In order to make the socks be waterproof and breathable, we used a layer of hydrophilic PU membrane in the middle.
The hydrophilic membranes has a solid structure that physically blocks water molecules from passing through the membrane and diffuses water vapor molecules to absorb and disperse sweat to achieve moisture permeability. It means that when you sweat when you are stressed or exercising, your feet will not feel wet and cold, because excess sweat can be released through the microstructure.
The chemical structure of the membrane is that the hydrophilic component absorbs water vapor molecules, and is driven by a large pressure and water vapor density to promote the diffusion of water vapor molecules from one hydrophilic component to another. That's why these waterproof socks can be both waterproof and breathable.