Surface/interface Self-assembly To Construct Mesoporous Polymers And Their Gas Sensing Properties

Due to regular,uniform and penetrating pores,high surface area and pore volume,adjustable pore size and type,unique nanostructure and morphology,etc.,mesoporous materials have shown attractive application prospects in many fields such as catalysis,adsorption,sensing,drug loading,energy conversion and storage,gas sensing/separation,etc..Nowadays,although a variety of mesoporous materials can be prepared by different synthesis methods,the types of materials are still mainly concentrated in silica,carbon,metal oxides and precious metals,etc..As for polymer,due to the complex polymerization process,volatile monomers,lack of suitable templates,etc.,the precise preparation of mesoporous materials with adjustable porous structure and material morphology still faces great challenges.The solution-based soft template co-assembly method can be directly used to obtain mesoporous materials with molecular-level or nano-level structural accuracy.Further introducing heterogeneous interfaces into the liquid reaction system can change the assembly behavior of micelles,the unique and abundant space of the interface can be also used to limit the growth of mesoporous materials or provide a platform for the synthesis of mesoporous polymer materials with specific morphologies and homogeneous or heterogeneous mesoporous materials that cannot be obtained in a single-phase synthesis system.Based on it,this thesis aims to design and construct a variety of solution-based interfaces(liquid-liquid,solid-liquid,gas-liquid interface),control the co-assembly behavior of micelles and precursors at different interfaces and study their assembly mechanism,and synthesize a variety of porous conductive polymers and biomimetic polymer materials with adjustable pore size and pore structure,and diverse morphologies.Furthermore,as gas-sensitive polymer materials,the intrinsic relationship between the sensing properties and their pore structure,morphology,and manufacturing process has been systematically studied.The specific research content is as follows:1.Solid-liquid interface micelles inducing self-assembly:constructing mesoporous conductive polymers on the carbon surfacesUse simple,efficient,and pollution-free air plasma irradiation to modify the surface of various carbon materials with oxygen-containing functional groups,though a micellar-oriented co-assembly strategy,a variety of mesoporous conductive polymers(such as polypyrrole,polyaniline)are grown in-situ on the solid(carbon)liquid(water)interface.In addition,by introducing water-soluble thiophene derivatives(3,4-ethylenedioxythiophene,EDOT)and dopant polystyrene sulfonate(PSS),we realized the synthesis of a unique mesoporous conductive polymer PEDOT:PSS and revealed its assembly mechanism.This research developed a new type of conductive polymer with mesopores,and realized the in-situ growth of highly electrochemically active materials on flexible conductive substrates,which provides an effective way for the fabrication of high-performance flexible devices.2.Solid-liquid interface self-assembly-growing mesoporous monolayer conductive polymers on different surfacesA simple and universal biomimetic modification strategy is proposed to induce the co-assembly of micelles and monomers at the solid-liquid interface,a large-area controllable synthesis of a series of mesoporous conductive monolayer polymers on the surface of materials with different characteristics and structures can be realized.Taking silicon wafers as an example,a variety of monolayer polymers were successfully prepared on the surface of silicon wafers,including polypyrrole,polyaniline,and PEDOT:PSS,which possess a mesoporous array with a regular arrangement,adjustable pore size(16-20 nm),and ultra-thin thickness(25 nm).The mesoporous monolayer polypyrrole grown in-situ assembled on the gas sensor element shows a highly sensitive response to low concentration(0.2 ppm)ammonia.Our studies have shown that the mesoporous structure and film morphology of sensitive materials,as well as the unique assembly method(in-situ growth)of the device bring rapid response and recovery,excellent selectivity,stability,and practicality.3.Liquid-liquid interface dual-template co-assembly:controlled preparation of mesoporous polydopamineThrough the dual-template co-assembly strategy,pure polymer materials with mesoporous structure and adjustable morphology were prepared by one-pot method at liquid-liquid interface.By constructing a series of morphological liquid-liquid interfaces,guiding monomers are assembled and polymerized at the interfaces,and ordered mesoporous polydopamine with different morphologies are obtained,including ultra-thin nanosheets,capsules,hollow nanospheres,and nanoparticles.Among them,the obtained nanosheets are characterized by regularly arranged ordered mesopores(diameter 10 nm)and ultra-thin thickness(30 nm).Further used for formaldehyde sensing at room temperature,they show high response sensitivity,fast response and recovery,excellent selectivity and stability.This excellent sensing performance is attributed to their high specific surface area and abundant amino active sites brought by the ordered mesoporous structure and sheet morphology.4.Micelle-assisting gas-liquid interface self-polymerization:large-area preparation of ordered mesoporous polymer filmsBy the micelle-assisted spontaneous polymerization at the gas-liquid interface,the large-area,mesoporous polymer films,including polydopamine,polyaniline,and polypolyphenol,have been realized.Polydopamine obtained by spontaneous oxidative polymerization at the common air/water interface has an ordered mesoporous(pore diameter 15 nm)structure,wafer size(>30 cm~2),adjustable thickness(20-60 nm),and further be easily transferred onto a variety of substrates.Thanks to its abundant amino active sites and unique surface mesoporous structure,the constructed polydopamine-based quartz crystal microbalance shows excellent response sensitivity to the organic volatile gas(heptanal),and with faster response/recovery speed,ultra-low detection limit concentration(0.2 ppm),excellent selectivity and stability.