Preparation And Properties Of DNA-involved Thermotropic Liquid Crystals From Catanionic Vesicles

Since the advent of DNA self-assembly nanotechnology,DNA acting as building blocks can self-assemble or co-assemble into a variety of DNA nanostructures at micro-and nano-scales.DNA assemblies have been widely used in the fields of biosensors,electronic devices and biomedicine.DNA systems are currently mostly used in solvents or solid materials,such as aqueous solutions,hydrogels,solid electrolytes,etc.which may limit the development of DNA materials because the solvent is volatile and difficult to store and solid DNA materials with greater rigidity are easy to fracture.DNA thermotropic liquid crystals(TLCs)is a kind of material with ordered microstructure and exhibit liquid crystal(LC)phase in a certain temperature range.DNA TLCs combine the excellent properties of solid and liquid materials,the sol vent-free characteristics are conducive to expand the application scenario of DNA.In view of the excellent properties of DNA and the huge demand for intelligent and flexible materials in today’s society,it is meaningful to study the DNA TLCs with orded structure and better flexibility,which will promote the development of DNA in fields such as optics and flexible electronic devices.DNA can interact with double-tailed cationic surfactants by electrostatic interaction to form DNA-based TLCs.Considering the complex synthesis of double-tailed surfactants,it may limits the fabrication of DNA TLCs to a certain extent.However,the preparation of TLCs by combining positively charged catanionic vesicles(composed by cationic and anionic surfactants)with DNA can expand the preparation method of LCs and overcome the difficulty of complex synthesis of surfactants.The type of surfactants used in the current work of preparing DNA TLCs from catanionic vesicles is single and there is no clear structure-activity relationship between the selection of surfactant and the properties of DNA TLCs,besides,the existing DNA TLCs have higher melting point and narrow LC phase region.Based on the current research status,in this thesis,we mainly use catanionic vesicles as building block to prepare a variety of DNA TLCs.Besides,the effect of DNA,chain length and groups of surfactants,doping nanoparticles on the properties of DNA TLCs are explored to deepen the understanding of DNA TLCs and lay the foundation for its practical application.The thesis consists of the following three parts:In Chapter Ⅰ,Introduction.Chapter I first covers the concept,construction methods and applications of TLCs,then introduces the structure of DNA and its abundant interaction sites in detail.After that,the applications of DNA in water environment and water-free environment are summarized,the development of DNA TLCs and urgent problems to be solved at present are described in detail.Finally,the research purpose and significance of this thesis are summarized.In Chapter Ⅱ:Alkyl chain length,functional group,counterions and other factors affect the performance of surfactants,and we believe that the performance of DNA TLCs fabricated by surfactants will also be affected by the above factors.So in this chapter,we verify the effect of the alkyl chain lengths,position of functional group of surfactants and DNA chain lengths on the properties of TLCs.We found that DNA-involved TLCs constructed by surfactants with same chain length present the excellent properties;the position of functional group of ferrocenyl surfactants greatly affects the formation of TLCs;the stronger electrostatic interaction between positively charged catanionic vesicles and DNA affect the formation of TLCs.Furthermore,we found that the shorter DNA strand length,the more consistent fit better with the vesicles to enhance the thermal stability of DNA TLCs and endowed with lower melting point and clearing point.In Chapter Ⅲ:Changing the types of DNA and surfactants can fundamentally regulate the properties of DNA TLCs.In addition,doping nanoparticles can not only enrich the performance of LC but also regulate the stability of LC phase.However,the preparation method of doped LC is relatively simple at present.In this chapter,DNA are used as template,blending DNA and the metal precursor solution uniformly,the metal nanoparticles are prepared by adding reducing agent,then the nanoparticles assemble with positively charged catanionic vesicles to fabricate the metal-based DNA TLCs.We found that the amount of nanoparticles can be adjusted by changing the molar ratio of metal precursor solution to reducing agent and then regulate the properties of metal-based DNA TLCs.Our results may direct the design and synthesis of functional DNA-based TLCs and lay the foundation of applications in the field of electrochemistry and flexible electronic devices.