Compatible Photochromic Systems for Opto-electronic Applications

Development of an Azobenzene-Based Cell Culture Photoresponsive Platform for In Situ Modulation of Surface Topography in Wet Environments

Azopolymers are light-responsive materials that hold promise to transform in vitro cell culture systems. Through precise light illumination, they facilitate substrate pattern formation and erasure, allowing for the dynamic control and creation of active interfaces between cells and materials. However, these materials exhibit a tendency to locally detach from the supporting glass in the presence of aqueous solutions, such as cell culture media, due to the formation of blisters, which are liquid-filled cavities generated at the azopolymer film-glass interface. These blisters impede precise structurization of the surface of the azomaterial, limiting their usage for surface photoactivation in the presence of cells. In this study, we present a cost-effective and easily implementable method to improve the azopolymer-glass interface stability through silane functionalization of the glass substrate. This method proved to be efficient in preventing blister formation, thereby enabling the dynamic modulation of the azopolymer surface in situ for live-cell experiments. Furthermore, we proved that the light-illumination conditions used to induce azopolymer surface variations do not induce phototoxic effects. Consequently, this approach facilitates the development of a photoswitchable azopolymer cell culture platform for studying the impact of multiple in situ inscription and erasure cycles on cell functions while maintaining a physiological wet microenvironment.

Modeling the Impact of Dye Concentration on Polymer Optical Properties via the Complex Refractive Index: A Pathway to Optical Engineering

This work investigates the potential to rely on the complex refractive index to correlate the chemical composition of polymers with their optical properties, including transmittance, reflectance and absorbance. The optical properties of polycarbonate slabs with various controlled concentrations of two dyes were initially measured and analyzed. The reflection and transmission measurements obtained were used to determine the corresponding complex refractive index over a wide range of wavelengths. Comparing it with that of a clear material provided the spectral deviation of the complex refractive index induced by the dye concentrations and resulted in assigning a spectral efficiency to both of them. A modification function of the complex refractive index was established based on this spectral efficiency, which acts as a spectral fingerprint related to each dye. Finally, two samples doped with the two dyes mixed were studied to assess the model's capabilities. On the one hand, based on the measured transmittance, the dye concentrations were determined within a deviation below 8% in comparison with the values provided by the manufacturer. On the other hand, when the dye concentrations were known, the model reproduced the optical properties with good accuracy beyond the limitations of the experimental setup. The model's effectiveness in correlating the chemical composition of polymer with its optical properties through the complex refractive index makes it a valuable asset in analyzing and formulating plastics with intended optical properties.

Synthesis and Study of the Optical Properties of a Conjugated Polymer with Configurational Isomerism for Optoelectronics

A π-conjugated polymer (PBQT) containing bis-(2-ethylhexyloxy)-benzo [1,2-b'] bithiophene (BDT) units alternated with a quinoline-vinylene trimer was obtained by the Stille reaction. The chemical structure of the polymer was verified by nuclear magnetic resonance (1H NMR), Fourier transform infrared (FT-IR), and mass spectroscopy (MALDI-TOF). The intrinsic photophysical properties of the solution were evaluated by absorption and (static and dynamic) fluorescence. The polymer PBQT exhibits photochromism with a change in absorption from blue (449 nm) to burgundy (545 nm) and a change in fluorescence emission from green (513 nm) to orange (605 nm) due to conformational photoisomerization from the trans to the cis isomer, which was supported by theoretical calculations DFT and TD-DFT. This optical response can be used in optical sensors, security elements, or optical switches. Furthermore, the polymer forms spin-coated films with absorption properties that cover the entire visible range, with a maximum near the solar emission maximum. The frontier molecular orbitals, HOMO and LUMO, were calculated by cyclic voltammetry, and values of -5.29 eV and -3.69, respectively, and a bandgap of 1.6 eV were obtained, making this material a semiconductor with a good energetic match. These properties could suggest its use in photovoltaic applications.