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The Relevance of the Collaborative Effect in Determining the Performances of Photorefractive Polymer Materials
Author(s) -
Angelone Rocco,
Ciardelli Francesco,
Colligiani Arturo,
Greco Francesco,
Masi Paolo,
Romano Annalisa,
Ruggeri Giacomo
Publication year - 2010
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.200900619
Subject(s) - chromophore , photorefractive effect , glass transition , differential scanning calorimetry , pockels effect , polymer , materials science , solubility , analytical chemistry (journal) , chemistry , organic chemistry , thermodynamics , optics , optoelectronics , laser , physics
Abstract A derivative of 2‐methylindole, 3‐[2‐(4‐nitrophenyl)ethenyl]‐1‐allyl‐2‐methylindole, NPEMI‐A, is studied for its photoconductivity and photorefractivity behaviour. Its blends with the organic polymer poly‐(2,3‐dimethyl‐ N ‐vinylindole), PVDMI, are also investigated. Due to the expected and devised mutual solubility of the two components of the blends, it is possible to carry out measurements with the weight percent of the chromophore NPEMI‐A changing from zero to 100. Films were produced by a squeezing process between two ITO‐covered glass sheets. No opacity phenomena, that are so common for many other organic blends due to the segregation of the dissolved chromophore, are observed. The photorefractive optical gain Γ 2 is obtained as a function of the chromophore content. Differential scanning calorimetry measurements (DSC) are also carried out to obtain the whole change of the glass transition temperature T g as a function of the amount of chromophore contained in the blends. From the experimental trend of T g a meaningful quantitative estimate of the value of the electrostatic interactions acting in the studied blends, is obtained. The importance of the value of T g , and of the electrostatic interactions, in determining the extent of the photorefractivity is clearly evident. The results are compared for NPEMI‐A ( Γ 2 =210 cm −1 ) and for NPEMI‐E ( Γ 2 ≈ 2000 cm −1 ) that has a N‐2‐ethylhexyl group instead of a N‐allyl group. The Pockels and Kerr contributions and—for the first time—a “collaborative effect” of the photorefractivity of NPEMI‐A are distinguished and quantitatively evaluated.