Nanoplate Alignment and Self-Assembly in Diblock Copolymer Nanocomposites

Polymer nanocomposites (PNCs) are formed by incorporating nanoparticles (NPs) into polymeric matrices. PNC characteristics depend not only on the material of each component, but also on the distribution, organization, and, for anisotropic NPs, the orientation of the inclusions. However, limited work has been completed to achieve precise alignment of anisotropic NPs in PNCs via self-assembly methods. This work investigates lamellar-forming poly(styrene-b-methyl methacrylate) (PS-b-PMMA, M_n= 38k-b-36.8k g/mol) with domains parallel to the substrate as a platform to align polyethylene glycol (PEG, M_n = 5 kg/mol) grafted ytterbium and erbium doped gadolinium trifluoride rhombic nanoplates (GdF₃:Yb/Er). The plates’ longest and shortest diagonals and thicknesses measure 35 nm, 22 nm, and 3 nm, respectively. The thin-film nanocomposites, prepared by spin-coating and thermal annealing, were characterized with electron microscopy. The GdF₃:Yb/Er not only segregate to the PMMA domain, but also align in the lamellae up 20 wt%. Beyond 20 wt%, the block copolymer is disordered and the nanoplates are randomly oriented. These results extend our understanding of PNC phase behavior, enabling us to create new, self-assembling materials with the potential for anisotropic throughput properties.