Simple and Rapid Preparation of Hydrophobic Polydopamine-Structured Colour Films on Flexible Cotton Fabrics

Dopamine (DA) can self-polymerize to form polydopamine (PDA) under weak alkaline conditions in the presence of oxygen, creating vibrant structures at the gas–liquid interface. However, the issue of the polydopamine film cracking and easily peeling off from the fabric surface remains unresolved. In this article, we report the rapid polymerization of dopamine in a CuSO 4 /H 2 O 2 system, resulting in the preparation of polydopamine-structured colored cotton fabrics through the stepwise addition of 3-aminopropyltriethoxysilane (KH550) and polyethyleneimine (PEI). Structured color cotton fabrics were hydrophobically treated by a simple impregnation technique using the hydrophobic agent cetyltrimethoxysilane (HDTMS). This improvement suggests that the covalent bonding of PEI with PDA, along with its assembly on the fabric surface, enhanced the homogeneity and continuity of the structural color film, resulting in a brighter and more uniform fabric surface color. After HDTMS treatment, the structural color film on PDA/KH550/PEI-Cotton was converted from a hydrophilic to a hydrophobic state, with a static water contact angle averaging approximately 152.375°. The hydrophobic treatment provided the structural color fabrics with good film stability and resistance to washing, while their surface coloration remained largely unaffected. This method provides a new research idea for eco-dyeing of cotton fabrics.