Mechanism of photoinduced step polymerization of thiophene by onium salts: Reactions of phenyliodinium and diphenylsulfinium radical cations with thiophene


Yagci Y. , JOCKUSCH S., TURRO N. J.

MACROMOLECULES, vol.40, no.13, pp.4481-4485, 2007 (Journal Indexed in SCI) identifier identifier

  • Publication Type: Article / Article
  • Volume: 40 Issue: 13
  • Publication Date: 2007
  • Doi Number: 10.1021/ma070586a
  • Title of Journal : MACROMOLECULES
  • Page Numbers: pp.4481-4485

Abstract

Laser flash photolysis and EPR studies were performed to elucidate the mechanism of photoinduced step polymerization of thiophene by using diphenyliodonium (Ph2I+) and triphenylsulphonium (Ph3S+) ions as photoinitiators. Photoexcitation of these ions generated phenyliodinium (PhI center dot+) and diphenylsulphinium (Ph2S center dot+) radical cations, which were readily quenched by thiophene with rate constants of k(q) = 1.26 x 10(10) and 1.7 x 10(5) M-1 s(-1), respectively. The transient absorption spectra of the corresponding thiophene radical cations were not directly detectable because of the spectral overlap with the precursor salts. However, the related electron-transfer reaction was confirmed by quenching of the PhI center dot+ radical cation with bithiophene to form the radical cation of bithiophene, which absorb strongly at 420 nm. EPR studies also confirmed the proposed electron-transfer mechanism through the direct detection of the radical cation of thiophene.