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Articles 1 - 12 of 12
Full-Text Articles in Chemistry
Patterning And Mechanical Analysis Of Fiber-Based Materials, Samuel A. Pendergraph
Patterning And Mechanical Analysis Of Fiber-Based Materials, Samuel A. Pendergraph
Doctoral Dissertations
The ability to define and control the topography of a surface has been studied extensively due to its importance in a wide variety of applications. The control of a non-planar topography would be very valuable since a number of structures that are pervasive in artificial applications (e.g. fibers, lenses) are curved interfaces. This potential of enabling applications that incorporate non-planar geometries was the motivation for this thesis. The first study of this thesis comprises the study of patterning the circumference of micrometer sized fibers. Specifically, a unique technique was described to pattern the fiber with a periodic array of colloids. …
Guanidinium-Rich Romp Polymers Drive Phase, Charge, And Curvature-Specific Interactions With Phospholipid Membranes, Michael T W Lis
Guanidinium-Rich Romp Polymers Drive Phase, Charge, And Curvature-Specific Interactions With Phospholipid Membranes, Michael T W Lis
Doctoral Dissertations
Protein transduction domains (PTDs) and their and their synthetic mimics are short sequences capable of unusually high uptake in cells. Several varieties of these molecules, including the arginine-rich Tat peptide from HIV, have been extensively used as vectors for protein, DNA, and siRNA delivery into cells. Despite the wide-ranging utility of PTDs and their mimics, their uptake mechanism is still under considerable debate. How the molecules are able to cross phospholipid membranes, and what structural components are necessary for optimal activity are poorly understood. This thesis explores how PTDMs interact with phospholipid membrane phase, anionic lipid content and negative Gaussian …
Functional Nanoparticles At Interfaces: Emulsion Stabilization And Triggered Inversion, Caroline Laure Marie Miesch
Functional Nanoparticles At Interfaces: Emulsion Stabilization And Triggered Inversion, Caroline Laure Marie Miesch
Doctoral Dissertations
Encapsulation of materials can be performed through the stabilization of fluid-fluid interfaces and the formation of emulsion droplets, which is commonly achieved with surfactants, including small molecules and polymers, as well as particles that are, typically, micron-scale in diameter. The worked contained in this dissertation centered on droplets that are stabilized by nanoparticles, including metallic nanoparticles and semiconductor quantum dots, which bring the conductive and fluorescent properties inherent to such nanoparticles into the droplet construction. Double emulsion droplets, both oil-in-water-in-oil (o/w/o) and water-in-oil-in-water (w/o/w) were formed using nanoparticles as the only surfactant in solution. Different types of nanoparticles were found …
On The Assembly Of Functionalized Cdse Nanorods, Sirinya Chantarak
On The Assembly Of Functionalized Cdse Nanorods, Sirinya Chantarak
Doctoral Dissertations
High aspect ratio (AR) CdSe nanorods (NRs) of well-defined sizes were synthesized to optimize the geometries of photovoltaic devices made from these nanorods. Long-range ordering of hexagonal arrays of high AR NRs is achieved by a combination of controlled solvent evaporation and the use of an applied electric field. Regioregular P3HT chains and oligothiophene were functionalized with ligating end-groups to provide contact to the NRs. Vertically oriented assemblies of CdSe NRs functionalized with terthiophene and polythiophene are also obtained. Hexagonal arrays of these nanocomposites were characterized by transmission electron microscopy (TEM). Three types of polythiophenes: poly(3-hexylthiol thiophene), poly(3-hexylamine thiophene), and …
Functional Phosphorylcholine Polymers: Prodrugs And Biomaterials, Samantha B.M. Page
Functional Phosphorylcholine Polymers: Prodrugs And Biomaterials, Samantha B.M. Page
Doctoral Dissertations
This thesis describes the synthesis and applications of multifunctional, hydrophilic polymers consisting of a methacrylate backbone and zwitterionic phosphorylcholine (PC) pendent groups, prepared by free radical polymerization of the zwitterionic monomer, 2-methacryloyloxyethyl phosphorylcholine (MPC). Advances in polymer chemistry, applied to PC polymers, allowed for the preparation of well-defined structures with controlled molecular weight, narrow polydispersity, and facile incorporation of functional comonomers, giving breadth to the range of materials accessible for different applications. Built-in functionality included fluorophores and reactive groups for post-polymerization transformations, such as drug conjugation or cross-linking. The ability to form well-defined structures based on the polyMPC backbone is …
Morphology Characterization Of Low Band Gap Polymer-Based Organic Photovoltaics, Feng Liu
Morphology Characterization Of Low Band Gap Polymer-Based Organic Photovoltaics, Feng Liu
Doctoral Dissertations
In bulk heterojunction (BHJ) thin film organic photovoltaics (OPV), morphology control is critical to obtain good device efficiency. Nanoscale phase separation that creates bicontinuous interpenetrating structure on a size scale commensurate with exciton diffusion length (~10 nm) is thought to be the ideal morphology. Results obtained from this work indicate that morphology can be affected by chemical structure of the polymer, processing conditions, blending ratio and post treatments. Physical properties of the material, such as crystallinity, crystal orientation, material interactions and miscibility, surface energy and particle aggregations are critical for determining the morphology and thus the device performance. Previous investigations …
Visualizing And Controlling Charge Transport In Conjugated Polymer Networks And Films, Andrew Davis
Visualizing And Controlling Charge Transport In Conjugated Polymer Networks And Films, Andrew Davis
Doctoral Dissertations
VISUALIZAING AND CONTROLLING CHARGE TRANSPORT IN CONJUGATED POLYMER NETWORKS AND FILMS MAY 2014 ANDREW R. DAVIS, B.S., UNIVERSITY OF VIRGINIA M.S., UNIVERSITY OF MASSACHUSETTS AMHERST Ph.D., UNIVERSITY OF MASSACHUSETTS AMHERST Directed by: Professor Kenneth R. Carter The desire for more commercially feasible flexible electronic plastics has led to the development of increasingly complex conjugated polymer architectures and device geometries. Through these efforts, tremendous advances have been made in the design and performance of electronic devices fabricated with solution-processable semiconducting polymers. However, none of these materials have yet reached commercial maturity, so the opportunity for their further exploration from both a …
Creasing Instability Of Hydrogels And Elastomers, Dayong Chen
Creasing Instability Of Hydrogels And Elastomers, Dayong Chen
Doctoral Dissertations
CREASING INSTABILITY OF HYDROGELS AND ELASTOMERS MAY 2014 DAYONG CHEN, B.S., TIANJIN UNIVERISTY M.S., TIANJIN UNIVERSITY M.S., UNIVERSITY OF MASSACHUSETTS AMHERST Ph.D., UNIVERSITY OF MASSACHUSETTS AMHERST Directed by: Professor Ryan C. Hayward Soft polymers placed under compressive stress can undergo an elastic creasing instability in which sharp folds spontaneously form on the free surfaces. This process may play an important role in contexts as diverse as brain morphogenesis, failure of tires, and electrical breakdown of soft polymer actuators. While the creasing instability has been used for collotype printing since as early as the 1850s, the scientific appreciation of this instability …
Ligand-Receptor Interactions For Supramolecular Disassembly With Applications In Screening And Drug Delivery, Diego Amado Torres
Ligand-Receptor Interactions For Supramolecular Disassembly With Applications In Screening And Drug Delivery, Diego Amado Torres
Doctoral Dissertations
Proteins have the capacity to bind specific sets of compounds known as ligands, these are small molecules with a recurrent theme in their molecular design that is a characteristic exploited here to (i) identify particular affinities of small molecules for proteins with the aim of using them as ligands, inhibitors, or targeting moieties in more complex systems by means of a methodology that screens small molecules based on protein affinity; (ii) decorate a self-assembling supramolecular system at different positions, making it responsive to a complementary protein with the aim of exploring differences in disassembly and sensitivity of the release of …
Ionic Copolymers For Alkaline Anion Exchange Membrane Fuel Cells (Aaemfcs), Tsung-Han Tsai
Ionic Copolymers For Alkaline Anion Exchange Membrane Fuel Cells (Aaemfcs), Tsung-Han Tsai
Doctoral Dissertations
The advantages of alkaline anion exchange membrane fuel cells (AAEMFCs) over proton exchange membrane fuel cells is the motivation for this dissertation. The objectives of this dissertation were to develop durable membranes with high anion conductivity and an understanding of the ion conductivity relationship with morphology. The research results presented in this dissertation focuses on developing different architectures of ionic copolymers including diblock copolymers and random copolymers for AAEMFCs. A novel, and stable cobaltocenium cation, was incorporated into polymer for stable AAEM. Because of its 18 electron closed valence-shell configuration, the cobaltocenium cation is promising for use in AAEMFC. Two …
Self-Assembly Of Block Copolymers For The Fabrication Of Functional Nanomaterials, Li Yao
Self-Assembly Of Block Copolymers For The Fabrication Of Functional Nanomaterials, Li Yao
Doctoral Dissertations
This dissertation explores the use of block copolymers which can self-assemble into different morphologies as templates to fabricate nanostructured materials. The first section (Chapters 2-4) reports the formation of mesoporous silica films with spherical, cylindrical and bicontinuous pores up to 40 nm in diameter through replicating the morphologies of the solid block copolymer (BCP) templates, polystyrene-b-poly(tert-butyl acrylate) (PS-b-PtBA), via phase selective condensation of tetraethylorthosilicate in supercritical CO2. Next, directed self-assembly was used to control the orientation of cylindrical domains in PS-b-PtBA templates. Large-area aligned mesochannels in silica films with diameters tunable between …
Photocleavable Junctions In Complex Polymer Architectures And Photoetchable Thermoplastics, Elizabeth Surles Sterner
Photocleavable Junctions In Complex Polymer Architectures And Photoetchable Thermoplastics, Elizabeth Surles Sterner
Doctoral Dissertations
Polymer materials have become important tools in nanomanufacturing due to their facile processing and ready attainment of the necessary feature sizes. The development of cleavable junctions has led to advances in the production of polymer nanotemplates. Photocleavage strategies have come to the forefront of the field because photons, as a cleavage stimulus, do not have the mass-transport limitations of chemical methods, and provide for targeted two- and three-dimensional feature control. This dissertation presents a method for producing photocleavable materials by one-pot copper-catalyzed azide-alkyne “click” chemistry (CuAAC), activator regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP) and activated ester …