| 1. |
- Wang, Xueting, 1991, et al.
(författare)
-
Methane Adsorption and Methanol Desorption for Copper Modified Boron Silicate
- 2018
-
Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 8:63, s. 36369-36374
-
Tidskriftsartikel (refereegranskat)abstract
- Boron silicate (BS) with a chabazite framework structure was synthesised using a direct route and rigorously characterized before it was ion-exchanged with copper to form Cu-BS. Employing in situ infrared spectroscopy, we show that Cu-BS is capable of oxidising methane to methoxy species and methanol interacts with the boron sites without deprotonation.
|
|
| 2. |
- Gårdebjer, Sofie, 1985, et al.
(författare)
-
Solid-state NMR to quantify surface coverage and chain length of lactic acid modified cellulose nanocrystals, used as fillers in biodegradable composites
- 2015
-
Ingår i: Composites Science and Technology. - : Elsevier BV. - 0266-3538. ; 107, s. 1-9
-
Tidskriftsartikel (refereegranskat)abstract
- The surface of cellulose nanocrystals (CNC) was chemically modified with polylactic acid. The modification was characterized by infrared spectroscopy, by monitoring the colloidal behavior of CNC in different solvents, and by quantitative analysis using solid-state NMR (ss-NMR). The quantitative analysis showed that grafted PLA chains on average comprised two lactic acid units attached to 48% of all available hydroxyl groups on the surface of the CNC. Both modified and unmodified CNC were incorporated as fillers in three different biodegradable materials: polylactide acid (PLA), poly(lactide-co-glycolide) (PLGA) and poly(3-hydroxybutyrate) (PHB). Composite films with up to 20 wt% of unmodified and modified CNC were produced via solvent casting. Compared to unmodified CNC, the modified CNC showed less aggregation in organic solvents and hydrophobic polymer materials and increased interaction was seen between the polymer and filler after surface modification. Using ss-NMR, our study shows that even as little as two units of PLA assures stabile CNC dispersions in organic solvents and distribute CNC in hydrophobic polymers.
|
|
| 3. |
- Idström, Alexander, 1983, et al.
(författare)
-
13C NMR assignments of regenerated cellulose from solid-state 2D NMR spectroscopy
- 2016
-
Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617. ; 151, s. 480-487
-
Tidskriftsartikel (refereegranskat)abstract
- From the assignment of the solid-state 13C NMR signals in the C4 region, distinct types of crystalline cellulose, cellulose at crystalline surfaces, and disordered cellulose can be identified and quantified. For regenerated cellulose, complete 13C assignments of the other carbon regions have not previously been attainable, due to signal overlap. In this study, two-dimensional (2D) NMR correlation methods were used to resolve and assign 13C signals for all carbon atoms in regenerated cellulose. 13C-enriched bacterial nanocellulose was biosynthesized, dissolved, and coagulated as highly crystalline cellulose II. Specifically, four distinct 13C signals were observed corresponding to conformationally different anhydroglucose units: two signals assigned to crystalline moieties and two signals assigned to non-crystalline species. The C1, C4 and C6 regions for cellulose II were fully examined by global spectral deconvolution, which yielded qualitative trends of the relative populations of the different cellulose moieties, as a function of wetting and drying treatments.
|
|
| 4. |
- Idström, Alexander, 1983
(författare)
-
Investigating cellulose structure using solid-state NMR spectroscopy
- 2015
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Cellulose is the most abundant polymer in nature and it is an important constituent in most flowers, trees, and even some animals. Cellulose has an established use in many important products, such as textile fibers, paper and paperboard, and recently new applications have received increased attention. The crystalline parts of the cellulose wood fiber can be extracted and this material can be used for applications such as forming thin films or as stabilizers in emulsions. New and more environmentally friendly processes to dissolve cellulose and produce textile fibers are also of interest. However, both native and regenerated cellulose build up complicated supramolecular structures that are, to some extent, still not completely resolved. In order to be able to utilize the cellulose material fully, additional knowledge of the material is needed. In the work covered in this thesis, solid-state NMR was used to gain information of the supramolecular structure of cellulose. Measurements were conducted on both native and regenerated cellulose, exposed to a range of different treatments. Using the 1D solid-state NMR spectrum, the effects on the material after a certain treatment could be followed and elucidated. During the production of regenerated cellulose, the structure of the material was altered by changing the properties of either the solvent or the coagulant, changing the initial cellulose concentration, or by post-treatment, e.g. drying and re-wetting. This latter process induces an irreversible pore collapse, called hornification. This phenomenon was seen for both native and regenerated cellulose and it was concluded from the studies that co-crystallization contributes to hornification. Using 2D solid-state NMR correlation spectroscopy, a full chemical shift assignment of the 1D NMR spectrum of regenerated cellulose was obtained. This assignment made it possible to follow treatments of the material from the full solid-state NMR spectrum. Using the chemical shift assignment, a global spectral deconvolution could be applied on the 1D spectrum of regenerated cellulose, making it possible to, with increased accuracy, determine the crystallinity of the material.
|
|
