Photochromic Polyurethanes Showing a Strong Change of Transparency and Refractive Index
by
Luca Oggioni 1,2, Chiara Toccafondi 3, Giorgio Pariani 1, Letizia Colella 1,2, Maurizio Canepa 3
, Chiara Bertarelli 2,4 and Andrea Bianco 1,*
Luca Oggioni 1,2, Chiara Toccafondi 3, Giorgio Pariani 1, Letizia Colella 1,2, Maurizio Canepa 3, Chiara Bertarelli 2,4 and Andrea Bianco 1,*
1
INAF—Osservatorio Astronomico di Brera, via Bianchi 46, 23807 Merate, Italy
2
Dipartimento di Chimica, Materiali ed Ingegneria Chimica, Politecnico di Milano, p.zza L. Da Vinci 32, 20133 Milano, Italy
3
OPTMATLAB, Dipartimento di Fisica, Università degli Studi di Genova, Via Dodecaneso 33, 16146 Genova, Italy
4
Center for Nano Science and Technology, @PoliMi, Istituto Italiano di Tecnologia, Via Pascoli 70/3, 20133 Milano, Italy
*
Author to whom correspondence should be addressed.
Polymers 2017, 9(9), 462; https://doi.org/10.3390/polym9090462
Received: 4 August 2017 / Revised: 2 September 2017 / Accepted: 13 September 2017 / Published: 20 September 2017
(This article belongs to the Special Issue Photo-Responsive Polymers)
Photochromic polymers have been studied as rewritable systems for optical elements with tunable transparency in the visible and refractive index in the NIR. Six diarylethene monomers have been synthesized to give thin films of photochromic polyurethanes. The absorption properties of the monomers in solution and of the corresponding polymeric films have been evaluated showing that a transparency contrast in the visible spectrum of the order of can be obtained by a suitable choice of the chemical structure and illumination wavelength. The change in the refractive index in the NIR have been determined by ellipsometry showing changes larger than . A trend of this variation with the absorption properties has been also highlighted. Fresnel lenses working on the basis of both a change of the transparency and the refractive index (amplitude and phase) have been demonstrated.
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Keywords:
photochromism; diarylethenes; polyurethanes; refractive index; holography
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited
MDPI and ACS Style
Oggioni, L.; Toccafondi, C.; Pariani, G.; Colella, L.; Canepa, M.; Bertarelli, C.; Bianco, A. Photochromic Polyurethanes Showing a Strong Change of Transparency and Refractive Index. Polymers 2017, 9, 462.
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