bluuebunny/crossref_metadata_2025 huggingface dataset:
Polymeric porphyrins as new photocatalysts in photodynamic therapy of cancer
Authors: Wöhrle D. , Ardeshirpur A. , Heuermann A. , Müller S. , Graschew G. , Rinneberg H. , Kohl M. , Neukammer J.
Published: March 2011

Photodynamic therapy and diagnosis (PDT) is described as an efficient clinical method for the treatment of cancer patients using hematoporphyrin derivative (Hpd) as sensitizer. Newly developed metal‐containing porphyrin type compounds are potential agents for PDT. A concept for covalently bound polymeric metal‐containing or metal‐free sensitizers is discussed. First results of these polymeric sensitizers are reported from in vivo experiments. High tumor accumulation up to 30% was observed. Results of fluorescence diagnosis are shown.
Applications of highly luminescent transition metal complexes in polymer systems
Authors: Demas J. N. , Degraff B. A.
Published: March 2011

Advances in understanding the photophysics and photochemistry of transition metal complexes offer opportunities to utilize these materials as luminescence sensors and probes. However, heterogeneity has an enormous effect on luminescence, quenching, and photochemistry. An intimate understanding of the detailed interactions between the complexes and their environment will be necessary before the rational design of new high performance sensors and probes can be achieved. Such understanding is fairly well established for homogeneous media, but it is still in its infancy in solid supports (surfaces and polymers). We present case studies involving luminescent metal complexes bound to a variety of polymer systems. Both their potential and the difficulties inherent in these composite systems are presented. We discuss tools that have proved useful or are likely to be valuable in unraveling these complex systems.
Oxidative phenol coupling catalyzed by polymer‐bound copper‐imidazole complexes
Authors: Challa G. , Chen W. , Reedijk J.
Published: March 2011

Polymer‐bound imidazole‐copper(II) complexes were investigated and applied as catalysts for oxidative coupling (polymerization) of 2,6‐dialkylphenols. These polymeric catalysts were also immobilized on silica particles through adsorption, quaternization and grafting. Especially, the grafted catalysts showed interesting catalytic properties, e.g. good specificity for C‐O coupling and very good stability during prolonged use in continuous processes. This stability furnished new information about the mechanism of the oxidative coupling polymerization. Finally, this reaction was optimized for the preparation of PPO‐type telechelics.
Hydrogenation catalytic behaviors of palladium complexes of chitin and chitosan
Authors: Wang Xin‐Xin , Huang Mei‐Yu , Jiang Ying‐Yan
Published: March 2011

Palladium complexes of chitin and chitosan have been shown to have catalytic activities for hydrogenation at room temperature and under atmospheric pressure. They could catalyze not only reduction of olefines but also aromatic nitro‐compounds and acrylic acid. And they are very active, stable and selective. They also show different catalytic behaviors in different pH solutions. It is noteworthy that the catalytic activities of the two polymer‐supported metal complexes in the cycle of pH 11 → pH 2 → pH 11 are reversible.
Syntheses of organometallic monomers containing cobalt and manganese
Authors: Miller Edward J. , Naughton Micheal J. , Weigelt Carolyn A. , Bradt Jean E. , Serth Judy A. , Ofslager Christian L. , O'Brien William J.
Published: March 2011

Direct electrophilic substitution of the cyclopentadienyl ring of cymantrene has been used to prepare five cymantrenyl‐monomers with unsaturated sidechains. Direct substitution of cymantrene with acryloyl‐ and methacryloyl chloride under Friedel‐Crafts conditions has led to acryloyl‐ and methacryloylcymantrene. The complexes have been characterized using 1H and 13C NMR, IR and elemental analysis. Both complexes polymerize under treatment with AIBN at 60–70°C. The chelated complex [n5‐C5H4(CH2CH=CH2)]‐Co[(NH)2C6H4], was prepared from the treatment of [n5‐C5H4(CH2CH=CH2)]Co(CO)2 with I2 followed by (NH)2C6H4 and base. The complex was characterized with 1H NMR and IR but failed to undergo free‐radical polymerization. The strategies used to prepare organometallic polymers are discussed.
Coordination properties of polymeric azacrown ethers
Authors: S. Psheshetsky V. , Lishinsky V. L. , Kokorin A. I. , Tsarkova L. A. , Rakhnianskaja A. A. , Pertsov N. V.
Published: March 2011

New polymeric aza‐crown ethers (PACE), soluble in water and organic solutions and cross‐linked ones, containing different macrocycles in side chains have been synthesised by polymerisation and chemical modification reactions. The coordination próperties of these PACE are studied. It is shown that during coordination of the VO2+, Cu2+ ions with PACE, cross‐linking of macromolecules by metal ions takes place by “sandwich” complex formation. The character of complexes distribution along PACE coils may be equal or nonequal, depending on polymer reactivity. The synthesised PACE are used as high specific polymer reagents for colloid rare metals recovery. It is shown that flocculation of negatively charged inorganic sols with PACE is due to electrostatic adsorption and specific binding. In acid and neutral media, dispersions of gold, silver, copper ferrocyanide and silicon dioxide undergo high flocculation as a result of non‐specific electrostatic adsorption. Alkaline media provide conditions for donor‐acceptor binding, increasing flocculation selectivity. In the uncharged state (pH 11,2) PACE exhibit high selectivity in binding gold particles. Stability of colloidal dispersions in the presence of monomer aza‐crown ether (ACE) indicates an important polymer influence on the fine metal particles flocculation.
Photoluminescent copolymer‐pendant Ru(BPY)32+ grafted onto non‐woven silk fabric and its application to oxygen sensor
Authors: Kaneko Masao , Takekawa Toshihiro , Asakura Tetsuo
Published: March 2011

Copolymer‐pendant Ru(bpy)32+ grafted onto silk fibroin was prepared by at first grafting copoly(4‐methyl‐4′‐vinyl‐2,2′‐bipyridine ‐ methylmethacrylate) onto non‐woven silk fabric, and then by reacting the grafted sample with cis‐Ru(bpy)2Cl2. Photoluminescence of this silk‐poly Ru complex and its quenching by oxygen were studied in gas, methanol and water phases. The relative emission intensity and the emission lifetime of the silk‐poly Ru showed that there are two kinds of sites for the Ru complex. The major, longer lifetime component (1070 ns, 77.1%, under Ar gas) is considered to be surrounded by polymer matrices, and the minor, shorter one (288 ns, 22.9%) seems to be exposed and is subjected to concentration quenching. The shorter lifetime species are quenched by oxygen more effectively than the longer ones. The mechanism of the quenching by oxygen and its application to oxygen sensor were discussed.
Conformational effects of polymer chains on the electron‐transfer reactions and luminescence behavior of Ru(bpy)3a+ in aqueous solutions of poly(acrylic acid)‐ and poly(methacrylic acid)‐bound Co (III) complexes
Authors: Kurimura Yoshimi , Sairench Yoshihiro , Nakayama Seiichi
Published: March 2011

The effects of the conformation of polymer chains on the electron transfer reactions and on the luminescence behavior of Ru(bpy)32+ in aqueous solutions of cis‐Co(A)PAA and cis‐Co(A)PMA ((A) = (en)2(OH2), en = ethylenediamine, PAA = poly(acrylic acid), and PMA = poly(methacrylic acid)) have been investigated by means of several spectrophotometric techniques. The results of the electron‐transfer reactions of the polymer Co(III) complexes with Cr(bpy)32+ and Fe(edta)2− revealed that, at low pH, part of the Co(III) complex moieties could hardly be reduced even in the presence of a large excess of the reducing agents when the degree of coordination of the Co(III) complex is very low. The magnitude of the degree of reduction of the Co(III) complex and the rate constants of the electron‐transfer reactions of Co(A)PMA are considerably affected by the conformational transition of the polymer chains.

The luminescence behavior of Ru(bpy)32+ in aqueous solutions of these polymer complexes at around pH 5 are essentially explained by the spontaneous luminescence decay of the ex cited state of Ru(bpy)32+ ions which are localized in the compact form of the polymer chains and that of the non‐shielded ones which have a similar lifetime as in water. Effects of the conformational transition of Co(A)PMA chain on the luminescence intensity and the lifetime of the excited state of Ru(bpy)32+ are discussed in the light of the results obtained.
Influence of polymer matrices on the photoelectrochemical properties of a molecular semiconductor by structural modification
Authors: Schlettwein D. , Jaeger N. I. , Wöhrle D.
Published: March 2011

Thin films of phthalocyaninatozinc(II) (PcZn) have been prepared by physical vapor‐deposition or from solutions in organic solvents in mixture with poly(vinylidene fluoride) PVDF. The molecular order, i.e. the structure of the van der Waals bonded crystals, depends on the preparation technique and on the chosen matrix. By annealing the thin films or by embedding the phthalocyanine in a polymer environment, the structure is effected significantly. This is demonstrated by electronic spectra. The activities of the films have been investigated in the photoreduction of oxygen dissolved in an aqueous electrolyte. The highest sensitivities towards visible light are observed in matrices of polymers with a high dipole moment. Aside from the influence of a polar polymer towards a more favourable crystallization of PcZn an active role in the charge carrier generation process is derived from a discussion of the results within the model of molecular semiconductors which is appropriate for phthalocyanines.
Complexing ability of poly[5‐vinylsalicylidene‐2‐aminopyridine] towards different metal(II) salts
Authors: El‐Shekeil Ali , El‐Sonbati Adel Z.
Published: March 2011

Mononuclear and binuclear complexes of poly (5‐vinylsalicylidene‐2‐aminopyridine) a)were prepared with Copper(II), Cobalt (II), Nickel(II), Cadmium(II), dioxuranium(II) and Palladium(II) salts. The metal (II) acetates and palladium chloride gave mononuclear complexes, while cupric chloride gave a binuclear complex. The polymer complexes have been characterized on the basis of elemental analysis, u.v., i.r. and magnetic susceptibilty. The stereochemistry and the nature of the complexes are markedly dependent upon the mole ratio of the reactants and the anions. In all complexes the homopolymer was chelated to the metal ion via the nitrogen atom of the azomethine group and oxygen atom of the phenolic, group. The low value of the magnetic moment of binuclear copper complexes is due to the antiferromagnetic interaction between two adjacent copper atoms. The ligand field parameters are calculated and related to the electronic environments.
Palladium cluster catalysts supported on chelate resin‐metal complexes
Authors: Toshima Naoki , Teranishi Toshiharu , Saito Yasukazu
Published: March 2011

The dry beads of chelate resin‐metal complexes have been prepared from metal ions and the chelate resin containing iminodiacetic acid moieties. The surface area of the chelate resin can be increased both by washing with an organic solvent miscible with water and by complexing with multi‐valent cations. Palladium clusters are supported on the chelate resin‐metal complexes by two methods, in which the order is reversed between “complexing of metal ions” and “supporting of palladium clusters”. The supported palladium clusters catalyze the hydrogenation of C=C bonds, and the catalytic activity greatly depends on the metal ions used for the complexation. In the case of typical metal ions, the complexing of metal ions after supporting of palladium clusters makes the surface area of the resin increase, but makes the catalytic activity decrease compared with the reverse order. In the case of lanthanoid ions, on the other hand, the same order makes both the surface area and the catalytic activity increase.
Polypyridine‐based catalysts: Epoxidation of olefins with supported peroxotungstic complexes
Authors: Gelbard Georges , Breton François , Charreyre Marie‐Thérèse , Dong Doan
Published: March 2011

Epoxidation of cyclohexene with hydrogen peroxide was performed with tungsten‐based catalysts in the form of polymer supported pyridinium peroxotungstate salts and betaines. These catalysts were obtained from copolymers of 4‐vinylpyridine and divinylbenzene or from aminomethylpyridines alkylated with chloromethylpolystyrene. The free bases and the corresponding N‐oxides were reacted with peroxotungstic acid to give the catalytic species.
Thermal characterization of macromolecular metal complexes of mo(VI) as heterogeneous oxidation catalysts
Authors: Ferruti P. , Ranucci E. , Tempesti E. , Casolaro Mario
Published: March 2011

Two multifunctional carboxylic resins were synthesized and characterized in terms of their CO2H content. The thermal stability of the resins was investigated by DTA and TG analysis before and after Mo(VI) complexation. Simultaneous IR analyses at various stages of the heating processes were also performed.
Structure and properties of superconducting and nonsuperconducting alkali‐metal fullerides axc60 (A = Na, K, Rb, or Cs)
Authors: Wiley John B. , Huang Shiou‐Mei , Cho Shinho , Diederich François , Whetten Robert L. , Holczer Károly , Kaner Richard B.
Published: March 2011

Shielding diamagnetism and X‐ray powder diffraction were used to characterize alkali‐metal fullerides of sodium, potassium, rubidium, and cesium. The superconducting phase in both the potassium and rubidium systems has the composition A3C60 and a face centered cubic structure with alkali metal filling all octahedral and tetrahedral sites of close packed C60, layers. High pressure magnetic susceptibility measurements on K3C60 showed a negative pressure dependence on the superconducting transition temperature of −0.78 K/kbar. No evidence for superconductivity was observed in either the sodium or cesium systems, even though Na3C60 appears isostructural with K3C60 and Rb3C60.
Tailored macromolecules by living carbocationic techniques
Authors: Kennedy Joseph P.
Published: March 2011

This presentation concerns our latest results for the controlled synthesis of various homopolymers, blocks, random copolymers, networks, by living carbocationic polymerization (LC⊕ Pzn). We start with an analysis of the Winstein ionicity spectrum, a roadsign toward LC⊕ Pzn systems. Living isobutylene (IB) homopolymerization can be effected by the addition of common anion salts to conventional polymerization charges, e.g., by adding nBu4NCl to a 2‐chloro‐2,4,4‐trimethylpentane (TMPCl)/TiCl4/IB system. Various AB diblocks have been prepared by sequential monomer addition. The first clean svnthesis of an AB poly(olefin‐b‐alkyl vinyl ether) diblock, ie., poly(isobutylene‐b‐methyl vinyl ether), by sequential monomer addition was accomplished. These novel amphiphilic diblocks promise to be excellent nonionic detergents. The field of linear A‐B‐A triblocks and three‐arm star blocks where A = glassy and B = rubbery (polyisobutylene) segment, is vigorously expanding. Several new thermoplastic elastomers (TPEs) have been prepared, characterized and tested, e.g., poly‐(indene‐b‐isobutylene‐b‐indene). The synthesis of random copolymers, e.g., isobutylene/2,4,4‐dimethyl‐1,3‐pentadiene, by living reactivity leveling has been demonstrated. Transformation of the polyisobutylene cations PIB⊕ and ⊕PIB⊕ yielded the corresponding anions PIB⊖ and ⊖PIB⊖, which upon block polymerization of butadiene (Bd) and methyl methacrylate (MMA), respectively, gave rise to the new diblock PIB‐PBd and triblock PMMA‐PIB‐PMMA. In the latter, the largely syndiotactic sPMMA endblocks were stereocomplexed with isotactic iPMMA and thus the upper use‐temperature of these novel TPEs was enhanced. Novel amphiphilic networks comprising hydrophilic polymethacrylates (e.g., dimethylaminoethyl methacrylate (DMAEMA) or hydroxyethyl methacrylate (HEMA)) crosslinked by methacrylate‐telechelic PIBs were prepared and their potential usefulness for biomedical applications has been studied.
The carbenium ion ‐ oxonium ion exchange processes related to vinyl and ring‐opening polymerization
Authors: Penczek Stanislaw , Szymanski Ryszard
Published: March 2011

It has previously been proposed (Ref. 1) that in the cationic vinyl polymerizations, proceeding with termination due to the collapse of ion pairs, addition of bases increases “livingness”, because of the fast convertion of the otherwise dead (within the time of polymerization) covalent species into the onium ions; these, in turn, fast convert into carbenium ions, the actually propagating species.

Equilibria between carbenium ions (CH3OCH2+A− has been used as a model) and their onium counterparts ((CH3)2O taken as a model base) as well as between covalent species (CH3OCH2OSO2CF3) and the corresponding oxonium ion (with a (CH3)2O ligand) have been studied by dynamic 1H and 19F NMR. Total ionization of methoxymethyl triflate (CH3OCH2OSO2CF3) has been shown to increase indeed from 104 (‐10°C) to 106 (‐70°C) times when 1,0 mol·L−1 of (CH3)2O is added.

Although this model system better describes polymerization of cyclic acetals than that of vinyl ethers, it shows at least qualitatively the importance of bases in ionization of covalent species, which may be responsible for reinitiation in the cationic polymerization of vinyl ethers.
Synthesis of functionalized poly(1,3‐dioxolane)
Authors: Franta E. , Kubisa P. , Kada S. Ould , Reibel L.
Published: March 2011

Classical initiation induces polymerization through cyclic tertiary oxonium ions which are responsible for the formation of an important quantity of cyclic oligomers. The activated monomer mechanism, i.e. polymerization in the presence of a diol, has been successful in the case of some substituted oxiranes such as epichlorohydrine and propylene oxide. It has also been used in the case of cyclic acetals [1,3‐dioxolane (DXL) and 1,3‐dioxepane (DXP)] and allows the preparation of dihydroxylated homopolymers as well as that of triblock copolymers. It was nevertheless shown that transacetalization leads to complications at the onset of the reaction. In order to shed some light on the reactions involved, we used a monoalcohol ‐ methanol ‐ instead of a diol. The products were separated and characterized: a monoadduct (methanol‐DXL) was observed, confirming the occurence of the active monomer mechanism, but dimethoxymethane was also observed, evidence of transacetalization between methanol and DXL. It was shown that fast equilibration takes place between the following compounds: (methanol + DXL), (monoadduct of methanol and DXL), (dimethoxymethane + ethyleneglycol).

When p‐isopropenylbenzyl alcohol was used, it was possible to prepare macromonomers, i.e. poly(DXL) chains carrying polymerizable double bonds at their ends. Nevertheless because of the transacetalization reaction described above, a mixture of products was obtained.
Furan chemistry and ionic polymerization: Mechanisms and structures
Authors: Gandini Alessandro , Salon Marie Christine , Choura Mekki , El Gharbi Rachid , Amri Hilmi , Hui Zuen
Published: March 2011

The polymerization of furanic monomers using cationic and anionic initiators often leads to peculiar responses due to the specific chemistry of the heterocycle. The understanding of these mechanisms can help minimizing the problems encountered or, better still, exploiting them to synthesize novel macromolecular structures. The examples given here comprise the preparation of block copolymers and functionalized, polyconjugated or telechelic oligomers, the investigation of colour‐forming and branching reactions and the elaboration of powerful Lewis‐base resins.
Cationic polymerization of ϵ‐caprolactone in the presence of diols via activated monomer mechanism
Authors: Rozenberg B. A.
Published: March 2011

The kinetics of noncatalytic and catalytic interaction of ϵ‐caprolactone (ϵ‐CL) with a variety of diols in the presence of onium‐type catalysts as well as the resulting products structure were investigated. The phenomenon of the direction change of the lactone ring opening during the interaction with hydroxyl‐containing compounds of different functionality was discovered. The features of the reactions investigated were discussed and their kinetic parameters were determined.
Copolymerization of β‐butyrolactone and β‐benzyl malolactone with aluminoxane catalysts
Authors: Zhang Yan , Lenz Robert W.
Published: March 2011

Poly (β‐hydroxylbutyrate‐co‐benzyl β‐malolactonate), (P‐HB‐co‐BML) copolymers, were prepared by the ring‐opening copolymerizations of β‐butyrolactone (BL) and benzyl β‐malolactone (BML) with several alkyl aluminoxane catalysts, including ethylaluminoxane (EAO), methylaluminoxane (MAO), and isobutylaluminoxane (IBAO). The copolymers had very broad molecular weight distributions with weight average molecular weights, M̄w, greater than 200,000. The products were fractionated by solubility into acetone‐soluble and insoluble copolymers. The former were random, atactic copolymers while the latter were stereoblock copolymers. Random, atactic copolyesters of these two monomers were also obtained with the diethylzinc‐water, ZnEt2‐H2O (0.6:1), and the (5,10,15,20‐tetraphenylporphinato)aluminium chloride, TPPAlCl, catalysts. The copolymerization reactions with the latter two catalysts gave much higher yields (up to 98%) and better control of both the copolymer compositions and the molecular weight distributions, but these copolymers had M̄w values of only 20,000 or less. The copolymer tacticities and comonomer sequences were determined by 13C NMR spectroscopy.
Novel ring opening polymerization induced by alkali metal anions
Authors: Jedliński Zbigniew
Published: March 2011

Novel homogeneous initiation systems consisting of organic alkali metal complexes: Me+/Ligand, Me− enable synthesis of “living” tailor made polymers and copolymers promising materials for engineering and biomedical applications. The mechanism of this polymerization has been elucidated.
Anionic polymerization of arylbismuth, lead and tin derivatives of styrene and α‐methylstyrene
Authors: Ignatious Francis , Delaviz Yadollah , Cabasso Israel , Smid Johannes
Published: March 2011

Styryl‐ and α‐methylstyryldiphenylbismuth (I and II, respectively), and styryl and α‐methylstyryltriphenyllead and the two corresponding tin‐containing monomers (III, IV, V and VI, respectively) were synthesized. Compounds III through VI were obtained pure, but I and II contain substantial quantities of Ph3Bi and di‐ and tri‐vinyl derivatives. Homopolymers of I, III and V, as well as copolymers with methyl acrylate were synthesized radically. Monomers III, V, and VI yielded narrow MWD polymers with anionic initiators such as the potassium salt of the α‐methylstyrene dimer carbanion in THF at −80°C, while I gave a broad, bimodal MWD. Monomers II and IV did not polymerize under these conditions due to side reactions with the initiator. Glass transition temperatures, thermal stabilities and radiopacities of a number of the polymers were determined.
Functionalization during anionic polymerization of heterocycles
Authors: Kazanskii Konstantin
Published: March 2011

General approaches to the synthesis of functional polymers based on heterocycles are considered. Most attention is paid to the living anionic polymerization with functionalization through initiation or deactivation. It is shown that demands of both high molecular weight and quantitative functionalization cannot be completely satisfied. Some examples of preparing functional polyethers and polyesters are given, namely dinitrophenyl derivatives and vinyl ether macromonomers of poly(ethylene oxide) as well as methacrylate macromonomers of β‐propiolactone. Some of perspective applications of these polymers are also touched upon.
Active centre structure and the stereoregulation process in anionic polymerization
Authors: Bywater Stanley
Published: March 2011

The mechanism of stereoregulation in the anionic polymerization of butadiene and isoprene is discussed in terms of what is known about the structure of the active centres. This includes the effect of the presence of cis and trans isomers and the dynamics of their interconversion and in the isoprene case, the effect of two distinct types having 1,4 and 4,1 structures.
Quasielastic light scattering as a method for determining the distribution of relaxation times in a polymer system
Authors: Burchard Walther , Lang Peter , Bauer Jörg
Published: March 2011

Amongst other techniques, dynamic light scattering may be used to obtain molar mass distributions. The first step in this process consists in the Laplace inversion of the time correlation function that was measured by dynamic light scattering. This inversion gives a distribution of diffusion coefficients. In order to convert this distribution into the corresponding molar mass distribution, a relationship between diffusion coefficient and molar mass of monodisperse fractions has to be known. Such a relationship can be derived for linear and star‐branched macromolecules from measurements of polydisperse systems, since the polydispersity of the distributions does not change with the molar mass. The problem is more involved with randomly branched materials, since in these cases the polydispersity increases strongly as the point of gelation is approached. A procedure is suggested for deriving the diffusion‐molar mass dependence of monodisperse samples from polydisperse systems.

After an outline of this background the method is applied to the three selected systems (i) radically polymerized linear PMMA, (ii) a star‐branched microgel where monodisperse arms are attached to a microgel center and (iii) a randomly branched poly(dicyanate) sample based on bisphenol A. The results are compared with the combined column chromatography SEC/LALLS/VISC. Good agreement was found up to molar masses of about 10 millions g/mol, but systematic deviations occured in the high molar mass region. These differences result from the limitations of size permeation chromatography. Finally it is shown that the size distribution can be determind by this method, even for associates.
Dynamic light scattering for characterization of latices
Authors: Killmann Erwin , Sapuntzjis Perikles , Maier Herbert
Published: March 2011

With photon correlation spectrometry the diffusion coefficients of colloid particles in highly diluted aqueous suspensions can be measured and average diameters and polydispersities of the samples can be determined. Electrokinetic and electroviscous effects caused by polarization of the electrostatic double layer influence the diffusion of the particles. The adsorption of macromolecules at the interfaces of the particles results in an increase of the hydrodynamic diameter and a decrease of the diffusion and sedimentation coefficients. The hydrodynamic thicknesses of the polymer layers can be evaluated. The thickness values and their dependences on adsorbed amount and molar mass can only be interpreted by the existence of long tails of the adsorbed macromolecules dangling from the interface into the solution. The resulting conformation model is supported by the new theory of Scheutjens‐Fleer. Special importance have those tails for the interaction of particles and their stability and flocculation in disperse systems.
Characterization of ultrahigh molar mass, water‐soluble, cationic polyelectrolytes
Authors: Kulicke W.‐M. , Jacobs A.
Published: March 2011

Four different cationic polyelectrolytes were investigated, which are used as flocculating agents in the dewatering of sediments from Hamburg harbour. The chemical structures of these polyelectrolytes were characterized by means of IR and 13C NMR spectroscopy. The substances concerned are the two copolymers of acrylamide formed with acrylate and methacrylate esters, and the homopolymers of these esters. The charge density was determined with the aid of titrimetric methods and quantitative evaluation of IGATED 13C NMR spectra. Determination of the molar mass and steric characterization were carried out by multi‐angle laser light scattering. In order to resolve the experimental problems which arise especially during light scattering in water‐soluble cationic systems, a special method of sample preparation has been devised to remove impurities, which will be described in detail. This method involves the combination of filtration and ultracentrifugation. Evaluation of the light scattering data provided the values for the molar mass Mw′ the second virial coefficient A2 and the radius of gyration 0,5Z, which also gives information about the solution structure. By comparing the curve of the scattering function extrapolated to zero concentration with model curves and with the aid of the a exponent of the [η]‐M‐relationship, it can be seen that the polyelectrolyte has a highly expanded coil structure in salt solution. This can be primarily attributed to the steric influence of the side groups.
Counterion binding by poly(styrenesulfonate)
Authors: Nordmeier Eckhard
Published: March 2011

Binding isotherms of poly(styrenesulfonate) with hydrogen and selected alkali ions have been determined by dialysis equilibrium and dye spectroscopy, employing Pb2+, Mg2+, and Ca2+ as the competing divalent ions. The observed degrees of counterion binding, Θz, defined as the number of bound counterfoils of valence z per poly ion site‐group, agree quite well with those predicted by Manning's two variable theory. The binding preference follows the order Cs+ > Rb+ > K+ > Na+ > H+ >Li+, indicating that the binding process is of a territorial nature. Independently performed light scattering measurements show that a plot of the radius of gyration, >S z>, against the actual polyion charge gives a sigmoidal curve. This result is taken to indicate that (1) a polyion is, in general, not completely neutralized in the Θ‐state and that (2) a polyion may be not fully stretched when the polyion charge density is largest.
Characterization of star polymers in solution by small angle neutron scattering
Authors: Willner L. , Jucknischke O. , Richter D. , Fetters L.J. , Huang J.S. , Farago B.
Published: March 2011

In this paper we present the small angle neutron scattering characterization of two polyisoprene and one poly(ethylenepropylene) star polymers in solution. In the limit of low scattering vector, Q, and low concentration, φ, the molecular characteristics were determined. The molecular weights obtained are in good agreement with light scattering data. Deviations in second virial coefficients are due to a difference in solvent quality. Radii of gyration of the stars are well determined by the use of Kratky plots as is shown by the good agreement with average values of Zimm and Guinier analysis. Additionally, some thermodynamic properties were investigated in dilute and semidilute solutions. We have found that the concentration dependence of the osmotic compressibility is influenced by an expected step at the overlap concentration in both concentration regions.
Modern methods for determining the molar mass distribution of polymers. General considerations and application to sedimentation equilibrium
Authors: Lechner M. Dieter , Mächtle Walter
Published: March 2011

A new procedure for the determination of the molar mass means Mn, Mw and Mz and of the molar mass distribution W(M) = f(M) of polymers is proposed and applied on measurements of the sedimentation equilibrium. The procedure includes the extrapolation of the experimentally determined polydisperse measurable quantity at different concentrations to zero concentration. From these values the molar mass distribution is calculated by nonlinear least squares routines of the integral equation. This method of calculation is, contrary to the inverse transformation of the integral equation, which has been used up to now, well conditioned and stable.

The proposed method has been applied to sedimentation equilibrium. In this case the reduced concentration profiles (interference optic, absorption optic) or reduced concentration gradient profiles (schlieren optic) measured at different concentrations must be extrapolated to zero concentration and followed by nonlinear regression of the integral equation Uw(X) = ∫ W(M) U(X,M) dM. Measurements on polystyrenes with different polydispersities and modalities (e.g. bimodal molar mass distributions), and on the polyelectrolytes sodium polystyrene sulfonate and polyethylene imine exhibit resonable results. The result of the investigation is, that the proposed procedure is a suitable and reasonable possibility for the determination of molar mass distribution of polymers by sedimentation equilibrium. For polyelectrolytes in particular this method is better than gel permeation or size exclusion chromatography.
Determination of molar mass distributions of poly(methacrylates) in the analytical ultracentrifuge with schlieren and UV optics
Authors: Ortlepp Bernhard , Panke Dietrich
Published: March 2011

The significance of the analytical ultracentrifuge (AUC) for industrial research has not decreased during the last decades and seems to be growing. The AUC is used for the development and for controlling the production of emulsion polymers (via measurement of particle size distributions) as well as for the determination of molar masses and molar mass distributions of polymers which cause difficulties with conventional methods like light scattering or size exclusion chromatography.

In order to speed up the principally very time‐consuming AUC measurements, our machines were equipped with multiplexers for multiple place rotors and with video systems for digital recording and processing of the schlieren images. Furthermore for measurements with the UV scanner the optical system had to be considerably improved in order to assess wavelengths down to 210 nm because of the unfavourable UV absorption of the poly(methacrylates).

The experimental methods and the data evaluation will be explained and discussed using a very high‐molecular‐weight poly(methylmethacrylate) and a cationic polyelectrolyte, viz. poly(trimethylammoniumethylmethacrylate hydrochloride), as examples.
Characterization of polyelectrolyte solutions by analytical ultracentrifugation
Authors: Ebert G.
Published: March 2011

In this paper some applications of ultracentrifugation on characterizing cationic polypeptides are reviewed. Especially the influence of α‐helix favoring, water‐structure breaking (chaotropic) anions (e.g. ClO4−) as well as that of strongly hydrated, water structure‐making anions (e.g. sulfate) on the sedimentation behaviour of (Lys)n and (Arg)n is considered. Moreover ultracentrifuge studies on the interaction between DNA and strong basic nucleoproteins (protamines) and on the solubilisation of the basic polypeptides mentioned before in reverse micelles are presented.
Molar‐mass distribution of celluloses
Authors: Saake Bodo , Patt Rudolf , Puis Jürgen , Linow K.‐J. , Philipp Burkhard
Published: March 2011

The investigation of polymers by gel permeation chromatography has become a standard method for the determination of the molecular weight distribution. In case of cellulose and pulps the samples are mostly carbanilated or nitrated in order to get them soluble in organic solvents. In this context it is important that the derivatives obtained represent the composition of the starting material. High molecular wood pulps were carbanilated and further prepared for chromatographic separation using different methods. For bleached and unbleached pulps, the influence of the refining conditions on the molecular weight distribution and on the percentage of the soluble portion of the derivatives was investigated. It could be shown that low‐molecular portions of the cellulose samples were lost applying those refining methods which included precipitation steps. For unbleached pulps, the risk existed that part of the derivatives remained insoluble and formed gel‐like particles. For some pulp samples better results could be obtained by elongation of the derivatization time. Some selected pulps were carbanilated and nitrated, and the corresponding results were compared.
CPF: Continuous polymer fractionation
Authors: Wolf B.A.
Published: March 2011

A method is presented by means of which it is possible to fractionate polymers according to their solubility on a technical scale. The CPF consists of a continuous counter‐current extraction process in which a homogeneous mixture of a molecularly or/and chemically non‐uniform high molecular weight product is divided into two portions of considerably lower non‐uniformity. The principle of the CPF is described in general terms and examples are given for the fractionation of homopolymers.
The application of the size exclusion chromatography/ viscometry technique to the determination of molar‐mass and long‐chain branching in polychloroprene
Authors: Krämer‐Lucas Helga , Ramthun Jürgen , Lucas Heinz W.
Published: March 2011

The coupling of a low‐pressure size exclusion chromatography (SEC) with a modified Ubbelohde capillary viscometer is described. This SEC/viscometry system measures the flow time of aliquot fractions (5ml) of the SEC effluent along with the refractive index change. This dual detection leads to the determination of the intrinsic viscosity as a function of the elution volume, thus allowing a precise use of Benoit's universal calibration. Moreover information of the branching factors (degree of long‐chain branching, long‐chain branching frequency) can be calculated under certain assumptions.

As an example the changes in molar‐mass distribution and branching factors during mechanical shear degradation (mastication) of special polychloroprene samples were investigated. It is shown that the SEC/viscometry system is especially suitable for the characterization of polymers with broad molar‐mass distribution and extremely high molecular tails. The data provided by this method are useful for the investigation of the viscoelastic behaviour of concentated polychloroprene solutions and for quality control of polymers in the rubber and adhesives industries.
Influence of mechanical stress on the molar mass distribution and the rheological behavior of polysaccharides
Authors: Windhab E. , Zu Höne T.
Published: March 2011

The mechanical stress acting on hydrocolloid macromolecules in flow processes may change the molecular structure, the rheological properties, affecting the technical function and thereby the properties.

This paper introduces a newly developed method for definite “mechanical stress treatment” of xanthan and guar gum. Rheological measurements (intrinsic viscosity) and chromatography (GPC) allowed the resulting rheological and structural changes to be quantified.
Characterization of polymer molecular mass distribution from rheological measurements
Authors: Fleissner M.
Published: March 2011

Various methods for the determination of molecular mass distribution from rheological measurements of polymer melts are introduced. Shear viscosity, entrance pressure loss, recoverable shear, and in particular the dynamic viscoelasticity data G' and G” are discussed as analytical tools to evaluate the molecular mass distribution. Well characterized samples and homologous series of the polymers PS, PE‐HD, PP, and PTFE were measured to check the methods. Precise and reliable results can be obtained by calculating the molecular mass distribution from the frequency dependence of the storage modulus.
Determination of molecular parameters from polymer solutions in shear flow
Authors: Link Alfred , Zisenis Mathias , Prötzl Brigitte , Springer Jürgen
Published: March 2011

A light scattering photometer with a double cylinder shear cell has been developed which allows detection not only in one plane as usual, but in a half‐spherical range around the scattering volume. The anisotropic scattering behavior of oriented and deformed polymer molecules in dilute solution was investigated. All measurements were performed on polystyrene in several viscous solvents. From measurements in the plane of flow the average orientation angle was determined. By variation of detector position and wavelength of the primary beam, the determination of all three axes of the molecular gyration space of polymer coils was possible. Compared to predictions of the well‐known dynamic theories by Kuhn, Rouse and Zimm, corresponding orientation data were found while the molecular deformation ratio shows much lower values than expected.
Determination of molar mass distribution of poly(tetrafluoroethylene)
Authors: Wu Chi
Published: March 2011

High‐temperature static and dynamic laser light scattering characterization of polytetrafluoroethylene in perfluorotetracosane has been accomplished after solving the following experimental difficulties: (1) constructing a high‐temperature laser light scattering spectrometer which can be operated at a temperature as high as 340 °C, (2) developing a new all‐glass apparatus for dissolving and filtering, (3) measuring the refractive index increment of polytetrafluoroethylene in perfluorotetracosane at 325 °C, and (4) establishing a scaling relation between the molecular weight (M) and the translational diffusion coefficient at both infinite dilution and the zero scattering angle from only two broadly distributed polytetrafluoroethylene samples so that we can convert the translational diffusion coefficient distribution to the molecular weight distribution. This paper presents a summary of our published results of the characterization of poly(tetrafluoroethylene), which emphasizes the experimental details of high‐temperature laser light scattering and the principle of the transformation from a translational diffusion coefficient distribution to a molecular weight distribution.
Molecular mass determination in the liquid crystalline state ‐ lyotropic cholesteric phase of a cellulose derivative
Authors: Zugenmaier Peter , Siekmeyer Maria
Published: March 2011

Lyotropic cholesteric phases of cellulose derivative/solvent systems exhibit a reflection wavelength or supermolecular helicoidal pitch dependency on molecular mass besides the well known variation of the pitch by temperature and concentration. This observation allows a molecular mass determination by spectroscopic means (UV/VIS‐, ORD‐, CD‐spectra) or by an evaluation of the colours seen in a polarizing microscope or by a direct measurement of the pitch with the Cano‐Grandjean technique.
Beyond the born approximation. The case of very long polymer chains adsorbed at an interface
Authors: Guiselin O. , Jannink G. , des Cloizeaux J.
Published: March 2011

Two experimental evidences are discussed of the reflectance discontinuity associated with very long adsorbed polymer chains.

The anomalous low reflectivity is compared to the Ramsauer‐Townsend effect in the scattering of slow electrons by rare‐gas atoms.
Adsorption of polymer solutions on heterogeneous surfaces
Authors: Joanny J. F. , Andelman D.
Published: March 2011

We discuss the adsorption of polymer solutions on chemically heterogeneous surfaces. Two types of heterogeneities are considered, annealed and quenched. In both cases, the disorder increases the adsorption. For a same adsorption strength, the adsorbed amount of polymer is higher on an annealed surface than on a quenched surface. The adsorption on an annealed surface can induce a two‐dimensional phase transition on the surface.
Nonlinear kinetics of spinodal decomposition, and dissolution of inhomogeneities formed by spinodal decomposition in polymer blends
Authors: Akcasu A. Ziya , Erman B. , Bahar I.
Published: March 2011

Nonlinear kinetics of both spinodal decomposition at early stages, and the dissolution of homogeneities formed during spinodal decomposition, is studied. Variation of the scattering intensity during a complete cycle consisting of a step temperature change from T1 in the one‐phase region to T2 in the two‐phase region, a period of spinodal decomposition followed by a temperature drop from T2 back to T1, and the subsequent relaxation to the original equilibrium state, is investigated at various wavenumbers. Step temperature changes within one‐phase region are also investigated.
Ordered structure of block polymer/homopolymer mixtures, 4. Vesicle formation and macrophase separation
Authors: Koizumi Satoshi , Hasegawa Hirokazu , Hashimoto Takeji
Published: March 2011

Self‐assembled structures in solvent‐cast films of binary mixtures of poly(styrene‐block‐isoprene) (SI) and homo‐polystyrenes (HS) were studied as a function of rs, the ratio of molecular weights of HS and polystyrene block (PS) in SI and of wHS, the weight fraction of HS. For rS<1 (a criterion for “wet brush”), HS tends to be solubilized into the microdomain of PS and to swell the PS chains, causing a change in microdomain morphology with long‐range order. Spherical microdomains composed of polyisoprene block (PI) dispersed randomly in the matrix of HS and PS (“spherical micelles”) are formed at the limit of high wHS (wHS→1). For rS≳1 (a criterion for “dry brush”), HS tends either to be segregated from SI, forming a macrophase‐separated morphology (at rS>>1), or to be solubilized into the PS microdomains without swelling PS or without a significant change of a degree of swelling with wHS, if any, (at rS≌1). In the latter case, HS does not significantly affect the lamellar domains of PI for the particular SI studied here, which by itself gives alternating lamellar microdomains of PS and PI, but increases the mean distance between them. AS wHS→1, the long‐range spatial order of the PI lamellae is lost, while keeping their thicknesses constant and uniform, resulting in morphologies of lamellar, cylindrical, and spherical vesicles. The vesicular morphology was analyzed by small‐angle X‐ray scattering and transmission electron microscopy. At rS>>1 (still in the criterion of dry brush), SI and HS undergo macrophase separation, forming SI domains composed of alternating lamellae in the matrix of HS.
Le developement de l'etude de la diffusion de la lumiere et des neutrons par les polymeres a strasbourg
Authors: Benoît Henri
Published: March 2011

In this paper one recalls the history of the development of scattering studies after the first world war in Strasbourg.

Tremendous progress has been made and some examples of this progress are discussed
Static and dynamic light scattering studies of the critical behaviour of polymer mixtures
Authors: Fischer E. W. , Meier G. , Momper B.
Published: March 2011

Critical fluctuations were studied in polymer mixtures of poly(dimethylsiloxane) and poly(ethylmethylsiloxane), which exhibit an upper critical temperature at Tc ⋍ 57 °C. The measurements were performed in a broad temperature range at three compositions in the miscible region close to the coexistence line. The temperature dependence of the static structure factor S(q=0) can be described by a mean field behaviour except for temperatures in the range of 6 K above Tc. There, a turnover to an Ising behaviour is observed according to a modified Landau‐Ginzburg criterion. The mean field spinodal temperature Ts was determined by extrapolation of S(0)−1 to zero. From the Ornstein‐Zernike representation of the angular dependence of S(q), the correlation length ζ of the concentration fluctuations can be determined and leads to a critical amplitude ζ0 = lim ζ(T→∞) = 20.5 Å.

The interdiffusion dynamics described by the mutual diffusion constant D has been measured by quasielastic light scattering. It shows for the critical composition ϕc a critical slowing down as T approaches the critical temperature Tc. Furthermore, the q2 scaling of the relaxation rate of the interdiffusion dynamics changes to q3 behaviour close to Tc according to the mode coupling theory by Kawasaki.