Conformal Growth of Ultrathin Hydrophilic Coatings on Hydrophobic Surfaces Using Initiated Chemical Vapor Deposition

Hydrophilic poly(2-hydroxyethyl methacrylate) (PHEMA) was deposited onto hydrophobic polytetrafluoroethylene (PTFE) surfaces using initiated chemical vapor deposition. By tuning the reactor conditions, the reaction kinetics were varied to achieve a wide range of deposition rates that spanned over 2 orders of magnitude (∼0.1-10 nm/min). Depositions rates at >1 nm/min were successful in overcoming the interfacial energy and wettability barriers between the hydrophobic and hydrophilic polymers and were found to achieve both conformal and ultrathin coatings. PHEMA coatings as thin as ∼10 nm over PTFE were able to transform a hydrophobic surface with a water contact angle of ∼110° to a hydrophilic one with an angle of ∼20°.