No description available.

Yes / Amphiphilic nucleobase-containing block copolymers with poly(oligo(ethylene glycol) methyl ether methacrylate) as the hydrophilic block and nucleobase-containing blocks as the hydrophobic segments were successfully synthesized using RAFT polymerization and then self-assembled via solvent switch in aqueous solutions. Effects of the common solvent on the resultant morphologies of the adenine (A) and thymine (T) homopolymers, and A/T copolymer blocks and blends were investigated. These studies highlighted that depending on the identity of the common solvent, DMF or DMSO, spherical micelles or bicontinuous micelles were obtained. We propose that this is due to the presence of A–T interactions playing a key role in the morphology and stability of the resultant nanoparticles, which resulted in a distinct system compared to individual adenine or thymine polymers. Finally, the effects of annealing on the self-assemblies were explored. It was found that annealing could lead to better-defined spherical micelles and induce a morphology transition from bicontinuous micelles to onion-like vesicles, which was considered to occur due to a structural rearrangement of complementary nucleobase interactions resulting from the annealing process. / European Research Council (ERC), University of Warwick, Engineering and Physical Sciences Research Council (EPSRC), National Science Foundation (U.S.) (NSF)

Yes / Herein, we report the preparation of nucleobase-containing synthetic amphiphilic diblock copolymers using RAFT polymerization. Well-defined spherical micelles can be formed in aqueous solutions through the self-assembly of the amphiphilic copolymers, with the nucleobase functionality sequestered in the core of the particles. Following assembly, copolymers with the complementary nucleobase were introduced into the preformed micellar solutions. This addition induced a change in nanostructure size and morphology and this reorganization was fully characterized by DLS, TEM, SLS and SAXS analysis. The insertion of copolymers with the complementary nucleobase into formed micelles was also confirmed by 1 H NMR and UV-vis spectroscopy. For micelles consisting of moderately short hydrophobic blocks, upon the addition of complementary nucleobase copolymer a decrease in size was observed but without any accompanying morphological change. For micelles formed from longer hydrophobic blocks, a morphological transition from spheres to cylinders and then to smaller spheres was observed upon increasing the amount of the complementary copolymer. This work highlights how complementary nucleobase interactions can be used to induce nanostructure reorganization and through a simple mixing process provide access to different nanostructure sizes and morphologies. / University of Warwick, China Scholarship Council (CSC), National Science Foundation (U.S.) (NSF), Engineering and Physical Sciences Research Council (EPSRC), European Research Council (ERC)

京都大学 / 新制・課程博士 / 博士(理学) / 甲第24442号 / 理博第4941号 / 新制||理||1706(附属図書館) / 京都大学大学院理学研究科化学専攻 / (主査)准教授 板東 俊和, 教授 深井 周也, 教授 秋山 芳展 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

Wide literature precedence exists for polymers containing electrostatic interactions and polymers containing hydrogen bonding motifs, however the combination of electrostatic and hydrogen bonding interactions is not widely investigated in current literature. Polyelectrolytes containing hydrogen bonding groups are expected to exhibit properties of both classes of supramolecular interactions. A series of adenine- and thyminecontaining PDMAEMA and tert-butyl acrylate copolymers were synthesized to investigate the effect of incorporating hydrogen bonding groups into a polyelectrolyte. Incorporation of the styrenic nucleobases significantly affected the solubility of these copolymers on aqueous solutions and showed salt-triggerability with higher contents of these groups. Polyelectrolytes are capable of binding and condensing DNA through electrostatic interactions with the negatively charged phosphate groups of the DNA backbone; however a high degree of cytotoxicity is also often observed for these gene delivery systems. The high level of cytotoxicity is attributed to high degree of cationic character for the polyplexes formed with these systems according to the proton-sponge hypothesis. One method of reducing the overall cationic character for these systems is incorporation of non-electrostatic binding mechanisms such as hydrogen bonding. A series of nucleobase-containing PDMAEMA copolymers were utilized in order to investigate the effect of incorporation of these groups on the cell viability, binding efficiency, and transfection efficiency of PDMAEMA. / Master of Science

Yes / The synthesis of nucleobase-containing polymers was successfully performed by RAFT dispersion polymerization in both chloroform and 1,4-dioxane and self-assembly was induced by the polymerizations. A combination of scattering and microscopy techniques were used to characterize the morphologies. It is found that the morphologies of self-assembled nucleobase-containing polymers are solvent dependent. By varying the DP of the core-forming block, only spherical micelles with internal structures were obtained in chloroform when using only adenine-containing methacrylate or a mixture of adenine-containing methacrylate and thymine-containing methacrylate as monomers. However, higher order structures and morphology transitions were observed in 1,4-dioxane. A sphere-rod-lamella-twisted bilayer transition was observed in this study. Moreover, the kinetics of the dispersion polymerizations were studied in both solvents, suggesting a different formation mechanism in these systems. / University of Warwick, Swiss National Science Foundation, EPSRC, Birmingham Science City, Advanatfe West Midlands (AWM), European Regional Development Fund (ERDF), Science City Research Alliance, Higher Education Funding Council for England (HEFCE)

No description available.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第21599号 / 理博第4506号 / 新制||理||1647(附属図書館) / 京都大学大学院理学研究科化学専攻 / (主査)教授 杉山 弘, 教授 秋山 芳展, 准教授 竹田 一旗 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

The main subject of this thesis is the synthesis and investigation of the properties and potential applications of a new class of hybrid compounds consisting of a rigid, electroactive 4,4’-bipyridinium core capped by nucleobase terminal groups with hydrogen bonding abilities. A new series of small molecules consisting in a 4,4’-bipyridinium unit carrying thymine or/and adenine as capping groups was synthetized. The synthesis strategy implied the regioselective alkylation of thymine and adenine bases respectively, followed by coupling of the alkylated precursors to 4,4’-bipyridine unit via Menschutkin reaction. Electrochemical, spectroelectrochemical and optical investigations revealed an intramolecular charge transfer (CT) relationship between nucleobases as donors and 4,4’-bipyridinium unit as acceptor which is accompanied by a change in color and a shift of the reduction potentials (approx. 60 mV). The viologen-nucleobase derivatives, particularly viologens capped by thymine, were used as building blocks to create self-assembled functional nanostructures in the presence of complementary templates such as oligonucleotides or ssPNA analogues via thymine-adenine interactions. The viologen-thymine derivatives were found to partially precipitate oligonucleotides or plasmid DNA by mean of coulombic interactions and form stable polyplexes that could be used as potential gene delivery vectors. It was found that the number of positive charges, as well as the number of thymine units per viologen-thymine derivative determines whether the interaction with DNA is dominated by electrostatic or by hydrogen bonding interactions. New electroactive ionic liquid crystals were prepared by ion pairing of viologen-nucleobase dicationic species with amphiphilic 3,4,5-tris(dodecyloxy)benzene sulfonate anion. The nucleobases with ability to self-associate by hydrogen bonding were found to influence not just the thermotropic behavior, by decreasing transition temperature from crystalline to mesophase state, but also the supramolecular arrangement in solution. A versatile approach to functionalize mesoporous TiO2 film with viologen-nucleobase derivatives was developed consisting of hydrogen bonding layer-by-layer deposition of viologen-nucleobase derivatives on TiO2 surface using the thymine-adenine molecular recognition as driving force for immobilization. This method is promising and represents an easy way to construct optoelectronic device components as was demonstrated with the construction of a switchable electrochromic device.

Ammonium ionenes are polycations that have quaternary nitrogens in their macromolecular backbone and are synthesized via step-growth polymerization technique. They offer interesting coulombic properties, and the synthetic design provides control over charge density. Non-covalent interactions including nucleobase hydrogen bonding and electrostatics were studied in ammonium ionenes. The non-covalent interactions are expected to increase the effective molecular weight of polymeric precursors and induce microphase separation due to intermolecular associations. The influence of non-covalent interactions on structure-property relationships of ammonium ionenes were studied regarding mechanical (tensile, DMA), thermal (DSC, TGA), and morphological (AFM, SAXS) properties. Hydrogen bonding interaction (10-40 kJ/mol) was introduced using DNA nucleobase pairs such as adenine and thymine. Novel adenine and thymine functionalized segmented and non-segmented ammonium ionenes were successfully synthesized using Michael addition chemistry. In non-segmented systems, we investigated the influence of spacer length on homoassociation and heteroassociation of complementary nucleobase-containing ionenes. Based on DSC analyses, complementary non-segmented ionenes made miscible blends. The Tgs of ionene blends with shorter spacer length (4 bonds between the nucleobase and secondary amine in the polymer backbone) followed the Fox equation, which indicated no intermolecular interactions. The longer alkyl spacer (9 bonds between nucleobase and secondary amine in the polymer backbone) provided efficient flexibility for the self-assembly process to occur. Thus, increasing the spacer length from 4-bonds to 9-bonds, the Tgs of the blends deviated from both Fox and Gordon-Taylor equations and demonstrated the presence of hydrogen bonding interactions. In segmented systems, we investigated the association between nucleobase-containing ionenes and their complementary guest molecules. Job's method revealed a 1:1 stoichiometry for the hydrogen-bonded complexes. These association constants for the 1:1 complexes, based on the Benesi-Hildebrand model were 94 and 130 M-1 respectively, which were in agreement with literature values for adenine and thymine nucleobase pairs (10-100 M-1). DSC thermograms confirmed no macrophase separation for 1:1 [ionene-A/T]:[guest molecule] complexes based on the disappearance of the melting peak of the guest molecule. Morphological studies including atomic force microscopy (AFM) demonstrated a reduced degree of microphase separation for the 1:1 complexes due to the disruption of adenine-adenine or thymine-thymine interactions. Poly(dimethyl siloxane)-based ammonium ionenes having various hard segment contents were synthesized. The charge density or hard segment content was tuned for appropriate application using low molecular weight monomer. The change in hard segment content had a profound effect on thermal, mechanical, rheological, and gas permeability. Microphase separation was confirmed using DSC and DMA in these systems. DMA showed that the rubbery plateau modulus extended to higher temperatures with increasing hard segment content. Tensile analysis demonstrated systematic increase in modulus of PDMS-ionenes with increasing hard segment content. Oxygen transmission rates decreased linearly as the wt% hard segment increased. / Ph. D.