Alignment frustration in block copolymer films with block copolymer grafted TiO2 nanoparticles under soft‐shear cold zone annealing

Abstract

AbstractBlock copolymers (BCPs) have received significant attention as promising candidates for sequestering nanoparticles and fabrication of aligned nanostructures with optimal optical or electrical properties. We investigate the influence of static and dynamic thermal field on the alignment of polystyrene‐block‐poly(methyl methacrylate) (PS‐b‐PMMA) BCP morphology with the loading of novel poly(methyl methacrylate‐block‐Polystyrene) (PMMA‐b‐PS)‐grafted‐TiO2 nanoparticles (BCP‐g‐TiO2). Observation of characteristics IR peaks for PMMA and PS in BCP‐g‐TiO2 nanoparticles and Transmission Electron Microscopy (TEM) results of the outer coating of core nanoparticle, validate the grafting to approach in synthesizing BCP‐g‐TiO2. Here we report that under the sharp dynamic thermal field, at low loading of BCP‐g‐TiO2, there is good dispersion of nanoparticles in unidirectionally aligned BCP matrix in film interior probed by GISAXS, while, at high nanoparticle loading (~10 wt%), there is local frustration in the unidirectional alignment of the BCP matrix due to aggregation of BCP‐g‐TiO2 nanoparticles. However, Grazing incidence small angle X‐ray scattering (GISAXS) shows clearly that the BCP films remain largely locally ordered at the domain scale, despite these large perturbations to long‐range ordering even at high loading level, while bringing in new TiO2 functionality to the BCP films, such as UVO absorptivity or biofouling prevention, important to potential new applications of such membranes.