As organic polymeric bases, polyamines are ubiquitous for many applications, ranging from biological drug deliveries 1-2 to carbon capture. Polyethyleneimine (PEI, i.e., a polymer of aziridine) has been used in various applications owing to its high loading of nitrogen bases (theoretically up to 23 mmol/g), hydrophilicity, and water solubility. In general, branched PEls are highly accessible. In contrast, linear and dendrimeric PEIs require sophisticated preparation and synthetic strategies despite having unique properties due to their uniform alkylation degrees on nitrogen atoms. Hydrophobic PEI is achievable via selective alkylations on the nitrogens, thereby enabling the control of PEI derivatives' solubility, structure, dynamics, and stimuli-responsive applications.