Novel photosensitive polyurethanes based on photochromic dithienylethene monomers: synthesis, characterization and photophysical properties of a new film-building material for photonic applications

Abstract

The synthesis of a novel photochromic dithienylethene-based polyurethane and its characterization by optical spectroscopy and scanning tunneling microscopy are presented. This linear polyurethane builds up perfect free-standing films suited for photonic applications. Moreover it may be extruded to long mechanically stable fibers. The photochromic reactions of the polyurethane, as being the electrocyclic ring-closure and ring-opening reactions of the dithienylethene unit in the polymer backbone, occur in a completely reversible and highly efficient fashion.

Photochromic Polyurethanes Showing a Strong Change of Transparency and Refractive Index

“…1 Tz-Ph and Tz-T were synthesized starting from the Suzuki coupling of the di-bromothiazole (5) with a formyl benzene boronic acid and formyl thiophen boronic acid, respectively. The formyl group of the resulting products (i.e., 6 and 10) was first protected to form the 1,3-dioxalane, then a Dixon reaction with perfluorocyclopentene was carried out to afford the diarylethenes (8) and (12), which were deprotected and finally reduced with NaBH 4 (see Scheme 2).…”

“…After solvent removal, flash chromatography using hexane:ethyl acetate (ratio from 8.5:1.5) afforded 1.13 g of 11 as a white powder in 76% yield. 1 (12) n-BuLi (1.48 mL, 2.5 M in n-hexane) was added dropwise to a stirred solution of 11 (1.20 g, 3.6 mmol) in 40 mL anhydrous THF at −78 • C. After 15 min, 240 µL of perfluorocyclopentene were added. The reaction mixture was allowed to warm to room temperature, poured into water, extracted with DCM, and dried over Na 2 SO 4 .…”

“…To achieve such goals, we proposed backbone photochromic polymers, where the photochromic units are part of the polymer main chain [11][12][13]. In particular, it has been shown that polyurethanes are good candidates, showing good resistance to solvents and allowing for versatile polymerization and processing.…”

Optical macromolecular indoaniline indicators for vinyl‐SiH curing of silicones for dental application

“…Apart from this, we reported about a solvatochromic polymerizable dye in a thermosensitive copolymer 8. We also synthesized photochromic poly urethanes 9. However, up to now poly siloxanes bearing dye molecule that may react with Si‐H functions were not yet investigated.…”

Control of optical properties through photochromism: a promising approach to photonics

“…Suitable processing methods have to be applied to guarantee good optical properties in thick filters. The second approach consists in the synthesis of photochromic materials that afford amorphous films, i. e. photochromic polymers both sidechain [21][22][23][24][25][26][27][28][29] or main-chain [30][31][32][33][34][35][36], small molecules with bulky groups that prevent crystallization [37][38][39][40], sol-gel matrices [41]. In these cases the concentration of the active moiety can be markedly increased and high contrast can be obtained in relatively thin films.…”