Reversible photo-switching interaction between spiropyrans and polymer pyridine residues in a solid polymer membrane

Abstract

A solid membrane of poly(2-ethylhexyl methacrylate-co-vinylpyridine) containing photochromic 69-nitrospiropyran was prepared. In the rubbery copolymer membrane (T g = 29 uC), the merocyanine (MC) form of the spiropyran isomerized into the spiro (SP) form by thermal decay after irradiation with UV light. The resulting decay showed two types of first-order kinetics, fast and slow. The activation energy for slow decay in the copolymer membrane was about 4 kcal mol 21 higher than that of fast decay. Furthermore, the standard enthalpy (DHu) of reversible isomerization (SP P MC) without photolysis in the copolymer membrane was negative, in contrast to positive DHu values obtained for a homopolymer membrane of poly(2-ethylhexyl methacrylate) and for a liquid pyridine solution of spiropyrans. It was deduced that some of MC molecules in the copolymer membrane were thermodynamically stabilized. Additionally, the stabilized MC form in the copolymer membrane emitted intense green fluorescence (l em = 570 nm), while the simple MC form in the homopolymer or pyridine solution showed weak red emission (l em = 620-630 nm). The green fluorescence of the copolymer membrane was photo-reversible. These results suggest the existence of a photo-switchable interaction between spiropyrans and polymer pyridine residues in the solid copolymer membrane.

UV light induced plasticization and light activated shape memory of spiropyran doped ethylene-vinyl acetate copolymers

“…According to the literature work on the thermal decay from the MC form to the SP form in methacrylate polymers substituted with spiropyran aer irradiation with UV light, two MC forms were presented within the methacrylate polymer: one which interacts with the ester residues of the polymer, and a simple, non-interacting form. 35,36 Two decay half times are also observed in this work, one with a short mean lifetime and another with a much longer mean lifetime. These observations may also be ascribed to the presence of two MC forms within the EVA matrix: one interacting with the ester groups of EVA, and a simple, non-interacting form.…”

Spiropyran as a Selective, Sensitive, and Reproducible Cyanide Anion Receptor

“…A 0 , A t , and A ∞ are the absorbance of the colored form at time 0, t, and infinity, respectively, and k is the first order coloration rate constant (s -1 ). In the case of thermal 1(SP) → 1(MC) isomerization process, [10] N O…”

Negative Photochromism Based on Molecular Diffusion between Hydrophilic and Hydrophobic Particles in the Solid State

“…17−19 Even at the photostationary state, the material was not colorless, which was explained by the dye aggregates, which absorb visible light. Negative photochromism has been observed for a spiropyran (SP) in solid doped in poly(2-ethylhexyl methacrylate-covinylpyridine) 13 and a SP covalently immobilized to silica nanoparticles. 20 In these cases, negative photochromism was not efficient because of the low population of merocyanine (MC).…”

“…Negative photochromic materials are expected to show an effective conversion efficiency thanks to the absence of reabsorption of excitation visible light by the photogenerated colorless isomer, − while that of the normal photochromic molecules is not high because of reabsorption of excitation light by the colored isomers. Negative photochromism of such molecules as dihydropyrenes, stenhouse salts, and spiropyrans in solution has been reported, − while negative photochromism in the solid state has scarcely been reported. − Negative photochromism of the crystals of N -salicylidenepyrenes and biindenylidenediones was reported from the colored isomer (the initial state of negative photochromism), which was stabilized by such intermolecular interactions as hydrogen bond and π–π stacking between adjacent molecules. − Even at the photostationary state, the material was not colorless, which was explained by the dye aggregates, which absorb visible light. Negative photochromism has been observed for a spiropyran (SP) in solid doped in poly­(2-ethylhexyl methacrylate- co -vinylpyridine) and a SP covalently immobilized to silica nanoparticles .…”

“…Negative photochromism of such molecules as dihydropyrenes, stenhouse salts, and spiropyrans in solution has been reported, − while negative photochromism in the solid state has scarcely been reported. − Negative photochromism of the crystals of N -salicylidenepyrenes and biindenylidenediones was reported from the colored isomer (the initial state of negative photochromism), which was stabilized by such intermolecular interactions as hydrogen bond and π–π stacking between adjacent molecules. − Even at the photostationary state, the material was not colorless, which was explained by the dye aggregates, which absorb visible light. Negative photochromism has been observed for a spiropyran (SP) in solid doped in poly­(2-ethylhexyl methacrylate- co -vinylpyridine) and a SP covalently immobilized to silica nanoparticles . In these cases, negative photochromism was not efficient because of the low population of merocyanine (MC).…”