bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

AbstractThis 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

AbstractIn 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

AbstractEnvironmentally 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

AbstractNew 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

AbstractA 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

AbstractThis 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

AbstractLow 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

AbstractRing‐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

AbstractThe 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

AbstractNumerous 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

AbstractThe 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

AbstractCellulose‐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

AbstractCorn 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

AbstractLarge 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

AbstractThe 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

AbstractThe 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

AbstractThe 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

AbstractAn 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

AbstractMany 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

AbstractWe 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

AbstractNew 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.