Photochemically and Thermally Programmed Optical Multi‐States from a Single Diacetylene‐Functionalized Cyanostilbene Luminogen

Abstract To develop advanced optical systems, many scientists have endeavored to create smart optical materials which can tune their photophysical properties by changing molecular states. However, optical multi‐states are obtained usually by mixing many dyes or stacking multi‐layered structures. Here, multiple molecular states are tried to be generated with a single dye. In order to achieve the goal, a diacetylene‐functionalized cyanostilbene luminogen (DACSM) is newly synthesized by covalently connecting diacetylene and cyanostilbene molecular functions. Photochemical reaction of cyanostilbene and topochemical polymerization of diacetylene can change the molecular state of DACSM. By thermal stimulations and the photochemical reaction, the conformation of polymerized DACSM is further tuned. The synergetic molecular cooperation of cyanostilbene and diacetylene generates multiple molecular states of DACSM. Utilizing the optical multi‐states achieved from the newly developed DACSM, switchable optical patterns and smart secret codes are successfully demonstrated.


4-(octyloxy)benzaldehyde (
The crude product was purified by column chromatography with silica gel using n-hexane:EA

Specific Notes
For smooth photochemical reactions of DACSM in solid state, DACSM thin films were prepared by shear coating at 60 ~ 70 °C using a bar coater (Elcometer 3530/2) with 5μm gap.

Characterization
The chemical structure and purity of intermediates and DACSM were confirmed by nuclear magnetic resonance (NMR, JEOL, JNM-EX400) in deuterated chloroform.Chemical shifts were quoted in parts per million (ppm) with tetramethylsilane (TMS) used as a reference.
NMR spectroscopy was also utilized to analyze the photoisomerization and cycloaddition of DACSM.Gas chromatography mass spectroscopy (GC/MS) was used to confirm the chemical structure of DACSM intermediates.Matrix-assisted laser desorption/ionization timeof-flight mass spectroscopy (MALDI-ToF/MS, Bruker, Bruker autoflex Ⅲ) was also used to identify DACSM.POM images at different temperatures were obtained by a cross-polarized optical microscope (POM, Nikon, ECLIPSE E600POL) with a microscope hot stage system (Mettler Toledo, HS82).Thermal phase transition behavior of DACSM was monitored using differential scanning calorimetry (DSC, Perkin Elmer, DSC 4000).To understand the molecular packing structure of DACSM, a wide-angle X-ray diffraction instrument (WAXD, Bruker, D8 ADVANCE) was used.The positions of diffraction peaks were calibrated with a silicon crystal (2θ = 28.466).The absorption (or transmittance) and emission properties of differently treated DACSM samples were investigated by UV-Vis spectrometer (Scinco, S-3100) and spectro-fluorophotometer (Shimadzu, RF-6000).The formation of polydiacetylene under 254 nm light and its conformational change was confirmed by Raman spectroscopy (Nanophoton, RAMAN Touch).Photoluminescence quantum yield and lifetime measurements were conducted using a spectro-fluorophotometer (Horiba, Fluorolog-3 with TCSPC).

Figure S13 .
Figure S13.a) Photoisomerization of DACSM from transto cis form.b) UV-Vis and c) PL spectra of DACSM in THF before and after UV irradiation.

Figure
Figure S14. 1 H NMR spectrum of DACSM in CDCl3 after UV irradiation.

Figure S20 .
Figure S20.CIE diagram for PL color of different moleulcar states.

Figure S21 .
Figure S21.PL quantum yield results of five different DACSM states.

Figure S22 .
Figure S22.PL lifetime decay of five different DACSM states.