Polyethylenimine, linear, is widely used in various industries due to its versatile properties. In biotechnology, it serves as a transfection reagent, facilitating the delivery of nucleic acids into cells for genetic research and therapy. Its cationic nature allows it to bind with DNA or RNA, forming complexes that can efficiently enter cells. In the field of water treatment, it acts as a flocculant, helping to remove suspended particles and impurities by promoting aggregation and sedimentation. Additionally, it is employed in the paper industry as a retention aid, improving the efficiency of the papermaking process by enhancing the retention of fine particles and fibers. In coatings and adhesives, it is used as a modifier to improve adhesion, durability, and performance. Its ability to form thin films also makes it valuable in surface modification and functionalization applications.