The cathode catalyst layer (CL) is one of the principal components for proton exchange membrane fuel cells. CL is typically prepared by drying a catalyst ink consisting of Pt-C (platinum on a carbon powder support), ionomer, and solvents (water/alcohol mixtures). The structure and stability of ionomer aggregates in solutions are the key to the physical properties of PEMs, including water distribution, conductivity, and mechanical response of the membrane. Thus, understanding the ionomer aggregation behaviors in solutions is of great importance to gain a deep insight into fundamental morphological characteristics of ionomer membranes. The characterization of the ionomer aggregate structures in solutions has also been extensively explored in detail using experimental measurements. In this study, self-assembly of ionomers in a mixture of 1-propanol (NPA) and water have been investigated using coarse-grained molecular dynamics simulations. The dependence of NPA content on the ionomer structures was studied by systematically changing the NPA content in the system. The self-assembly behavior of ionomers into cylindrical bundle-like aggregates was observed and the aggregate size was found to be dependent on the NPA content in solutions. The effects of drying process on the ionomer aggregations will also be discussed in the presentation using the dimensionless Peclet number, which is used to describe the importance of evaporation to diffusion in a film of initial thickness.