A facile route to calculate the effective volume fractions in block copolymers during solvent vapor annealing*

The nano-scale domains obtained from self-assembly of block copolymers (BCPs) have attracted significant attention. In a BCP system, solvents are oftentimes used to plasticize the polymer molecules and reduce the unfavorable interactions in between to facilitate the microphase separation. However, it is not straight-forward to predict the final morphology of a BCP system due to the critical impacts of the annealing condition on the nanostructure. The effective volume fraction of each block remains constant when a neutral solvent is used, while selective solvents can significantly change this parameter and encourage the formation of a distinct morphology. To monitor morphology changes, advanced in-situ techniques, such as X-ray or neutron scattering, which are not readily accessible, are required. In this work, we present a facile route to predict the morphology of BCPs during solvent vapor annealing by simultaneous calculation of the Flory-Huggins theory coupled with mass conservation. This results in the prediction of effective volume fractions of each block, which can significantly reduce the number of required experiments in morphological studies.