Study On Assembly Structure Induced By Fluorophilic Effect Of Fluoroalkane Unit And Its Application

Many excellent properties of fluoride and fluorinated polymer are derived from the unique properties of their fluorinated units.For example,the working principle of fluorosurfactants is ascribed to the lipophilicity of fluoroalkane units,and the performance of fluorine-containing coatings and antifouling materials is ascribed to the low surface free energy characteristics of fluoroalkane units,and the thermal stability of fluorothermoplastic elastomers is derived from the thermal stability of the fluoroalkane units.In a word,it is mainly derived from the unique properties of its basic fluorinated unit that the excellent performance of fluorinated polymer.Although fluorine-containing materials have achieved rapid development in both industry and academia in recent years,most researches have focused on the overall performance of fluorine-containing compounds or polymers as materials rather than the basic fluorinated unit.In fact,the unique properties of fluorocarbon chains still need to be further developed,promoting the development of fluorine materials.Binary phase diagram studies find no cosolubility of fluoroalkane units with other chains.Besides,fluoroalkane units can associate with each other through C-F...F-C interactions.In the meanwhile,fluoroalkane units tend to phase separate,inducing the formation of distinct micro-and nanosize domains(fluorophilic efect).On the other hand,the hindered internal reorientation about C-C bonds and reduced occurrence of gauche defects facilitate fluoroalkane units stacking,ordering and crystallization.Furthermore,the fluorine interactions present in fluorine-rich organic compounds often induce unique regular architectures.The research of basic fluorinated units will provide theoretical knowledge for structure-performance design of fluorine-containing materials,further developing fluorine industry.In this thesis,we will research fluorophilic effect of fluoroalkane units from the following aspects.1.Reduction-induced crystallization-driven self-assembly of main-chain-type alternating copolymers:transformation from 1D lines to 2D plateletsThe regular structure formed by fluoroalkane units is the lowest-dimensional ordered structure,which is difficult to express in an isolated research system.Herein,we try to introduce fluoroalkane units into the study of self-assembly,expressing the lowest-dimensional ordered structure formed by fluoroalkane units more clearly.Fluoroalkane units are introduced into main-chain-type liquid crystalline alternating copolymers to obtain perfluoroalkane-containing alternating copolymers CFCI666 with periodic C-I bonds in polymer backbones via step transfer-addition and radical-termination(START)polymerization in this thesis,followed by iodine elimination reaction of C-I bonds to obtain CFC666.Through the study of their solution self-assembly behavior,it has been found that a great expression for the low-dimensional ordered structure formed by fluoroalkane units.CFC666 will show crystalline-driven self-assembly(CDSA)of alternating copolymers and we put forward a novel concept of "reduction-induced crystallization-driven self-assembly"(RI-CDSA)of main-chain-type alternating copolymers for the first time.Besides,we propose the folded-chain mechanism and model to explain the RI-CDSA behavior and its rationality has been proved by the corresponding experimental results and density functional theory(DFT)calculations.This work provides a novel idea to promote core-crystallization of alternating copolymers and caves a new path to investigate the self-assembly behavior of alternating copolymers,especially for main-chain-type alternating copolymers.2.Molecular "fence" based on metallopolymers with rigid backbone induced by fluorophilic effect of fluoroalkane unitsThe above work shows that fluoroalkane units can induce a regular self-assembly structure,but no direct experimental evidence for it.In order to directly observe the regular structure induced by fluoroalkane units,we further introduce fluoroalkane units into the metallopolymers,expecting the most intuitive evidence for fluorophilic effect of fluoroalkane units.Herein,we demonstrate the metallopolymer here to build the molecular"fence" model,synthesized by the coordination of Ru(Ⅱ)and bis-terpyridine-end-capped-phenyl(BTP)ligand modified with fluoroalkyl chains.Taking advantage of scanning tunneling microscopy(STM),well-aligned periodic linear layered structure can be apparently observed,providing the most direct observation to prove ordered structure induced by fluoroalkane units for the first time meanwhile deepening the understanding of fluorophilic effect of fluoroalkane units in favor of structure-performance research.What’s more,combining the ultraviolet-visible(UV-vis)absorption spectra and theoretical calculation,we find that fluoroalkane units provide a septation effect between polymer backbones and restrain the occurrence of interchain charge-transfer transition(ICCT)by their closed packed structure resulting in larger gap between individual metallopolymer chains.Hence,an alternating conduction-insulation molecular "fence"model is proposed at the molecular level,guiding the expansion of structure-property in the metallopolymer system and providing potential applications in material science.3.The application of fluoroalkane units in liquid crystal polymer networksThe ordered structure formed by fluoroalkane units has been proved in the above work.It is a meaningful work that how to apply the fluorophilic effect of fluoroalkane units to the development of new fluorine-containing materials.Herein,with the help of a new polymerization strategy(START),we further introduce fluoroalkane units into NIR-doped liquid crystal polymer networks periodically and successfully design a stable NIR-controlled reciprocating piston pump to transport liquid.Experimental results show that the introduction of fluoroalkane units can induce a more regular liquid crystal texture,improving the mechanical properties and anti-fatigue property of liquid crystal elastomer materials.Amazingly,if the NIR light source is fixed to cycle on for 15 s and off for 20 s automatically,the as-prepared NIR photo-controlled pump can transport 0.5 mL of liquid each cycle(35 s)and work uninterruptedly for more than 1.0 h without any manually assisted operation.4.The application of fluoroalkane units in field-effect transistorsIn order to further expand the application field of fluoroalkane units,we introduce fluoroalkane units into the molecular structure of the organic semiconductor material with naphthalene diimide(NDI)as the conjugate center.Through continuous attempts and optimization of the molecular structure,we obtain the corresponding single crystal.Finally,we prepare the corresponding field-effect transistor device and successfully develop a new n-channel organic semiconductor material with excellent air stability,providing a novel idea for the development of n-channel organic semiconductor materials.