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The self-assembly behavior of arborescent polystyrene-<em>graft</em>-poly(ethylene oxide) copolymers (PS-<em>g</em>-PEO) at the air-water interface and the solubilization/release properties of arborescent polystyrene-<em>graft</em>-poly(2-vinylpyridine) (PS-<em>g</em>-P2VP) copolymers were investigated. These amphiphilic dendritic molecules are covalently bonded unimolecular micelles incorporating a highly branched hydrophobic polystyrene core surrounded by a hydrophilic poly(ethylene oxide) or poly(2-vinylpyridine) shell. Molecules of PS-<em>g</em>-PEO copolymers spontaneously formed supramolecular assemblies at the air-water interface. The type of superstructures formed was found to depend upon copolymer composition, while the level of association was more directly related to the branching density of the polymers. At low surface pressures the PEO segments apparently remained adsorbed on the water subphase, but desorbed into water at very high surface pressures, in the condensed monolayer state. Controlled degradation of the PEO chains with UV light greatly enhanced molecular association, resulting in the formation of either large clusters or long ribbon-like superstructures. The PS-<em>g</em>-P2VP copolymers were found to efficiently solubilize and release hydrophobic small molecules in aqueous media. The partition coefficient and solubilization capacity of the copolymers for hydrophobic polyaromatic hydrocarbons increased with the polystyrene content of the copolymers, while the rate of solubilization decreased with increasing branching functionality of the copolymers. The release profiles for two model drugs displayed an initial burst in release followed by gradual approach to equilibrium. The diffusion coefficients of the drugs in the micelles increased with the branching functionality and the generation number of the micelles, presumably due to increased electrostatic repulsions of the protonated vinylpyridine units.

The self-assembly behavior of arborescent polystyrene-<em>graft</em>-poly(ethylene oxide) copolymers (PS-<em>g</em>-PEO) at the air-water interface and the solubilization/release properties of arborescent polystyrene-<em>graft</em>-poly(2-vinylpyridine) (PS-<em>g</em>-P2VP) copolymers were investigated. These amphiphilic dendritic molecules are covalently bonded unimolecular micelles incorporating a highly branched hydrophobic polystyrene core surrounded by a hydrophilic poly(ethylene oxide) or poly(2-vinylpyridine) shell. Molecules of PS-<em>g</em>-PEO copolymers spontaneously formed supramolecular assemblies at the air-water interface. The type of superstructures formed was found to depend upon copolymer composition, while the level of association was more directly related to the branching density of the polymers. At low surface pressures the PEO segments apparently remained adsorbed on the water subphase, but desorbed into water at very high surface pressures, in the condensed monolayer state. Controlled degradation of the PEO chains with UV light greatly enhanced molecular association, resulting in the formation of either large clusters or long ribbon-like superstructures. The PS-<em>g</em>-P2VP copolymers were found to efficiently solubilize and release hydrophobic small molecules in aqueous media. The partition coefficient and solubilization capacity of the copolymers for hydrophobic polyaromatic hydrocarbons increased with the polystyrene content of the copolymers, while the rate of solubilization decreased with increasing branching functionality of the copolymers. The release profiles for two model drugs displayed an initial burst in release followed by gradual approach to equilibrium. The diffusion coefficients of the drugs in the micelles increased with the branching functionality and the generation number of the micelles, presumably due to increased electrostatic repulsions of the protonated vinylpyridine units.

Self-assembly is an autonomous process where components organize themselves into structures via noncovalent interactions without human intervention. Ultrashort amphiphilic peptides are typical self-assembly molecules with specific sequence motifs which consist of three to seven amino acids. Due to their amphiphilic structure which carries a dominant hydrophobic tail and a polar head group, these peptides can self-assemble to construct nanofibrous scaffolds system to form hydrogels, organogels or aerogels. The nanofibrous scaffolds formed by amphiphilic peptides are very similar to the fiber structure found in collagen which plays an essential role in extracellular matrix showing the potential of applying these peptide scaffolds together in culturing native human cells. Thus the derivate of amphiphilic peptides depsipeptide in which we replaced one amide bond with an ester bond is also worthwhile to explore a novel penitential material for Tissue Engineering. At the same time, because of the perfect biocompatibility of amphiphilic peptides made up of natural l-amino acids and also the excellent gelation properties providing a solution for zinc dendrite growth in Zn batteries, it will be also meaningful to combine the rationally designed peptide gelation system to Zn batteries. This dissertation describes how to characterize and use ultrashort amphiphilic depsipeptide for tissue engineering and use ultrashort amphiphilic peptide for the electrolyte of Zn batteries. The first chapter provides us with an introduction to self-assembly material, 3D bioprinting, and Zn batteries. The second chapter introduces a novel method to synthesize the depsipeptide fully based on solid phase peptide synthesis (SPPS) and also shows the different properties, especially the gelation behavior by clarifying its mechanism via doing the characterization of depsipeptide. At the end of the second chapter, depsipeptide is proved to be a potential material in 3D bioprinting. The third chapter reveals how we synthesized and characterized the amphiphilic peptide and applied it to the Zn batteries. The cycling stability got promoted compared with bard Zn batteries in symmetrical Zn-Zn cells while the formation of Zn dendrite was also suppressed. The promising results suggest peptide gelation systems are promising electrolytes for use in Zn batteries.

Many emerging technologies would greatly benefit from reliable methods for the production of functional materials with well-defined 3D nanoscale structure. Conceptually, approaches to produce such architectures are divided into two broad classes; top down and bottom up manufacture. In the top down approach, nanoscale structure is created through the controlled removal of material from a bulk starting object. Top down methods have a proven record of reliability in the fabrication of extended two dimensional arrays with fine control over nanoscale features. However, such approaches become increasingly cumbersome when attempting to define structure in three dimensions rather than two. Bottom up methods promise a more reliable route to the formation of such materials. Here, molecular scale building units self-assemble to form a desired structure, driven by pre-defined interactions between individual motifs. Due to the highly specific molecular recognition properties of nucleic acids, along with their relatively simple synthesis and wide range of potential chemical modifications, DNA nanotechnology is now regarded as a prime route for the bottom up fabrication of nanostructured materials. However, current approaches to the formation of designed 3D DNA crystals are complicated by the difficulties in designing sub-units able to assemble in a predictable fashion over length-scales orders of magnitude larger than themselves. Amphiphiles are able to self-assemble into a variety of 3D crystalline phases driven by the frustrated micro-phase separation of hydrophobic and hydrophilic domains, with the structural properties reliant primarily on overall topology of the molecules rather than their exact chemical and geometrical features. Although the mechanism underlying amphiphile self-assembly is robust, it inherently limits control over the fine-scale structural details. This thesis reports on a new class of self-assembling DNA motifs; amphiphilic cholesterol-functionalised DNA nanostars, \emph {C-stars}. C-stars combine key advantages of all-DNA motifs and conventional amphiphilic molecules -- allowing for the preparation of expanded crystalline frameworks with tunable properties and embedded functionality.

The overall emphasis of this doctoral dissertation is on the design, synthesis, detailed characterization and application of amphiphilic hyperbranched fluoropolymers (HBFPs) crosslinked with poly(ethylene glycols) (PEGs) in complex polymer coatings as anti-biofouling surfaces. This dissertation bridges synthetic polymer chemistry, materials science and biology to produce functional coatings capable of fouling prevention, demonstrating thermo-controlled healing and acting as a benchmark surface to understand component:property relationships prior to increasing formulation complexities. A two-dimensional array of HBFP-PEG coatings was produced by the co-deposition of uniquely composed HBFPs with varying weight percentages of PEG. Bulk and surface properties were evaluated and assigned to formulation trends. Based on these findings, the most viable candidates were replicated and their fouling responses were assessed against three marine fouling organisms. An active mode of biofouling resistance was covalently grafted onto the surface of HBFP-PEG. The presentation of the settlement-deterrent molecule noradrenaline (NA) works in tandem with the highly-complex surface, to act as a dual-mode, anti-biofouling coating NA-HBFP-PEG. Secondary ion mass spectrometry (SIMS) was employed to quantify the extent of NA substitution. Biological assays against oyster hemocytes confirmed the activity of the grafted NA and cyprid settlement assays supported that the overall anti-biofouling ability of NA-HBFP-PEG was increased by 75%. Thermally-reversible crosslinks were installed as healable units throughout the framework of the networks, with the goal of generating coatings that could possess a greater resistance to mechanical failure. Small molecule and linear polymer models were probed by nuclear magnetic resonance (NMR) spectroscopy and gel permeation chromatography (GPC) to demonstrate the controlled reversibility of the crosslinks. Optical microscopy was employed to visualize surface scratch healing and fluorescence microscopy was used to identify the adsorption behavior of fluorescently-labeled proteins. A benchmark, anti-biofouling surface was generated through thiol-ene crosslinking of a linear fluoropolymer with pendant alkenes (LFPene) with pentaerythritol tetrakis(3-mercaptopropionate) (PETMP). Core constituents were evaluated spectroscopically and surfaces of LFPene-PETMP, along with two model surfaces that largely expressed a single component, were analyzed to understand how individual elements and blending contributed to the physical, mechanical and anti-biofouling properties to generate a performance baseline to compare against future generations.

Master of Science / Department of Grain Science and Industry / X. Susan Sun / One of the leading causes of death following traumatic injury is exsanguination. The body addresses bleeding through the process of hemostasis which includes the formation of a fibrin mesh structure that holds a blood clot together. During traumatic injury, hemostasis may be unable to stop excess bleeding. Fibrin based hemostatic agents have been developed, however, these studies often use fibrin obtained from biological sources, which poses risk of infection. A novel amphiphilic peptide (h9e) has been studied to form three dimensional nanofibers networks. In this research, we studied the ability to form a synthetically produced, fibrin-mimic, hemostatic material from the h9e peptide sequence. The objective of this study was to determine the blood gelation strength of the h9e peptide necessary to arrest bleeding in the Wistar Rat model. Commercial mouse blood was used for blood gelation in vitro studies. Dynamic rheometer was used to determine the gelation kinetics at varied h9e peptide concentrations ranging from 1-5% wt. By directly mixing the h9e peptide with blood, we observed that the blood gelation strength right after mixing increased as the h9e peptide weight % concentration increased, from 67 to 1086 Pascals in the peptide concentration from 1 to 5%, respectively. After 24 hours, final gelation strength of all concentrations with commercial mouse blood was lower than the instantaneous strength but consistent throughout testing. Similar testing was conducted using commercial Wistar Rat blood with weight % concentrations of 1, 3, and 5% of h9e peptide. The gelation strength was 500, 1665, and 1914 Pascals, respectively. We also determined the gelation strength of Wistar Rat blood components, such as red blood cells, serum, and plasma with 1% h9e peptide. We observed the gelation response induced with individual blood components; however, the strength is weaker than whole blood. In vivo, we applied the cut-tail method by dipping the cut-tail of Wistar Rats into the h9e peptide solutions for 10 seconds and then took it out for blood lost collection. We observed that h9e peptide solution at 1, 3, and 5% weight concentrations can all generate hemostatic function. The h9e peptide solution at 5% weight concentration (1914 Pa) was able to outperform a commercial hemostatic material (Moore Medical CELOX* Hemostatic Granules), significantly reducing both bleeding time and blood lost: h9e peptide at 5% had a bleeding time of 94 sec and 0.75 mL blood lost, while the Celox hemostatic granules had a bleeding time of 225 sec and 1.5 mL blood lost. Transmission Electron Microscopy and Spinning Disk Confocal Microscope imaging indicated a blood component reinforced, web-like, h9e nanofiber structure similar to the structure formed by fibrin in a blood clot. This study showed that h9e peptide has the potential to be used to induce hemostasis.

The aim of this thesis is to investigate the structural and thermodynamic properties of biologically and technological relevant macromolecules when placed at soft interfaces. In particular two amphiphilic macromolecules characterized by different topologies have been investigated namely amphiphilic dendrimers and linear block copolymers. This goal is achieved using a multiscale approach which includes all-atom, united atom and coarse grained models by means of molecular dynamic simulations.Amphiphilic dendrimers have shown to be promising building blocks for a range of interfacial materials and can be used in applications such as surface-base sensors or surface nanopatterning. In this part of the thesis by means of all-atom molecular dynamics simulations, we investigated the structure and stability of alkyl-modified polyamido-amide (PAMAM) dendrimers at the air/water interface as a function of the number and the relative position of the modified end groups. We found that the PAMAM dendrimer with all terminal groups functionalized is more stable at the interface than the Janus dendrimer, where only half the amine groups are modified. These results indicate that monolayers of fully functionalized molecules could be as stable as (or more stable than) those self-assembled from Janus molecules.The second part of the thesis is devoted to model a particular family of amphiphilic triblock copolymer sold as Pluronics, consisting of poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO) arranged as PEO–PPO–PEO. There is evidence that this class of amphiphilic materials can be used for different biological applications. A fuller understanding of the molecular mechanisms underpinning their interactions with living cells is essential for ensuring the polymers safety and efficacy in biomedical applications. Using united-atom molecular dynamics simulations and membrane lysis assays, we investigated the relationship between the molecular conformations of a subset of the Pluronic copolymers (L31, L61, L62 and L64) and their haemolytic activity. Our computational studies suggest that the hydrophilic blocks in these copolymers interact with the polar head groups of lipid molecules, resulting in a predicted modification of the structure of the membranes. Parallel membrane lysis assays in human erythrocytes indicate differences in the rates of haemolysis, as a result of incubation with these polymers, which correlate well with the predicted interactions from the atomistic simulations. The computational data thus provide a putative mechanism to rationalize the available experimental data on membrane lysis by these copolymers. The data quantitatively agree with haemoglobin release endpoints measured when copolymers with the same molecular weight and structure as of those modelled are incubated with erythrocytes. The data further suggest some new structure– function relationships at the nanoscale that are likely to be of importance in determining the biological activity of these otherwise inert copolymers.In order to visualise the effect of Pluronics at a length and time scale closer to the experimental one, in the third part of the thesis we developed a coarse-grained model for the amphiphilic copolymers within the framework of the MARTINI forcefield (Marrink et al., J. Phys. Chem. B, 2007, 111, 7812). The MARTINI force field is usually parameterized targeting thermodynamic properties. In addition to this, we further parameterized it based on atomistic simulations validating the parameters against structural properties of the copolymers. The ability of the model to predict several structural and thermodynamic properties of the atomistic system have been explored. The aim of this work is to be able to simulate the polymer/lipid interface at polymer concentration similar to the experimental one.