Browsing by Author "Wei, Wenjing"

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    Biomimetic polymer reactor: design and modulation of novel tandem catalysts.
    (Cranfield University, 2021-09) Wei, Wenjing; Chianella, Iva; Thakur, Vijay Kumar; Koziol, Krzysztof
    Tandem catalysis can perform multi-step catalytic reactions in one-pot sequentially, which not only improves the efficiency of reactions significantly, but also decreases time, energy and the amounts of reagents needed. However, as there is always more than one active site (catalyst) in tandem reactors, it is critical to separate different sites and ensure each step is conducted individually. Moreover, it is often challenging to control the whole reaction processes due to the complexity of the systems. In this research, several bio-inspired catalytic reactors were proposed and developed to address the two challenges of site separation and smart control of tandem catalysis. First of all, the goal of sites separation has been achieved in this work through an enzyme-inspired molecularly imprinted polymer reactor MIP-Au-NP-BNPC and a core-shell structure catalytic nanoreactor AMPS@AM-Ag. Two molecularly imprinted cavities were created in MIP-Au-NP-BNPC. The different channels of the two catalytic sites in the reactor enabled different catalytic reactions to occur in different regions, resulting in the process of tandem reactions. As a result of the radial distribution of catalytic sites and mass transfer, the core-shell structure of AMPS@AM-Ag enabled the nanoreactor to perform different catalytic processes sequentially. Hence, the nanoreactor demonstrated the ability to conduct tandem catalysis with successful site separation. Then a biomimetic switch was introduced into the reactor to achieve the smart control of the catalytic process. Firstly, a new type of catalytic reactor consisting of a three-layer mussel-inspired polymer, MIP-AgPRS, was developed. The smart switchable layer composed of mussel-inspired self-healing copolymer was prepared between two MIP layers. This middle smart layer was able to react to different temperatures, permitting either simple or tandem reactions by closing and opening the access of the intermediate products. Secondly, a bilayer polymer reactor, DPR, composed of two different temperature-sensitive polymer layers was prepared. The two functional layers were not only able to respond to different specific temperatures, but each also contained different catalytic sites. Because of the two different phase transition processes of the two layers, the polymer reactor demonstrated to be able to perform simple/tandem catalysis in different temperature regions. As a result, this new type of bilayer polymer reactor was capable of achieving smart control of the tandem reactions. Finally, a three-layer switchable polymer reactor, PRS, with two MIP layers and a PNIPAM-PAM switchable layer in the middle was prepared. In an aqueous environment, when the temperature was low (lower than 47 °C), it exhibited an open access (hydrophilic condition), while when the temperature was high (higher than 47 °C), it became closed (hydrophobic condition). Furthermore, a comonomer (AM) was introduced in the middle layer with different ratios to adjust the responsive temperature range, enabling a more comprehensive range of practical uses. Therefore, a fast responsive and stable polymer reactor with self- controlled catalytic property was obtained. By preparing different types of new catalytic reactors, the research carried out here has shown the ability to achieve a smart control of the tandem catalysis while separating the catalytic sites effectively. Therefore, this study has highlighted new solutions to address the challenges present in tandem catalysis and has provided novel inspiration on how to exploit functional polymers while performing complicated catalytic reactions.
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    Self-switchable polymer reactor with PNIPAM-PAm smart switch capable of tandem/simple catalysis
    (Elsevier, 2021-10-11) Wei, Wenjing; Thakur, Vijay Kumar; Li, Songjun; Chianella, Iva
    In this paper, we report a novel three-layer polymer reactor capable of simple/tandem self-controlled catalysis. The top and bottom layers were composed of two different molecularly imprinted polymers respectively containing two catalytic sites (an acidic site catalyzing hydrolysis and metal nanoparticles catalyzing reduction), performing two selective tandem reactions without interference between each other. The middle layer was composed of a copolymer of poly-N-isopropylacrylamide (PNIPAM) and polyacrylamide (PAm) in different ratio, acting as a temperature-responsive switch for the tandem catalysis process. In an aqueous environment, when the temperature is lower than the Lower Critical Solution Temperature (LCST) of the copolymer, the reactor exhibited an open middle access (hydrophilic condition) of intermediate, allowing the tandem processes from hydrolysis to reduction. When the temperature is higher than the LCST, the channels of the middle layer were closed (hydrophobic condition), which obstructed the access of reactants. As a result, the reactor could only conduct simple hydrolysis processes. Therefore, with the three-layer structure, the polymer reactor has led to a self-controlled catalysis. This new multi-layer polymeric reaction concept can expand the practical use of functional catalysts by permitting the control of processes in large temperature ranges.
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    Towards next generation “smart” tandem catalysts with sandwiched mussel-inspired layer switch
    (Elsevier, 2020-05-18) Wei, Wenjing; Thakur, Vijay Kumar; Chew, Y. M. John; Li, Songjun
    In this paper, we prepared a novel reactor with switchable ability to address present challenges in tandem catalyst. By introducing mussel-inspired moiety, this goal was achieved via preparing a “smart” polymer reactor which can open or closes the entry tunnel of the targeted substrate in cascade reactions. The catalyst consisted of two functional layers acting as tandem catalytic parts and one smart layer with mussel-inspired moieties as a controlled middle switch. The top and the bottom layer were made of molecularly imprinted polymers and catalytic components, like acidic parts and metal nanoparticles, respectively. The middle layer made of polymeric dopamine (PDPA) and acrylamide with self-healing ability will allow or inhibit the intermediate product for the reaction, thus controlling the process of the tandem catalysis. As a result, the novel catalyst exhibited self-controlled tandem catalysis, which provides new opportunities to design smart tandem catalysts, showing a promising prospect in this area.