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Tesi etd-02122009-093928


Thesis type
Tesi di dottorato di ricerca
Author
GRECO, FRANCESCO
URN
etd-02122009-093928
Title
Monomer and polymer indole-derived systems having NLO properties for very high optical gain photorefractive materials. The role of the electrostatic interactions.
Settore scientifico disciplinare
CHIM/05
Corso di studi
SCIENZE CHIMICHE
Commissione
Relatore Prof. Colligiani, Arturo
Relatore Prof. Ruggeri, Giacomo
Parole chiave
  • two-beam coupling
  • supramolecular arrangements
  • polymers
  • photorefractivity
  • photoconductivity
  • organic amorphous materials
  • NLO chromophores
  • optical amplifiers
  • NLO
  • materials science
  • Kerr effect
  • interactions
  • indole
  • electrooptic cells
  • data storage
Data inizio appello
20/02/2009;
Consultabilità
completa
Riassunto analitico
Object of the present research is the study of some indole-based<br>photorefractive (PR) materials. Novel indole-based NLO chromophores have<br>been synthesized and their photoconductive (PC) and PR behaviour have been<br>investigated when employed both alone (as low molecular weight glass<br>forming multifunctional PR moieties) as well as in blends with a PC<br>indolyl polymer, namely poly-(N-vinyl-2,3-dimethylindole). The aim was to<br>get more insight in the onset of PR effect and to evaluate various<br>contributions to it related to intermolecular interactions occurring among<br>the components of a PR material. The introduction of increasing contents<br>of polymer counterpart in PR blends containing the novel NLO chromophores<br>permitted to follow these interactions in their onset and the<br>establishment of new supramolecular arrangements, expected to be<br>responsible for dramatic changes of electrooptic properties. In this way,<br>it has been also possible to look for the proper formulation in order to<br>take advantage of such interactions for the achievement of the best PC and<br>PR performances. The joint analysis of the results of PC, PR and thermal<br>(DSC) behaviour of the investigated materials revealed itself as<br>particularly useful, due to the complexity of the many processes occurring<br>simultaneously in organic PR materials. A careful comparison with numerous<br>theoretical treatments permitted to rationalize the obtained results and<br>to put in evidence the prominent role played by intermolecular<br>interactions. On the other hand, the obtaining of long-term phase<br>stability of amorphous PR materials, desirable for their practical use in<br>a number of applications, was also a challenge. Many PR materials<br>described in the past, indeed, although having good photorefractive<br>properties, showed the undesirable drawback of fast recrystallization of<br>one or more of their molecular components, leading to opacization of films<br>and to the rapid loss of PR properties. Such aspect has been faced during<br>this research obtaining indefinitely stable materials. As concerns PR,<br>very large values of the photorefractive optical gain Γ (a main PR<br>figure of merit) have been achieved in many cases, classifying the<br>materials object of this research among the most efficient PR materials.
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