A new class of biodegradable cationic macromolecules for DNA binding and condensation was developed by end-group-functionalization of poly(trimethylene carbonate). A series of one- and two-armed structures was synthesized and their interaction with DNA was evaluated. To aid data interpretation, a non-linear modeling method was applied to show efficient DNA binding that was intimately related to cationic charge density and macromolecular architecture. One-armed, low charge density structures were consistently found to bind to DNA at lower charge ratios than their two-armed, high charge density counterparts. This suggests that polymer backbone structure and characteristics are important considerations in the development of efficient cationic polymer systems for DNA condensation and delivery.