Characterization and Analysis of Self-Assembled PI-b-PS-b-PDMAEMA Triblock Terpolymer Thin Film Structures

Abstract

Self-assembled block copolymer (BCP) thin films are known to provide nanostructures useful in various applications ranging from templates to membranes and more, making the nanocharacterization of their morphology especially critical. Conventional techniques such as small angle X-ray scattering (SAXS), atomic force microscopy (AFM), and electron microscopy (EM) may provide complementary information on the films, which together allows a better understanding of their structure. In addition to those methods, optical super-resolution microscopy (OSRM) has emerged in recent years—following its well-developed implementation in biology—as an alternative way to characterize polymer morphology. This work describes the self-assembly of a triblock terpolymer poly(isoprene)-b-poly(styrene)-b-poly(N,N-dimethylamino ethyl methacrylate), PI-b-PS-b-PDMAEMA or simply ISA, into thin films with surface access to all three blocks. Structural thin film characterization revealed a co-continuous network structure after solvent vapor annealing of the spin-coated films. Adding hydrophilic ultrasmall nanoparticle probes enabling OSRM to the BCP solution before spin-coating resulted in slightly swollen films with similar surface structures as the parent films. Application of statistical optical reconstruction microscopy (STORM) to these films suggested that the probes reside in the PDMAEMA majority block. In analogy to biological studies, this approach opens up pathways to multicolor OSRM characterization of BCP surface nanostructures by simply mixing different color probes with different surface chemistries into the different blocks of the BCP.