Efficient High-Refractive-Index Azobenzene Dendrimers Based on a Hierarchical Supramolecular Approach

Abstract

Real-time manipulation of light in a diffractive optical element made with an azomaterial, through the lightinduced reconfiguration of its surface based on mass transport, is an ambitious goal that may enable new applications and technologies. The speed and the control over photopatterning/ reconfiguration of such devices are critically dependent on the photoresponsiveness of the material to the structuring light pattern and on the required extent of mass transport. In this regard, the higher the refractive index (RI) of the optical medium, the lower the total thickness and inscription time can be. In this work, we explore a flexible design of photopatternable azomaterials based on hierarchically ordered supramolecular interactions, used to construct dendrimer-like structures by mixing specially designed sulfur-rich, high-refractive-index photoactive and photopassive components in solution. We demonstrate that thioglycolic-type carboxylic acid groups can be selectively used as part of a supramolecular synthon based on hydrogen bonding or readily converted to carboxylate and participate in a Zn(II)−carboxylate interaction to modify the structure of the material and fine-tune the quality and efficiency of photoinduced mass transport. Compared with a conventional azopolymer, we demonstrate that it is possible to fabricate high-quality, thinner flat diffractive optical elements to reach the desired diffraction efficiency by increasing the RI of the material, achieved by maximizing the content of high molar refraction groups in the chemical structure of the monomers.

Wavelength-Dependent Shaping of Azopolymer Micropillars for Three-Dimensional Structure Control

“…Azobenzene-containing materials can provide new strategies for creating controlled 3D mesostructures on a surface based on light-driven mass migration that results from the cyclic photoisomerization of azobenzene chromophores upon exposure to UV–visible light. Typical material systems involve the inclusion of azobenzene molecules in a polymer matrix (azopolymers), although many studies have shown that different material design strategies can be used to tune the efficiency of mass transport. , The resulting mesostructure geometry can be controlled by the distribution of the light intensity, the local direction of the electric field (light polarization), and the shape of the irradiated wavefront, , opening up the unprecedented possibilities of a fully vectorial photolithography. In addition, a structure inscribed on an azomaterial surface can be erased by either unpolarized light irradiation or thermal treatment.…”

Temperature Dependence and Molecular Interactions Studies from Refractive Indices of 6-(4-Chlorophenyl)-1, 2, 3, 4-Tetrahydro-4-Oxo-2- Thioxopyrimidine-5-Carbonitrile in 60% Aqueous Dimethyl Sulphoxide

“…Study of refractive indexes of organic compounds has gained more attentions due to its application in solid waste management (1) , drug discovery (2) , supramolecular chemistry (3) , etc. It is the optical property describing the relative speed of light through medium.…”