Multifunctional Stimuli-Responsive Micro-Nano Materials: Synthesis, Functionalization, And Applications

Nanomaterials functionalization process based on Chemistry and ChemicalEngineering technical methods, will endow nanomaterials with new functionality,strengthen its existing performance, overcome the bottleneck of the application ofexisting materials, and expand application areas of nanomaterials. Therefore, thisstudy aims to endow the existing nanomaterials with stimuli-sensitivity, and tobroaden the design space of nanomaterials by introducing anisotropy intonanomaterials. Based on the understanding and resolving a number of bottlenecks thatexist in current process for nanomaterials functionalization, practical strategies fornanomaterials will be explored and developed.Based on the fact that RAFT polymerization can offer the characteristics ofdisulfide–thiol exchange reaction to polymers, RAFT polymerization is used tosynthesize PNIPAAm-grafted dextran nanogels with dual-stimuli sensitivity. Thesenanogels have the following three self-assembly properties:（1） DexPNI nanogels candirectly self-assemble into stable spherical nanostructures through dodecylnoncovalent crosslinking points;（2） elevation of environment temperature willindirectly result in the formation of collapsed nanostructures;（3） DexPNI nanogelscan transform into thiol-terminated versions by aminolysis of trithiocarbonate groups,and further into chemical （disulfide） cross-linked versions （SS-DexPNI） by oxidation,and the self assembly of SS-DexPNI nanogels can be selectively directed by thechange in either external temperature or redox potential. Besides, turbidimetry resultsshow that the phase transition behaviors of DexPNI are greatly dependent onPNIPAAm chain length and polymer concentration.The current process for nanomaterials functionalization often face severalobstacles, including hardly-retained or even destroyed properties of the originalnanomaterials, instability and weak dispersibility against harsh conditions, andnarrowed application areas. Based on the understanding of the chemical structure andtemperature-responsive nature of DexPNI, we have demonstrated a universalfunctionalization platform based on PNIPAAm grafted dextran smart polymers for,but are not limited to, carbon and gold nanomaterials. These functionalized nanomaterials are simultaneously endowed with well-retained properties of interest,excellent stability and smart properties: they exhibit superior stability under variousconditions and the solution colors, absorption properties, fluorescent properties,aggregation behaviors, and catalytic activities can be smartly regulated by temperature,NIR light, and pH.In order to enhance the design space of nanomaterials, we have successfullyextended the application of EHD co-jetting technique from producingmulticompartmental soft materials to generating bicompartmental inorganic particles.After solving the problem that the conventional “reactive” jetting process cannot beused to prepare inorganic particles, we have developed the “non-reactive” EHDco-jetting process and produced three kinds of polymer-inorganic compositedparticles. After calcination, the sacrificing polymer template can be removed and theinorganic precursors are condensed into inorganic oxides. Either before and aftercalcination, the particles have well-defined spherical shapes and the bicompartmentalproperties can be proved by the clear interface between the two distinct compartments.CNT can be selectively grown from one hemisphere of the TiO₂Janus catalysts,indicating that the multicompartmental inorganic particles can be used as anisotropiccatalysts for spatially controlled catalytic reaction.