Preparation And Application Of SiO₂/Polymer Composite Nanoassemblies Based On Polymerization-induced Self-assembly

Silicon dioxide（SiO₂）nanoparticles are widely used in the preparation of composite materials for their high specific surface area,high hardness,high stability and reasonable price.Polymerization-induced self-assembly（PISA）is a new self-assembly method developed in recent years,which can complete self-assembly while achieving polymerization,with the advantages of simple preparation steps,easy preparation of high solid content,and various and easy control of assembly morphology,being widely used in the design and preparation of polymer assembly particles with different morphologies.On the basis of pure polymer assemblies,various methods based on PISA for the preparation of organic/inorganic composite nanoparticles have been gradually developed.In this paper,a new method based on PISA is used to compound polymer and SiO₂nanoparticles to prepare composite nanoparticles,as well as three PISA-based methods are mainly used to study the preparation and application of SiO₂/polymer composite nanoassemblies,mainly including the following three methods.1."Chemical grafting to":the SiO₂@GMA composite monomer was prepared by"chemical grafting to",followed by the further polymerization of the above composite particles to successfully prepare the first solvent-friendly block polymer SiO₂@PGMA,then the first block polymer was used as a reagent for RAFT to initiate the polymerization and self-assembly of the second hydrophobic block PHPMA,resulting in the successful preparation of SiO₂@PGMA-b-PHPMA composite assemblies with vesicle shape.Subsequently,the shape of the composite assemblies was found to be vesicular under different feeds by adjusting the feeds of the two block polymer monomers,which proved that the shape of the composite assemblies was not affected under different feed changes.Furthermore,by changing the type of the second block polymer monomer（like HEMA,MEA）,it was found that the composite assemblies with vesicle shape could be prepared,which further proved the versatility of the method.Finally,when the above-mentioned composite assemblies were applied as coatings,the prepared heat-reflective coatings not only showed excellent heat-reflective functionality,but also showed better stability compared with the conventional heat-reflective coatings.2."Chemical grafting from":RAFT reagent was successfully grafted onto the surface of SiO₂nanoparticles by surface treatment of SiO₂nanoparticles,after which the polymerization of the first solvent-friendly block polymer SiO₂@PHPMA was triggered on the surface,with the above mentioned first block being used as the first block to further trigger the polymerization of the second block.The second hydrophobic block SiO₂@PHPMA-b-PBz MA was further polymerized and self-assembled,leading to a vesicle shaped composite assembly.The effect on the morphology of the composite assemblies was explored by varying the polymer monomer feed,and it was found that the change in feed did not have a significant effect on the morphology of the composite assemblies.3."in situ growth methods":Firstly,the tri-block polymeric assemblies PEG-b-PDMAEMA-b-PBz MA were prepared by PISA,in which the second solvent-friendly block PDMAEMA was easily protonated and thus possessed electrostatic properties,subsequently,the polymeric assemblies were protonated and electrostatically adsorbed by SiO₂nanoparticles.TEOS precursor was adsorbed onto the surface of the assemblies,and the hydrolysis and condensation of the TEOS precursor were catalyzed in situ to grow SiO₂nanoparticles in situ on the surface of the assemblies,which led to the successful preparation of composite nanoassemblies with vesicle shape.The effects of SiO₂nanoparticle precursors and the protonated block polymer PDMAEMA on the content of in situ grown SiO₂nanoparticles as well as the polymer assemblies were investigated by adjusting their ratios.Finally,the composite assemblies were used as bio-based rubber fillers for filling applications,and it was found that the rubber filled with composite assemblies performed better in terms of mechanical properties compared with silica-filled rubber,with the tensile strength and elongation at break being higher than those of ordinary silica-filled rubber.