The interest for polymeric nanocomposites has rapidly grown during the last decades, fuelled by the great potential and superior properties of nanoparticles (NPs). The production volumes of commercial NPs have increased exponentially during the last ten years, and the quality has been significantly improved. The aim of this study was to design polymer grafted commercially available metal-oxide NPs, and graphene oxide (GO), to develop isotropic (homogeneous) and anisotropic (heterogeneous) polymer nanocomposites for dielectric applications. The motivation was to formulate functional insulation materials for compact components in future power-grid systems using high-voltage direct-current (HVDC) or high-voltage alternating-current (HVAC), and to fabricate responsive sensor materials for monitoring e.g. temperature and voltage fluctuations in so called “Smart Grids”. Aluminium oxide (Al2O3), zinc oxide (ZnO) and reduced GO (rGO) NPs were modified with sparse polymer grafts via a controlled “covalent route” and were mixed with silicone (PDMS) or polyethylene matrices (EBA and LDPE) commonly used in HV-cable systems. The graft length and the graft-to-matrix compatibility were tailored to obtain nanocomposites with various self-assembled NP-morphologies, including well-dispersed, connected and phase-separated structures. The graft length was used to adjust the inter-particle distance of nanocomposites with continuous morphologies or connected (percolated) NPs. It was found that nanocomposites with percolated NPs and short inter-particle distances exhibited 10-100 times higher conductivity than the unfilled (neat) polymer, or displayed a rapid non-linear increase in conductivity (~1 million times) with increasingelectric field, while well-dispersed NPs with long inter-particle distances exhibited 10-100 times lower conductivity (i.e. higher resistivity) as an effect of their trapping of charge carriers. These tunable and functional properties are desirable for HV-insulation, field-grading applications, and flexible electronics. In addition it was shown that GO modified with dense polymer grafts via a “physisorption route” formed suspensions with liquid crystals, or matrix-free GO-composites with well-dispersed GO in isotropic or nematic states. These materials were reinforced by the GO, and exhibited elevated glass transition temperatures and a rapid thermo-responsive shape-memory effect, and are thus proposed to have a great potential as sensor materials and responsive separation membranes. / Intresset för polymera nanokompositer har snabbt ökat under de senaste decennierna, drivet av den stora potentialen och de överlägsna egenskaperna hos nanopartiklar (NPs). Produktionsvolymerna för kommersiella NP har ökat exponentiellt under de senaste tio åren, och kvaliteten har förbättrats avsevärt. Syftet med denna studie var att polymer-ympa kommersiellt tillgängliga metalloxid-NPs, och grafenoxid (GO), för att designa isotropa (homogena) och anisotropa (heterogena) polymera nanokompositer för dielektriska tillämpningar. Motiveringen var att formulera funktionella isoleringsmaterial för kompakta komponenter i framtida kraftnätssystem som använder högspänd likström (HVDC) eller högspänd växelström (HVAC), samt att tillverka responsiva sensormaterial för övervakning av t.ex. temperatur- and spänningsvariationer i så kallade "Smart Grids". Aluminiumoxid (Al2O3), zinkoxid (ZnO) och reducerad GO (rGO) NPs modifierades med glesa polymerympar via en kontrollerad "kovalent väg" och blandades med silikon (PDMS) eller polyeten matriser (EBA och LDPE) som är vanliga i HV-kabelsystem. Ymplängden och ymp-till-matrix kompatibiliteten skräddarsyddes för att erhålla nanokompositer med olika självordnande NP-morfologier, inklusive väldispergerade, länkade och fasseparerade strukturer. Ymplängden användes för att justera partikelavståndet i nanokompositer med förbundna morfologier eller länkade NPs. Man fann att nanokompositer med länkade NPs och korta interpartikelavstånd uppvisade 10-100 gånger högre konduktivitet än den ofyllda (rena) polymeren, eller erhöll en snabb icke-linjär ökning i konduktivitet (~1 miljon gånger) med ökande elektriskt fält, medan väldispergerade NPs med långa interpartikelavstånd uppvisade 10-100 gånger lägre ledningsförmåga (dvs. högre resistivitet) som en effekt av deras infångande av laddningsbärare. Dessa inställbara och funktionella egenskaper är önskvärda för HV-isolering, fältstyrande applikationer och flexibel elektronik. Dessutom visades att GO, som modifierats med täta polymerympar via en "fysisorptionsväg", bildade suspensioner med flytande kristaller, eller matrisfria GO-kompositer med väldispergerad GO i isotropa eller nematiska tillstånd. Dessa material armerades av GO och uppvisade förhöjda glastransitionstemperaturer och en snabb värmeresponsiv form-minneseffekt, och föreslås därigenom ha en stor potential som sensor-material och responsiva separationsmembran. / <p>QC 20170323</p>

Electrospun nanofibers have improved physicochemical properties compared to macroscalar fibers and are therefore increasingly investigated for use in novel food packaging systems. The objectives of this study were to electrospin nanofibers and to evaluate the effect and feasibility of surfactants and surfactant aggregates to modulate properties and functionalities of electrospun nanofibers. Nanofibers were fabricated by electrospinning a mixture of cationic chitosan and noncharged poly(ethylene oxide) (PEO) in aqueous acetic acid. To improve spinnability and nanofiber morphologies, surfactants were added to biopolymer/polymer solutions and their influence was investigated. Solution properties were evaluated by rheological, surface tension, and conductivity measurements. Fibers were characterized by scanning and transmission electron microscopy, differential scanning calorimetry, and Fourier transform infrared spectroscopy. Addition of PEO and surfactants induced spinnability producing larger fibers with diameters ranging from 40 to 240 nm, while pure chitosan did not form fibers and was instead deposited as beads. Compositional analysis suggested that nanofibers consisted of all solution constituents with chitosan concentrations being significantly lower in fibers than in solution, indicating that surfactants may have decreased polymer-polymer interactions responsible for entanglement. Poly(vinyl alcohol) nanofibers were used as novel delivery system for eugenol carrying Surfynol®465 micelles (microemulsion). Solution properties were not significantly altered after addition of microemulsion regardless of surfactant and/or eugenol concentration. Transmission electron imaging revealed a homogeneous distribution of microemulsion throughout the nanofibers. Release studies suggested a burst release mechanism of encapsulated eugenol microemulsion, potentially due to hydrophilicity of the polymeric carrier, while faster release was observed in samples with a higher eugenol loading ratio in the microemulsion. Antimicrobial activity of produced nanofibers carrying phytophenol microemulsions was evaluated against two strains of Salmonella Typhimurium and Listeria monocytogenes. Overall, the functionalized nanofibers had higher antimicrobial efficacies against Gram-negative than Gram-positive bacterial strains and were also more effective than pure eugenol microemulsion added at respective concentrations to the test system possibly due to a faster exhaustion and loss of antimicrobial activity in free microemulsions. Results of this study suggest that composite solutions of biopolymers, synthetic polymers, and micellar surfactant solutions can be successfully electrospun potentially offering a new means to functionalize biopolymeric nanofibers.

This thesis describes the synthesis and application of a new series of amphiphilic graft copolymers with a hydrophobic polyolefin backbone and pendent hydrophilic poly(ethylene glycol) (PEG) grafts. These copolymers are synthesized by ruthenium benzylidene-catalyzed ring-opening metathesis polymerization (ROMP) of PEG-functionalized cyclic olefin macromonomers to afford polycyclooctene- graft-PEG (PCOE-g-PEG) copolymers with a number of tunable features, such as PEG graft density and length, crystallinity, and amphiphilicity. Macromonomers of this type were prepared first by coupling chemistry using commercially available PEG monomethyl ether derivatives and a carboxylic acid-functionalized cycloctene. In a second approach, macromonomers possessing a variety of PEG lengths were prepared by anionic polymerization of ethylene oxide initiated by cyclooctene alkoxide. This methodology affords a number of benefits compared to coupling chemistry including an expanded PEG molecular weight range, improved hydrolytic stability of the PEG-polycyclooctene linkage, and a reactive hydroxyl end-group functionality for optional attachment of biomolecules and probes. The amphiphilic nature of these graft copolymers was exploited in oil-water interfacial assembly, and the unsaturation present in the polycyclooctene backbone was utilized in covalent cross-linking reactions to afford hollow polymer capsules. In one approach, a bis-cyclooctene PEG derivative was synthesized and co-assembled with PCOE-g-PEG at the oil-water interface. Upon addition of a ruthenium benzylidene catalyst, a cross-linked polymer shell is formed through ring-opening cross-metathesis between the bis-cyclooctene cross-linker and the residual olefins in the graft copolymer. By incorporating a fluorescent-labeled cyclooctene into the graft copolymer, both oil-water interfacial segregation and effective cross-linking were confirmed using confocal laser scanning microscopy (CLSM). In a second approach, reactive functionality capable of chemical cross-linking was incorporated directly into the polymer backbone by synthesis and copolymerization of phenyl azide and acyl hydrazine-functional cyclooctene derivatives. Upon assembly, these reactive polymers were cross-linked by photolysis (in the phenyl azide case) or by addition of glutaraldehyde (in the acyl hydrazine case) to form mechanically robust polymer capsules with tunable degradability (i.e. non-degradable or pH-dependent degradability). This process permits the preparation of both oil-in-water and water-in-oil capsules, thus enabling the encapsulation of hydrophobic or hydrophilic reagents in the capsule core. Furthermore, the assemblies can be sized from tens of microns to the 150 nm - 1 µm size range by either membrane extrusion or ultrasonication techniques. These novel capsules may be well-suited for a number of controlled release applications, where the transport of encapsulated compounds can be regulated by factors such as cross-link density, hydrolytic stability, and environmental triggers such as changes in pH.

Utilizing the diverse functionality of amino acids, a new class of amphiphilic graft copolymers has been synthesized, characterized, and explored for applications in biomaterials and nucleic acid delivery. This thesis research focused on the syntheses of oligopeptide-functionalized polyesters and polyolefins. Polyester functionalization was geared towards applications in biomaterials, tissue engineering, and drug delivery by incorporating sequences that promote cell-adhesion. These polyester-graft-oligopeptide materials were prepared by a 1,3-Huisgen cycloaddition reaction, “click” chemistry, of an azide-terminated oligopeptide (prepared by Fmoc-based solid phase peptide synthesis (SPPS)) and alkyne-containing polyester (synthesized by ring-opening polymerization). Following the syntheses of these materials, they were analyzed by nuclear magnetic resonance (NMR) and organic gel permeation chromatography (GPC). The oligopeptide-functionalized polyolefins were designed for nucleic acid complexation, and therefore the oligopeptide sequences were intended to incorporate positively-charged moieties (e.g., oligolysine) for DNA and short interfering RNA (siRNA) complexation. These graft copolymers, prepared by SPPS followed by ring-opening metathesis polymerization, have highly tunable structures that enable control over charge density and polymer backbone rigidity. Moreover, non-ionic hydrophilic grafts such as polyethylene glycol were integrated into these polyelectrolytes such that the charges along the polymer backbone are spaced accordingly while maintaining the hydrophilicity of the polymer. While numerous applications for such charged, “bio-tailored” materials can be envisioned, this work is geared towards positively-charged polyelectrolytes for their potential application in nucleic acid therapy, specifically the delivery of plasmid DNA and siRNA. These graft copolymers were characterized (1H, 13C NMR, organic and aqueous GPC), studied for their solution properties (static and dynamic light scattering), and investigated as polyplexes with plasmid DNA.

Mutation and loss of p53 function are common features among human breast cancers. We use BALB/c-Trp53+/- mice as a model to examine the sequence of events leading to mammary tumors. Mammary epithelium proliferation rates were similar in both BALB/c-Trp53+/- mice and wild type controls. Among the 28 mammary tumors collected from BALB/c- Trp53+/- mice, loss of heterozygosity for Trp53 was detected in more than 90% of invasive mammary tumors. Transplantation of Trp53+/- ductal hyperplasias indicated an association between loss of the wild type allele of Trp53 and progression to invasive carcinomas. Expression of biomarkers such as ERα, PR, Her2/Neu and activated Notch1 varied among the tumors suggesting that multiple oncogenic events collaborate with loss of p53 function. The majority of the tumors expressed both luminal and basal cytokeratins (59%). Gene expression analysis showed ligands and receptors of stem cell related pathways, such as Notch and Wnt, were increased in the tumors. These results indicate that mammary tumors in BALB/c Trp53+/- mice might initiate from bipotent mammary progenitor cells. Using magnetic nanoparticles for cancer thermotherapy. Alternating magnetic field (AMF) heating of magnetic nanomaterials provides a promising method for executing therapeutic thermal treatment for cancer patients. In order to explore the potential of magnetic nanoparticles (MNPs) for hyperthermia treatment, we synthesized iron oxide MNPs with various passivation by citric acid, folate, trimethylamine carboxylic acid, or albumin. The albumin passivated MNP (MNP-A) surpassed other MNPs, showing efficient heating with very low inherent cytotoxicity. Confocal microscopy located MNP-A (FITC tagged) accumulation in both cell nucleus and cytosol after 24hr incubation with HeLa cells. The quantity of cell bound MNP-A (including internalized and cell membrane bound MNP-A) was positively associated with MNP-A concentration and incubation time with cells. The MNP-A bound to cells was sufficient to increase the temperature in the cell pellet Δ7°C after 8min exposure to AMF. No significant temperature increase or cell death was detected in control groups. Our data demonstrate that MNP-A provides a selective tool for AMF-induced thermal treatment, as well as useful dosing information for future preclinical animal studies.

This dissertation describes the development and application of various mechanical characterization techniques to four types of polymer composite materials. The composite nature of these materials ranges from molecular to macro-scale, as do the size scales probed by the techniques chosen. The two main goals of this work are to evaluate the suitability of existing characterization methods to new composite materials (and augment the methods as needed), and to use these methods to determine optimal composite system parameters to maximize the desired mechanical response. Chapter 2 employs nondestructive ultrasonic spectroscopy for characterizing the stiffness response of both micron-scale woven composites and macro-scale glass-polymer-glass laminates. Both traditional wavespeed measurement as well as aspects of resonant ultrasonic spectroscopy are applied to determine material parameters. The laminates are also examined in Chapter 3, which utilizes both large-scale and small-scale quasi-static and dynamic puncture tests to elucidate the size- and rate-dependence of dynamic behavior. Because of limitations encountered with these methods, a smaller-scale, more fundamental test is developed and applied which focuses solely on the deformation and delamination of the polymer. These two processes, which account for the vast majority of energy absorbed during a puncture event, can be evaluated in terms of self-similar process zone propagation process models. Identifying and optimizing the relevant model parameters can promote the design of systems with maximum energy absorption. Exploratory work on nanocomposite systems is presented in Chapter 4. The polymer matrix from the laminated systems of the previous chapter is used to produce nanosilica composites. A range of techniques are employed to determine the level of dispersion and the mechanical reinforcement provided. The final project presented investigates copolycarbonates, or molecular composites, that have been developed to lessen the detrimental effect of aging on mechanical properties. Mechanical and thermal measurements can elucidate the effect of structure, specifically molecular mobility, on susceptibility to physical aging. The differences in molecular mobility contribute to differences in energy absorption by plastic deformation and damage, which is required for material toughness. Thus, understanding the molecular structure allows for determination of an optimal structure or copolymer concentration to maximize fracture toughness.

Polymeric betaines gain considerable attention for their interesting solution properties, but even more so, for their favorable bio- and haemocompatible properties. When incorporated into materials or used as surface coatings, some of these zwitterionic polymers strongly resist protein absorption due to their hygroscopic nature, making betaines promising candidates for medical diagnostics, drug delivery, and tissue engineering applications. This dissertation introduces novel norbornene-based polybetaines as foundational materials for biological applications, including non-fouling coatings and antimicrobial macromolecules. Sulfo- and carboxybetaines, composed of backbones that do not contain hydrolyzable units under physiological conditions, as well as new polymers that carry a dual functionality at the repeat unit level, coupling a zwitterionic functionality with an alkyl moiety varied to adjust the amphiphilicity of the overall system, are introduced. How structural changes, backbone chemistry, hydrophilicity/amphiphilicity, and coating surface roughness impact their non-fouling properties is investigated.

Co-continuous structures generated from the phase separation of polymer blends present many opportunities for practical application. Due to the large interfacial area in such structures and the incompatibility between the components, such non-equilibrium structures tend to coarsen spontaneously into larger sizes and eventually form dispersed morphologies. Here, we utilize various strategies to kinetically stabilize the co-continuous structures in polymer blend systems at nano- to micro- size scales. In the partially miscible blend of polystyrene and poly(vinyl methyl ether), we took advantage of the spinodal decomposition (SD) process upon thermal quenching, and arrested the co-continuous micro-structures by the addition of nanoparticles. In this approach, the critical factor for structural stabilization is that the nanoparticles are preferentially segregated into one phase of a polymer mixture undergoing SD and form a percolated network (colloidal gel) beyond a critical loading of nanoparticles. Once formed, this network prevents further structural coarsening and thus arrests the co-continuous structure with a characteristic length scale of several microns. Our findings indicate that a key to arresting the co-continuous blend morphology at modest volume fractions of preferentially-wetted particles is to have attractive, rather than repulsive, interactions between particles. For the immiscible blend of polystyrene and poly(2-vinyl pyridine) (PS/P2VP), we presented a strategy to compatibilize the blend by using random copolymers of styrene and 2-vinylpyridine, controlling the degree of immiscibility between PS and P2VP. Based on such compatibilization, co-continuous structured membranes, having characteristic size down to tens of nanometers, were fabricated in a facile way, via the solvent-induced macrophase separation of polymer blend thin films. The feature size was controlled by controlling the film thickness and varying the molecular weight of the PS homopolymer and the random copolymers. As the processing method (solution casting) is simple and the structures are insensitive to the solvent or substrate choices, this approach shows great potential in the large scale fabrication of co-continuous nanoscopic templates on flexible substrates via roll-to-roll processes. Moreover, we proposed a quasi-binary blend system based on the PS/P2VP pair with the addition of a common solvent. An experimentally accessible phase mixing temperature was achieved, and the co-continuous morphologies were generated via thermally induced spinodal decomposition. The addition of solid particles significantly slowed down the coarsening kinetics and, in some cases, arrested the co-continuous structures at ∼6 µm for a short period of time. This study suggests an alternative means to achieve co-continuous structures in polymer solutions and also provides better understanding of the thermodynamics and kinetics of polymer blend phase separation. Our research demonstrates several means of kinetically trapping the non-equilibrium interconnected structures at sub-micron to tens-of-nanometer size scales that are germane to several functions including active layers of photovoltaic cells and polymer-based membranes.

Polymer-based amphiphilic systems that self-assemble into micelles are widely studied, promising molecular designs for the delivery of hydrophobic drug molecules, which are otherwise difficult to deliver due to their poor water solubility. Incorporating stimuli-sensitive character into these polymeric assemblies has elevated the usefulness of these molecular systems in drug delivery applications due to their ability to unload non-covalently encapsulated guest molecules in response to specific stimuli. Among these nano-sized polymeric micelles, dendrimer-based micellar assemblies have received particular attention due to the fact that dendrimers are well-defined-monodispersed molecular architectures. The monodisperse nature of dendrimers provides a unique advantage in studying the structure-property relationship of amphiphilic supramolecular assemblies and stimuli-sensitive disassemblies. In this dissertation, we incorporate stimuli-sensitive characteristics into facially amphiphilic dendrimers designed and synthesized by our group. Our design principle renders these dendrimers responsive to different stimuli such as proteins, redox potential and light. We first study the self-assembly and encapsulation properties of these stimuli-responsive dendrimers in aqueous media. Next, it is demonstrated that these dendritic micellar assemblies disassemble in response to (i) an external stimulus such as light, ( ii) protein-ligand interactions, and (iii) a combination of an enzymatic reaction and redox potential. In the third molecular design, we show that combination of two stimuli enhances the release kinetics of guest molecules as compared to the independent effect of each stimulus. We also demonstrate that disassembly of these dendritic supramolecular assemblies takes place with a concomitant release of hydrophobic guest molecules trapped within the assembly.

This thesis describes the synthesis and applications of a new series of amphiphilic homopolymers and copolymers consisting of hydrophobic polyolefin backbone and hydrophilic phosphorylcholine (PC) pendant groups. These polymers are synthesized by ring opening metathesis polymerization (ROMP) of a novel PC- cyclooctene monomer, and copolymerization of various functionalized cyclooctene comonomers. Incorporation of different comonomers into the PC-polyolefin backbone affords copolymers with different functionalities, including crosslinkers, fluorophores, and other reactive groups, that tune the range of applications of these polymers, and their hydrophobic/hydrophilic balance. The amphiphilic nature of PC-polyolefins was exploited in oil-water interfacial assembly, providing robust polymer capsules to encapsulate and deliver nanoparticles to damaged regions of a substrate in a project termed `repair-and-go.' In repair-and-go, a flexible microcapsule filled with a solution of nanoparticles probes an imperfection-riddled substrate as it rolls over the surface. The thin capsule wall allows the nanoparticles to escape the capsules and enter into the cracks, driven in part by favorable interactions between the nanoparticle ligands and the cracked surface (i.e., hydrophobic-hydrophobic interactions). The capsules then continue their transport along the surface, filling more cracks and depositing particles into them. The amphiphilic nature of PC-polyolefins was also exploited in aqueous assembly, forming novel polymer vesicles in water. PC-polyolefin vesicles ranged in size from 50 nm to 30 µm. The mechanical properties of PC-polyolefin vesicles were measured by micropipette aspiration techniques, and found to be more robust than conventional liposomes or polymersomes prepared from block copolymers. PC-polyolefin vesicles have potential use in drug delivery; it was found that the cancer drug doxorubicin could be encapsulated efficiently in PC-polyolefin vesicles. In another application, PC-polyolefins were used as antifouling coatings for ultrafiltration (UF) and reverse osmosis (RO) water purification membranes. These polymers were found to reduce surface fouling in both UF and RO membranes. Finally, PC-substituted ruthenium benzylidene catalysts were synthesized and evaluated for ROMP in water. PC-substituted catalysts proved effective towards productive metathesis of water soluble cyclic olefins including PEG-substituted oxanorbornene.