Steric effects in photochromic polysiloxanes with spirooxazine side groups

Abstract

Synthesis and properties of linear and cyclic polysiloxanes with photochromic spirooxazine side groups were investigated. The photochromic groups were connected to the main chains through a flexible (CH2)" spacer. The number of photochromic groups that can be incorporated in the polymer by a polymer analogous reaction is restricted for the short spacer (CH2)3 to ~50%, while the photochromic groups with the longer spacer (CH2)e can be added to practically each polymer unit. The rates of the thermal decoloration reactions are also determined by the spacer lengths and the spirooxazine content. At high content, a deviation from first-order kinetics was observed for the color decay. The effects are explained by the steric interactions of the bulky photochromic groups. Computer simulation of the molecular movement in the macromolecules confirmed the explanation.

Optical Properties of Functional Hybrid Organic–Inorganic Nanocomposites

“…[119,120] Strong interactions between the dye and the host matrix reduce the dye mobility and thus the thermal decoloration rate. In such systems, the spacer length between the dye and the matrix network [121] could optimize the rate of photochromic reactions.…”

Photochromic Polymers

“…46 The photochromic behavior of poly(tetrahydrofuran) incorporating viologen units in the main chain was studied in detail. 47 A polycationic polymer (17) having the tetrakis [3,5-bis(trifluoromethyl)phenyl]borate anion (TFPB -) as counterion displayed broad absorption bands due to an ion-pair charge-transfer complex between the bipyridinum moiety and the anion. Photoirradiation in vacuo with light exciting the charge-transfer band (>365 nm) resulted in the formation of colored species ascribable to cation radicals with blue coloration.…”

“…Gel permeation chromatography indicated an equivalent molecular weight of 4000. (17) The reaction scheme for the preparation of 17 46 is shown in Figure 6. Dried THF was stirred in Ar for 15 min at room temperature in the presence of trifluoromethanesulfonic anhydride as a catalyst.…”

Synthesis and characterization of diblock copolymers based on poly(3-hexylthiophene) and photo-responsive poly(methyl methacrylate-random-2-methyl methaspirooxazine)

“…[1][2][3][4] Photochromic SP compounds are molecules containing a condensed ring-substituted 2H- [1,4]oxazine in which the carbon atom in position 2 of the oxazine ring is involved in a spiro linkage. Under UV light irradiation, SP, in its colorless form, isomerizes to form the blue-colored merocyanine (MC) (or the open form) by homolytic cleavage of the carbon-oxygen single bond of the oxazine ring.…”