| 1. |
- Gårdebjer, Sofie, 1985, et al.
(author)
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The impact of interfaces in laminated packaging on transport of carboxylic acids
- 2016
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In: Journal of Membrane Science. - : Elsevier BV. - 0376-7388 .- 1873-3123. ; 518, s. 305-312
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Journal article (peer-reviewed)abstract
- The permeability of oleic and acetic acid through low density polyethylene (LDPE) and ethylene acrylic acid (EAA) have been measured using diffusion cells. In addition, the permeability through combinations of LDPE and EAA in the form of laminates with different numbers of layers has been determined. Oleic acid shows an almost 30 times higher permeability compared to acetic acid, which was partly explained by the adsorption of oleic acid to the film surface during the permeability experiment. In addition, the permeability is lower for both oleic and acetic acid in the laminates compared to the pure films. The decreased permeability can be explained by the presence of crystalline domains close to the interface. This is supported by SAXS data which suggests an ordering of polymer chains in the EAA film close to the interface. In summary, the results show that it is possible to create barrier materials with decreased permeability, which is interesting for example in the packaging industry.
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| 2. |
- Andersson Trojer, Markus, 1981, et al.
(author)
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Charged microcapsules for controlled release of hydrophobic actives. Part III: The effect of polyelectrolyte brush- and multilayers on sustained release
- 2013
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In: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9084 .- 1463-9076. ; 15:17, s. 6153-6165
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Journal article (peer-reviewed)abstract
- Poly(methyl methacrylate) microspheres have been prepared by the internal phase separation method using either of the three conventional dispersants poly(vinyl alcohol) (PVA), poly(methacrylic acid) (PMAA), or the amphiphilic block copolymer poly(methyl methacrylate)-block-poly(sodium methacrylate). The block copolymer based microsphere, which has a polyelectrolyte brush on the surface, was surface modified with up to two poly(diallyldimethylammonium chloride)-poly(sodium methacrylate) bilayers. The microspheres were loaded with the hydrophobic dye 2-(4-(2-chloro-4-nitrophenylazo)-N-ethylphenylamino)ethanol (Disperse Red 13) and its release from aqueous dispersions of microspheres with the different surface compositions was measured by spectrophotometry. The burst fraction, burst rate and the diffusion constant were determined from a model combining burst and diffusive release. Out of the three dispersants, the block copolymer gave the slowest release of the dye, with respect to both burst release and diffusive release. A very pronounced further reduction of the diffusion constant was obtained by applying polyelectrolyte multilayers on top of the microspheres. However, the diffusion constant was very weakly dependent on further polyelectrolyte adsorption and one polyelectrolyte bilayer appeared to suffice.
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| 3. |
- Andersson Trojer, Markus, 1981, et al.
(author)
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Directed self-assembly of silica nanoparticles in ionic liquid-spun cellulose fibers
- 2019
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In: Journal of Colloid and Interface Science. - : Elsevier BV. - 1095-7103 .- 0021-9797. ; 553, s. 167-176
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Journal article (peer-reviewed)abstract
- The application range of man-made cellulosic fibers is limited by the absence of cost- and manufacturing-efficient strategies for anisotropic hierarchical functionalization. Overcoming these bottlenecks is therefore pivotal in the pursuit of a future bio-based economy. Here, we demonstrate that colloidal silica nanoparticles (NPs), which are cheap, biocompatible and easy to chemically modify, enable the control of the cross-sectional morphology and surface topography of ionic liquid-spun cellulose fibers. These properties are tailored by the silica NPs’ surface chemistry and their entry point during the wet-spinning process (dope solution DSiO2 or coagulation bath CSiO2). For CSiO2-modified fibers, the coagulation mitigator dimethylsulphoxide allows for controlling the surface topography and the amalgamation of the silica NPs into the fiber matrix. For dope-modified fibers, we hypothesize that cellulose chains act as seeds for directed silica NP self-assembly. This results for DSiO2 in discrete micron-sized rods, homogeneously distributed throughout the fiber and for glycidoxy-surface modified DSiO2@GLYEO in nano-sized surface aggregates and a cross-sectional core-shell fiber morphology. Furthermore, the dope-modified fibers display outstanding strength and toughness, which are both characteristic features of biological biocomposites.
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| 4. |
- Andersson Trojer, Markus, 1981, et al.
(author)
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Encapsulation of actives for sustained release
- 2013
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In: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9084 .- 1463-9076. ; 15:41, s. 17727-17741
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Research review (peer-reviewed)abstract
- Encapsulation of actives in miniature reservoirs, called microcapsules, is used for protection and in particular controlled release of the active. Regarding controlled release applications, the most common function of the microcapsule is to sustain or extend the release of the active. A number of encapsulation methodologies are available including; internal phase separation, interfacial polymerization, formation of multiple emulsions, Layer-by-Layer adsorption of polyelectrolytes and soft templating techniques, all of which are reviewed in this Perspective. The choice of method depends on the nature of the active (hydrophilic/hydrophobic, size, physical state) and on the intended release rate and release profile. Ways to manipulate the release of the active by tailoring the physicochemical properties of the microcapsule are reviewed. Moreover, appropriate diffusion models are introduced to describe the release profile from a variety of microcapsule morphologies, including Fickian diffusion models and Brownian motion, and the meaning and the misuse of the term ``zero-order release'' are briefly discussed.
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| 5. |
- Andersson Trojer, Markus, 1981, et al.
(author)
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Quantitative Grafting for Structure-Function Establishment: Thermoresponsive Poly(alkylene oxide) Graft Copolymers Based on Hyaluronic Acid and Carboxymethylcellulose
- 2019
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In: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 20:3, s. 1271-1280
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Journal article (peer-reviewed)abstract
- © 2019 American Chemical Society. A series of thermoresponsive graft copolymers, gelling at physiological conditions in aqueous solution and cell growth media, have been synthesized using quantitative coupling between a small set of amino-functionalized poly(alkylene oxide) copolymers (PAO) and the carboxylate of the biologically important polysaccharides (PSa) carboxymethylcellulose and the less reactive hyaluronate. Quantitative grafting enables the establishment of structure-function relationship which is imperative for controlling the properties of in situ gelling hydrogels. The EDC/NHS-mediated reaction was monitored using SEC-MALLS, which revealed that all PAOs were grafted onto the PSa backbone. Aqueous solutions of the graft copolymers were Newtonian fluids at room temperatures and formed reversible physical gels at elevated temperatures which were noncytotoxic toward chondrocytes. The established structure-function relationship was most clearly demonstrated by inspecting the thermogelling strength and the onset of thermogelling in a phase diagram. The onset of the thermogelling function could be controlled by the global PAO concentration, independent of graft ratio.
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| 6. |
- Andersson Trojer, Markus, 1981, et al.
(author)
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A highly hydrophobic anionic surfactant at oil-water, water-polymer and oil-polymer interfaces: Implications for spreading coefficients, polymer interactions and microencapsulation via internal phase separation
- 2013
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In: Colloids and Surfaces A: Physicochemical and Engineering Aspects. - : Elsevier BV. - 1873-4359 .- 0927-7757. ; 436, s. 1048-1059
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Journal article (peer-reviewed)abstract
- Multicore-shell particles consisting of a poly(methyl methacrylate) shell and multiple dodecane cores have been prepared via the internal phase separation method using the oil-soluble anionic surfactant sodium 1,5-dioxo-1,5-bis(3,5,5-trimethylhexylocy)-3-((3,5,5 trimethylhexyloxy)carbonyl)pentane-2-sulfonate (TC4) and the water-soluble polycation poly(diallyldimethylammonium chloride) (PDADMAC) in combination as a dispersant pair. The multicore-shell particles have been investigated using SEM, light microscopy and microelectrophoresis. The detailed influence of TC4 on the oil-water, water-polymer and oil-polymer interfaces and its interaction with PDADMAC have been investigated using a quartz crystal microbalance with dissipation monitoring (QCM-D) and different optical tensiometry methods. TC4 stabilizes in particular the polymer-water interface in the presence of PDADMAC instead of the oil-water interface in contrast to water-soluble surfactants. In addition, the oil-polymer interface is stabilized by TC4 which prevents coalescence of the oil droplets and leads to multicore-shell morphology rather than single core-shell.
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| 7. |
- Andersson Trojer, Markus, 1981, et al.
(author)
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Charged microcapsules for controlled release of hydrophobic actives. Part 1: encapsulation methodology and interfacial properties
- 2013
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In: Soft Matter. - : Royal Society of Chemistry (RSC). - 1744-6848 .- 1744-683X. ; 9:5, s. 1468-1477
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Journal article (peer-reviewed)abstract
- Highly charged microcapsules have been prepared using the internal phase separation technique. The charges are introduced by using ionic dispersants, which have been characterized with respect to surface activity with a quartz crystal microbalance with dissipation monitoring and with optical tensiometry. The long-term stability of the microcapsule suspension without excess dispersant, as well as the stability at high ionic strength, have been investigated. Three types of ionic dispersants have been evaluated: a weak polyacid (poly(methacrylic acid)), a small set of ionic amphiphilic block copolymers of poly(methyl methacrylate)-block-poly(sodium (meth) acrylate) type and an oil-soluble anionic surfactant, sodium 1,5-dioxo-1,5-bis(3,5,5-trimethylhexyloxy)-3-((3,5,5-trimethylhexyloxy)carbonyl)pentane-2-sulfonate, in combination with a water-soluble polycation, poly(diallyldimethylammonium chloride). The block copolymer based microcapsule suspension is characterized by a long-term stability, even at high ionic strength, provided by electrostatic and steric stabilization. The weak polyacid based microcapsule suspension is stable for a few weeks, after which aggregation starts due to desorption of the dispersant. The surfactant-polycation based microcapsules appear to have a multicore morphology in contrast to the weak polyacid or block copolymer based microcapsules, which are core-shell particles.
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| 8. |
- Andersson Trojer, Markus, 1981, et al.
(author)
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Charged microcapsules for controlled release of hydrophobic actives Part II: Surface modification by LbL adsorption and lipid bilayer formation on properly anchored dispersant layers
- 2013
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In: Journal of Colloid and Interface Science. - : Elsevier BV. - 1095-7103 .- 0021-9797. ; 409, s. 8-17
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Journal article (peer-reviewed)abstract
- Charge microcapsules with a dodecane core and a poly(methyl methacrylate) (PMMA) shell have been prepared via the internal phase separation method using ionic dispersants. The microcapsules have subsequently been surface modified with polyelectrolyte multilayers and lipid bilayers. Two types of ionic dispersant systems have been investigated: a small set of ionic amphiphilic block copolymers of poly(methyl methacrylate)-block-poly(sodium (meth)acrylate) type and an oil-soluble anionic surfactant, sodium 1,5-dioxo-1,5-bis(3,5,5-trimethylhexyloxy)-3((3,5,5trimethylhexyloxy)car bonyl)pentane-2-sulfonate, in combination with a water-soluble polycation, poly(diallyldimethylammonium chloride). The Layer-by-Layer adsorption of the polyelectrolyte pair poly(diallydimethylammonium chloride) (350,000 g/mol) and poly(sodium methacrylate) (15,000 g/mol) was successfully made on both microcapsule systems with the formation of very thin multilayers as indicated with quartz crystal microbalance with dissipation monitoring (QCM-D) measurements on model surfaces. Formation of a lipid bilayer on the surface of the microcapsules from liposomes with a charge opposite that of the capsule surface was also proven to be successful as indicated by the C-potential of the microcapsules, the characteristic frequency shift as measured with QCM-D and fluorescence recovery after photobleaching (FRAP) on model systems. However, the proper anchorage of the dispersants in the underlying PMMA surface was key for the successful surface modification.
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| 9. |
- Andersson Trojer, Markus, 1981, et al.
(author)
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Imidazole and Triazole Coordination Chemistry for Antifouling Coatings
- 2013
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In: Journal of Chemistry. - : Hindawi Limited. - 2090-9063 .- 2090-9071. ; 2013
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Journal article (peer-reviewed)abstract
- Fouling of marine organisms on the hulls of ships is a severe problem for the shipping industry. Many antifouling agents are based on five-membered nitrogen heterocyclic compounds, in particular imidazoles and triazoles. Moreover, imidazole and triazoles are strong ligands for Cu2+ and Cu+, which are both potent antifouling agents. In this review, we summarize a decade of work within our groups concerning imidazole and triazole coordination chemistry for antifouling applications with a particular focus on the very potent antifouling agent medetomidine. The entry starts by providing a detailed theoretical description of the azole-metal coordination chemistry. Some attention will be given to ways to functionalize polymers with azole ligands. Then, the effect of metal coordination in azole-containing polymers with respect to material properties will be discussed. Our work concerning the controlled release of antifouling agents, in particular medetomidine, using azole coordination chemistry will be reviewed. Finally, an outlook will be given describing the potential for tailoring the azole ligand chemistry in polymers with respect to Cu2+ adsorption and Cu2+ Cu+ reduction for antifouling coatings without added biocides.
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| 10. |
- Andersson Trojer, Markus, 1981
(author)
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Modification of microcapsules for controlled release
- 2012
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Doctoral thesis (other academic/artistic)abstract
- Fouling of marine organisms such as algae and barnacles on the boat hull is an enormous problem for the shipping industry. The negative consequences for the society are both economical and environmental. To prevent fouling in general, biocides are typically incorporated directly into the paint. Premature leakage of the biocides is a drawback which reduces the lifetime of the coating and pollutes the surrounding ecosystems. Microencapsulation is an efficient way of encapsulating active substances for controlling the release and thereby prolonging the antifouling properties of the coating. The microcapsules used in this work consist of an oil core and a hydrophobic polymer shell. The rate of release into the marine environment may be further tailored by modifying the microcapsules. Triggered release is achieved by rendering the microcapsule shell water sensitive. This may be accomplished by incorporating salt into the shell using imidazole coordination chemistry. On the other hand, extended release is achieved by improving the barrier properties of the microcapsule. This may be realized by providing the microcapsule with an additional shell, such as a highly charged polyelectrolyte multilayer or a lipid bilayer. The objective of this thesis is subsequently twofold: 1) To synthesize and characterize imidazole containing shell materials with a view to obtain triggered release. 2) To surface modify microcapsules with polyelectrolyte multilayers and lipid bilayers toward extended release.Imidazole containing polymers were synthesized using vinyl and maleimide radical polymerization, as well as grafting techniques comprising maleimide bond formation and epoxide ring opening. The imidazole-containing polymeric materials, with and without the salts CuCl2 or ZnCl2, were characterized using differential scanning calorimetry, electron paramagnetic resonance (EPR) and vibrational spectroscopy. The coordination chemistry of the imidazole-metal ion complex was investigated using vibrational spectroscopy, EPR and ab initio calculations.The imidazole coordination to the transition metal ions Cu2+ and Zn2+ in polymeric materials generates cross-links. The interaction between the imidazole moiety and the transition metal ions is very strong and specific. As a consequence, the coordinating polymer is rendered insoluble in conventional solvents, excluding only strongly coordinating solvents.The specificity and strength of the imidazole-transition metal ion interaction may be used for a variety of applications. However, with respect to the microencapsulation route used in this project, the limited solubility of the coordinating polymer material is unfortunate. The use of strongly coordinating solvents during the microencapsulation results in aggregation and phase separation instead of microcapsule formation.Routes for synthesising highly charged microcapsules for further surface modification were investigated using three types of ionic dispersants; a weak polyacid, a small set of amphiphilic block copolymers and a hydrophobic anionic surfactant in combination with a polycation. The charged microcapsules were subsequently modified with polyelectrolyte multilayers using the Layer-by-Layer technique and with lipid bilayers using lipid vesicle spreading. The microcapsules and model systems thereof were characterized mainly using micro-electrophoresis, light microscopy, optical tensiometry and quartz crystal microbalance with dissipation (QCM-D). The release behaviour in aqueous suspension of a hydrophobic model compound was investigated using UV-Vis spectroscopy.The use of the ionic dispersants facilitated the formation of highly charged microcapsules and the subsequent polyelectrolyte multilayer assembly and lipid bilayer formation were also successful. In particular, the block copolymer based microcapsules displayed excellent properties with respect to high and stable surface charge, as well as long term colloidal stability through electrostatic and steric stabilization. The release of the hydrophobic model compound was considerably reduced after modification with polyelectrolyte multilayers. In addition, the type of dispersant had a significant impact on the release. The block copolymer based microcapsules with a higher charge density had a much lower release compared to the weak polyelectrolyte based microcapsules.The polyelectrolyte multilayer is an efficient barrier against hydrophobic molecules and the low permeability is clearly a result of the high charge density. As of yet, the effect of the lipid bilayers on the release has not been investigated but has a large potential since the permeability may be altered by the lipid composition. A microcapsule consisting of an oil core, a hydrophobic polymer shell, a polyelectrolyte multilayer and a lipid bilayer is a complex release system with large degrees of freedom for tailoring the release behaviour.
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