bluuebunny/crossref_metadata_2025 huggingface dataset:
Excited state processes in photoinitiators of polymerization in microheterogeneous media
Authors: Lougnot Daniel‐Joseph , Fouassier Jean‐Pierre
Published: March 2011

A comprehensive investigation of the photopolymerization in microheterogeneous structure is carried out with a view to elucidate the role played by the excited states in the initiation process.

The radical initiation of methyl methacrylate in either anionic or cationic micelles or of acrylamide in reverse microemulsion is thus examined by UV spectroscopy, steady state photolysis and time resolved laser spectroscopy. The question of the localization of the initiator is dealt with special attention. Moreover, the influence of several parameters is also considered (concentration of reactants, incident light intensity, temperature or presence of external magnetic field).

This contribution demonstrates the importance of a general approach involving a thorough knowledge of the elementary steps of initiation in the understanding of any polymerization conducted in a microheterogeneous medium.
Kinetic and thermodynamic aspects of miniemulsion copolymerization
Authors: Delgado Joaquin , El‐Aasser Mohamed S.
Published: March 2011

Miniemulsion polymerization involves initiation of polymerization in preformed stable monomer emulsion droplets with average droplet diameter of 50–500 nm. At the end of the polymerization, only a fraction of the initial number of monomer droplets become polymer particles. The emulsifier system used for the preparation of such emulsions comprises a mixture of ionic surfactant and a fatty alcohol or long chain alkane (termed cosurfactant). The cosurfactant is essential for the formation of stable emulsion droplets and in addition it plays an important role in the interparticle monomer transport.

Kinetic results are presented on conventional emulsion and miniemulsion copolymerization of different pairs of monomers, showing the main differences for both processes. These differences were related to the particle formation mechanism and the influence of the cosurfactant in the miniemulsion process.

A theoretical model was developed, based on mass balances and equilibrium thermodynamics, which was found to describe accurately the experimentally generated data on comonomer distribution during the course of the copolymerization process and the interdroplet mass transport process.
Non‐seeded semi‐continuous emulsion polymerization
Authors: Šňupárek Jaromír , Skoupil Jan , Podzimek Štêpán , Kaštánek Alois
Published: March 2011

Semi‐continuous emulsion polymerization of acrylic monomers was investigated from the point of view of the particle growth. In the process no seed latex was used and the monomers were fed in an emulsion form. Oscillations of surface tension and particle number indicated a periodical generation and flocculation of particles during the polymerization. Investigation of particle size and molecular weight changes in the first tens of seconds of polymerization has shown that the coagulation process proceeds even in the earliest stage of the polymerization. Initial emulsifier concentration in the reactor strongly affects the particle growth and the final particle number.
Emulsion polymerization in the presence of polymerizable emulsifiers and surface active initiators
Authors: Tauer Klaus , Goebel Karl‐Heinz , Kosmella Sabine , Stähler Katrin , Neelsen Jens
Published: March 2011

A survey is given of recent developments in emulsion polymerization regarding improved auxiliary materials, e.g. vinyl tensides and surface active initiators. Results of the emulsion polymerization of styrene are presented with 3‐(alkyloxycarbonyl‐acryloyloxy)propanesulfonates (2) as polymerizable emulsifiers and with surface active azo initiators. The results show, that the content of water soluble surface active compounds in the latexes can be reduced. Investigations of the molecular weight of the polymers show the great importance of the initiator‐emulsifier system. Azo initiators leading to higher molecular weights than persulfate. Under the same conditions the highest molecular weights were obtained with a surface active azo initiator.
Grafting of polyethylene powder by vinyl monomers in heterogeneous systems
Authors: Bartuš Ján , Beniska Jozef , Macho Vendelín
Published: March 2011

Polyethylene powder bearing hydroperoxide groups was used for grafting of different monomers in aqueous and nonaqueous media. Polymerization of methyl methacrylate in the matrix of photooxidized polyethylene proved to be a sensitive method for detection of early stages of photodegradation. A new redox‐initiation system was developed for grafting of vinyl chloride onto hydroperoxidized polyethylene powder.
Polymerization in inverse microemulsion
Authors: Vašková Viera , Juraničová Viera , Bartoň Jaroslav
Published: March 2011

Homopolymerization of acrylamide as well as that of methyl methacrylate and the copolymerization of acrylamide with methyl methacrylate and/or styrene in inverse microemulsion toluene/water 10: 1 by weight have been studied. Water‐soluble ammonium peroxodisulfate, partially water‐soluble 2,2′‐azobisisobutyronitrile, and oil‐soluble dibenzoyl peroxide were used for initiation of these polymerizations at 60°C. Redox initiation system consisting of ammonium peroxodisulfate and tetramethylethylenediamine has been used for an effective initiation of the reactions studied at 30°C. Polymerizations in inverse microemulsions were found start in the interlayer oil macrophase/water microphase. The initial rates of copolymerizations reactions studied depended only on the comonomer mixture composition. The type of the initiator used affected only the exhibited inhibition period.
Polymerization of micelles under irradiation with UV light
Authors: Arai Kenichiro
Published: March 2011

Micelle formation behavior of sodium salts of fatty acids containing double bond at the chain end, sodium 10‐undecenoate (Na‐10‐U) and sodium 8‐nonenoate (Na‐8‐N), was examined with measurement of electric conductivity of their aqueous solutions, and the plot of the electric conductivity against the concentration for each fatty acid was found to show two break points; at 0,044 and 0,12mol/1 for Na‐10‐U and at 0,16 and 0,44 mol/1 for Na‐8‐N. The similar behaviors of the aqueous solutions were also found with the measurements of the maximum amount of solubilized benzene into the aqueous solution and of the solution viscosity, and the concentrations corresponding to the break points were assumed to be first and second critical micelle concentrations (CMC's), respectively. Polymerization of the sodium salts under irradiation with UV light was investigated. For each fatty acid, the amount of the obtained polymer was very small at very low concentrations of the fatty acid, but it increased rapidly with increasing concentration of the monomer at concentrations higher than the first CMC and then mildly at the concentrations higher than the second CMC. Number‐average degrees of polymerization of the polymers obtained were measured with a gel permeation chromatography technique and found to be up to 13 for Na‐10‐U and 8,5 for Na‐8‐N.
Chain transfer reactions in emulsion polymerization of butadiene/styrene
Authors: Wendler Karin , Nghiep Phan Hong
Published: March 2011

Calculation of regulating index r from M̄W values determined by experiments is proposed. The calculation is based on the assumption that the M̄W values only depend on the conversion and the regulating index in emulsion polymerization. On this basis the calculation of regulator concentration in the latex particles was also possible. M̄W values calculated in this way and experimental M̄W values show good agreement.
One‐shot block copolymerization
Authors: Saegusa Takeo , Chujo Yoshiki , Aoi Keigo , Miyamoto Masatoshi
Published: March 2011

This paper describes a new method of the preparation of block copolymer, in which a mixture of two monomers is subjected to polymerization (simultaneous feeding) by the aid of an initiator. The new method is performed with the polymerization of a family of 2‐oxazolines, which proceeds via electrophilic propagating species, cation or covalent bond having electrophilic reactivity. The key to the block copolymer formation with one‐shot feeding of monomers is the difference of reactivity of polymerization (nucleophilicity) between the two monomers. First the monomer of higher reactivity is polymerized to completion, and then the monomer of decreased reactivity is polymerized starting from the propagating species of the first polymerization. For the high selectivity of the production of block copolymer, each of two propagations should be of “living mechanism”. Two combinations of monomers, i.e., 2‐methyl‐2‐oxazoline/2‐(heptafluoro‐n‐propyl)‐2‐oxazoline and 2‐phenyl‐2‐oxazoline/2‐(pentafluoroethyl)‐2‐oxazoline, together with an initiator of methyl tosylate were found to follow the pattern of the new process. Block copolymer of the former monomers' combination was water‐soluble, and its aqueous solution showed an excellent value of surface tension.
Homogeneous and multiphase poly(methyl methacrylate) graft polymers via the macromonomer method
Authors: Desimone J. M. , Hellstern A. M. , Siochi E. J. , Smith S. D. , Ward T. C. , McGrath J. E. , Gallagher P. M. , Krukonis V. J.
Published: March 2011

Anionic and group transfer polymerization processes were used to synthesize controlled molecular weight methacryloyloxy functionalized poly(dimethylsiloxane) and poly(methyl methacrylate) macromonomers having a narrow molecular weight distribution and high percent functionality. These macromonomers were anionically copolymerized with methyl methacrylate (MMA) to afford poly(methyl methacrylate)‐graft‐poly(methyl methacrylate) (PMMA‐g‐PMMA) and poly(methyl methacrylate)‐graft‐poly(dimethylsiloxane) (PMMA‐g‐PDMS) polymers having not only narrow molecular weight distribution graft parts but also backbone parts. The PMMA‐g‐PDMS system was fractionated using supercritical chlorodifluoromethane to determine its chemical composition distribution (CCD). The CCD for the PMMA‐g‐PDMS copolymerized in a living manner was substantially more narrow than the free radically copolymerized material. The PMMA‐g‐PMMA system was used to study the dilute solution properties of branched homopolymers. The appropriateness of the universal calibration gel permeation chromatography (GPC) method for branched systems exhibiting long chain branching was reaffirmed.
Anionic synthesis of chain‐end functionalized polymers
Authors: Quirk Roderic P. , Yin Jian , Guo Shao‐Hua , Hu Xiao‐Wei , Summers Gabriel , Kim Jungahn , Zhu Lin‐Fang , Schock Laurel E.
Published: March 2011

The use of living, alkyllithium‐initated anionic polymerization to prepare chain‐end functionalization reactions is discussed. The scope and limitations of termination reactions with a variety of electrophilic species is illustrated for carbonation, hydroxyethylation, amination, and sulfonation. The methodology of using substituted 1,1‐diphenylethylenes to provide a general, quantitative functionalization method is outlined and illustrated with examples of phenol end‐functionalization and amination.
Group transfer and anionic polymerization: A critical comparison
Authors: Müller Axel H. E.
Published: March 2011

The mechanism of group transfer polymerization (GTP) of methacrylates in THF is investigated by using data on kinetics of homo‐ and copolymerization, polymer microstructure and molecular weight distribution. By comparison with corresponding data on anionic polymerization it is concluded that the mechanisms of monomer addition to the active chain end is very similar for both anionic and group transfer polymerization and that GTP is ionic in character. On the other hand, GTP uniquely is characterized by the existence of a catalyst exchange equilibrium. The position of this equilibrium determines the rates of polymerization, and the dynamics determine the molecular weight distribution.
On the nature of active species in cationic ring‐opening polymerization of cyclodimethylsiloxanes
Authors: Sigwalt Pierre , Stannett Vivian
Published: March 2011

Contrarily to cationic ring‐opening polymerization of cyclic ethers and of some other cyclic monomers, for which direct identification of the various types of active centres has been made in a few cases, the nature of the species active in the polymerization of cyclo‐dimethylsiloxanes is not yet known. However, some provisional conclusions about the possible mechanisms may be deduced from the wide variation in the types of products and in the kinetics observed according to either the size of the cyclic monomer (D3, D4, D5, D6) and to the type of initiation (chemically, or radiation induced).

For polymerizations with either protonic or non‐protonic initiators, made in CH2Cl2 near room temperature, the smaller cycle D3 behaves quite differently from D4, D5 and D6. D3 is more reactive in both homo‐ and copolymerizations. It gives small cycles of other types and the effect of water on the reaction may be quite different. A discussion of the data leads to the conclusion that polymer growth for most cyclosiloxanes involves activated esters, while it may occur for D3 on different sites such as oxonium or silanol groups.

Polymerization of D3, D4 and D5 initiated in bulk at 90°C by high energy radiation, in high purity conditions, has also been shown to be cationic but the active centres concentration is much lower, and the propagation rate constants much higher, than in chemically initiated polymerizations. The global rates, the monomer reactivities in copolymerization and the types of cycles are similar for D3, D4 and D5, which is attributed to propagation occurring on very reactive silicenium ions, either free or in the same solvation state.
Living polymerizations of acrylic monomers with aluminioporphyrin
Authors: Inoues Shohei , Aida Takuzo , Kuroki Masakatsu , Hosokawa Yasunori
Published: March 2011

Aluminioporphyrin was found to be an excellent initiator for the living polymerizations of methacrylates, acrylates, and methacrylonitrile. Porphinatoaluminium thiolate and enolate were effective in the dark, different from methylporphinatoaluminium which requires irradiation by visible light. The addition of pyridine was necessary for the polymerization of methacrylonitrile, which was accelerated by visible light. By using the living polymer of methyl methacrylate as initiator, block copolymers from acrylic monomers could be synthesized. A system composed of aluminioporphyrin and trialkylaluminium was found highly active for the polymerization of methacrylates.
The features of cationic polymerization of lactones under the action of onium salts
Authors: Rozenberg Boris
Published: March 2011

Results on the kinetics of polymerization of ϵ ‐caprolactone (ϵ ‐CL) under the action of quaternary onium salts with complex counterions are reported. The structure and molecular weight distribution (MWD) of polymerization products, and of the catalysts and active propagating centers were studied by gel permeation and gas chromatography, IR and UV spectroscopy, chemical and X‐ray analysis. The role of photochemical transformations at ϵ ‐CL polymerization in the presence of onium salts with counterion FeCl4 was revealed. The mechanism of polymerization is discussed.
Developments in the theory of cationic polymerisation. Part IX some effects of the complex formation between cations and monomers
Authors: Plesch P. H.
Published: March 2011

The formation of complexes P+nM between a propagating carbenium ion P+n and the monomer, M, is considered from several points of view ‐ (i) Under the most usual conditions the formation of the P+nM reduces the population of ion‐pairs, P+nA−, drastically. This can account for the frequently found nil‐effect of common ion salts on the rate of attack of carbenium ions on alkenes in initiation, model reactions, and polymerisations. ‐ (ii) The formation of P+nM increases the degree of dissociation α of P+nA−, so that all the estimates of α on which kinetic schemes have been based, are too low. ‐ (iii) The very high polymerisation rates found for n‐donor monomers, say 4‐MeO‐styrene or N‐vinylcarbazole compared to styrene, may be attributable not, primarily, to a difference in rate‐constants, but to a difference in ionic population. This is because the fast P+nM is in greater excess over the slow P+nA− for more strongly complexing n‐donors than for the π‐donors. ‐ (iv) Since the nature of the P+nM is different for every monomer, a comparison of their propagation rate‐constants k+pM is hardly meaningful and valid comparisons can only be made between the k+p of the P+n. The measurement of these requires extreme conditions, either extrapolations to [P+n] = 0 and [M] = 0, or the use of highly polar solvents in which neither M nor the anion can compete with the solvent for the solvation of the P+n.
Functional polymers based on high hydrophilicity of poly(2‐methyl‐2‐oxazoline)
Authors: Saegusa Takeo , Chujo Yoshiki
Published: March 2011

Polymers of the family of 2‐substituted 2‐oxazolines have the general structure of poly(N‐acylethylenimine), whose hydrophilic/lipophilic properties vary according to the substituent, i.e., the acyl group of the polymer. Of special interest is the polymer of 2‐methyl‐substituted monomer, which has a strong affinity for water. Another useful feature of the 2‐oxazoline family is the fact that its polymerization reaction is quite clean without disturbance by chain transfer and termination. On the basis of the above characteristics, three kinds of novel materials of functional polymers have been explored:

Non‐ionic polymeric surfactants.

Non‐ionic hydrogels.

Block copolymer with silica gel: Organic/inorganic polymers hybrids.
Copolymer sequence control by ring‐opening polymerization of prestructured cyclic monomers
Authors: Cho Iwhan
Published: March 2011

In search for the new synthetic methods which may lead to the copolymers of controlled mer sequences, several new carbocyclic and heterocyclic monomer systems such as 1,1‐disubstituted 2‐vinylcyclopropanes, 1‐(p‐anisyl)‐2‐vinylcyclopropanes, substituted 3,4‐dihydro‐2H‐pyrans, substituted 4‐vinyl‐2‐oxetanones and α‐vinyl cyclic sulfones were synthesized and their polymerization behaviors were investigated. And other promising monomer systems were also examined.
Synthesis of chitin derivatives and their metal complexes
Authors: Choi Kyu Suk
Published: March 2011

Thiosemicarbazide, phosphoric acid and amidoxime derivatives of chitosan were synthesized and their ability for metal ion adsorptions was discussed. Thiosemicarbazide derivative, synthesized by treating chlorodeoxychitosan with ammonium thiocyanate followed by treatment with hydrazine, was considered to have cross‐linked network structure. Phosphoric acid derivative containing both N‐phosphonic acid and phosphoric acid groups was synthesized by cyanoethylation of chitosan using acrylonitrile, followed by treatment with hydroxylamine. These derivatives were found to adsorb effectively infinitesimal concentration (ppb order) of uranyl ion in seawater. Stability constants of some metal ion chitosan chelates were determined. To improve the selectivity in the adsorption of metal ions, a novel method utilizing metal ion as a template was adopted, and the results are discussed.
Sequentially ordered, thermotropic aromatic copolyesters: Synthesis and comparison of their properties with random copolyesters
Authors: Jin Jung‐Il , Chang Jin‐Hae , Jo Byung‐Wook , Sung Ki‐Youn , Kang Chung‐Seock
Published: March 2011

Synthetic methods of aromatic copolyesters having ordered comonomer sequence are described. In order to obtain a regular sequence copolyester, one first has to prepare a dimeric or trimeric compound with a predesigned sequence via a multistep route and then polycondense it with another difunctional compound. Low reaction temperature is required to avoid the occurrence of undesired interchange reactions that would lead to randomization of the comonomer sequence. Sequentially ordered copolyesters exhibit significant differences in thermal transitions, crystalline properties, and occasionally even in liquid crystallinity when compared with the properties of the corresponding random copolyesters. According to the preliminary results randomization in comonomer sequence of sequentially regular aromatic copolyesters above their melting points is rather rapid.
Synthesis of novel conducting polymers by cyclopolymerization of dipropargyl derivatives
Authors: Choi Sam‐Kwon
Published: March 2011

Cyclopolymerization of dipropargyl derivatives which leads to new conjugated polymers was examined by various transition‐metal catalyst systems. The highly colored polymers with average molecular weights of 10000–47000 were soluble in common organic solvents. Poly(dipropargyl derivatives) which possess polyene structures having cyclic recurring units in the polymer backbone, have been investigated for their physical properties such as solubility, the nature of doping process, electrical conductivity, and oxidation stability.
Membrane research and development activities in Korea
Authors: Kim Un Young , Kim Jae‐Jin
Published: March 2011

In this paper, the general status of membrane research and development activities in Korea is described. Korean membrane markets are also reviewed. Some results of basic researches are summarized and government ‐ sponsored research projects are introduced briefly.
Polymer membranes with selective gas and vapor permeation properties
Authors: Strathmann H. , Bauer B. , Kerres J.
Published: March 2011

Since many years synthetic membranes have been used in reverse osmosis or ultrafiltration for the separation of aqueous mixtures. More recently the separation of gases and vapors by selective membrane permeation has gained significant technical and commercial interest. The recovery of hydrogen from petrochemical purge gases and ammonia production processes or the removal of CO2 from natural gas by selective membrane permeation are today state of the art procedures. The recovery of organic solvents from waste air streams is another very promising application of synthetic membranes. In this paper the main parameters determining the performance of a membrane in gas and vapor separation are described. The requested intrinsic properties of the polymer to be useful as a barrier for a selective gas and vapor transport are discussed. The preparation of appropriate membranes is described. Their performance in practicle applications is illustrated in selected examples.
Polyurethane IPN membranes
Authors: Kim G. S. , Lee J. H. , Lee Y. K. , Kim S. C.
Published: March 2011

Hydrophilic PU and hydrophobic PS IPN membranes were prepared and the effect of the synthesis pressure on the pervaporation characteristics of ethanol water mixture was evaluated. Cationic/anionic IPN membranes were prepared from the cationic PU and the anionic acrylic copolymer, and the effects of the composition and the ionic concentration on the permeation characteristics were analyzed. The gas (oxygen and nitrogen) transport of the IPN membranes of PU/PS were also examined. The effect of synthesis temperature and composition of the IPN membranes were analyzed.
Photosensitization of poly(vinyl alcohol)/cerium complexes to produce ion‐exchange resins by graft copolymerization
Authors: Hill David J.T. , Mcmillan Alison M. , O'Donnell James H. , Pomery Peter J.
Published: March 2011

Acrylamide can be graft copolymerized onto poly(vinyl alcohol) in aqueous solution with initiation by cerium(IV) under acid conditions in order to produce an appropriately functionalized polymer directly or by subsequent chemical modification. Initiation proceeds through the decomposition of a complex between the PVA1 and Ce(IV) and under normal conditions occurs only through the 1, 2‐glycol units in the PVA1. Illumination by light in the absorption wavelength range of the complex accelerates the rate of graft copolymerization. Moreover, initiation now proceeds through the 1,3‐glycol units.
Recent development in photosensitive resin in Korea
Authors: Hong Sung Il
Published: March 2011

The aim of the review is to introduce some recent progress in the photosensitive polymers in Korea. It is focused to review the research works performed recently in this country, especially in the academic world. As photosensitive polymers, cinnamates of various polymers, azides and diazido compounds, oximeesters or oxime containing polymers, and some other sensitizing polymers were treated, and also sensitizing effects were evaluated.
Biodegradable polymeric matrix for long‐acting and zero‐order release drug delivery systems
Authors: Li You‐Xin , Feng Xin‐De
Published: March 2011

Three types of biodegradable triblock copolymers, ABA, ABC and ACB, where A is polycaprolactone (PCL), B is polylactide (PLA) and C is polyglycolide (PGA), were used as matrix to test their controlled release behavior of Levo‐Norgestrel in the form of microsphere. It was verified that the overall release kinetics changes from in vitro first order to zero order when the percentage of PCL segments in all of the block copolymers decreases from 85 % to 60 −65 % with a long‐acting release time of 5 months or more. It is ascribed to the two release mechanisms, the diffusion release, contributed by the PCL segment, and the erosion‐caused release by PLA or PGA segment. At a certain ratio of segments the two release ways make a compromise to a constant rate of release, i. e. a zero‐order kinetics in these multiphase block copolymers.
Stimuli sensitive polymers for drug delivery systems
Authors: Kwon I. C. , Bae Y. H. , Okano T. , Kim S. W. , Berner B.
Published: March 2011

Temperature sensitive and electric field sensitive hydrogels were prepared for use in modulated drug release systems. Crosslinked poly(N‐isopropyl‐acrylamide) and its networks, modified with hydrophobic components by copolymerization or by interpenetrating polymer networks (IPNs) formation, were utilized as temperature sensitive hydrogels. Indomethacin (a model solute)‐release from polymer matrix and permeation through polymer membrane demonstrated “on‐off” regulation with temperature fluctuation. This was the result of polymer surface properties rather than bulk swelling, as temperature was changed past the swelling transition temperature range of the polymer. The on‐off regulation in an electric field was also obtained with a positively charged solute (Edrophonium chloride) release in distilled‐deionized water from a matrix of crosslinked poly(2‐acrylamido‐2‐methylpropanesulfonic acid‐co‐butyl methacrylate). This was attributed to the ion exchange between Edrophonium ion and protons produced at the anode. The swelling changes produced by local pH or ionic strength changes affected non‐charged solute release.
Design of target‐specific polymer conjugates and complexes for biomedical application
Authors: Kabanov Victor A.
Published: March 2011

The new effective method of synthesis of protein‐protein and protein‐water soluble linear polymer conjugates based on using of hydrated reversed micelle systems is described. Such conjugates are of a great potential importance in particular for biomedical applications. One example represents a new family of receptor specific screened immunotoxins (respecrins) whose toxic effect develops only with respect to the target but not to the other cells. Respecrin is a toxin covalently bound to a target‐equivalent macromolecule then complexed with an antitarget antibody. Another example relates to artificial immunogenes which are conjugates of antigens or haptenes with non‐natural linear polyelectrolytes. The general mechanism of a search and recognition of target immune cells by such conjugates in vivo was confirmed in model experiments using cell‐mimetic particles. It is also shown that complexing of the DNA plasmide with the carbochain polycation results in formation of membrane active polycomplex much more active in transformation of competent cells than pure plasmide.
Surface modification of polyurethane for enhanced blood compatibility
Authors: Kim Young Ha , Han Dong Keun , Jeong Seo Young , Ahn Kwang‐Duk
Published: March 2011

Surfaces of commercial polyurethanes (PUs) were modified by poly(ethylene oxide) (PEO) grafting and/or heparin immobilization or sulfonation to investigate the effect to antithrombogenicity. The hydrophilicity of the modified PUs surface was significantly increased. All the PEO‐grafted PU surfaces displayed very little platelet adhesion and activation. The coupled heparin or sulfonate at the end of PEO exhibited anticoagulant activity to extend APTT. Lowering in vitro platelet adhesion of modified PUs led to a prolongation in the ex vivo occlusion time. In particular, the sulfonated PU‐PEO surface showed the most enhanced blood compatibility due to the synergistic effects of PEO and SO3 groups.
Movement of dopants in redox reaction of electro‐conductive polymers
Authors: Ko J. M. , Rhee H. W. , Kim C. Y.
Published: March 2011

Polypyrrole, formed in an organic solvent, shows higher density and better quality in electrical conductivity and mechanical strength than that formed in water. On electrochemical reduction in an aqueous system the laurylsulfate anion, used as dopant, sticks to the polymer. During reduction a cation moves into the polymer and on oxidation it leaves the polymer. The anion, however, leaves the polymer on reduction in an organic solvent system and cannot penetrate into the polymer on re‐oxidation. The redox reaction in the aqueous system reveals a surface reaction process, while the reaction in the organic solvent system undergoes a diffusion‐controlled process. This penomenon is consistant with the results of the ion concentration profile.
The two‐dimensional NMR spectroscopy of macromolecules
Authors: Bovey Frank A. , Mirau Peter A.
Published: March 2011

Two‐dimensional (2D) NMR is a versatile technique which exists in many versions. Two broad classes of 2D techniques are (1) correlated spectroscopy and (2) J‐resolved spectroscopy. The first of these may be divided into two further subdivisions: COSY, which permits correlations of resonances via J‐coupling, and NOESY, which allows direct measurement of intenuclear (usually interproton) distances by the nuclear Overhauser effect. COSY greatly facilitates the interpretation of complex spectra and spectral interpretation in terms of stereochemical sequences is placed on a firmer foundation. NOESY provides direct information concerning the local conformations of polymers in solution. By use of J‐resolved 2D NMR, we can separate J‐couplings and chemical shifts on different axes and thus achieve a degree of resolution of both these parameters far beyond what is attainable in the 1D spectrum. Finally, we may combine correlated and J‐resolved spectroscopy and achieve the benefits of both in 3D NMR, in which the 2D cross peaks exhibit J‐coupling fine structure. These techniques are illustrated for a variety of polymers including poly(methyl methacrylate), poly(vinyl fluoride), poly‐y‐benzyl L‐glutamate, and poly(propylene oxide).
Frequency dependence of nuclear magnetic resonance parameters in poly(methyl methacrylate)
Authors: Chûjǒ Riichirǒ
Published: March 2011

Using 26 NMR spectrometers, the Research Group on NMR, the Society of Polymer Science, Japan observed the 1H NMR chemical shift, resolution, and signal intensity; 13C NMR chemical shift, resolution, and signal intensity; the effect from initiator fragment signal; 1H spin‐lattice relaxation times; 13C spin‐lattice relaxation times; and 13C nuclear Overhauser enhancement of radically polymerized poly(methyl methacrylate). Excellent reliability was found after comparison between the data from different spectrometers. Molecular motion of this polymer was analyzed with a term of 3τ model.
Nuclear magnetic relaxation in polyelectrolyte solutions
Authors: Leyte J. C.
Published: March 2011

Some applications of nuclear magnetic relaxation in the investigation of aqueous polyelectrolyte solutions are discussed. The main topics are solvent dynamics, counterion ‐ polymer interaction, main chain mobility and diffusion.
Mesomorphic phases of poly(DI‐n‐alkylsiloxane)s
Authors: Möller Martin , Siffrin Stefan , Kögler Gerhard , Oelfin Dieter
Published: March 2011

The phase behavior of poly(dialkylsiloxane)s which are symmetrically substituted with ethyl, n‐propyl, and n‐butyl side groups has been investigated by solid state NMR and differential scanning calorimetry. All polymers exhibit disordering transitions before isotropization. The observation of conformational and motional changes is correlated to the different thermal transitions. Diffusive rotation of the chain segments around the molecule long axis is indicated by 29Si‐NMR below the isotropization transition. The remarkably fluid character is explained in part by the coexistence of anisotropic and isotropic motional states of the ‐OSiEt2‐ segments. Molecular motion below the upper disordering transition is restricted but still fast with respect to the 29Si‐NMR time scale. Long range reorganization processes have to be considered to explain the difference between α2‐PDES and β2‐PDES. The stepwise disordering at the onset of different motional processes, which results in the formation of a columnar liquid crystalline phase of these highly flexible chain molecules, is discussed with respect to the amphiphilic constitution of the molecules having an inorganic backbone substituted by organic side groups.
Segmental and crosslink point motion in networks
Authors: Dickinson L. C. , Chien J.C.W. , MacKnight W. J.
Published: March 2011

13C‐ and 31P‐NMR spin lattice relaxation in the rotating frame have been measured on a series of networks prepared from monodisperse and deliberately bimodal poly(propylene glycols) (PPG) crosslinked with tris(4‐isocyanatophenyl) thiophosphate. The T1pC minima correspond to loss maxima in the DMTA (Dynamic Mechanical Testing) measured at 10Hz. The T1pP minima fall at higher temperatures than those of T1pC for the same network indicating that these crosslinks lag the segments in frequency of motion at a given temperature. The carbon relaxation is biphasic below Tg of the segments indicating two relaxation domains which we assign to bulklike PPG segments and PPG segments proximal to he crosslink. Lineshape analysis by a diffusional model indicates crosslink reorientation is not isotropic until well above Tg. Relaxation and lineshapes for the bimodal networks indicate that junctions are not uniformly plasticized by the segments.
NMR and infrared study of crystalline forms of stereoregular poly(methyl methacrylates)
Authors: Schneider Bohdan , Spêváček Jiří , Straka Jaroslav , Štokr Jan
Published: March 2011

13C CP MAS NMR spectra and infrared spectra of amorphous and semicrystalline samples of stereo‐regular poly(methyl methacrylates) were measured. The spectra of the crystalline phases of isotactic PMMA, syndiotactic PMMA and of the so‐called stereocomplex PMMA were obtained by a computer difference technique. These spectra are discussed in relation to the conformational structure of the studied systems.
NMR microscopy ‐ limitations and applications in material sciences ‐
Authors: Kuhn W. , Eichhoff U.
Published: March 2011

Alongside the numerous applications of NMR spectroscopy in analytical chemistry, materials sciences and morphological studies by magnetic resonance imaging (MRI), NMR microscopy makes possible a whole new range of applications in materials sciences such as the development and non destructive testing of polymers and ceramic materials. This includes imaging of microscopic structures and structural changes in such materials. The contrast in the images is determined by the NMR specific parameters chemical shift δ, spin density ρ, spin lattice relaxation time T1, spin spin relaxation time T2 and spin lattice relaxation time in the rotating frame T1ρ. The numerous well developed methods available make it possible to study dynamic processes by fast imaging, the measurement of diffusion constants of solvents or liquids, the mobility of fluids in polymers or ceramics or the three dimensional evaluation of pore sizes in porous materials.
Multifrequency ESR and ENDOR studies of ionomers
Authors: Schlick Shulamith
Published: March 2011

We describe methods for determining the local environment of cations and the process of ionic clustering in ionomers, using electron magnetic resonance spectroscopy. The distance between Cu2+ cations in perfluorinated membranes (Nafion) containing terminal sulfonic groups and swollen by water has been deduced from an analysis of ESR spectra at L (1.25 GHz), S (2.36 GHz) and X (9.36 GHz) bands, in membranes containing cupric ion concentrations in the range 1–30 percent of the total amount needed to fully neutralize the pendant acid groups. At higher cation concentrations ESR spectra indicate the presence of aggregated cations. The intercation distance determination is based on the simulation of spectra from isolated cations using distribution widths δg11 and δA11 and extraction of the residual width ΔHR, which is due to dipolar interactions. No aggregation is detected in membranes swollen by less polar solvents such as methanol, dimethylformamide (DMF) and tetrahydrofuran (THF); these results are in contrast to SAXS experiments in membranes swollen by methanol, which exhibit the “ionic peak”. Cu2+‐Cu2+ and Ti3+‐Ti3+ dimers have been detected in Nafion swollen by water, methanol, DMF and THF, and have been characterized by an analysis of the spin‐forbidden half‐field Δms=2 transition, and by computer simulations. The intercation distance in the cupric dimers, deduced from the intensity ratio of the Δms=2 and Δms=1 dimer transitions, is 5.0±0.2 Å. A model for the dimer has been proposed, which explains the crosslinking of the polymer chains by the metal cations. ENDOR signals from 1H, 2H and 19F nuclei have been detected in Nafion neutralized by Ti3+. The ENDOR results allow determination of the local environment of the paramagnetic cations, to a distance of ∼10 Å.
Photoinduced ultrafast processes in phenyl‐substituted poly(phenylenevinylene) s studied by picosecond absorption, fluorescence and conductivity measurements
Authors: Rentsch S. , Yang J. P. , Lenzner M. , Bergner H.
Published: March 2011

Transient absorption, fluorescence and conductivity were measured on phenylated poly(phenylenevinylene)s (P‐PPV) in solution and in film after UV pulse excitation in picosecond region. Transient absorption bands of distinguishable rise and decay kinetics were observed. The fluorescence shows two exponential decay times in ps‐ and ns‐region, resp, Transient photoconductivity also exhibits a ps‐ and a ns‐time component. The mobility of carriers was estimated.
Spin dynamics in conducting polymers
Authors: Mizoguchi Kenji
Published: March 2011

It is demonstrated that spin dynamics study is useful for what kinds of systems, on what theoretical basis of analysis, with what kinds of techniques and to get what kinds of information, showing a nice example of polyacetylene. Usefulness of electron spin resonance (ESR) study is stressed especially in a wide frequency range from 5 to 24000 MHz.
Dielectric properties of conducting polymers
Authors: Kremer F. , Rühe J. , Meyer W. H.
Published: March 2011

The frequency and temperature dependence of the complex conductivity σ* is measured for several different conducting polymeric systems: (i) for poly(p‐styrene sulfonate) salts of polypyrrole, (ii) for salts of poly(cycloalkyl[c]pyrroles) and for ion conducting polymers such as ionenes. The results are discussed in terms of a modified Debye‐Hückel‐Falkenhagen theory.
Conductive thin films and membranes their scientific foundations and industrial applications (pt. 2)
Authors: Bahador Sardar Khan
Published: March 2011

Beside the fundamental studies on polymerization processes, conduction mechanism and chemical stability of conductive polymers, attention was focused on the application feasibilities of these materials. Although the major application of conducting polymers was suggested in several types of advanced energy conversion and storage devices, their specific features such as plasticity, thin film fabrication with ease, chromatic contrast and the like offers ample possibilities for the utilization of such materials in many instances of modern technology. Consequently, among several conductive polymers investigated, in this communication, as part of a project work, perfluorosulfonate ionomer (e.g. Nafion) and polyaniline modified electrodes were taken into account. Typical examples of application, such as in fuel cells and chlor‐alkali membrane cells etc., are provided. Characterization and performances of the material as well as the kinetics and mechanism of the corresponding reactions are briefly considered. In the case of polyaniline, the electropolymerization process, characterization of the product film, its application in high energy density Li‐batteries together with the kinetics and mechanism of polymer doping, the charge‐discharge reactions, including the parameters affecting the cell efficiencies, are discussed in some details. Merits and problem of the process and corresponding devices are pointed out. A cell having the configuration Pb/PbO2/H2SO4/PAN/Pt was constructed, accordingly various characteristics of the electrode materials and cell system are extensively discussed.
Matrix polymerization and polyelectrolyte complex formation
Authors: Rätzsch Manfred , Fanghänel Egon
Published: March 2011

We developed a model of the formation of symplexes by photoinitiated matrix polymerization. Symplexes are insoluble in water and all known solvents. They result from contrarily charged polyelectrolytes. In our model a polyelectrolyte is matrix and binder simultaneously. At the matrix a contrarily charged monomer is polymerized radically to the second polyelectrolyte. Different mechanisms are discussed for the matrix polymerization. As polymerizable monomers acrylic compounds with terminal tertiary amino group were used. Modified styrene/maleic acid copolymers served as polyanion. The influence of the composition of the components in this layers on the polymerization rate was investigated. The sensitivity of the developed photo‐material is compared with other photo‐polymerization systems and the conventional photographic materials basing on silver halogenides. A high resolution and an easy fixation result.
Holographic recording on poly(vinylcarbazole)
Authors: Kuwae Yoko , Sugawa Etsuko , Taniguchi Naosato , Kuwayama Tetsuro , Kushibiki Nobuo
Published: March 2011

A reflection type volume‐phase hologram was recorded on poly(vinylcarbazole) (PVCz) in the presence of CI4. The grating with a half‐height width of 19nm was made with an argon ion laser at 488nm or 514. 5nm. The sections of PVCz and a dichromated gelatin (DCG) hologram, responsible for the diffraction efficiency, were observed by scanning electron micrography (SEM) and transmission electron micrography (TEM). Those micrographs showed that the amplitude of the index modulation in the hologram is formed bý voids. The diffraction efficiency was simulated with the parameters observed by TEM and showed that a thin PVCz hologram film attains the same diffraction efficiency as the thick DCG sample, because of the large refractive index of PVCz.
Synthesis and electrophysical properties of doped copolymers of functional derivatives of acetylene
Authors: Zalisnaya N. F. , Davydov B. E. , Mavrenkova G. V. , Zhuravleva T. S.
Published: March 2011

WCL‐catalyzed bulk copolymerization of phenyl‐acetylene (PhA) with 3‐bromo‐1‐propyne was carried out. Soluble, colored products with different comonomer content were obtained. The copolymer structure was estimated by IR spectroscopy and elemental analysis; their molecular weight being 2000–3000. These copolymers were used to study the ability of doping with such acceptors as FeCL3, Sn(Ph)4, tetracyanobenzoquinone (TCNQ). The conductivity of the copolymers was found to increase from 10−13 to 10−3/cm with doping. Substitution of the lithium derivative of the polymer with SnCL3 for Li leads to an increase of conductivity as well.
Tailoring of polymer blends with copolymers
Authors: Hellmann G. P. , Kohl P. R. , Herth J. , Neumann H. J. , Andradi L. N. , Löwenhaupt B.
Published: March 2011

Miscibility can particularly easily be “tailored” with blends P (AxB1‐x)/P (AyB1‐y) of random copolymers and with blends P (Ax‐b‐B1‐x)/P (Ay‐b‐B1‐y) of diblock copolymers, where the blend components differ only in composition. The former class of blends is discussed in some generality, the latter only in one special example, where the components are a homopolymer (x=0) and a symmetric copolymer (y=0.5). Phase diagrams and phase morphologies are shown.
Toughening behavior of polyamide‐rubber blends
Authors: Gaymans R. J. , Borggreve R. J. M. , Oostenbrink A. J.
Published: March 2011

The impact behavior of nylon 6‐ rubber blends is studied by varying the rubber concentration (0–26 vol. %), rubber particle size (0.1 ‐ 2.0 μm) and rubber properties.

The brittle to tough transition shifts to lower temperatures by increasing the rubber concentration, decreasing the particle size and by lowering the modulus of the elastomer. With very small particle sizes, however, the transition temperature increases again.

The toughness of the blends above their transition temperature increases with the rubber concentration, but the particle size has only some effect. Very small particle sizes decrease the impact behavior.

The postulated deformation mechanism is cavitation of the rubber followed by shear deformation of the matrix.
Soluble LC polyesters and their blend behavior
Authors: Heitz Walter , Schmidt Hans‐Werner
Published: March 2011

Poly(p‐phenylene terephthalate) with substituents on the hydroquinone or on both monomer units were synthesized with the aim to obtain soluble LC polyesters. Focus was given to phenylalkyl substitution. With one phenylalkyl group in the repeating unit the polyesters are crystalline with melting points > 300°C. With two substituents the crystallinity is very low or the polymers are amorphous. These polyesters are soluble in chloroform forming isotropic solutions. Isotropic films of polyesters obtained from these solutions either crystallize or become anisotropic if heated above the glass transition temperature. The exponent in the Kuhn‐Mark‐Houwink equation is 0.95. Some of the polyesters form homogenous ternary solutions with polycarbonate. Films of the blends show additivity of modulus with respect to both components.
Rheology and morphology of polymer blends in melt and solid state
Authors: Kulichikhin V. G. , Vasil'eva O. V. , Litvinov I. A. , Parsamyan I. L. , Platá N. A.
Published: March 2011

The rheological properties of polymer mixture melts containing polysulfone and LC‐polyester have been investigated in this work in terms of the morphology and physical‐mechanical characteristics of extrudates. The perculiarities of rheological behaviour are accounted for by morphology of stream which is maintained also in solid extrudates. The reinforcement of an isotropic mixture by LC‐polymers as well as formation of an anisotropic surface layer lead to a specific change in the strength properties of compositions. An increase in strength and initial modulus was observed for blends containing not more than 10% LC‐polymer.
Formation of crazes in polymer blends
Authors: Michler Goerg H.
Published: March 2011

High‐voltage electron microscopy was used to study the micromechanical processes of deformation directly on thin deformed samples of rubber‐modified, high‐impact polymers. In these polymers the microprocesses are closely connected with the initiation and formation of crazes. Craze formation with its effects on the fracture toughness are discussed in dependence on several important morphological factors, particularly on the rubber volume content, particle diameter, and particle diameter distribution.
Zero shear viscosity in miscible polymer blends of polystyrene and poly(2,6‐dimethylphenylene ether)
Authors: Stadler Reimund , de Araujo Marco Aurelio
Published: March 2011

The dynamic viscosities of blends of high molecular weight, narrowmolecular‐weight distributed polystyrene and poly(2, 6‐dimethylphenylene ether) are studied. The zero shear viscosity ηo depends on the weight average molecular weight M̄w and on the average entanglement molecular weight M̄e in the blend according to ηo ≈︁ M̄3.4 w(blend)/M̄2.4e(blend).