Overview
Polyethylenimine (PEI) is a synthetic polymer composed of repeating ethyleneimine units. It exists in linear or branched forms, with the latter being more common commercially. PEI’s high density of amine groups makes it a versatile cationic polymer, widely adopted in industrial and biomedical fields. First synthesized in the 1930s, PEI gained prominence for its ability to bind negatively charged molecules, such as DNA in gene delivery. Its scalability and tunable properties (e.g., molecular weight, branching) allow customization for specific applications, from wastewater treatment to coatings.
Physical and Chemical Properties
PEI’s properties depend on its structure. Branched PEI has a higher charge density and viscosity than linear variants. It is hygroscopic, absorbing moisture from the air, and exhibits pH-dependent solubility—fully soluble in acidic conditions but partially insoluble at neutral pH. The polymer’s amine groups protonate in water, enabling strong electrostatic interactions with anions. This property underpins its role as a flocculant in water treatment. PEI also forms stable complexes with biomolecules, making it valuable in biotechnology. Thermal stability is moderate, with decomposition starting around 200°C.
Main Applications
In water treatment, PEI removes suspended solids and heavy metals via charge neutralization. The paper industry uses it as a retention aid and sizing agent to improve fiber bonding. PEI’s adhesive properties benefit coatings and primers, particularly for plastics and metals. Biomedical applications include gene transfection, where PEI condenses DNA into nanoparticles for cellular delivery. It also serves as a surface modifier for diagnostic devices due to its protein-binding capacity. Emerging uses include battery separators and antimicrobial coatings.
Safety and Storage
PEI is corrosive and requires careful handling. Direct contact can cause skin burns and eye damage; always use nitrile gloves and safety goggles. Ensure adequate ventilation to avoid inhalation of vapors or aerosols. Store PEI in tightly sealed containers at room temperature, away from oxidizers and acids. Shelf life is typically 1–2 years for liquid forms. For large-scale storage, stainless steel or polyethylene tanks are recommended to prevent degradation.
B2B Procurement Guide
When sourcing PEI, specify: (1) molecular weight (e.g., 25 kDa for gene delivery, 2 kDa for coatings), (2) branching ratio (branched for high charge density, linear for controlled viscosity), and (3) purity (≥99% for biomedical use). Suppliers often provide samples for viscosity and pH testing. Bulk orders (100+ kg) may qualify for discounts. Verify certifications like ISO 9001 and REACH compliance. Lead times vary; stock availability is common for standard grades, while custom formulations require 4–8 weeks.
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