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| 2. |
- Tsianou, Marina
(författare)
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Association Phenomena Involving Hydrophobically Modified Polymers. Electrostatic and Hydrophobic Contributions
- 1999
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The electrostatic and hydrophobic interactions in aqueous solutions of hydrophobically-modified water-soluble non-ionic or ionic polymers, their mixtures with a second polymer, nonionic or of opposite charge, and their mixtures with surfactants of opposite charge have been investigated. The relative strength of the electrostatic and hydrophobic contributions has been modulated by a variation of the polymer charge density and the solution pH, and by a variation in the degree and strength of the hydrophobic modifications, respectively. The repercussions of such interactions on the thermodynamics and dynamics of the systems under study have been quantified experimentally with the aid of phase behavior, rheology, and light scattering techniques, and have been rationalized theoretically in the context of dynamic scaling theory. The association between two oppositely charged hydrophobically modified polyelectrolytes can lead to the formation of soluble or insoluble mixtures depending on the mixture composition, the total polymer concentration, and the charge density of the polyions. The simultaneous presence of ionic and hydrophobic groups in both polymers results in a broad miscibility region (instead of the precipitate expected if only electrostatics were in effect), where the viscosity is three to four orders of magnitude higher than that of the solutions of the individual polymers. The physical networks obtained through the formation of mixed aggregates are especially reinforced in the proximity of phase separation as revealed by the existence of two relaxation modes, a fast diffusive mode and a slow mode (attributed to enhanced hydrophobic associations) in the time correlation data obtained from light scattering measurements. The network dynamics are strongly affected by the presence of the hydrophobic moieties and by the mixture composition, thus making the hydrophobically modified polyelectrolyte mixtures exhibit rheological properties of complex scaling behavior. However, the binary mixtures of unmodified polyelectrolytes as well as the single polyelectrolyte solutions exhibit a viscosity scaling behavior in good agreement with recent predictions of the dynamic scaling theory of polyelectrolytes in the semidilute regime. The interactions between polymers and surfactants of opposite charge in aqueous solutions can lead to the formation of transient networks, the rheological properties of which have been modulated via the addition of cyclodextrins. Cyclodextrins can form inclusion complexes with the hydrophobic moieties of surfactants, and thus they disrupt the polymer-surfactant network as evidenced by their ability to reverse the high viscosities exhibited by such networks.
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| 3. |
- Buch-Rasmussen, Thomas
(creator_code:cre_t)
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A device for the administration of a liquid medicament suspension
- 1998
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Patent (övrigt vetenskapligt/konstnärligt)abstract
- In an ampoule for a medicament the space accommodating the medicament is defined by an ampoule wall (1) a pierceable seal (5) closing one end of the ampoule and a piston (7) closing the other end of the ampoule. A metal containing fixation element (8) is secured to one of the parts defining the medicament accommodating space. A mixing element (9, 10) also containing a metal and having a density larger than 1,0 g/cm<3> is movable in medicament accommodating space. At least one of the elements, the fixation element (8) and the mixing element (9, 10), can be attracted by a magnet, and at least one of these elements is a magnetic element, the magnetic strength being so that the mixing element (9, 10) can during normal handling of the ampoule be fixed relative to this ampoule by the magnetic attraction between the fixation element (8) and the mixing element (9, 10) but may be released from its fixed position by manual operation.
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| 4. |
- Buch-Rasmussen, Thomas
(creator_code:cre_t)
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Coating system providing low friction
- 1999
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Patent (övrigt vetenskapligt/konstnärligt)abstract
- The present invention relates to a coating system, in particular to a coating system for articles where plastic materials slide against flexible rubber materials. The coating system is a silicone oil based coating having a viscosity of at least 200,000 centistokes, i.e. a high viscosity coating. The coating comprises in a preferred embodiment a silicone oil based block or graft copolymer, or segmented copolymer. Further the invention relates to a process of producing a component of an article coated as described above, comprising adding the coating material to the component material prior to molding and subsequently molding the component from the mixture, or molding the component from the component material and subsequently applying the coating material to the at least one surface of the component, as well as an article coated with a silicone oil based coating as defined above. Such an article is preferably a medical article, such as a container or an injection cylinder and a stopper. The coatings according to the present invention are especially suited to use for permanently coating internal surfaces of containers equipped with stoppers for storage and administration of liquid protein preparations. The coatings providing low friction between the two components, such as a container wall and a rubber stopper, result in high-precision dosing. The described coatings are particularly useful for coating containers for storage and administration of liquid protein solutions, such as insulin formulations.
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| 5. |
- Hakkarainen, Minna, et al.
(författare)
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Solid phase microextraction (SPME) as an effective means to isolate degradation products in polymers
- 1997
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Ingår i: Journal of environmental polymer degradation. - 1064-7546 .- 1572-8900. ; 5, s. 67-73
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Tidskriftsartikel (refereegranskat)abstract
- A new sample preparation technique, solid phase microextraction (SPME), was compared with direct headspace-GC-MS with respect to the type and amount of identified compounds. Three types of LDPE films containing photosensitising additives according to the Scott-Gilead patents and pure LDPE were used as model substances. The polyethylene films were thermally aged at 80 degrees C after the induction period was surpassed by subjecting the materials to 100 h of UV radiation. The new SPME method was developed using nonpolar poly(dimethylsiloxane) and polar carbowax fibers to extract the low molecular weight products formed in the polyethylene films during aging. Many more products were identified after SPME followed by CC-MS than after direct headspace-GC-MS of the samples. The SPME method allowed the identification of homologous series of carboxylic acids, ketones, and furanones, while direct headspace-GC-MS identified only a few carboxylic acids (C1-C6) and small amounts of some ketones and furanones. In general, SPME was more effective in extracting less volatile products, and in particular, the polar carbowax fiber identified also C7-C12 carboxylic acids and 4-oxopentanoic acid. By SEC and FTIR we confirmed that the number and amount of former degradation products correlated well with the decrease in molecular weights and the amount of formed carbonyl compounds.
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| 6. |
- Rasmussen, Thomas-Buch
(creator_code:cre_t)
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Medical article with coated surfaces exhibiting low friction and low protein adsorption
- 1999
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Patent (övrigt vetenskapligt/konstnärligt)abstract
- The present invention relates to a medical article for containing a pharmaceutical protein preparation comprising at least a first component and a second component, having at least one surface coated with a coating to reduce the friction between the two components and to reduce the protein adsorption to the coating. The coating is a hydrophilic coating whereby the hydrophilicity of the surface of the coating as measured by the water contact angle is below 90°, and the long term static friction forces between the first and the second component are below 14 N. The coatings according to the present invention are especially suited for permanently coating internal surfaces of containers equipped with stoppers for storage and administration of liquid protein preparations, such as insulin preparations. The coating is preferably a silicon-containing coating, such as a poly(dialkyl siloxane) oil or copolymer. The invention further relates to a process of producing a component of a medical article coated as described above, comprising adding the coating material to the component material prior to molding and subsequently molding the component from the mixture, or molding the component from the component material and subsequently applying the coating material to the at least one surface of the component, and hydrophilizing the coating material prior to the molding or after the molding. Also the invention relates to a coating as defined above for articles having at least a first component and a second component.
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| 9. |
- Borgström, Johan
(författare)
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Phase separation, aggregation and gelation of a charged helixforming polysaccharide in aqueous salt solution
- 1997
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The phase behaviour and gelation of the anionic polysaccharide kappa-carrageenan (KC) in different salt solutions was studied. The specific site binding of certain anions and certain cations to the KC helix was used as a means of controlling the interactions. In the presence of a binding anion (I-) the charge density of the helix increases and the aggregation of helices, and thereby the gelation, is prevented. By gradually introducing a site binding cation (Cs+) the effective charge density of the helix is reduced, as is the electrostatic repulsion between the helices. Most experiments were performed in 0.1 M salt solution of the mixed salts NaI/CsI. The molecular weight of the KC was varied. For a low molecular weight in 0.1 M NaI, a chiral nematic phase was observed above 5% KC. The volume of the chiral nematic phase was found to depend sensitively on the helical content which demonstrates a coupling between the coil-helix transition and the isotropic-nematic phase transition. From the liquid crystalline phase behaviour, the persistence length of the kappa-carrageenan helix was estimated to be in the range 90-120 nm. The development of the nematic phase was very slow for the high molecular weight KC, due to the high viscosity and slow diffusion for these large molecules. KC of a high molecular weight in 0.1 M NaI produced weak gels above 1% KC with - for KC - unusually low storage moduli. These “gels” were found to be caused by helix entanglements. The effect of mixing different proportions of specific and non-specific ions on the transition enthalpy was investigated experimentally by DSC for a wide range of salt compositions. Under conditions where no aggregation occurred (and thus no gelation), the variations in the observed enthalpies could be reproduced by Poisson-Boltzmann model calculations, taking into account the specific binding of ions to the helix. A change in the macroscopic properties, from isotropic/nematic phase separation to gelation, was found to occur above a certain cesium content in the mixed NaI/CsI salt solution. Studies on dilute solutions by cryo-TEM, viscometry, optical rotation and light scattering showed that at and above this molar ratio of cesium, the kappa carrageenan helices aggregate into rigid super-helical rods. These rods are not soluble, but self-aggregate in turn, giving rise to the gel. Thus, the properties of the gel seem to depend on the properties of this higher order kappa-carrageenan aggregate (the super-helical rod), rather than on the properties of the individual kappa-carrageenan helix.
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| 10. |
- Johansson, Hans-Olof, et al.
(författare)
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Effects of ions on partitioning of serum albumin and lysozyme in aqueous two-phase systems containing ethylene oxide/propylene oxide co-polymers
- 1996
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Ingår i: Biochimica et Biophysica Acta. General Subjects. - : Elsevier BV. - 0304-4165. ; 1290:3, s. 289-298
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Tidskriftsartikel (refereegranskat)abstract
- Aqueous two-phase systems composed of ethylene oxide/propylene oxide random co-polymers, EO30/PO70 or Ucon (EO50/PO50), in the top phase and dextran T500 in the bottom phase, have been studied. The cloud point diagram for EO30/PO70 in water solution was determined. EO30/PO70 has a cloud point of 32oC at a concentration of 10% (w/w). The phase diagram for the system EO30/PO70-dextran T500-water was determined. Salt effects have been studied on the partitioning of two model proteins, bovine serum albumin and hen egg white lysozyme, in EO30/PO70-dextran and Ucon-dextran systems. Ions with different hydrophobicity, i.e., with different position in the Hofmeister or lyotropic series, were investigated with reference to their effect on protein partition. The counterion hydrophobicity was shown to have a strong influence on the partitioning of BSA and lysozyme. Most extreme partitioning was obtained with hydrophobic (chaotropic) ions like ClO-4 and I-. A comparison of protein partitioning between PEG-dextran and EO30/PO70-dextran has been done. A more extreme protein partitioning was obtained in the EO30/PO70-dextran containing system. Temperature-induced phase separation was studied with EO30/PO70 at 45oC. Both BSA and lysozyme were completely partitioned to the water phase formed above the cloud point of EO30/PO70. Model calculations, based on Flory-Huggins theory of polymer solutions, have been done which could reproduce the salt effect on the protein partitioning in aqueous-two phase system.
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