All MD simulations are run using version 3 Mar 2020 of the LAMMPS simulation package. Polymers are described using parameters obtained from the all-atom Optimized Potentials for Liquid Simulations (OPLS-AA) force field, and water is described using the extended simple point charge model (SPC/E). All analysis presented in the main text derives from simulations performed at 300 K. Except for polyethylene, all polymers studied can be found in a crystalline, amorphous, or (most likely) semicrystalline state at 300 K (see Supporting Information, Section S2); simulations thus reflect behavior for idealized morphologies. Additional details regarding the protocols for system preparation and simulation are in Section S3 of the Supporting Information.