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Single molecule tracking studies of solvent-swollen microdomains in cylinder-forming polystyrene-Poly (ethylene oxide) diblock copolymer filmsSapkota, Dol Raj January 1900 (has links)
Master of Science / Department of Chemistry / Takashi Ito / Solvent swelling of block copolymer microdomains plays an essential role in the improvement of microdomain alignment by solvent vapor annealing and in chemical separations using block copolymer monoliths. Here, investigation of the effects of solvent swelling on the molecular permeability and dimensions of cylindrical microdomains in polystyrene-block-poly(ethylene oxide) (PS-b-PEO) films is done by using single molecule tracking. These films are prepared by sandwiching benzene (with/without methanol) or THF (with/without methanol) solutions containing 5 nM sulforhodamine B (SRB) between two glass substrates. The PEO microdomains are aligned in the solution flow direction during the film preparation. The diffusional motions of individual SRB molecules are measured at different drying times to assess the microdomain radius and permeability. These parameters, on average, gradually decrease with an increase in drying time; however the trend differs slightly from one solvent system to another. A sharp decrease of microdomain radius is observed for benzene, benzene-methanol, THF and THF-methanol swollen films at initial drying condition (for example 2 days). In contrast, microdomain permeability does not decrease sharply; instead a gradual decreasing trend is seen for all solvent systems. In addition, mixing of a small amount of methanol (14% in PEO microdomains) either with benzene or with THF does not produce noticeable difference in the swelling of PEO microdoamins. Importantly, both benzene and THF offer similar microdomain swelling behavior at the same drying temperature, which is evident from the microdomain radius values, however THF shows comparatively larger microdomain permeability and better correlation between permeability and microdomain radius compared with benzene.
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SINGLE CRYSTAL ENGINEERING OF LINEAR TRI-BLOCK COPOLYMERS:CRYSTALLIZATION AND POLYMER BRUSHESXiong, Huiming 05 October 2006 (has links)
No description available.
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Laser Lithography of Diblock Copolymer FilmsParete, Joseph 09 1900 (has links)
Laser lithography was used to create novel patterns in thin diblock copolymer
films. These patterns were characterized and an examination of their
formation and growth was conducted. The patterns occurred only in diblock
films, due to the interaction between thermal gradient induced Marangoni flow
and the self assembly of the molecules. Growth of the patterns was found to
be strongly dependent on absorbed power. The impact of film thickness on
pattern growth was mainly due to the corresponding changes in sample reflectance, however a periodic patterning was observed suggesting that growth is also dependent on the amount of 'excess' material (over that required to form complete lamella) available. It was also shown that the pattern growth can occur independently of laser lithography and the Marangoni effect, though laser lithography was required to direct this growth. / Thesis / Master of Applied Science (MASc)
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Indium Tin Oxide Nanoparticles Formation for Organic ElectronicsYu, Hyeonghwa January 2016 (has links)
Indium tin oxide is a transparent conductive oxide electrode which is widely used for organic electronics. Morphology of ITO plays an important role in the performance of organic electronics. To understand the influence of the substrate morphology in device performance, a controllable route for producing periodic and aperiodic roughness of ITO surfaces are necessary. In this thesis, this was attempted by using various approaches to forming ITO nanostructures. Initially, ITO was deposited by a traditional sputtering procedure. However, the roughness distribution of the sputtered ITO resulted in a s Gaussian distribution, unsuitable to further studies of roughness. ITO nanostructures can also be formed by depositing ITO nanoparticles on an ITO sub- strates. Using acetate and chloride precursors, ITO films were produced from solution and formed into nanoparticles using the reverse micelles deposition approach. The acetate route (InAc+SnCl2+ethanol), was the most successful prior to the nanoparticle formation, showing high quality ITO with bixbyte crystal structure and Sn percentages of 20%, low enough to form a conductive film. Nanoparticles were fabricated with diblock copolymer reverse micelles(PS-b-P2VP). Reverse micelles were found to act as a nano reactor, restricting the size of nanoparticles by having hydrophilic reactants undergo chemical reactions inside the micelles. However, nanoparticles from the reverse micelles revealed Sn percentages much above 20%. This was attributed to the solubility difference of the precursors leading to displacing or preventing of pre- cursor loading into the reverse micelles. The change of the stirring time, the micelles concentration, the sequence of precursors loading, and the weight of precursors were not found to affect the Sn concentration; moreover, large variations in Sn concentrations were observed. From quantitative nano mechanical testing of the micelles, a maximum load amount for the precursors was observed, confirming that the high concentration of Sn was likely due to the solubility differences between the precursors and their ability to penetrate the micelle. By manipulating the nanoparticles distribution through spin coating speeds, micelles concentration, and deposited volume, several degrees of order were obtained, though hexagonal packing was not observed. In general, even though Sn concentration were found to be above 20%, nanoparticles were successfully fabricated with reverse micelles, confirming that the reverse micelle technique is a good strategy for future studies of roughness. / Thesis / Master of Applied Science (MASc)
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Block Copolymers via Reverse Addition-Fragmentation Chain Transfer Polymerization as a Viable Resin for Packaging CoatingsLascu, Claudia M. 26 June 2015 (has links)
No description available.
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Sensitivity of Block Copolymer Self-Assembly to the Modification of a Single MonomerRehel, Desiree January 2024 (has links)
In this project, the sensitivity of the phase behaviour of AB diblock copolymers to the addition a single C-monomer is investigated using self-consistent mean-field theory. The reference diblock copolymers are composed of the minority A block with N_A = 12 monomers and the majority B block with N_B monomers. The blocks are mutually repulsive and their interaction is characterised by χ_{ij} and acts over range σ_{ij}, where i and j represent the monomer species. When a C-monomer is added to the junction of the diblock copolymers, we observe a notable shift of the phase boundaries to the larger NB and smaller χ_{AB}. The shift to larger NB is due to an increased polymer stretching. When the C-monomers is nearly-neutral, the shift does not strongly depend on the interaction strength. Similarly, the shift is not visibly affected by changing σ_{AC} and σ_{BC}. However, when the the strength of the interaction is selective such that χ_{AC} = χ_{AB} + α and χ_{BC} = χ_{AB} − α, the shift size decreases with increasing α. Conversely, when the selective C-monomer is added to the majority end, the phase boundaries are shifted to the smaller N_B, with the smallest α giving the largest shift. The shifts can be generically understood to be cause by the interplay between the changes in the interfacial tension and polymer stretching due to the C-monomer. These results demonstrate sensitivity of phase behaviour of AB diblock copolymers to the addition of a C-monomer and may provide a useful link between experiment and theory. / Thesis / Master of Science (MSc)
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Synthesis and Protein Adsorption Studies of Pegylated-Polyester Nanoparticles with Different Peg ArchitecturesMontenegro-Galindo, Gladys Rocio January 2013 (has links)
No description available.
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Fabrication and characterization of sub-micron and nanoscale structures in commercial polymersIbrahim, Fathima Shaida January 1900 (has links)
Doctor of Philosophy / Department of Chemistry / Takashi Ito / This dissertation describes the fabrication and characterization of nanoscale structures in commercially available polymers via multiphoton ablation and bottom-up self assembly techniques. High-resolution surface imaging techniques, such as atomic force microscopy (AFM) and chemical force microscopy (CFM) were used to characterize the physical features and chemical properties, respectively, of these nanoscale structures. Fabrication using both top-down and bottom-up methods affords flexibility in that top-down allows random, user-defined patterning whereas bottom-up self assembly produces truly nanoscale (1-100nm) uniform features. Multiphoton induced laser ablation, a top-down method, was used to produce random sub-micron scale features in films of poly(methylmethacrylate) (PMMA), polystyrene (PS), poly(butylmethacrylate) (PBMA) and poly[2-(3-thienyl)ethyloxy-4-butylsulfonate] (PTEBS). Features with 120-nm lateral resolution were obtained in a PMMA film which was concluded to be the best polymer for use with this method. It was also found that etching resolution was highest for polymers having high glass transition temperatures, low molecular weights and no visible absorption. Bottom-up self assembly of polystyrene-poly (methylmethacrylate) (PS-b-PMMA) diblock copolymer and UV/acetic acid treatment produced nanoscale cylindrical domains supported by a substrate. AFM imaging at the free surface showed metastable vertical PMMA domain orientation on gold substrates. In contrast, horizontal orientation was obtained on oxide-coated silicon regardless of surface roughness and annealing conditions. The horizontal domain orientation on silicon substrates was ideal to probe simultaneously the difference in surface charge and hydrophilicity of the two distinct nanoscale domains of UV/AcOH treated PS-b-PMMA films. CFM on UV/acetic acid etched PS-b-PMMA revealed the presence of –COO- groups which were found to be more abundant inside the etched trenches than on the unetched PS matrix as shown by ferritin adsorption onto etched PS-b-PMMA. Lastly, the PS-b-PMMA was cast as a free-standing monolith at the end of a quartz micropipette. AFM revealed circular PMMA dots at the free surface, indicating alignment parallel to the long axis of capillary. Ion conductance within nanochannels indicated surface –charge governed ion transport at low KCl concentrations and flux of negatively-charged sulphorhodamine dye demonstrated the permselective nature of nanochannels.
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Characterization of cylindrical nano-domains in thin films of polystyrene-poly(methyl methacrylate) diblock copolymer studied via atomic force microscopyMaire, Helene C. January 1900 (has links)
Doctor of Philosophy / Department of Chemistry / Takashi Ito / We have investigated the orientation of cylindrical domains in thin films of a polystyrene–poly(methylmethacrylate) diblock copolymer (PS-b-PMMA) on planar substrates having different surface roughnesses and hydrophilicities. The research in this dissertation covers the substrate surface modifications, the enhancement of the diblock copolymer film coating, and the refinement of the treatments leading to nanoporous material.
Treatment of the substrate with organic mercaptans forming self-assembled-monolayer (SAM), leading to various hydrophilicities of the surfaces, was inconclusive as far as orienting the PMMA domains in the PS matrix due to thermal instability of some thiols. This directed us to a different approach involving substrate roughness. PS-b-PMMA films of 20~200 nm thick were prepared via spin-coating on silicon, gold or indium tin oxide (ITO) substrates, and annealed in vacuum at 170 °C for 60 hours to induce the formation of cylindrical PMMA domains. Atomic force microscopy (AFM) images indicated the domain orientation at the free surface. In PS-b-PMMA films much thicker than the domain periodicity (L0), the domains were oriented perpendicularly to the free surface regardless of underlying substrates, reflecting the balanced interactions of PS and PMMA blocks at the polymer–vacuum interface. In films having thickness similar to L0, vertically oriented domains were observed on the Au and ITO surfaces that are covered with nanoscale grains, whereas horizontal domains were observed on the smooth Si substrates. In particular, the cylindrical PMMA domains were efficiently perpendicularly aligned when the grain size nearly was equal to L0. The perpendicular domain alignment induced by the substrate roughness was corroborated using cyclic voltammetry (CV) for gold substrates coated with PS-b-PMMA films whose PMMA domains were removed by UV and subsequent acetic acid treatments. The CV data also suggested that
the PMMA domains were successfully removed, leaving a nanoporous stable PS matrix on the substrate.
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Photo-crosslinked and pH sensitive polymersomes for triggering the loading and release of cargoGaitzsch, Jens, Appelhans, Dietmar, Gräfe, David, Schwille, Petra, Voit, Brigitte 31 March 2014 (has links) (PDF)
Crosslinkable and pH-sensitive amphiphilic block copolymers are promising candidates to establish pH-stable and permeable vesicles for synthetic biology. Here, we report the fabrication of crosslinked and pH-stable polymersomes as swellable vesicles for the pH-dependent loading and release of small dye molecules. / Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.
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