Extended Data Fig. 4. Hydrophobicity of microplastics governs their water contact angle and surface electrification.

a, Microplastic-water interface hydrophobicity quantified by contact angle. Simulated ratio of surface dangling OH groups (defined as water without any acceptor (X) within an intermolecular O···X distance less than 3.5 Å and with an H–O···X angle (β) smaller than 50°) versus water contact angle. Water contact angle (θ) reported from Accu Dyne Test™ Surface Energy Database³⁷. b, Surface electrostatics from water electrification correlates with hydrophobicity at plastic-water interface³⁵. All polymers show negative surface potential, with hydrophobic ones exhibiting stronger negativity. Polyolefins without polar groups are more hydrophobic and negatively charged than polymers bearing hydrophilic functionalities such as esters. Figure adapted with permission from ref. ³⁵, Wiley.