Robust PEDOT films by covalent bonding to substrates using in tandem sol–gel, surface initiated free-radical and redox polymerization

Abstract

Poly(3,4-ethylenedioxythiophene), PEDOT, films are used as antistatic coatings on electrically insulating substrates such as plastic and glass. A novel method for the synthesis of conducting PEDOT films on insulators relies on sol–gel chemistry to attach a di-Si(OEt)₃ functionalized free radical initiator (AIBN) on oxidized surfaces, followed by: (a) attachment of 3,4-(vinylenedioxy)thiophene (VDOT: an analogue to EDOT susceptible to radical addition through its vinylenedioxy group); and, (b) oxidative (with FeCl₃) co-polymerization of surface-confined VDOT with 3,4-ethylenedioxythiophene (EDOT). In conjunction with classical photolithography, the method yields thin (∼150 nm) yet dense, pinhole-free (confirmed electrochemically), hard (>6H), extremely adhesive (5B), patterned, highly conducting (52 mho cm⁻¹) films. The process is applied mainly on glass but it works equally well on oxidized metal surfaces (aluminum, steel, Pt). Control studies related to “grafting from” with surface-confined AIBN were conducted by growing inexpensive poly(styrene) and poly(methylmethacrylate) films.