  Layer-by-Layer (LbL) assembly was attractive as a versatile tool to address
the flammability of cotton, while the washing fastness of LbL coating stayed an
issue. Aiming to tackle this issue, LbL layers consisted of phenylphosphonic
acid (PHA) and 3-aminopropyltriethoxysilane (APTES) was deposited on
polydopamine (PDA)-coated cotton. The prepared cotton reached 31.4% of limiting
oxygen index (LOI), and extinguished immediately after removing the ignitor.
Peak of heat release rate (pHRR) attenuated around 36 % compared with pure
cotton. A combined barrier and quenching mechanisms were proposed. Moreover,
enhanced washing durability (24.1% of LOI) was achieved even after 50 detergent
laundering cycles. A facile, boosted LbL approach with proposed {\pi}-{\pi}
stacking interactions between PDA abundant aromatic structures and benzene ring
in PHA from LbL layers, is first to put forward to construct durable efficient
flame retardant (FR) cotton. This work attempted to enlighten more thoughts and
design for durable FR cotton fabrics.
