Optimizing the photochromic performance of naphthopyrans in a rigid host matrix using poly(dimethylsiloxane) conjugation

Abstract

A series of methoxy substituted 2,2-diaryl-2H-naphthopyran photochromic dyes were assembled incorporating hydroxy functionality to allow their subsequent attachment to flexible poly(dimethylsiloxane) oligomers. The photochromic performance of the generated PDMSnaphthopyran conjugates was studied in a thermoset host matrix and compared to non-conjugated, electronically equivalent control dyes. Both coloration and decoloration speeds were found to be greatly improved with critical T 1/2 decoloration times reduced by 42-80%. The extent of solution-like performance provided by PDMS conjugation in the rigid host was examined with reference to the fade performance of control dyes in solution, and found to range from 20 to 90%. These measures are believed to be influenced by the electronic nature and steric interactions of the photochromic dyes. Scheme 1 Generic photochromic reaction for substituted 2,2-diaryl-2Hnaphtho[1,2-b]pyrans.

A fluorescence switch based on a controllable photochromic naphthopyran group

“…This difference is likely to be caused by the different coloration rates of naphthopyran in solution and in PMMA film. The steric hindrance and free volume around NP molecule are bigger in solid film than those in solution and provide more restriction effect on rotational mobility of NP molecules [17,20]. Therefore, the coloration process of NP in solution is faster than that in PMMA film and the combining rate of BPI with opened-form NP in solution is bigger than that in PMMA film.…”

“…The two forms can be converted to each other either by irradiation of UV-vis light or by thermal stimulation [16,17]. However, photoswitchable fluorescence switches based on photochromic naphthopyran are virtually unknown.…”

Highly efficient light-induced reversible micellization of amphiphilic polymer based on photochromism of naphthopyran in aqueous solution

“…This produces a distribution of open geometrical isomers (MC) with extended conjugation and quasi-planar conformations. In the absence of UV irradiation, the colored isomers gradually revert back thermally or photochemically to the closed naphthopyran form, undergoing a significant intramolecular rotation during the conversion [29]. The photo-induced isomerization of the NP molecules change the spatial configuration of NP and further change the NP molecules arrangement inside the micelles, which resulted that the polymeric micelles may not necessarily fall apart but the aggregate pattern of the micelles are changed and the mechanical stability of the micelle should be weakened.…”

Control of optical properties through photochromism: a promising approach to photonics

“…As regards the coloration and fading processes, it is required to achieve a fast response in both directions to follow abrupt changes in the illumination conditions. Many studies have been published on the features of switching in polymer matrices, showing the effects of the free volume available for the isomerization that is related to the polymer properties (i. e. glass-transition temperature, T g ) and to chemical interaction between the dye and the matrix [50][51][52][53][54][55]. Moreover, the UV-triggered modulation of color is influenced by temperature that balances the effect of light by favoring the fading process.…”