Basic Composition and Synthesis Process and Representative Molecule of the Branched Polyethyleneimines With Low Molecular Weight

ABSTRACT Branched polyethyleneimines (B‐PEIs) have been widely used in industries and researches, such as the papermaking, water treatment, and enzyme immobilization. However, they exhibit a complex composition, leading to ambiguity in understanding the B‐PEIs' synthetic process and relevant influencing factors. Additionally, no representative molecule of B‐PEIs has been identified, leading to subjective selections when studying structure–performance relationships. This study focused on three commercially low‐molecular‐weight B‐PEIs: 300, 600, and 1800. It identified that they primarily consisted of C, H, and N elements in the form of methylene and primary, secondary, and tertiary amine groups. The ratios of amine groups were also revealed, offering guidance for application. Moreover, the types of polymerization degrees and their proportions were determined, with the free ends identified as primary amino groups. Based on these, this study proposed synthetic processes and potential influencing factors. This provided valuable insights into the synthesis of B‐PEIs with varying compositions and properties. Furthermore, the stability of over 527 potential molecular structures was calculated. By weighing above features, the representative model molecules used to analyze B‐PEIs' structure–performance relationships was identified. These results had significant implications for the synthesis, application, and functional analysis of B‐PEIs.