Supramolecular Self‐Assembled Dendritic Nonlinear Optical Chromophores: Fine‐Tuning of Arene–Perfluoroarene Interactions for Ultralarge Electro‐Optic Activity and Enhanced Thermal Stability

Abstract

Organic second-order nonlinear optical (NLO) materials are being actively pursued due to the increasing potential for application in photonic devices, such as high-speed electro-optic (EO) modulators, optical switches, and frequency converters. [1] For the fabrication of practical EO devices, critical material requirements, such as large EO coefficients, high thermal stability, and low optical loss need to be simultaneously optimized. One of the major problems in optimizing organic EO materials lies in the translation of high molecular nonlinearity into macroscopic EO activity by poling-induced acentric ordering of the dipolar chromophores.[2] Extensive experimental and theoretical studies have shown strong intermolecular electrostatic interaction among high-dipole-moment (m) chromophores to be the major factor defining the EO activity of electric-field-poled organic materials. These studies also suggest that the maximum realizable EO activity could be enhanced by controlling the chromophore shape to prevent stacking. [3] Owning to the unique characteristics of dendrimers (globular and void-containing shape, core encapsulation, structural uniformity, and high end-group functionality), dendritic NLO materials are of particular interest, because they provide opportunities for nanoscale architectural control and molecular and supramolecular engineering to simultaneously improve macroscopic EO activity and thermal stability. Dendritic NLO materials also introduce other auxiliary properties, including optical transparency, chemical and photochemical stability, and compatibility in composite materials.[4] For example, dendritic encapsulation of multiple dendron-modified chromophores [5] and multichromophore dendrimers, [6] as well as the use of dendronized side-chain EO polymers [7] created by post-functionalization, have recently been shown to lead to significantly enhanced EO coefficients in comparison with the conventional chromophore/polymer composites. In order to simultaneously improve their thermal stability and solvent resistance, a novel lattice-hardening approach using a sequential poling and cross-linking process based on the Diels-Alder cycloaddition reaction has been successfully developed to overcome the commonly observed nonlinearity-stability tradeoff in organic EO materials. [8] However, this approach adds a significant complication to both molecule design and the poling process for these highly efficient dendritic EO materials.The arene-perfluoroarene (ArH-ArF) interaction, [9] known as a strong face-to-face interaction between perfluorinated and nonfluorinated aromatic rings, was recently utilized to control supramolecular organization in reversible media including modulating the behavior of liquid-crystalline phases, [10] formation of hydrogels, [11] and templation effects in both solid-state photopolymerization and solution-state organic synthesis.[12] The ArH-ArF interaction was also used to create tightly packed molecular assemblies leading to a new class of supramolecular materials for el...

Complementary medicine for fatigue and cortisol variability in breast cancer survivors

“…In 2007, by using aromatic/pentafluoroaromatic dendron‐substituted NLO chromophores through the presence of these complementary Ar‐Ar F interactions, Jen and coworkers53 developed a new class of molecular glasses (Supporting Information Chart S1), which exhibited the improved poling efficiency and much enhanced macroscopic NLO effects (Supporting Information Chart S2). Two years later, they observed the same phenomenon again in another series of dendritic NLO chromophores containing pentafluoroaromatic as the dendron 54. Inspired by their wonderful results, also considering that the properties of the hyperbranched polymers were partially dominated by the nature of their large amounts of end groups in the periphery, we designed and synthesized a series of azo chromophore‐containing AB 2 ‐type hyperbranched polytriazoles ( PS1–PS4 , Supporting Information Chart S3) bearing pentafluoroaromatic rings in different part of these hyperbranched polymers 45.…”

Theory-Guided Design of Organic Electro-Optic Materials and Devices

“…Molecular cooperativity also affects nanoscale viscoelasticity and the thermodynamics (energetic) of various phases of matter including phases of reduced dimensionality. The viscoelastic properties can be characterized by nanoscopic measurement techniques such as shear modulation force microscopy (SM-FM) [76][77][78][79] and intrinsic friction analysis (IFA) [80]. They can also be studied by dielectric relaxation spectroscopy (DRS) [81,82] and by differential scanning calorimetry (DSC).…”

Synthesis of novel polyarylate with elecrooptical chromophores as side chain as electro-optic host polymer

“…Although the first-order hyperpolarizability of a specific chromophore is relatively large, the macroscopic EO coefficients are not very ideal due to the influence by spatial arrangement of the chromophores in the polymer host. If the chromophore loaded at a higher concentration, a significant reduction in the EO effect due to chromophore aggregation would be observed, which is usually driven by strong intermolecular electrostatic interactions [12][13][14][15]. In order to reduce the electrostatic attraction, many isolated groups were introduced to NLO chromophore.…”