Self-assembly Preparation Of Polypyrrole-based Porous Materials And Their Gas Sensing Performance

In recent decades,with the rapid development of nanotechnology,conductive polymer(CPs)-based nanomaterials,such as poly(3,4-ethylenedioxythiophene)(PEDOT),polyaniline(PANI),polythiophene(PTh),and polypyrrole(PPy),have attracted intensive attention and been widely used in novel gas sensors.At the same time,some specific functional groups can be anchored on the molecular skeleton of the precursor of the conductive polymers,and their morphologies can be fine-tuned by virtue of the weak interaction with the template.At present,through different methods,researchers have synthesized CPs with different morphologies,such as nanospheres,nanofibers,nanorods,and nanosheets.Similar to porous inorganic materials,the introduction of self-assembled templates in the synthesis process of conductive polymers can create porous structures,expose more active sites and carrier transport channels and possess the advantages of fast response/recovery,low cost,and high sensitivity,thus showing attractive prospects in the field of gas sensing.In addition to traditional templates,photo-responsive block copolymers have both the self-assembly properties and photo-responsive capabilities of block copolymers.It is also worth exploring to study its self-assembly behavior in solution and orient to prepare porous polypyrrole.In addition,the traditional conductive polymer-based gas sensors show poor selectivity and stability,which bring great challenges to their commercial applications.The introduction of nanometals can effectively repair defects,adjust material surface energy band structure,and accelerate the transfer and transport of carriers.Therefore,researchers have also tried to develop the strategy of combining conductive polymers and metals to improve their sensing performance.Although the preparation of conductive polymer/metal hybrid materials has been reported in the literatures,while the steps are complicated and the components are unevenly distributed.The simple synthesis of such composite materials and the precise control of the growth of their components are still major challenges.1.Controllable synthesis of two-dimensional macropore polypyrrole by the self-assembly of light responsive block copolymersBy introducing Azobenzene group(Azo)into common block copolymer,the light-responsive PEO-b-PM11AZCN block copolymers were synthesized via three-step column chromatography and atom transfer radical polymerization(ATRP).The as-synthesized PEO-b-PM11AZCN can self-assemble into various morphologies in the mixture of THF/DMF/H₂O by adjusting the ultraviolet light and the proportion of the solvents.Employing the PEO-b-PM11AZCN as templates,PPy nanospheres,nanorods and nanosheets can be obtained,respectively.Under the condition of THF/DMF=4:1(V/V)mixture,PPy nanosheets with uniformed macropores(50-70 nm)can be achieved.The morphologies of the two sides of the sheet were different,one side was smooth and showed clear pores,the other side was composed of spherical PPy.Importantly,m PPy-N-based gas sensor showed the sensitivity of 38.4%exposed to 100 ppm NH₃ and represented good selectivity,which are better than that of pure PPy,2.Soft Template-Mediated Coupling Construction of Sandwiched Mesoporous PPy/Single-Crystal Ag NanoplatesSynchronous construction of heterogeneous materials from distinct molecular units into functional hybrids within one synthesis system holds large potential for customizing properties and applications,but which requires the elaborate coordination of individual growth,assemblies,their interactions and even dynamic behaviors,thus still remains an enormous challenge.Here we develop a simple soft template-mediated coupling construction approach to achieve an unexplored sandwiched mesoporous polypyrrole(PPy)nanocoating/single-crystal Ag nanoplate hybrid by a one-step inorganic/organic redox reaction at the liquid interface.The chemically oxidative polymerization of pyrrole accompanies the reduction of Ag⁺at room temperature,and the amphiphilic template confines the growth of the single-crystal Ag nanoplate and synchronously guides the formation of the mesoporous PPy nanocoating by hydrogen bond and chelation interaction,emerging into a novel sandwiched nanohybrid with adjustable regular mesopores(20?40 nm),changeable thickness(150?300 nm),strong near-infrared absorption and Raman enhancement effect.As a chemiresistive material in a planar-configuration gas sensor,it delivers a shorter response(7 s)and recovery time(21 s)than those for previously reported sensors and remarkable sensing response sensitivity to NH₃(11.6%for 1 ppm,with the real detection limit to 200 ppb).