In Situ Study of FePt Nanoparticles‐Induced Morphology Development during Printing of Magnetic Hybrid Diblock Copolymer Films

Wei Cao,Suzhe Liang,Matthias Schwartzkopf,Markus Gallei,Oliver Janka,Matthias Opel,Martina Plank,Peter Müller‐Buschbaum,Manuel A Scheel,Martin Bitsch,Shanshan Yin,Stephan V Roth

doi:10.1002/adfm.202107667

Abstract

AbstractThe development of magnetic hybrid films containing diblock copolymers (DBCs) and magnetic nanoparticles (NPs) by printing is a highly promising method for scalable and low‐cost fabrication. During printing, the drying and arrangement kinetics of the DBC and magnetic NPs play an important role in the film formation concerning morphology and magnetic properties. In this study, the morphology evolution of ultrahigh molecular weight DBC polystyrene‐block‐poly(methyl methacrylate) and magnetic iron platinum (FePt) NPs is investigated with grazing‐incidence small‐angle X‐ray scattering (GISAXS) in situ during printing. For comparison, a pure DBC film is printed without FePt NPs under the same conditions. The GISAXS data suggest that the addition of NPs accelerates the solvent evaporation, leading to a faster film formation of the hybrid film compared to the pure film. As the solvent is almost evaporated, a metastable state is observed in both films. Compared with the pure film, such a metastable state continues longer during the printing process of the hybrid film because of the presence of FePt NPs, which inhibits the reorganization of the DBC chains. Moreover, investigations of the field‐dependent magnetization and temperature‐dependent susceptibility indicate that the printed hybrid film is superparamagnetic, which makes this film class promising for magnetic sensors.

Highlights

Magnetic films have captured great research attention in applications of magnetic sensors, inductors, magnetic energy, and data storages.[1,2,3,4] For some special applications, flexible magnetic films are essential.[5,6,7,8] For example, in case of wearable magnetic sensors, their ability to withstand mechanical deformation depends of the flexibility of the magnetic films
Compared to the pure film, the hybrid film exhibits a faster shrinkage of the PMMA domains due to the addition of NPs, which accelerates the solvent evaporation
Since the presence of the FePt NPs hinders the reorganization of the polymer chains, a longer metastable state is observed during the printing of hybrid film compared with the pure film

Summary

Introduction

Magnetic films have captured great research attention in applications of magnetic sensors, inductors, magnetic energy, and data storages.[1,2,3,4] For some special applications, flexible magnetic films are essential.[5,6,7,8] For example, in case of wearable magnetic sensors, their ability to withstand mechanical deformation depends of the flexibility of the magnetic films. Www.advancedsciencenews.com www.afm-journal.de (DBCs) have been proven as a powerful matrix and an effective template to host NPs, due to the ability to form various periodic nanostructures (such as cylinders, lamellae, and spheres).[10,11,12] the DBC-assisted magnetic NPs assembly is an effective approach to control the NP arrangement inside the polymer matrix due to the different interactions of the NPs with the two blocks of the DBC Various methods, such as spin coating, solution casting, spray coating, and printing, have been developed for the wet chemical fabrication of magnetic hybrid NP-DBC films.[13,14,15] For instance, Konefał et al prepared magnetic hybrid films by spin coating, in which iron oxide (magnetite, Fe3O4) NPs were dispersed uniformly inside the P4VP domains of the DBC polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP).[13] Hammond et al fabricated nanocomposite films containing a cylindrical polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) DBC and spindle type hematite (α-Fe2O3) NPs via a solution casting method.[14] The alignment of the α-Fe2O3 NPs can be further improved by employing a uniaxial external magnetic field during solution casting. The obtained magnetic data show that the printed magnetic hybrid NP-DBC film is superparamagnetic, which is beneficial to scale up the flexible magnetic film fabrication for magnetic sensors.[16,26] the present work provides a profound insight for the future optimization of printed magnetic hybrid NP-DBC films, as well as other hybrid NP-DBC systems (such as zirconium oxide NP-DBC and gold NP-DBC).[10,11]

Surface Morphology of the Final Printed Films

Morphology Evolution during Printing

Visualization of the Main Morphology Evolution

Magnetic Properties

Conclusion

Experimental Section