for the monitoring of the adsorption process of individual colloid particles and may lead to a quantitative description of the adsorption process. For a better understanding of the underlying principles and interactions organic model surfaces which meet the requirements of the different methods are required.
Role of adsorption in liquid chromatography of macromolecules and potential of liquid chromatography in assessing adsorption of macromolecules onto solid surfaces
Authors: Berek Dušan
Published: March 2011

Many liquid chromatographic (LC) separations of macromolecules are influenced or directly based on adsorption of solutes on column packing. In the case of well known size exclusion chromatography (SEC), adsorption effects are usually unwanted and therefore suppressed. Still they appear in many SEC systems and may badly affect precision of results obtained. In other LC methods applicable to high polymers, adsorption is deliberately combined with exclusion. The aim is to discriminate complex polymer systems which exhibit more than one single distribution of their molecular characteristics. The main goals of such combinations include either a controlled increase or a full suppression of separation selectivity according to one molecular characteristics. Most important so far known exclusion‐adsorption compensation methods allowing to suppress dependence of LC retention volumes on polymer molar mass are reviewed. The discussion is accomplished with a presentation of newly developed full adsorption ‐ desorption (FAD) method which can be combined with various LC procedures. A very useful combination represents the on‐line FAD/SEC procedure which enables also to study adsorption and desorption phenomena in the systems solid surface ‐ solvent ‐ macromolecules.
Polymer thin film properties as a function of temperature and pressure
Authors: Kleideiter Gerd , Prucker Oswald , Bock Harald , Frank Curtis W. , Lechner Manfred Dieter , Knoll Wolfgang , Prucker Oswald , Kleideiter Gerd
Published: March 2011

We report on evanescent wave optical measurements of the glass transition temperature, Tg, of spin‐cast PMMA films as a function of film thickness and molecular weight. It was found that for films of high molecular weight PMMA (Mn > 100,000 g mol−1) a strong Tg depression occurs for films that are thinner than 100 nm in case they are deposited on hydrophobic substrates. This strong Tg depression of up to 25°C decreases if similarly thick films of PMMA of low molecular weights are investigated and vanishes completely for PMMA with Mn < 12,000 g mol−1. For films made of these materials Tg is found to be identical to that of the bulk even for films as thin as 5 nm. The results might be interpreted in terms of free volume considerations. To check this assumption we also designed and built a pressure cell that can be used together with the evanscent wave optical techniques for similar measurement, but with the additional option to do the measurements at different pressures up to ca. 100 MPa to further vary the free volume of these polymer films in constrained geometry. Some first results obtained with this setup are also described.
Thin layers of cellulose derivatives ‐ selected analytical aspects
Authors: Plagge Andreas , Stratmann Martin , Kowalik Thomas , Adler Hans‐Jürgen
Published: March 2011

New hairy‐rod like cellulose polymer layers were developed as a model system for corrosion protection and adhesion promotion in medical technology. Using the Langmuir‐Blodgett technique a mixture of a cinnemate containing and a phosphate containing cellulose were transferred on titanium and steel surfaces. The cinnemate can be crosslinked by ultraviolet light (UV). Differences in the formation of multilayers were found and analyzed by atomic force microscopy, scanning auger microscopy and ellipsometric measurements.

Phosphate cellulose forms homogenous layers at all substrate surfaces. With increasing layer thickness a mixture with low phosphate content becomes homogenous, too. Only mixtures with high content of phosphate keep imperfections with increasing layer thickness. For the pure component cinnemate cellulose the imperfections arise only in the case of titanium surfaces.
Adsorption and displacement of beta‐2‐microglobulin at solid/liquid interfaces
Authors: Werner Carsten , Pilz Martin , Eberth Grit , Menning Anke , Lemke Horst‐Dieter , Eichhorn Klaus‐Jochen
Published: March 2011

Adsorption of beta‐2‐microglobulin from aqueous solution onto unmodified and methylated silicon wafers and subsequent displacement of the small globular protein by fibrinogen were studied by spectroscopic ellipsometry, immunosorbent assays and atomic force microscopy.

The results provide evidence that hydrophobicity of the substrate increases the maximum adsorbed amount of beta‐2‐microglobulin and the resistance of the adsorbed protein to displacement from the interface by competing species, respectively. Further, the dynamics of beta‐2‐microglobulin adsorption was found to induce significant differences in the degree of displacement achieved at given conditions. The observed variations in displacement behavior of adsorbed beta‐2‐microglobulin were interpreted based on information on the layer structure gained by atomic force microscopy. More compact and relatively smooth protein layers were formed on the hydrophobic surface corresponding to lower displacement by fibrinogen.
Deposition and bioadhesion properties of polymer multilayers: An in‐situ‐ATR‐FTIR‐study
Authors: Müller Martin , Rieser Theresia , Köthe Marcello , Keßler Bernd , Brissova Marcela , Lunkwitz Klaus
Published: March 2011

The multilayer formation by consecutive deposition of oppositely charged polyelectrolytes and the protein adsorption at the outermost layer was investigated by in‐situ attenuated total reflection Fourier transform infrared (ATR‐FTIR) spectroscopy. For the polyelectrolyte multilayer generation the polycation / polyanion pairs poly(diallyldimethylammonium chloride) (PDADMAC) / sodium poly(maleic acid‐co‐propylene) (PMAPP) and poly(ethyleneimine) (PEI) / poly(acrylic acid) (PAC) respectively, were used. The v(CO)‐ and the vas(COO)‐band due to COOH‐ und CO−‐groups of the polyacid/polyanion as well as the v(OH) band due to desorbed water were used for monitoring the multilayer build up.

By the multilayer surface modification we were able to diminuish or enhance significantly the adsorption of the model plasma protein human serum albumine (HSA), as a measure for bioadhesion, in dependence on the character of the outermost layer. This protein resistence mainly was attributed to the repulsion between the like charges of the outermost adsorbed polyanion layer (e.g. PAC) und the acidic HSA (IEP=4.7). Vice versa it could be shown, that HSA was bound by an outermost polycation layer by a factor >10 stronger compared to an outermost polyanion layer. Furthermore studies on protein adsorption at multilayers built up by the reactive polymer pair poly(butadienepoxide) (PBDE) / poly(allylamine) (PAA) were introduced.
Sorption and swelling in ultra‐thin polymer films
Authors: Meier Frank , Schiewe Beate , Esker Alan , Wegner Gerhard
Published: March 2011

Different polymers were investigated with respect to the sorption of solvents and gases. Depending on the chemical nature of the polymers this sorption leads to polymer swelling. The degree of swelling D/D0 was measured utilizing Small angle X‐ray scattering (SAXS) as well as Surface plasmon resonance (SPR). From the change in film thickness after swelling in different solvents Hildebrand parameters of the polymers were determined. By crosslinking of the polymer films the degree of swelling can be controlled. In the case of ultra‐thin polyimide films a higher degree of crosslinking led to a decreased selectivity of the transport of gases through the membrane. Reptation of macromolecules was also investigated and the influence of polymer swelling in different solvents has a great influence on the selectivity and diffusion coefficient.
Relaxation study of poly[(4‐oligodimethyl‐siloxanyl)styrene]s by solid state 29Si NMR
Authors: Kawakami Yusuke
Published: March 2011

Quantitative evaluation of spin‐lattice relaxation time (T1) was made at each silicon atom of the side chains by solid‐state 29Si NMR. It was found that the closer the silicon atoms were to main chain, the more the motion was restricted. Such local mobility of side chains was correlated to the gas permeation behavior through the polymer membrane.
The superstructure of carbosilane dendrimers with perfluorinated end groups in bulk and in solution
Authors: Stark B. , Lach C. , Frey H. , Stühn B.
Published: March 2011

Carbosilane dendrimers of generation 1 to 4 are functionalized with perfluorinated (‐C6F13) end groups. Extending the spacer between the central Si and the first layer of branching points allows the synthesis of the 4th generation. The superstructure of these systems in bulk observed with X‐ray scattering is the result of the microphase separation between the carbosilane scaffold and the end groups. It varies with generation from a layered to a columnar structure. In dilute solution only the second generation dendrimer shows a tendency for aggregation. The others form compact particles consisting of single molecules with a core shell structure.
New polymer electrolyte membranes for low temperature fuel cells
Authors: Ennari J. , Hietala S. , Paronen M. , Sundholm F. , Walsby N. , Karjalainen M. , Serimaa R. , Lehtinen T. , Sundholm G.
Published: March 2011

Partially fluorinated proton exchange materials were synthesised by pre‐irradiation grafting of styrene into poly(vinylidene fluoride) films with subsequent sulfonation. The grafted and sulfonated membranes, PVDF‐g‐PSSA membranes, have been studied with respect to water uptake, ion and water clustering, ion conductivity and water diffusion coefficients. Water associates with the membranes in three different ways: bound non‐freezable water, freezable bound water and freezable free water. The proton conductivity of the membrane is strongly dependent on the hydration, it decreases more rapidly than the water self diffusion with decreasing water content. Ion clusters with a Bragg distance of 25 Å form the conducting channels in the membranes.
Rheo‐optical FT‐IR spectroscopy of solid poly(acrylic acid) films
Authors: Mavinkurve Amar A.
Published: March 2011

This paper describes experimental work where the mechanical behaviour of relatively dry, solid poly(acrylic acid) films at room temperature was correlated with changes in hydrogen‐bonding in the polymer. Hydrogen‐bonding between the carbonyl and the hydroxyl groups was followed by FT‐IR spectroscopy while the films were stretched uniaxially. Limited mobility of the polymer below its Tg led to small but detectable changes in bonding. A characteristic strain‐hardening behaviour was observed if no bound water was detected in the samples.
The role of intermolecular interactions in the viscoelastic properties of polymer melts
Authors: Fatkullin Nail , Kimmich Rainer
Published: March 2011

The exact microscopic expression for the stress tensor in polymer liquids contains a tensor product of the the segment position vector with the total, intra‐ plus inter‐chain, force acting on the segment. On the other hand, the widely accepted theory of viscoelasticity of polymer melts1) is based on the assumption, that contributions from interchain interactions to the viscosity of polymer melts is negligible relative to the effectively intrachain entropic interactions. Starting from the exact Green‐Kubo formula for the viscosity, the Rouse dynamic correlation functions, and Newton's second law, we show that the intrachain assumption is inadequate. Rather, the intrachain and interchain forces acting on polymer segments cancel each other largely. The intrachain contribution therefore cannot be dominant as anticipated in the usual treatment1), or, in other words, the interchain contribution cannot be ignored. The main contribution to viscoelastic properties of polymer melts can only arise from a part of the total stress tensor as already suggested by M. Fixman based on a different argument2). It is concluded that the viscosity is of a purely interchain nature, and is determined by the tensor product of the vector connecting the centers‐of‐mass of neighboring macromolecules on the one hand, and the total force by which macromolecules interact, on the other, just in the case of simple liquids.
An improved theory of polymer dynamics in solution: Probe diffusion and viscosity
Authors: Ngai K. L.
Published: March 2011

A more complete coupling/scaling theory of polymer dynamics in solution is presented and applied to explain several anomalous properties of probe diffusion and viscosity. Similar properties are found in totally physically and chemically different systems. These similarities strongly support the need of a general approach to these problems as given here.
Steady‐state properties and dynamic behavior of polymer chains in dilute solution under elongational flow
Authors: Cifre José Ginés Hernández , De La Torre José García
Published: March 2011

The behavior of polymer chains in dilute solution under a steady, homogeneous elongational flow has been studied employing Brownian dynamics simulation. We first consider the dependence of polymer properties in steady state on the elongational rate, ϵ. When this rate exceeds some critical value, ϵc, the properties show a dramatic change from the values typical of the coil state to those of a stretched conformation. We describe the dependence of ϵc on chain length for different polymer/solvent conditions. Following the trajectories of individual molecules, we have characterized dynamic aspects of the coil‐stretch transition. Each chain suffer the transition after some time, ttrans, has elapsed after the flow start‐up. The values of ttrans vary remarkably from one molecule to another, and we have characterized the statistical distribution of this quantity. We also determine the kinetics of the coil‐to‐stretch process, which seems to follow a first‐order kinetics after some induction time. The dependence of the statistical and kinetic parameters on chain length and elongational rate has been determined.
The effect of polyolefin's molecule and supermolecule structures on some industrial processes
Authors: Mamedov Sheval , Kovun Ahmet , Varol Selçuk , Alekperov Velayet , Lenger Yeşi M. , Öksüz Selcen
Published: March 2011

In this study, the raw materials and their structural properties were analyzed in synthetic polymer pipe production by the following events: 1) The effect of extruder processes to dynamic‐mechanical properties of polyethylene (PE) and polypropylene (PP) pipes in pipe production; 2) The effect of the fiber direction on dynamic‐mechanical properties and extruder materials; 3) The heat process on welding during the pipe production and the effect of polymer structure on welding duration; 4) Physical properties and structural changes of pigmented PE and PP raw materials. 5) The relationship between dynamic‐mechanical properties of polymers with thermodynamic and kinetic concepts and effect of temperature. The results (that were) derived after several measurements are as follows: 1) The best stability properties were observed on the pipe samples which have same fibre direction. In samples with opposite and vertical fiber directions the stability properties are 30% lower. 2) The maximum dynamic‐mechanical properties of the pipe samples were observed when the extruder temp. Is 463 k. These properties were lower in the pipe compared to the samples taken from the inner and outer part of the extruder. For the sample during this time the concentration of the oxygen groups are at the lowest and amorphous regions are at the highest level. These results prove that the temperature, the pressure and the cooling rate of the material taken from the extruder have too much effect on polymer structure. 3) Welding duration is investigated without changing the fibrillar structure. The best welding conditions have been obtained in case of deformation graphs with minimum areas. The results can be explained with the difference in polymer structures at different temperatures during pipe manufacturing process. 4) The σ, τ, γ values differ greatly in the samples taken from different companies (∼ 50%). The analyses of IR spectra and microphotographs show that this difference depends on the differences of the polymer structures and the initial data.
A study of the optical properties of polypropylene based polymer composite films
Authors: Boydag F. Senel , Mamedov Shaval V. , Alekperov Vilayet A. , Kandemir Gulcin
Published: March 2011

The optical clarity of the polymeric material can be influenced by changing the preparations parameters and thus the polymer structure. In this study, the transmittance, absorptance and reflectance of the polypropylene (PP) based polymer composites, synthesized by pressing method, changing the thickness between 8 — 29 μm, are investigated. Infrared and ultraviolet spectra of PP/diamond and PP/fiber composite in the wavelength range 200–25000 nm are examined. Optical absorption spectra recorded in the UV‐Visible range are presented; the determined values of energy gaps are listed. The results indicate that both mechanism, direct and indirect transitions may exist. The analysis of absorption peaks corresponding to oxygen groups, for PP/diamond (0.3–0.5 %) and PP/fiber (20–30 %) composites, show low optical densities which complies with our other studies.