An indole-based low molecular weight glass-former giving materials with high cooperative photorefractive optical gain

Rocco Angelone, Marco Angiuli, Francesco Ciardelli, Arturo Colligiani, Francesco Greco, Annalisa Romano, Giacomo Ruggeri, Elpidio Tombari

Research output: Chapter in Book/Report/Conference proceedingConference contribution

3 Citations (Scopus)


A derivative of 2-methylindole, namely 3-[2-(4-nitrophenyl)ethenyl]-1-(2-ethylhexyl)-2-metylindole (NPEMI-E) has been synthesized. Materials obtained from this molecule have been studied as thin films between two ITO layers. The study revealed that NPEMI-E collects in itself both photoconductivity and NLO characteristics. Differential Scanning Calorimetry (DSC) measurements showed the formation of stable glass films characterized by a T g temperature lower than room temperature. Blends with the photoconductive poly-N-vinyl-2,3-dimethylindole (PVDMI) were also studied, giving again stable glass films independently of the wt.% contents of NPEMI-E. Photorefractivity measurements on both pure and blended NPEMI-E allowed to measure a value of the optical gain Γ = 627 cm -1 at an applied electric field E = 60 V/μm. This high value of Γ corresponds to a sharp maximum of the experimental trend of F as a function of the wt.% content of NPEMI-E. The corresponding content was wt.% = 91.5. The presence of this maximum induced us to make the hypothesis that, besides the well known reorientational contribution to the photorefractivity, a further mechanism (recently theoretically studied) is active in our blends. This mechanism arises in the interactions among the NLO polarized and polarizable moieties (cooperative effect). It can produce a rapid variation of some of the electrooptical parameters conditioning the extent of the photorefractivity. This can happen at a well defined mean intermolecular distance and hence at a well defined concentration of the NLO molecules.

Original languageEnglish
Title of host publicationOrganic Optoelectronics and Photonics II
Publication statusPublished - 2006
Externally publishedYes
EventOrganic Optoelectronics and Photonics II - Strasbourg, France
Duration: 2006 Apr 32006 Apr 6


OtherOrganic Optoelectronics and Photonics II



  • Cooperative contribution
  • Low-molecular-weight-glass-forming molecules
  • Photorefractivity
  • Poly(1-vinylindoles)
  • Supramolecular systems

ASJC Scopus subject areas

  • Electrical and Electronic Engineering
  • Condensed Matter Physics

Cite this

Angelone, R., Angiuli, M., Ciardelli, F., Colligiani, A., Greco, F., Romano, A., Ruggeri, G., & Tombari, E. (2006). An indole-based low molecular weight glass-former giving materials with high cooperative photorefractive optical gain. In Organic Optoelectronics and Photonics II (Vol. 6192). [61922M]