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Microphysiological systems are three-dimensional (3D) in vitro systems that recapitulate crucial biological aspects of cell heterogeneity and native tissue architecture by mimicking complex structures that are impossible in two-dimensional (2D) cell cultures. Microelectrode arrays (MEAs) are biosensors used to spatially and temporally monitor the activity of microphysiological systems by transducing cellular signals into electronic signals to provide quantitative data on the in vitro system. Conventional MEAs are typically planar in nature, however, 3D MEAs offer several advantages such as better simulation of an in vivo cellular environment and improved signal-to-noise ratio and cell-electrode coupling. MEA fabrication utilizing traditional cleanroom methods is rather extensive, expensive, and specialized, therefore this thesis presents a transition from 2D MEAs fabricated via the cleanroom approach to 3D MEAs fabricated via the makerspace approach utilizing polymers. The first study in the thesis discussed the fabrication and characterization of 2D MEA devices using cleanroom methods and investigated post-processing methods to address limitations that arise for planar devices. The next study introduced the makerspace approach, where benchtop techniques were used to successfully fabricate and characterize a fully functional 3D MEA. A subsequent study investigated another benchtop method to define an electrical insulation using a pour-spin method of polystyrene solution. However, there was a challenge of adhesion of the PS to the substrate, which was improved by both utilizing another type of printer and functionalizing these surfaces with polydopamine. In the final study of the thesis, a benchtop technique called electrospinning was used to define synthetic polymer-based nanofibers atop of the 3D MEAs to simulate extracellular matrices as well as demonstrate their potential as drug delivery systems. This thesis demonstrates the highly versatile nature of makerspace microfabrication utilizing polymers to allow for new processes that offer advanced functionalities when producing microdevices such as 3D MEAs interfacing with microphysiological systems.

This thesis focuses on the manipulation of polymers and composites on length scales ranging from the nanoscopic to microscopic. In particular, on the microscopic length scale electric fields were used to produce instabilities at the air surface and at polymer interfaces that lead to novel three dimensional structures and patterns. On the nanoscopic length scale, the interaction of ligands attached to nanoparticles and polymer matrix were used to induce self-assembly processes that, in turn, lead to systems that self-heal, self-corral, or are patterned. For manipulation at the micron length scale, electrohydrodynamic instabilities were used in trilayer system composed of a layer of poly(methyl methacrylate) (PMMA), a second layer of polystyrene (PS) and a third layer of air. Dewetting of the polymer at the substrate at the polymer/polymer interface under an applied electric field was used to generate novel three dimensional structures. Also, electrohydrodynamic instabilities were used to pattern thin polymer films in conjunction with ultrasonic vibrations and patterned upper electrodes. Self-assembly processes involving polymers and nanoparticles offer a unique means of generating pattern materials or materials that self heal. Simple polymer/nanoparticle composites were investigated. Here, in the absence of interactions between the poly(ethylene oxide) ligands attached to the nanoparticles and PMMA polymer matrix, the opportunity to generate self-healing systems was opened. The size of the nanoparticle was varied and the effect on diffusion of nanoparticle in the polymer matrix was studied. CdSe nanorods were also assembled on a substrate templated with or guided by microphase separated diblock copolymers. The nanorods were incorporated in the diblock copolymer thin films by spin coating the co-solution of nanorods and polymer, surface adsorption of nanorods on to the patterned diblock copolymer films and surface reconstruction of PS/PMMA diblock copolymer thin film. Further, the interactions between the PMMA polymer matrix and the tri n-octyl phosphine oxide ligands attached to an anisotropic nanoparticle, i.e. nanorods, were used to influence the dispersion of the nanorods in the polymer. This led to a novel assembly, termed self-corralling where under an applied electric field highly oriented, highly ordered arrays of nanorods form. Further, self corralling of nanorods was directed by chemically patterned substrates.

Biodegradable hydrogels show great promise in the area of biomaterials and specifically for tissue engineering applications. While much work in the past has studied the various biochemical signals associated with cell growth, more recent work has highlighted the importance of the mechanical environment as a stimulus for growth. This dissertation focuses on associative network hydrogels formed for poly(lactide)-b-poly(ethylene oxide)-b-poly(lactide) [PLA-PEO-PLA] triblock copolymers and the factors that influence their mechanical properties, assembly, and structure. By controlling the stereospecificity of the PLA endblocks hydrogels with either amorphous or crystalline hydrophobic domains were formed as characterized using both X-ray and neutron scattering techniques. This change in structure directly impacted the mechanical properties of the hydrogels. Furthermore, complications in synthetic techniques introduced contaminants (asymmetric triblock copolymers or "effective" diblock copolymers) that impacted the assembly of the network to again impact the mechanical properties. Ultimately, the PLA-PEO-PLA triblock copolymer was chemically modified so that the self-assembled physical network served as a template for the covalently crosslinked network formed by photocrosslinking. The photocrosslinked hydrogels maintained their mechanical integrity in an aqueous environment; however, the measured mechanical properties were dependent on the assumed constitutive relationship.

Dendrimers, due to their well-controlled size and shape, have emerged as interesting macromolecular scaffolds for fundamental applications in materials to medicine. Amphiphilic dendrimers are among the attractive molecular systems for applications in drug delivery due to their ability to solubilize hydrophobic guest molecules in water. This thesis focuses on a class of amphiphilic biaryl dendrimers that self-assembles to form solvent-dependant supramolecular assemblies, and discusses the following: (i) Molecular design and synthetic strategies for incorporating a single probe unit at specific locations of the dendrimer backbone for understanding microenvironment variation in dendrimer molecules. (ii) Study on the self-assembling properties of amphiphilic dendrimers that are functionalized with bioactive moieties. (iii) Demonstration of the disassembly of the amphiphilic assemblies of these dendrimers using both enzymatic and non-enzymatic proteins. It also elaborates the disassembly-driven release of hydrophobic guest molecules from the assembly interiors. The findings of this dissertation would provide molecular level understanding on both self-assembling properties of amphiphilic macromolecules and strategies to disassemble the amphiphilic assemblies using biological triggers such as proteins.

Room temperature ionic liquids (ILs) are a unique class of solvents which are characterized by non-volatility, non-flammability, electrochemical stability and high ionic conductivity. These properties are highly desirable for ion-conducting electrolytes, and much work has focused on realizing their application in practical devices. In addition, hydrophilic and ionophilic polymers are generally miscible with ILs. The miscibility of ILs with ion-coordinating polymers makes ILs effective plasticizers for gel polymer electrolytes. Due to their unique properties, ILs present a means to realize the next generation of energy storage technology. In this dissertation, the fundamental interactions between poly(ethylene oxide) (PEO) and a variety of room temperature ILs were investigated. ILs with acidic protons were demonstrated to form a stronger interaction with PEO than ILs without such protons, suggesting that hydrogen bonding plays a dominant role for PEO miscibility with ILs. The hydrogen bonding interaction is selective for the PEO block of a PEO-b-PPO-b-PEO block copolymer (BCP). Therefore, blending these copolymers with the strongly interacting IL 1-butyl-3-methylimidazolium hexafluorophosphate ([BMI][PF6]) induced microphase separation into a well-ordered structure, whereas the neat copolymer is phase mixed. At sufficient quantities, the interaction between [BMI][PF6] and PEO suppresses PEO crystallinity entirely. In addition, the induced microphase separation may prove beneficial for ion conduction. Therefore, microphase separated copolymer/IL blends were investigated as potential gel polymer electrolytes. Cross-linkable block copolymers which microphase separate when blended with [BMI][PF6] were synthesized by modifying PPO-b-PEO-b-PPO copolymers with methacrylate end-groups. Cross-linking these copolymers while swollen with an IL generates ion gels with high ionic conductivities. The copolymer/IL blends vary from a well-ordered, strongly microphase separated state to a poorly ordered and weakly microphase separated state, depending upon the molecular weight. Stronger microphase separation results in higher mechanical strength upon cross-linking. However, this does not greatly affect ion conductivity. Nor is conductivity affected by forming gels from cross-linked PEO homopolymers when compared to BCPs. It was found that BCPs can be beneficial in producing gel electrolytes by allowing sequestration of phase selective cross-linkers away from the conducting block. Cross-linker molecules that are selective for the PPO blocks can be used to increase the mechanical strength of the gels with only a small effect on the conductivity. When cross-linkers that partition to the mixed PEO/IL block are used, the conductivity decreases by nearly a factor of 2. These studies show how ILs interact with PEO and how gel polymer electrolytes can be constructed with the IL [BMI][PF6]. While BCPs cannot directly be used to increase ion conductivity, they do allow for greater mechanical strength without sacrificing conductivity. This suggests many new approaches that may be used to simultaneously achieve high ionic conductivity and mechanical strength in solid and gel polymer electrolytes.

Recent progress in nanotechnology research has witnessed its impact in wide variety of emerging fields starting from electronics to medicine. Our interest in nanotechnology is to ‘create new nanomaterials’, or ‘new methods to make nanomaterials’, to understand and to utilize them for various applications. We discuss our findings on the formation and application of nanostructures made through self-assembly in solution, followed by self-assembly at the interior of nanopores. Self-assembly can be induced in molecules by manipulating the noncovalent interaction, solvophilic and solvophobic forces. We are interested in creating various selfassembled nanostructures that could be tuned by modifying the amphiphilic building blocks during their synthesis. When these building blocks are grown in a perfectly branched fashion the obtained macromolecules are called amphiphilic dendrimers, whereas the linearly grown building blocks are called amphiphlic homopolymers. Here we show that the biaryl dendrimer can be made into temperature sensitive micelles, and can be used in molecular encapsulation. We further extend our developed concept to acrylamide-based homopolymers that can, not only form micelles and inverted micelles, but also can be tuned to make vesicles. By making the amphiphilic homopolymer in a noncovalent fashion, we show that the formed nanoassembly can be disassembled using proteins and the differential nature of disassembly was used for protein sensing. The self-assembled structures in apolar solvent, known as inverted micelles, were utilized for pI-dependent isolation of peptides. We show that polymers can be self-assembled inside membrane nanopores to make functionalized nanotubes, which can be utilized for separating molecules based on charge, size and hydrophobicity. We also show that by using dendrimers the pore size of the nanotubes can be precisely controlled and can be exploited for molecular separations.

This thesis is divided into two research initiatives: The fabrication and study of bulk, co-continuous, cellulosic-polymer composites with the aid of supercritical CO2 (SC CO2); and the study of poly(vinyl alcohol) (PVOH) modification and surface activity in ionic liquids. The first part of this thesis utilizes the tunable solubility, gas-like diffusivity, and omniphilic wettability of SC CO2 to incorporate and subsequently polymerize silicone and poly(enemer) prepolymer mixtures throughout various cellulosic substrates. Chapters two and three investigate the mechanical properties of these composites and demonstrate that nearly every resulting composite demonstrates an improved flexural modulus and energy release rate upon splitting. Fire resistance of these composites was also investigated and indicates that the heat release rate, total heat released, and char yield were significantly improved upon for all silicone composites compared to the untreated cellulosic material. Chapter four looks specifically at aspen-silicone composites for thermo-oxidative studies under applied loads in order to study the effect of silicone incorporation on the failure kinetics of aspen. The aspen-silicone composites tested under these conditions demonstrated significantly longer lifetimes under the same loading and heating conditions compared with untreated aspen. The second part of this thesis focuses on studying ionic liquids as potentially useful solvents and reaction media for poly(vinyl alcohol). Two ionic liquids (1-Butyl-3-methylimidizolium chloride and tributylethylphosphonium diethylphosphate) were found to readily dissolve PVOH. More importantly, we have demonstrated that these solvents can be used as inert reaction media for PVOH modification. Both ionic liquids were found to facilitate the quantitative esterification of PVOH, while only the phosphonium ionic liquid supports the quantitative urethanation of the polymer. In an attempt to tune the surface properties of ionic liquid/polymer solutions, PVOH was also partially esterified with low surface energy substituents. Both surface tension and surface composition of the ionic liquid/polymer solutions can be manipulated by the stoichiometric addition of low surface energy acid chlorides. This work on the modification of PVOH can be directly applied to the modification of polysaccharides such as cellulose which could have important implications from a sustainability and energy standpoint.

The three projects utilized polymer physics theories to investigate polymer aggregation mechanics. Dynamic light scattering (DLS), static light scattering (SLS) and small angle light scattering (SALS) were the primary characterization tools. The goal of the first project was to study the aggregation of bovine βL-crystallin and apply that knowledge towards cataract formation, which is caused by aggregation of the crystallins. The first series of experiments characterized the kinetics of α-crystallin and β L-crystallin in water at room temperature. α-crystallin’s equilibrium hydrodynamic radius value was kinetically independent. β L-crystallin formed an aggregate with an Rh that was kinetically dependent. The packing structure of the aggregate formed by βL-crystallin was determined to be loosely packed using SLS. α -crystallin was uniquely demonstrated to be a chaperone in a way that indicated electrostatics played a significant role in aggregation. The role of electrostatics led to an investigation into sodium chloride. Sodium chloride proved to reduce the βL-crystallin aggregate size. The next series of experiments simulated biological conditions using a phosphate buffered saline (PBS). The experiments were performed at 35°C. α -crystallin and βL-crystallin were shown to be kinetically independent and demonstrate equilibrium Rh values on the time scale that the experiments were performed. A pH study revealed that multiple size-scales were present only at physiological pH. Above and below physiological pH, only two aggregate size-scales existed. A charge model was made of β L-crystallin to compare theory with experimental results. The future goal of project is to reproduce these experiments with human crystallins. In the second project, by changing the order and arrangement of β-spiral elastin (E) and α -helical COMPcc (C) the macroscopic structure was controlled. The EC diblock exhibited a fast and slow mode below the transition temperature of 25°C and single mode behavior above the transition. Phase separation occurred above the transition. CE showed three different size-scales below the transition of 15°C and demonstrated spinodal decomposition above the transition. The ECE triblock demonstrated bimodal behavior below the transition of 25°C and one micellar size above the transition. α-helical COMPcc has the ability to bind to small molecules, making the findings from this project instrumental in creating a drug delivery vehicle. The third project investigated sodium polystyrene sulfonate and polyethylene oxidepolypropylene oxide-polyethylene oxide in solution. Both systems self-assemble into aggregate structures at specific conditions. The significant difference between these two polymers is that sodium polystyrene sulfonate is a polyelectrolyte. It is well known that aggregate structures can be formed by variation in temperature and concentration. However, by having a charged polymer in solution with a neutral polymer the aggregate structure can also be controlled by changing the pH and adding salt to the solution, as was performed in the first project. The third project is an excellent conclusion to the previous two because it allows for the aggregate structure to be controlled even more so than in the previous projects by mediating the polydispersity index, molecular weight and concentration of each component. Each project focused on a different method of mediating the aggregate structure. A better understanding of aggregation has applications in industry and medicine. Polymer physics theory is instrumental in understanding aggregation mechanics.

I närvaro av fukt och lokaliserade fältförbättringar kan vattenträd utvecklas inom polymerisoleringen av HV subsea kraftkablar. Vattenträd tenderar att växa obemärligt och försämra isolationsegenskaperna med tiden. Fuktigheten i isoleringen kan effektivt reduceras genom applicering av halvledande svällningsband. Halvledande svullnadstejp ger en unik kombination av elektrisk ledningsförmåga och stor vattenhållande kapacitet. Detta hänför sig till förekomsten av ledande kolsvart (CB) respektive superabsorberande polymer (SAP) partiklar. För att förstå massatransportegenskaperna hos vattenånga inom ett svällande tejp bestämdes transportkoefficienterna. Sorptionen av vattenånga avslöjade koncentrationsberoende transportkoefficienter och en allmän ökning i diffusion och löslighet med ökande vattenaktivitet. Detta tillskrives SAP-komponenternas hygroskopiska och polyelektrolytegenskaper och resulterade i en ökning i diffusiviteten med en faktor 100, vid ökning av relativ fuktighet (RH) från 7 till 65%. Vid högre vattenaktivitet antogs att bildandet av immobila vattenklyftor minskade diffusionen av vattenånga. Flera sorptionslägen föreslogs för sorptionsbeteendet hos tejpen mellan 10 och 80% RH. Införandet av konduktivitet inom bandet minskar potentiella skillnader genom flera kabelskikt och efterföljande fältförbättringar. Konduktivitets- och vattensorptionsegenskaperna hos det halvledande svällningsbandet kan emellertid ändras genom mekaniska kompressioner, som utövas av omgivande kabelkomponenter. Den elektriska resistiviteten hos ett fuktigt svällande tejp under belastning bestämdes därför. På grund av bandets anisotropi utfördes elektriska resistivitetsmätningar över (radiell riktning) och tillsammans med (axiell riktning) tejpen. Bandens radiella och axiella riktningar dominerades av närvaron av SAP och CB. En signifikant minskning av bandets radiella resistivitet observerades när fuktigheten ökades från 40% till 60% RH. Resistiviteten minskade med en faktor 100. Ingen signifikant effekt av kompression observerades, men tejpen visade en minskande trend i resistivitet med ökande kompression. Vid 60% RH-radiell resistivitet närmade sig axiell resistivitet, och påverkan av SAP sänks. Den axiella resistiviteten var omkring 18 Ωcm. Tejpens axiella resistivitet påverkades mindre av fuktighet och kompression än den radiella resistiviteten. Åldrande avslöjar försämring av svullnadshöjd, men hade ingen inverkan på bandresistivitet. / In presence of moisture and localized field enhancements water trees might develop within the polymeric insulation of HV subsea power cables. Water trees tend to grow unnoticeable and deteriorate the insulation properties with time. The humidity within the insulation can efficiently be reduced through the application of semiconducting swelling tapes. Semi conducting swelling tapes provide a unique combination of electrical conductivity and a large water retention capacity. This is attributed to the presence of conductive carbon black (CB) and superabsorbent polymer (SAP) particles, respectively. To understand the mass transport properties of water vapor within a swelling tape, transport coefficients were determined. The sorption of water vapor revealed concentration dependent transport coefficients and a general increase in diffusion and solubility with increasing water activity. This was attributed to the hygroscopic and polyelectrolyte properties of the SAP components and resulted in an increase in diffusivity by a factor of 100, when increasing the relative humidity (RH) from 7 to 65 %. At higher water activity, it was assumed that the formation of immobile water clusters reduced the diffusion of water vapor. Several sorption modes were suggested for the sorption behaviour of the tape between 10 to 80 % RH. The introduction of conductivity within the tape reduces potential differences throughout several cable layers and subsequent field enhancements. However, conductivity and water sorption properties of the semi-conductive swelling tape can be altered by mechanical compressions, exerted by surrounding cable components. The electrical resistivity of a humid swelling tape under load was therefore determined. Due to the anisotropy of the tape, electrical resistivity measurements were performed across (radial direction) and along with (axial direction) the tape. The radial and axial directions of the tape were dominated by the presence of SAPs and CBs, respectively. A significant reduction in radial resistivity of the tape was observed when increasing the humidity from 40 % to 60 % RH. The resistivity decreased by a factor of 100. No significant effect of compression was observed, but the tape showed a decreasing trend in resistivity with increasing compression. At 60 % RH radial resistivity approached axial resistivity, and the influence of SAPs is reduced. The axial resistivity was around 18 Ωcm. The axial resistivity of the tape was less affected by humidity and compression than the radial resistivity. Ageing reveal deterioration of swelling height, but had no influence on tape resistivity.