Tandem Polymer Reactors And Their Adjustable Tandem Catalysis

Catalysis is one of the indicators reflecting the level of national industries,which is much related to the domestic economy.In the modern industries,it is an urgent task to make the process of tandem catalytic reaction modulatable.The recent progress in smart polymers,such as reactors consisting of poly-N-isopropylacrylamide（PNIPAM）supported metal nanoparticles,has created conditions for addressing this issue.Supporting metal nanoparticles on polymers not only prevents the aggregation of metal nanoparticles,resulting in maximum catalytic efficiency,but also provides additional catalytic active sites when the polymer itself contains the desired functional groups.Meanwhile,some inspirations for realizing the modulatable tandem catalytic process will be provided by introducing molecular imprinting technology into catalytic reactors.The currently most critical task for this goal is to rationally design the reactors with accurate controlling its active sites,so both new methods and advanced techniques are needed.In this theme,the following research works has been done on design and synthesis of modulatable tandem catalytic reactors.With the aim at realizing modulatable tandem catalytic process,a double-layered smart polymer reactor,SVA-MIP-Ni（“S”refers to switchable behavior,“V”refers to1-vinlyimidazole,“A”refers to 2-acrylamido-2-methylpropanesulfonic acid,“MIP”represents the imprinted polymer hydrogel,and“Ni”means nickel nanoparticles）was designed in the first part of this theme.The catalytic reactor consists of two functional layers,with each responsible for a coupled process.The first layer of the reactor was composed of temperature-responsive copolymeric 1-vinylimidazole（VIm）and2-acrylamido-2-methylpropanesulfonic acid（AMPS）.The temperature sensitivity gives the catalyst“on”and“off”functions.The nudity of the catalytic reactor activity sites can be controlled by temperature,which enables the catalytic reactor to“capture”and“decompose”p-nitrophenyl acetate（NPA）.Such functions validated by depending upon the temperature and led to an adjust entrance for the active sites in the catalysts,which made the possible“capture”and"decomposition"of 4-nitrophenylacetate（NPA）.The second layer of the reactor is molecularly imprinted polymer layer,which was prepared using acrylamide（AM）as the monomer and a complex of nickel ions and p-nitrophenol（NP）as the template,which constitutes the basis of“predator-prey”action.However,only the target intermediate（NP）,which is the product of NPA the hydrolyzed product（NP）,can enter the imprinted species for the reduction reaction,which provides the conditions for modulating the tandem reaction.This polymer catalytic reactor provides the way for the modulatable capacity of the tandem reaction processes.Based on the experiments from the first part,we prepared a double-layer modulatable tandem catalytic reactor（DTR）（“D”means double response;“T”means temperature;“R”means reactor）with dual temperature response is designed in the second part of this paper,in order to achieve the precise control of the catalytically active sites in tandem reaction processes,and to modulate the hydrolysis-reduction tandem reaction of NPA.The first layer is composed of AMPS and AM copolymers（AMPS provides the acid active sites required for catalysis）,in which the weak intermolecular interaction forces lead a low phase transition temperature（37℃）.In addition,the second layer is composed of trifluoromethacrylic acid（PTFMA）and VIm copolymers with strong interaction.Moreover,the second layer possesses a high phase transition temperature（50℃）.As the catalytic reactor is at lower temperature（<37℃）,both catalytic activity sites are closed and NPA could not react,When the temperature is from 37℃to 50℃,only the acidic catalytic activity sites are activated,so only the hydrolysis of NPA take place,and the product NP can not be reduced further.At a higher temperature（>50℃）,however,the channels of metal nanoparticles are opened and both catalytic sites are activated.At the same time,NPA can be hydrolyzed and reduced.The catalytic reactor can control the"on/off"of the double catalytic sites through the temperature,thus achieving the purpose of controlling the series catalytic process.In the third part of this paper,efforts were devoted to solve the problems of disorder of tandem catalytic reaction,poor selectivity of tandem catalytic reactor,easy agglomeration of metal nanoparticles,as well as low catalytic efficiency.Here,a hollow core-shell nano-polymer catalytic reactor（Ag-H-MIP）with specific recognition function is designed,which immobilization of Ag nanoparticles with hollow silica as a carrier（“Ag”means silver nanoparticles,“H”shows hollow structure,“MIP”represents the imprinted polymer hydrogel）.Firstly,the surface of SiO₂ was modified by SiO₂ coated with Ag nanoparticles,then molecularly imprinted polymer（AMPS was used as functional monomer and NPA was used as template molecule）was grafted on the surface of SiO₂,and then the SiO₂ was etched by HF and the template was removed,namely,the Ag-H-MIP catalytic reactor.Ag-H-MIP can specifically hydrolyze and reduce NPA.Through regulation,it can ensure that each Ag-H-MIP catalytic reactor is composed of one Ag nano-nuclear.The high specific surface area and hollow structure of Ag-H-MIP contribute greatly to the improvement of catalytic efficiency.Through the above research work,the modulatable catalytic action of the reactor is clarified,which enriched the variety of tandem polymer catalytic reactors and provides the regular technical support for the more effective development and use of the tandem catalytic mechanism.