Formation of Porous Films with Hydrophobic Surface from a Blend of Polymers

An original method of obtaining hydrophobic surfaces from blends of immiscible polymers by creating porosity through removing one of the components of the blend is considered. Polymethylpentene and polyisobutylene are used as polymers. The first polymer, which is crystallizable, is the basis for the creation of a coating, while the second polymer is amorphous and easily and completely extractable from the blend with heptane. Blends containing from 5 to 55% polyisobutylene are studied. They are characterized by the non-Newtonian behavior and low viscosity that does not reach the viscosity of the polymer matrix owing to the interlayer slip. Removing the amorphous polymer from the blend makes it possible to attain a surface porosity of 45%, which acts as a fractal surface roughness. As a result, the contact angle of polymethylpentene film with water and ethylene glycol increases from 108° to 137° and from 78° to 132°, respectively. The low viscosity of the blends provides their easy processing, including the method of 3D printing, in order to create chemically resistant hydrophobic coatings.