An anionic polyelectrolyte hybrid for wood-polyethylene composites with high strength and fire safety via self-assembly

•An anionic polyelectrolyte hybrid was fabricated via self-assembly.•Physical crosslinking network in hybrid was formed by ionic and hydrogen bonding.•The network led strain to transfer effectively from HDPE chains to wood fibers.•High graphitization of char residue induced an optimum flame retardancy.•The hybrid simultaneously endowed WPC with flame retardancy and high strength.