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Identifier

000353091

Title

Εγγραφή μεσοσκοπικών δομών σε διαλύματα πολυμερών με ακτίνες LASER : συνθήκες και μηχανισμός του φαινομένου

Alternative Title

Writing mesoscopic structures in polymer solutions using LASER beams: Conditions and mechanism of the phenomenon

Author

Ανυφαντάκης, Εμμανουήλ Γ.

Thesis advisor

Φαράντος, Σταύρος

Abstract

The subject of the present thesis is the study of the unexpected response of transparent semidilute polydiene solutions to weak visible LASER irradiation. A detailed experimental investigation was carried in order to establish a clear phenomenology of the observed effect and try to gain insight into the underlying coupling mechanism and to establish micropatterning routes in these materials. An imaging method based on Quantitative Phase Contrast Microscopy was established as a powerful experimental tool allowing detailed study, in particular of the kinetics of the process. A number of new important facts have been established: - Surprisingly, depending on the solvent used, the polydiene solutions can respond to the optical field either by increasing or lowering the polymer concentration inside the irradiated volume. - The reversibility of the writing process was found to depend on the irradiation time and unexpectedly, prolonged irradiations led to long-lived structures that could not be redissolved in good solvents for the polymers. For short exposures, the LASER-induced patterns are reversible. - A clear analogy to non linear optical phenomena occurring in other Soft Matter systems, such as Optical Spatial Solitons and Modulation Instabilities was recognized. - It has been shown that LASER writing can be successfully used to create impressive effects, such as the formation of very long fibrilar structures and the demonstration of Self Induced transparency. - Rationalizations based on expected light-matter couplings cannot account for the observed phenomenology Though the responsible mechanism still remains unclear, the obtained knowledge concerning the various patterning possibilities offered by the different polydiene solutions can open an avenue for much needed 3D micropatterning.

Language

English

Issue date

2010-01-18

Collection

School/Department--School of Sciences and Engineering--Department of Chemistry--Doctoral theses

Type of Work--Doctoral theses

Views

273

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