Revealing The Kinetic Phase Behavior of Block Copolymer Complexes Using In Situ Solvent Vapor Isotherms

Controlling the self-assembled morphologies in block copolymers heavily depends on their molecular architecture and processing conditions. Solvent vapor annealing is a versatile processive pathway to obtain highly periodic self-assemblies from high chi (χ) block copolymers (BCP) and supramolecular BCP complexes. Despite the importance of navigating the energy landscape, controlled SVA has not been investigated in BCP complexes, partly due to its intricate multicomponent nature. We introduce in situ measurements of characteristic absorption-desorption solvent vapor isotherms as an effective way to understand swelling and morphological evolution of BCP complexes. Using the sorption isotherms, we identify the glass transition points, polymer-solvent interaction parameters, and bulk modulus. These parameters indicate that complexation completely screens the polymer interchain interactions. Furthermore, we establish that the sorption isotherm of the homopolymer blocks serves to deconvolute the intricacy of BCP complexes. We applied our findings by developing annealing pathways for grain coarsening while preventing macroscopic film dewetting under SVA. Here, grain coarsening obeyed a power law, and the growth exponent revealed a kinetic transition point for rapid self-assembly. Overall, SVA-based sorption isotherms emerge as a critical method for understanding and developing annealing pathways for BCP complexes.