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Improvement of ligand economy controlled by polymer morphology: the case of polymer-supported bis(oxazoline) catalysts.

A functionalized chiral bis(oxazoline) is used as a chiral monomer in polymerization reactions leading to homo- and copolymers of different morphology. Polymers with a high content of chiral monomer lead to enantioselectivities that are higher than those obtained with the soluble ligand, but the chiral ligand is not used in an optimal way. A hyperbranched polymer, obtained by using a hexavinyldendrimer as the cross-linker, leads to the same enantioselectivities with a more efficient use of the chiral ligand.

Catalysis↗

Bioimprinting of polymers and sol-gel phases. Selective detection of yeasts with imprinted polymers.

Coated quartz crystal microbalances were modified with a surface-imprinting process using whole yeast cells. These molded polymer and sol-gel surfaces show honeycomb-like structures as shown by atomic force microscopy. Reinclusion of cells allows a selective on-line monitoring of these microorganism concentrations in water over 5 orders of magnitude. The sensitivity to cells holds up in growth media up to 21 g/L. Even cell fragments can be detected in flowing conditions. The highly robust polymers on the sensor devices are suitable for biotechnological applications.

Gels↗

Development of biocompatible interpenetrating polymer networks containing a sulfobetaine-based polymer and a segmented polyurethane for protein resistance.

Interpenetrating polymer networks (IPNs) were prepared by the modification of a segmented polyurethane (SPU) with a cross-linked sulfobetaine methacrylate (SBMA) polymer. The IPN films that were prepared can effectively resist nonspecific protein adsorption when the distribution of SBMA units within the SPU film is well controlled, and they retain high mechanical strengths inherent from the base SPU films. Furthermore, the zwitterionic and biomimetic nature of sulfobetaine and the ease of SBMA preparation make SBMA-based materials very attractive for a wide range of applications. It is challenging to control the diffusion of highly polar SBMA into the hydrophobic network of SPU. In this study, various parameters governing the formation of IPNs containing SBMA were studied. The chemical composition depth profile of the IPN films was determined by confocal Raman microscopy. The morphology and thickness of these IPN films were examined by atomic force microscopy and scanning electron microscopy. The amount of adsorbed proteins on the IPN films was determined by an enzyme-linked immunosorbent assay. Results show that the amount of adsorbed proteins on the IPN films depends on the incubation conditions, including solvent polarity, incubation time, SBMA monomer ratio, and incubation concentration. It appears that the IPN films prepared in a mixed solvent of higher polarity with long incubation time lead to very low protein adsorption. This study not only introduces a new IPN system containing SBMA, but also provides a fundamental understanding of various parameters governing the formation of IPNs.

Adsorption↗

Polymer-micelle incarcerated scandium as a polymer-supported catalyst for high-throughput organic synthesis.

A novel immobilization technique for Sc(OTf)3, a polymer-micelle incarcerated (PMI) method, has been developed. PMI Sc(OTf)3 is highly active in several fundamental carbon-carbon bond-forming reactions. The catalyst is recovered quantitatively by simple filtration and reused several times without loss of catalytic activity, and no Sc leaching was observed in all reactions (<0.1 ppm). In addition, several solvents are available, and these aspects are suitable for high-throughput organic synthesis (HTOS). To the best of our knowledge, this is the first example of immobilization of Lewis acids utilizing polymer micelles.

Catalysis↗

Novel polymer incarcerated palladium with phosphinated polymers: active catalyst for Suzuki-Miyaura coupling without external phosphines.

[reaction: see text] Immobilization of a palladium catalyst with use of new phosphinated polymers was carried out utilizing the polymer incarcerated (PI) method. This phosphinated PI Pd catalyst showed excellent activity in Suzuki-Miyaura couplings without addition of external phosphine ligands. No leaching of Pd was observed in this reaction, and the catalyst was recovered quantitatively by simple filtration and reused several times without loss of activity.

Catalysis↗

Polymer cryoprotectants in the preservation of biological ultrastructure. I. Low temperature states of aqueous solutions of hydrophilic polymers.

The solid states formed by vitrified and frozen aqueous solutions of some hydrophilic polymers, able to act as biological cryoprotectants, have been studied by differential scanning calorimetry and freeze fracture electron microscopy. Glass transitions, devitrification, recrystallization and melting behaviour of aqueous solutions of polyvinylpyrrolidone, hydroxyethyl starch and dextran have been established. The vitrified polymer solutions exhibit a characteristic microspheral morphology which is not induced by the quench cooling process but is an inherent feature of the solutions themselves.

Cryoprotective Agents↗

Optical visualization of polymer-polymer interactions.

Surface-enhanced absorption (SEA) has been used to monitor interactions of biomolecules and to observe structural changes of polymers. Such interactions of biomolecules are of interest in high-throughput screening and diagnostics. The structural changes of synthetic polymers can be exploited in optical sensorics. Based on SEA we have developed a technique that enables us to transfer the interaction of polyelectrolytes between two flat, solid surfaces into a visible color change, exploiting nanoscopic metal clusters. The polyelectrolytes are coated onto electrochemically oxidized aluminum, glass, and polycarbonate substrates. The change of surface color is monitored with a flat-bed scanner, and the interactions are analyzed kinetically. The results are interpreted with regard to adhesion, surface tension, electrostatic interactions, and miscibility.

Colorimetry↗

Wang resin-type linker containing a nitro group for polymer support oligosaccharide synthesis: polymer-supported glycosyl donor.

A nitro-introduced Wang resin-type linker for soluble and insoluble polymer support oligosaccharide synthesis is described. The linker was used for connecting glycosyl donors and polymer supports, and was completely stable under the glycosylation conditions tested. The cleavage of the linker was performed under reductive conditions without affecting the protecting groups to release disaccharides.

Carbohydrate Sequence↗

Studies on copolymers of collagen and a synthetic polymer. First report--experimental study on biocompatibility of laminar copolymers of collagen and a synthetic polymer.

To develop biomaterials for semiparmanent substitution, we are studying copolymers of collagen and a synthetic polymer. In this study, in order to test tissue compatibility, the laminar copolymers were prepared from bovine collagen treated with proctase to remove telopeptides and synthetic polymers such as polyethylene, polyvinylalcohol, silicon gum etc., by the OKAMURA-HINO metthod, namely polymerization achieved by the introduction of cross-lincages, applying plasma discharge and gamma-irradiation. These copolymers were implanted into dorsal subcutaneous tissue in rabbits and removed after 1, 2, 3, 4 and 6 weeks to be examined by light microscope and electron microscope. One or two weeks after implantation, we observed that a large number of fibroblasts gathered on the surface of the grafted collagen. After 3 or 4 weeks, bridges of collagen fibrils were observed between the copolymers and rabbit tissue. These copolymers were firmly adhered to the tissues and separable only with difficulty. These results showed that the copolymers maintain the capacity for extreme strong bonding for at least 6 weeks and possess high tissue compatibility. From that we concluded copolymers are useful as a biomedical material.

Animals↗

Idiotypic analysis of hybridoma antibodies to branched synthetic polymer (Tyr, Glu)-Ala-Lys: idiotypic relationship with antibodies to linear random polymer (Glu60, Ala30, Tyr10).

The expression of three anti-GAT idiotypes, CGAT, Gte, and GA-1, on 17 C57BL/10 and four C3H.SW hybridoma anti-(T,G)-A--L antibodies was analyzed. These hybridoma anti-(T,G)-A--L antibodies exhibited two patterns of fine antigen binding specificity. The majority of the hybridoma antibodies bound the (T,G)-A--L, GT, and GAT polymers but not the GA polymer, and were designated as GT-reactive hybridoma antibodies. A minor population of hybridoma anti(T,G)-A--L antibodies bound to (T,G)-A--L but not to GT, GAT, or GA, i.e., (T,G)-A--L-specific. A complete correlation between fine antigen binding pattern and the expression of CGAT idiotype was demonstrated. None of the 21 hybridoma anti-(T,G)-A--L antibodies expressed the GA-1 idiotype. All of the GT-reactive and none of the GT-nonreactive hybridoma anti-(%,G)-A--L antibodies expressed the CGAT idiotype. Furthermore, the Gte idiotype was found on the majority of CGAT+-bearing C57BL/10 hybridoma anti-(T,G)-A--L antibodies. These results indicate that C57BL/10 anti-(T,G)-A--L antibody repertoire can be grouped into a minimum of three families; i.e., CGAT+ Gte+, CGAT+ Gte-, and CGAT- Gte- families, with the CGAT+ Gte+ family as the major compartment. This is confirmed by the high percentage idiotype binding of serum anti-(T,G)-A--L antibodies with anti-CGAT idiotypic antisera. Finally, anti-idiotypic antisera made against CGAT+ hybridoma anti-GAT or anti-(T,G)-A--L antibodies crossreact extensively with other CGAT+ hybridoma anti-GAT and anti-(T,G)-A--L antibodies. However, additional experiments demonstrated that CGAT+ hybridoma anti-(T,G)-A--L antibodies also possess private idiotypes.

Animals↗

[Possibility of influencing drug release from polymers--using the example of bead polymers].

By the example of the model drug phenobarbital, the authors report of the possibilities of influencing the liberation of drugs from acrylate-based bead polymers. The drug-containing bead polymers produced were studied in vitro (half-change method, beaker device according to Moldenhauer, artificial digestive juices according to Münzel, without addition of enzymes). The composition of a unit-dose preparation, composed of several batches prepared under different conditions, is dealt with. The release values obtained largely meet the requirements made on depot preparations.

Acrylic Resins↗

[Polymer-containing eye drops. II. Isotonicity and pH adjustment of polymer solutions].

Authors studied potentials for isotonizability and isohydria adjustment of viscous eye-drops. Various non-ionic, anionic, linear chain, and/or crosslinked polymers were applied in order to increase viscosity. They have found that rheological features of the solutions do not change either upon the addition of electrolytes or upon change in pH value. Modification in equilibrium viscosity values indicate the onset of dehydration. Such change occurs in concentrated polymer solutions only.

Electrolytes↗

[Polymer-containing eyedrops. III. Surface tension of polymer solutions].

Therapeutical effect of ophthalmological solutions is markedly influenced by their surface tension which is also responsible for the irritating effect of the eye drop. Authors studied the effect of different polymers on surface tension. They found that each of the water soluble polymers studied decreased the surface tension of solutions against air. This surface tension decreasing effect is independent from the concentration of the solution. Its value is slightly influenced by the pH of the solution, while it is increased by its electrolyte content.

Electrolytes↗

Effect of combined changes in delayed extraction time and potential gradient on the mass resolution and ion discrimination in the analysis of polydisperse polymers and polymer blends by delayed extraction matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Data reported here show that, in the delayed extraction matrix-assisted laser desorption/ionization time-of-flight (DE-MALDI-TOF) mass spectrometric analysis of synthetic polydisperse polymers, different experimental conditions of spectral recording are required to optimize the signal in all the m/z regions of the spectrum. The effect of combined changes in delay time and grid voltage % values on both mass resolution and mass accuracy of DE spectra of a polyethylene glycol sample (PEG(mix), with a well-defined molar distribution of its components) is discussed. The necessity of a compromise between the values of these two parameters is shown. Furthermore, the occurrence of analyte discrimination, which can invalidate the composition analysis especially in the case of polymer blends, is demonstrated. Copyright 1999 John Wiley & Sons, Ltd.

Journal Article↗

Size-based separation of synthetic polyelectrolytes in entangled polymer solution capillary electrophoresis: the effect of binary mixtures of separating polymers differing in molecular mass.

The influence on the electrophoretic behavior of polystyrenesulfonates of the percentage of high-molecular-mass chains in an entangled poly(ethylene oxide) solution having a bimodal molecular mass distribution has been investigated and compared with the results obtained for similar solutions of unimodal molecular mass distribution. The comparisons between the different separating polymer solutions were made at a constant total mass concentration, so as to keep constant the mesh size and to highlight the sole effect of the network dynamics. The use of binary polymer mixtures of two different molecular masses but of same nature can be a convenient alternative to modulate the dynamics of the network and the viscosity of the separating medium. A 20-30% content of high-molecular-mass chains in an entangled poly(ethylene oxide) solution having a binary molecular mass distribution appears to be a good compromise for a moderate viscosity and a good separation selectivity in comparison with a solution containing only chains of high molecular mass at the same concentration.

Electrophoresis, Capillary↗

Bioadhesive polymers as platforms for oral controlled drug delivery III: oral delivery of chlorothiazide using a bioadhesive polymer.

Bioadhesive polymers that bind to the gastric mucin or epithelial cell surface are useful in drug delivery for the purposes of (a) retaining a dosage from in the GI tract and (b) increasing the intimacy and duration of contact of drug with the absorbing membrane. Polycarbophil has previously been shown to have bioadhesive properties in the rat stomach and small intestine and was employed in the present study with a sustained-release delivery system to demonstrate improved drug delivery. Using chlorothiazide as the model drug, drug containing albumin beads were prepared and used as the sustained-release system. The beads were physically mixed with equally sized particles of polycarbophil and placed in a capsule to produce a bioadhesive dosage form. When the dosage form contacts the stomach, the gelatin capsule dissolves, exposing the polycarbophil to the bathing fluid. The bioadhesive polymer rapidly hydrates, retaining the albumin beads and attaching to the mucin coating of the stomach. Plasma drug levels in rats showed a longer duration of action and greater bioavailability for the bioadhesive dosage form than for either albumin beads or drug powder alone. The results suggest that the principle of bioadhesion can significantly improve therapy, due to a reduced rate of gastric emptying, an increase in contact time, and the intimacy of contact of the drug with the absorbing membrane.

Acrylic Resins↗

Study of the miscibility and segmental motion of STMAA-PBMA polymer blends and semi-interpenetrating polymer networks by an ESR spin probe method.

Linear polymer blends and semi-interpenetrating polymer networks (IPNs) with controlled hydrogen bonding interactions based on poly(styrene-co-methacrylic acid) (STMAA) and poly(butyl methacrylate) (PBMA) were studied by an ESR spin probe method. The observed composite ESR spectra with fast- and slow-motion components in all the samples were ascribed to two-phase morphology. For linear blends, the temperatures T(a) corresponding to appearance of the fast motion, T(d) corresponding to the disappearance of slow motion, T(5mT) and the rotational correlation times tau(c) increased with increasing carboxylic acid content in STMAA. It was concluded that the degree of mixing of the blends was improved with increasing carboxylic acid content, owing to the enhanced hydrogen bonding interactions between the carboxylic acids in STMAA and the ester groups in PBMA. With respect to semi-IPN samples, there existed a competition in the microphase structure between the intercomponent hydrogen bonding interactions, which improved the miscibility of the samples and the intracomponent cross-linking, which might lead to phase separation in the systems with strong specific interactions. When the semi-IPN contained 29 mol% carboxylic acid, the temperatures T(d), T(5mT) and tau(c) reached their minimum values, which indicated that the sample reached its maximum miscibility.

Journal Article↗

Solvent-free low-dimensional polymer electrolytes for lithium-polymer batteries.

The development of solvent-free low-dimensional polymer electrolytes intended for use in solvent-free lithium batteries operating at ambient or sub-ambient temperatures is described. The synthetic routes to the amphiphilic polymers I having 5-alkoxy-3,4-phenylene units connected with oligoethoxy segments via polyester-ether or pure polyether links (abbrev. CmOn, m = 12, 16, 18, n = 1-5) and to the copolymers CmO1-CmOn are described. The structures, thermal properties and SAXS long spacings of their complexes with lithium salts (type A) and with long chain n-alkane or alkyl side chain intercalation (type B) are discussed. However, high ambient conductivities (10(-4)-10(-3) S cm(-1)) are observed in type C systems when a second copolymer based on polytetramethylene oxide segments (II) is incorporated as a microphase between the lamellae of I and serving as an ion bridge or "glue". DC polarization between Li electrodes also gives ambient conductivities >/=ca.10(-3) S cm(-1). In type D systems the I/II interface is stabilized by including a copolymer III, promoting high reproducibility in performance. Copolymers I of CmO1-CmO5 having CmO1 in excess give optimum conductivities with low temperature-dependence. This, together with molecular modeling, suggests uncoupled ion mobilities by hopping between small aggregates in the interlamellar spaces.

Journal Article↗