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  • 1.
    Bydén Sjöbom, Malin
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Edlund, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Lindström, Birger
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    BinaBinary Phase Equilibria and Structure of the Two α-Methyl-Substituted Surfactants Sodium (R)-2-Methyldecanoate and Racemic Sodium 2-Methyldecanoate ry Phase Exuilibria and Structure of the Chiral α-Methylsubstituted Surfactants Sodium (R)-2-Methyldecanoate and Racemic Sodium 2-Methyldecanoate1999Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 15, nr 8, s. 2654-2660Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this study, we present the binary phase diagrams for the aqueous systems of the alkyldecanoic salts racemic sodium 2-methyldecanoate and sodium (R)-2-methyldecanoate, respectively. Both systems form a micellar solution phase, as well as a normal hexagonal, a cubic, and a lamellar liquid crystalline phase. They also form a very narrow intermediate phase, situated between the hexagonal and cubic liquid crystalline phases. The methods used for characterization were crossed polaroids, polarizing optical microscope and 2H NMR quadrupolar splittings combined with SAXS studies. The cubic phase gave a well-resolved SAXS diffraction pattern, with eight peaks present, which establishes the bicontinuous cubic structure as Ia3d. A significant difference in these two phase diagrams, compared to those of unsubstituted alkanoates with the same chain length, is the very low Krafft boundary.

  • 2. Carlsson, Håkan
    et al.
    Edlund, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Persson, Gerd
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Lindström, Birger
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Competition Between Monovalent and Divalent Counterions in a Surfactant / Water System1996Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 180, nr 2, s. 598-604Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Competition between mono- and divalent ions in the association of counterions to the headgroups of amphiphiles was studied in one surfactant system with organic counterions (piperidine+/piperazine2+octanesulfonate) and one with inorganic counterions (Na+/Ca2+octyl sulfate). By conductivity and13C NMR chemical shift measurements the critical micelle concentration (CMC) was found to decrease drastically when small amounts of divalent counterions were present in the system. Self-diffusion coefficients of surfactant ions and organic counterions were measured in the micellar phase by the Fourier transform pulsed-gradient spin-echo (FT-PGSE) NMR method. The degree of counterion binding in the micellar system with piperidine+/piperazine2+counterions was obtained from FT-PGSE NMR measurements. It was observed that the divalent counterions were more strongly bound than the monovalent counterions. The experimental results were compared with theoretical Poisson–Boltzmann calculations. The cell model was used to study the electrostatic effects. Good agreement between electrostatic theory and experiment was observed; however, an attractive force exists between the monovalent piperidine counterions and the micelle, probably because of hydrophobic interactions.

  • 3.
    Edlund, Håkan
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Bydén, Malin
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Lindström, Birger
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Khan, Ali
    Phase Equilibria and Structure of the 1-dodecyl Pyridinium Bromide-Dodecane-Water System1998Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 204, nr 2, s. 312-319Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The isothermal ternary phase diagram for the 1-dodecylpyridinium bromide/dodecane/water system was determined at 40°C by 2H NMR and polarizing microscopy methods. Two liquid crystalline phases, a large cubic area and a normal hexagonal phase, and one isotropic normal micellar solution phase were characterized, and their ranges of existence were determined. The micelles were found to be probably small and spherical at lower concentrations of surfactant, and were found to grow at higher concentrations and on addition of oil. The two-phase areas, L1 + H1 and H1 + I, are both very narrow. The comparatively large cubic area, containing 43-63 wt% surfactant and 3-10 wt% dodecane, is probably consistent of more than one structure. SAXS experiments indicate two different structures built of discrete micellar aggregates.

  • 4.
    Edlund, Håkan
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Bydén, Malin
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Lindström, Birger
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Khan, Ali
    Ternary Phase Equilibria of the 1.dodecyl Pyridinium Bromide-Dodecanol-Water System1997Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 196, nr 2, s. 231-240Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The isothermal ternary phase diagram for the 1-dodecylpyridinium bromide (1-DPB)–water–dodecanol system was determined at 40°C, using2H NMR, polarizing microscopy, and SAXS methods. All of the phases were characterized, and their ranges of existence were determined. The surfactant is easy to dissolve in water, yielding a normal micellar solution phase. After the normal micellar phase, on the binary surfactant–water axis, a normal hexagonal liquid crystalline phase is found at higher surfactant concentrations. On addition of dodecanol, four more phases are formed, i.e. a cubic, a lamellar, and a reverse hexagonal phase, followed by a reverse micellar solution phase. The lamellar liquid crystalline phase dominates the ternary phase diagram. The structures of the liquid crystalline phases were further examined using SAXS measurements, and the results are discussed in terms of the critical packing parameter, cpp, and electrostatic forces. The SAXS experiments show a pronounced swelling of the rods in the hexagonal phase, from 28.5 to 33 Å on addition of dodecanol, whereas the cylindrical aqueous core of the reverse hexagonal phase has a diameter of 18–21 Å, depending on sample composition. The average bilayer thickness of the lamellar phase is about 24 Å.

  • 5.
    Karlsson, S.
    et al.
    Department of Physical Chemistry, Åbo Akademi University, Porthaninkatu 3-5, FI-20500 Turku, Finland.
    Friman, R.
    Department of Physical Chemistry, Åbo Akademi University, Porthaninkatu 3-5, FI-20500 Turku, Finland.
    Björkqvist, M.
    Laboratory of Industrial Physics, Department of Physics, University of Turku, FI-20014 Turku, Finland.
    Lindström, Birger
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Backlund, S.
    Department of Physical Chemistry, Åbo Akademi University, Porthaninkatu 3-5, FI-20500 Turku, Finland.
    Phase behavior and characterization of the system acetic acid-dodecylamine-water2001Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 17, nr 12, s. 3573-3578Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The phase behavior of carboxylic acid/alkylamine mixtures in water is largely dictated by a proton transfer from the acid to the amine, which will lead to charged species. If the distribution of carbon atoms is unequal between the acid and the amine, the result will be an ionic surfactant with an organic counterion. In this work the phase diagram for the ternary system acetic acid-dodecylamine-water at 298.2 K has been determined. Dodecylamine forms a lamellar phase with water, but when,acetic acid is added up to an equimolecular ratio between acid and amine, three new phases appear. These phases are an isotropic solution phase, a hexagonal liquid crystalline phase, and a cubic liquid crystalline phase. These three phases are not able to incorporate any excess amine. The solution phase shows the existence of micelles, which are spherical at high dilution, but show an elongation close to the phase border to the hexagonal phase.

  • 6.
    Karlsson, S.
    et al.
    Department of Physical Chemistry, Åbo Akademi University, Porthaninkatu 3-5, Turku, FI-20500, Finland.
    Friman, R.
    Department of Physical Chemistry, Åbo Akademi University, Porthaninkatu 3-5, Turku, FI-20500, Finland.
    Lindström, Birger
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Backlund, S.
    Department of Physical Chemistry, Åbo Akademi University, Porthaninkatu 3-5, Turku, FI-20500, Finland.
    Self-assembly in the system decanoic acid-butylamine-water2001Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 243, nr 1, s. 241-247Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The phase behavior of alkanoic acid-alkylamine mixtures in water is mainly dictated by a proton transfer from the acid to the amine. For an asymmetric distribution of carbon atoms in the alkyl chains, the result will be an ionic surfactant with an organic counter-ion. In this study the phase diagram at 298.2 K for the ternary system decanoic acid-butylamine-water has been determined. The phase diagram is dominated by a large isotropic solution region. The selfdiffusion, viscosity, and conductivity measurements in the solution phase for an equimolecular ratio between the acid and the amine indicate a continuous transition from aqueous spherical mixed micelles to highly interacting hydrated acid-amine complexes passing through a bicontinuous region. One liquid crystalline lamellar phase, existing at excess acid, has been found. The small angle Xray scattering results indicate that the amine, due to its slightly amphiphilic character, is distributed between water and the bilayer.

  • 7.
    Norgren, Magnus
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Edlund, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Wågberg, Lars
    Lindström, Birger
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Annergren, Göran
    Aggregation of Kraft Lignin Derivatives under Conditions Relevant to the Process. Part I. Phase Behaviour2001Ingår i: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 194, nr 1-3, s. 85-96Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Aggregation of a commercial, polydisperse softwood kraft lignin (Indulin AT) in diluted aqueous alkaline solutions was investigated experimentally, by means of turbidity measurements. The influence of temperature, salt concentration and pOH and the role of a divalent counterion on the aggregation behaviour were studied. When the temperature was increased, an increased tendency of aggregation in samples containing high concentrations of sodium chloride was found. Phase separation could be detected even at pOH=2 at 175°C and the effect was pronounced when the concentration of hydroxide ions decreased. The phase transition from soluble to precipitated lignin was found to be irreversible concerning temperature change. Small amounts of calcium ions were seen to induce dramatic effects on the system stability, even at relatively high hydroxide concentrations (pOH 1-2). At a given temperature and pOH, the coagulation was found to appear at a certain critical coagulation concentration (CCC) of the added electrolyte. Furthermore, calculations were carried out to compare with the outcome of the experimental observations. A theoretical model, based on the DLVO theory, was found to predict the kraft lignin solution behaviour well.

  • 8.
    Norgren, Magnus
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Lindström, Birger
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Dissociation of Phenolic Groups in Kraft Lignin at Elevated Temperatures.2000Ingår i: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 54, nr 5, s. 519-527Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The dissociation of the phenolic groups in a polydisperse, low molecular weight kraft lignin (Indulin AT) was studied in alkaline aqueous solutions in the temperature interval 21-70°C, using a UV-spectrophotometric method. It was found that at a constant concentration of hydroxide ions, the degree of dissociation was decreasing when the temperature was elevated. Dissociation curves and apparent pK0 values were also calculated for the polydisperse sample at the same conditions, using the van't Hoff and the Poisson-Boltzmann equations. At degrees of dissociation exceeding α ≈ 0.4, the outcome of the theoretical approach showed to be in good agreement with the experimentally obtained results. Furthermore, calculations were performed for different molecular weights of kraft lignin and from this it was found that the apparent pK0 is shifted to higher values by increasing molecular weight, due to an increased electrostatic attraction of the hydrogen ions, which is arising from a less curved surface. Predictions of the dissociation behavior at temperatures reached in the kraft process were performed and under these conditions, higher molecular weight lignin fragments seem never to reach the point of complete dissociation. It was also found that an increase in temperature results in phase separation in kraft lignin solutions with high ionic strengths and pH values close to the pKa of the phenolic groups.

  • 9.
    Norgren, Magnus
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Lindström, Birger
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Physico-Chemical Characterization of a Fractionated Kraft Lignin2000Ingår i: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 54, nr 5, s. 528-534Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A kraft lignin was leached from a softwood pulp and fractionated by ultrafiltration. The fractions were characterized in respect to phenolic group content, molecular weight distributions and self-diffusion coefficients. The 1H-Pulsed Field Gradient (PFG) NMR self-diffusion measurements and the High-Pressure Size Exclusion Chromatography (HPSEC) analysis of the fractions, were seen to correlate fairly well. From the self-diffusion measurements, the mass-weighted median hydrodynamic radii of the diffusants in the fractions, were calculated assuming spherical fragments. Furthermore, the content of phenolic groups in the fractions, was found to decrease by increasing hydrodynamic radius and molecular weight, but the calculated median surface charge densities of the macromolecules, were determined to be constant in the range of oligomers up to at least 65 structural units.

  • 10.
    Norgren, Magnus
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Lindström, Birger
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Physicochemical characterization of fractionated kraft lignins: Pre-symposium to the 9th ISWPC1997Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Kraft lignins are known to associate and form large clusters in aqueous solutions at pH values close to pKa. Some physicochemical properties related to association, such as the amount of free phenolic groups and hydrodynamic radius, have been determined in ultrafiltrated fractions of leached softwood kraft lignins and Indulin AT. Average diffusion coefficients were measured by the 1H PFG-NMR method in 2 % w/w lignin solutionsof 0.1 M LiOH/D2O. The hydrodynamic radius were calculated using the Stoke-Einstein expression. Conductometric titrations were used to determine the average amount of free phenolic groups in the fractions. The repulsive electrostatic potential, F0, originating from the phenolic charges, was calculated at different pH values for one of the fractions, using the Poisson-Boltzmann cell model.

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