The generic enhancement of photochromic dye switching speeds in a rigid polymer matrix


The switching or isomerization speed of photochromic dyes in a rigid polymeric matrix (such as an ophthalmic lens) is generally significantly slower than that observed in the mobile environment of a solution. Here we describe that the attachment of flexible oligomers having a low glass-transition temperature—such as poly(dimethylsiloxane)—to photochromic dyes greatly increases their switching speeds in a rigid polymer matrix. The greatest impact was observed in the thermal fade parameters T1/2 and T3/4—the times it takes for the optical density to reduce by half and three quarters of the initial optical density of the coloured state—which were reduced by 40–95% and 60–99% respectively for spirooxazines, chromenes and an azo dye in a host polymer with a glass-transition temperature of 120 °C. The method does not alter the electronic nature of the dyes but simply protects them from the host matrix and provides greater molecular mobility for the switching process. In addition to ophthalmic lenses, the generic nature of the method may find further utility in data recording or optical switching.

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Figure 1: Structural changes of spirooxazines, chromenes and azo compounds during photochromic switching.
Figure 2: Near solution-like decolourization speed of a spirooxazine in a rigid polymer matrix.
Figure 3: Intramolecular interaction of PDMS oligmer with dye.
Figure 4: Enhancement of photochromic switching speeds of a chromene and azo dye in a rigid matrix.


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We acknowledge the Cooperative Research Centre for Polymers for funding and the Australian Research Council for the award of an Australian Professorial Fellowship to T.P.D.

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Correspondence to Richard A. Evans.

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Evans, R., Hanley, T., Skidmore, M. et al. The generic enhancement of photochromic dye switching speeds in a rigid polymer matrix. Nature Mater 4, 249–253 (2005).

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