Controlled Assembly Of Metal Nanoparticles In Amphiphilic Block Copolymers

The nanocomposites formed by the co-assembly of block copolymer(BCP)and metal nanoparticles(NPs)have broad applications in the fields of nanotechnology and nanomaterials owing to the unique physical properties of metal nanocrystals and assemblies of block polymer micelles.In general,most studies focused on the controlling the nanostructures,morphology and functions of nanoparticles.The detail encapsulation process of metal NPs into micelles is difficult to track mainly due to the fast encapsulation kinetics and narrow time window of detection.In this work,through the solution thermal annealing strategy,the incorporation process of pre-synthesized metal NPs with different sizes into the PS-b-P4VP-b-PEO triblock copolymer micelles was monitored and precisely controlled.As a result,the monodisperse core-shell hybrid naocomposite particles with uniform size were successfully prepared via ex-situ method.Moreover,the factors affecting the co-assembly process of metal NPs and micelles were also investigated.By synthesis the Palladium(Pd)nanocubes with different sizes,we study the coassembly of PS-b-P4VP-b-PEO triblock copolymer and Pd NPs,which can generate uniform and monodisperse Pd@PS-P4VP-PEO hybrid nanospheres with different sizes by thermal annealing at 90 oC.Two different encapsulation pathways were considered based on the size of Pd NPs.For smaller Pd NPs size,the Pd NPs were incorporated inside the micelles with annealing time.For larger Pd NPs size,the Pd NPs will absorb the outside micelles around the Pd surface,then micelles will reorganized and encapsulate the large Pd NPs to reduce the surface energy.By synthesis the large gold(Au)nanoparticles with different shapes,we monitoring the co-assembly process of PS-b-P4VP-b-PEO triblock copolymer and large Au NPs as a function of annealing time.We obtained uniform and monodisperse Au@PS-P4VP-PEO hybrid nanospheres with different shapes by thermal annealing at 90 oC.The size dependent encapsulation pathway was further confirmed,which can be considered as a universal behavior upon thermal annealing.In addition,we also replaced micellar system of two blocks of PS-b-PEO to verify such behavior.The results showed the Au@PS-b-PEO composite nano-spheres were successfully prepared as expected,and the morphology was consistent with the Au@PS-b-P4VP-b-PEO composite nano-spheres.In general,the monodisperse core-shell hybrid composite nanoparticles were effectively fabricated by thermal annealing.The effect of NPs size on the encapsulation mechanism of different metal nanoparticles was summarized.These results can not only help us have a deeper understanding of the encapsulation,stabilization and delivery of nanoparticles,but also provide guidance for the preparation and regulation of organicinorganic hybrid nanoparticles.