Browsing by Author "Rojas, Orlando, Prof., Aalto University and North Carolina State University, USA"

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Supported ultrathin films and non-woven fibre mats from polysaccharide containing bicomponent polymer blends
(2014) Taajamaa, Laura
School of Chemical Technology | Doctoral dissertation (article-based)
Compared to petroleum based chemicals, polysaccharides enable sustainable approaches and environmentally friendly products. Cellulose is the most abundant polymer in the biosphere and it has recently gained wide interest as a source for nanomaterials with remarkable strength and liquid crystalline properties. This work is aimed at gaining knowledge on ultrathin cellulose films on solid supports. The morphology, formation and modification of ultrathin cellulose films were investigated from the fundamental point of view. In addition to novel non-covalent surface modification methods in ultrathin cellulose films, the resulting films were converted from 2D structures into 3D fibre systems. Forming functional systems with high surface-to-volume and aspect ratios is an important driver in nanoscience. One challenge is creating nano- and micronscale structures on ultrathin polymer films. A straightforward bottom-up approach to pattern polymeric films is using the spin coating technique for binary polymer blend solutions. Phase separation in the ultrathin films formed results from thermodynamic instabilities generated during the rapid spin coating process and surface patterns emerge from the interactions between the polymer blend components, the solvent and the substrate. The polymer blend films can be used in fundamental studies as well as in applications spanning from controlled drug release to organic light emitting diodes. Ultrathin blend films consisting of cellulose and a hydrophobic polymer were introduced, followed by a method to quantitatively modify the surface chemistry and morphology of the ultrathin cellulose films. A cellulosic template for nanoparticle immobilisation was created. The tailored properties were achieved by the choice of the solution blend ratio used in spin coating. The second part of the thesis focused on the blends of two polysaccharide derivatives. The construction of bicomponent cellulose films with phase-specific pore formation was discussed, along with reasons explaining the genesis and evolution of the given morphologies. Finally, a method to prepare cellulose derivative blend fibre mats by electrospinning that could be selectively modified after fibre formation was unveiled. This thesis represents a fundamental endeavour to deepen our understanding of various polymer blend architectures. It encompassed a set of investigations related to the construction and modification of supported ultrathin films and non-woven fibre mats from blends containing cellulose derivatives. It is expected that results presented in this interdisciplinary area of science can pave the way for the increasing cooperation, enabling future discoveries.