| 1. |
|
|
| 2. |
- Rahm, Martin, 1982-
(författare)
-
Green Propellants
- 2010
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- To enable future environmentally friendly access to space by means of solid rocket propulsion a viable replacement to the hazardous ammonium perchlorate oxidizer is needed. Ammonium dinitramide (ADN) is one of few such compounds currently known. Unfortunately compatibility issues with many polymer binder systems and unexplained solid-state behavior have thus far hampered the development of ADN-based propellants. Chapters one, two and three offer a general introduction to the thesis, and into relevant aspects of quantum chemistry and polymer chemistry. Chapter four of this thesis presents extensive quantum chemical and spectroscopic studies that explain much of ADN’s anomalous reactivity, solid-state behavior and thermal stability. Polarization of surface dinitramide anions has been identified as the main reason for the decreased stability of solid ADN, and theoretical models have been developed to explain and predict the solid-state stability of general dinitramide salts. Experimental decomposition characteristics for ADN, such as activation energy and decomposition products, have been explained for different physical conditions. The reactivity of ADN towards many chemical groups is explained by ammonium-mediated conjugate addition reactions. It is predicted that ADN can be stabilized by changing the surface chemistry with additives, for example by using hydrogen bond donors, and by trapping radical intermediates using suitable amine-functionalities. Chapter five presents several conceptual green energetic materials (GEMs), including different pentazolate derivatives, which have been subjected to thorough theoretical studies. One of these, trinitramide (TNA), has been synthesized and characterized by vibrational and nuclear magnetic resonance spectroscopy. Finally, chapter six covers the synthesis of several polymeric materials based on polyoxetanes, which have been tested for compatibility with ADN. Successful formation of polymer matrices based on the ADN-compatible polyglycidyl azide polymer (GAP) has been demonstrated using a novel type of macromolecular curing agent. In light of these results further work towards ADN-propellants is strongly encouraged.
|
|
| 3. |
|
|
| 4. |
|
|
| 5. |
- Antoni, Per, et al.
(författare)
-
Pushing the Limits for Thiol-Ene and CuAAC Reactions : Synthesis of a 6th Generation Dendrimer in a Single Day
- 2010
-
Ingår i: Macromolecules. - : American Chemical Society (ACS). - 0024-9297 .- 1520-5835. ; 43:16, s. 6625-6631
-
Tidskriftsartikel (refereegranskat)abstract
- Dendrimer synthesis should not be tedious and time-consuming. By utilizing an AB(2)-CD2 approach and having orthogonal, "clickable" groups on each monomer, the time for dendrimer assembly can be drastically reduced. This was shown by preparation of a sixth generation dendrimer from starting monomer units in a single day.
|
|
| 6. |
- Bergenudd, Helena, et al.
(författare)
-
Heterogeneous iron(II)-chloride mediated radical polymerization of styrene
- 2009
-
Ingår i: Journal of Molecular Catalysis A. - : Elsevier BV. - 1381-1169 .- 1873-314X. ; 306:1-2, s. 69-76
-
Tidskriftsartikel (refereegranskat)abstract
- In an attempt to perform atom transfer radical polymerization (ATRP) with a more environmentally friendly mediator, polymerization of styrene in the presence of iron(II)-chloride and EDTA was explored from a mechanistic point of view. The presence of EDTA, which normally can form a complex with FeCl2, had no influence on the polymerization results as both the mediator and EDTA were insoluble in the polymerization medium. A mechanism is suggested for the heterogeneous polymerization of styrene mediated by iron (II)-chloride in p-xylene at 50 °C. Varying the mediator amount more than 10-fold revealed that the rate limiting step at low mediator amounts was the adsorption of the initiator or dormant polymer to the mediator surface, whereas at higher mediator amounts, the rate limiting step was instead the activation step in the ATRP equilibrium. The mechanism changed to free radical polymerization in solution at a certain conversion, resulting in lower apparent rate constant and an increased amount of transfer and termination reactions. Chain extension with MMA showed that a significant proportion of the polymer chain ends were active also at high conversions.
|
|
| 7. |
- Bouit, Pierre-Antoine, et al.
(författare)
-
Dendron-decorated cyanine dyes for optical limiting applications in the range of telecommunication wavelengths
- 2009
-
Ingår i: New Journal of Chemistry. - : Royal Society of Chemistry (RSC). - 1144-0546 .- 1369-9261. ; 33:5, s. 964-968
-
Tidskriftsartikel (refereegranskat)abstract
- Cyanine dyes decorated with 2,2-bis(methylol) propionic acid (bis-MPA) based dendrons up to third generation were synthesized. Dendrons were attached to the chromophore using a "click chemistry'' reaction. Photophysical characterizations of these dyes show intense absorption and emission in the near-infrared (NIR), while nonlinear transmission experiments of the dendron-decorated chromophores indicate that properties in the IR of the parent dyes are conserved. This synthetic approach is a crucial preliminary step towards the preparation of solid functional materials for optical limiting (OL) applications in the IR.
|
|
| 8. |
- Carlmark, Anna, et al.
(författare)
-
ATRP grafting from cellulose fibers to create block-copolymer grafts
- 2003
-
Ingår i: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 4:6, s. 1740-1745
-
Tidskriftsartikel (refereegranskat)abstract
- Cellulose fibers, in the form of a conventional filter paper, have been modified by reacting the hydroxyl groups on the fiber surface with 2-bromoisobutyryl bromide, followed by grafting using ATRP conditions. The papers were first grafted with methyl acrylate (MA), rendering the paper very hydrophobic as reported in an earlier work. The papers were analyzed by gravimetry, FT-IR, ESCA, and AFM. To verify that the polymerization from the surface was living, a second layer of another, hydrophilic, polymer, 2-hydroxyethyl methacrylate (HEMA), was grafted upon the PMA layer, creating a block-copolymer graft from the fibers. After the layer of PHEMA had been attached, contact angle measurements were no longer possible, because of the absorbing nature of PHEMA-grafted layer. This indicates that a copolymer had indeed been formed on the surface. FT-IR showed a large increase in carbonyl content after the PHEMA-grafting, which further proves that a layer of PHEMA was attached to the PMA layer. This goes to show that the hydrophilic/ hydrophobic behavior of a cellulose surface can be tailored by the use of living/controlled radical polymerization methods such as ATRP.
|
|
| 9. |
- Claesson, Hans, et al.
(författare)
-
Semi-crystalline thermoset resins : tailoring rheological properties in melt using comb structures with crystalline grafts
- 2004
-
Ingår i: Progress in organic coatings. - : Elsevier BV. - 0300-9440 .- 1873-331X. ; 49:1, s. 13-22
-
Tidskriftsartikel (refereegranskat)abstract
- Thermosetting resins with semi-crystalline grafts have been synthesized. An amorphous resin with epoxide groups was first functionalized with hydroxyl groups using 2,2-bis(methylol) propionic acid, bis-MPA in bulk at 155 degreesC. Functionalization with bis-MPA was monitored using FT-IR, FT-Raman and SEC. The reaction was complete in 30 min. Grafts of poly(epsilon-caprolactone) were then grown from the hydroxyl functional resin and end capped with methacrylate groups. The polymerization Of epsilon-caprolactone, performed in bulk at 110 degreesC using Sn(Oct)(2), was characterized using H-1 NMR and SEC. The obtained molecular weights agreed well with theoretical values. The final end capping was performed using methacrylic anhydride, and monitored with SEC and H-1 NMR, which indicated full substitution. Two combs were synthesized with different arm lengths, DP 10 and 20, and the obtained M-W were close to calculated values. The complex viscosity was measured from low to high temperature for the crystalline resins, the amorphous resin and blends thereof. Rheological data show a rapid decrease in viscosity within a temperature change of 10-15 degreesC for the crystalline resins while the amorphous resin exhibited a slow softening. The blends exhibited a behavior in-between that of the crystalline and the amorphous resin. Films were prepared from the pure resins and the blends. The films were cured using UV irradiation. The comb architecture of these resins has advantages such as crystallinity, high molecular weight and low viscosity, facilitating leveling and resulting in smooth films. The final film properties varied with the ratio of crystalline to amorphous resin, where increase in the amount of crystalline resin correlated with increased the flexibility.
|
|
| 10. |
- Claesson, Hans, et al.
(författare)
-
Synthesis and characterisation of star branched polyesters with dendritic cores and the effect of structural variations on zero shear rate viscosity
- 2002
-
Ingår i: Polymer. - 0032-3861 .- 1873-2291. ; 43:12, s. 3511-3518
-
Tidskriftsartikel (refereegranskat)abstract
- A series of branched polyesters consisting of poly(epsilon-caprolactone) (PCL) (degree of polymerisation: 5-200) initiated from hydroxy-functional cores and end-capped with methylmethacrylate have been prepared. The cores were third-generation hyperbranched polyester, Boltorn, with approximately 32 hydroxyl groups, a third-generation dendrimer with 24 hydroxyl groups and a third-generation dendron with eight hydroxyl groups. Finally, a linear PCL was synthesised as a reference material. All initiators were based on 2,2-bis(methylol) propionic acid (bis-MPA). C-13 NMR spectra of the polymers showed that those with shorter arms contained unreacted hydroxyl groups on the core. Rheological measurements of zero shear rate viscosity, eta(0), showed that the branched polyesters had a considerably lower eta(0) than linear polyester with similar molecular weight. The low melt viscosity and the crystallity produced a theological behaviour suitable for the film formation process for powder coatings. Measurements of mechanical properties of cured films showed that those with low arm molecular weight, M-a, were amorphous while those of high M-a were crystalline.
|
|
