Self-doped conductive polymer–silicon hybrids from atom transfer radical graft copolymerization of sodium styrenesulfonate with polyaniline covalently tethered on the Si(100) surface

Abstract

Polyaniline (PANi) with grafted poly(styrenesulfonic acid) (PSSA) side chains from atom transfer radical polymerization (ATRP), and covalently immobilized on the hydrogen-terminated Si(100) surface (Si–H surface), was prepared via: (i) UV-induced coupling of 4-vinylaniline (VAn) on the Si–H surface (Si–VAn surface), (ii) oxidative graft polymerization of aniline with the aniline moieties of the Si–VAn surface (Si–VAn–PANi surface), (iii) reaction of the Si–VAn–PANi surface with chlorosulfonic acid (ClSO₃H) to introduce the sulfonyl chloride (–SO₂Cl) on the PANi chains, (iv) surface-initiated ATRP of sodium 4-styrenesulfonate (NaStS) to give the Si–VAn–PANi–g–P(NaStS) surface, and (v) hydrolysis of the grafted NaStS polymer (P(NaStS)) on PANi to PSSA to give rise to the self-doped (self-protonated) PANi and a conductive Si–VAn–PANi–g–PSSA surface. Kinetic studies revealed a linear increase in the graft concentration of P(NaStS) with reaction time, indicating that the chain growth from the SO₂Cl-modified Si–VAn–PANi surface was consistent with a ‘controlled’ or ‘living’ process. The persistence of an active P(NaStS) chain end was confirmed by using the latter as the macroinitiator for the subsequent block copolymerization of poly(ethylene glycol) monomethacrylate (PEGMA) to give rise to the Si–VAn–PANi–g–P(NaStS)–b–PPEGMA surface. AFM images revealed that the surface graft copolymerizations had proceeded uniformly on the functionalized Si–H surface.