Diffusion of polyethyleneimine with different molecular weights into cotton fibers at low concentration

The adsorption and diffusion behavior of polyethyleneimine with different molecular weights on cotton fibers was evaluated at a typical concentration of 1 g/L in textile industry by titration and fluorescence labeling techniques. Directly observing the penetration extent of fluorescently labelled polyethyleneimine inside the pore structure of cotton fiber by fluorescent microscopy provided the underlying mechanism for the traditional titration methods. The adsorption behavior of polyethyleneimine was shown to be highly dependent on its molecular weight. Polyethyleneimine with molecular weight of 10,000 was limited to the outermost surface of the yarn, and polyethyleneimine with molecular weight of 1800 uniformly adsorbed on the single fiber with few of them diffusing inside the fiber, while polyethyleneimine with molecular weight of 600 easily penetrated into the pores throughout the fiber cell wall. Additionally, extending the time, increasing the temperature, adjusting the pH and increasing the PEI concentration can also promote the diffusion of PEI into the fiber to a certain extent. Graphic abstract The distribution of labelled PEI on the cotton yarn