The scanning electron microscopy (SEM) images of the prepared materials show that the modification with silica and subsequent hydrophobization lead to the formation of smaller sized PHI particles, which is possibly due to the formation of SiO2 around PHI, favouring its dispersibility (for detailed analysis of SEM images see Supplementary Information, Figure ). The SEM-EDX elemental analysis shows the presence of Si in all modified samples and evidences the reduction of potassium concentration upon the sol-gel modification and hydrophobization procedures (see Supplementary Information, Figure ).