New paper in Materials Horizons – Highly Transparent Photochromic Films

New paper in Materials Horizons – Highly Transparent Photochromic Films

14 Aug 2020

New publication in Materials Horizons journal entitled “Highly Transparent Photochromic Films with Tunable and Fast Solution-like Response” authored by Dr. Héctor Torres, Dr. Daniel Ruiz-Molina and Dr. Claudio Rsocini. The published paper is a result of the advances carried under the support of Futurechromes S.L.

In this work, the authors reported a novel solid photochromic material obtained through the entrapment of oil nanodroplets, containing the photochromic dye, into a material, which is cleverly used as both
nanoemulsion stabilizer and film-forming polymer. Although nanoemulsions have been broadly used in several applications, they were never exploited before for the preparation of photochromic films/coatings. Liquid-like photochromic response in the solid-state is thus easily achieved. With this new approach most of the challenges hampering the spread of photochromic materials in different applications are overcome: i) fast color-changing and easily tunable responses in the solid-state, ii) high optical transparency, iii) enhanced fatigue resistance, iv) straightforwardness and iv) scalability. The nanoemulsion entrapment approach grants access to new advanced stimuli-responsive transparent materials, providing unprecedented, easy and fine control of the optical properties in the solid-state, which is not possible otherwise.

ABSTRACT: The increasing interest towards photochromic films and their practical applications are driving researchers to the continuous design and synthesis of novel organic photochromic dyes with optimized performances in polymeric matrices. However, whereas their photochromic properties could be readily rationalized in organic liquid solutions, these could not be directly extrapolated to polymers as their performance changes unpredictably upon integration into a solid matrix. This leads to a time-consuming synthetic re-tuning of the dye chemical structure and/or the polymeric medium. To avoid this, herein we report an efficient, straightforward and universal strategy to embed commercial T-Type organic photochromic dyes of different nature in a polymeric material without compromising their optimum solution absorption and isomerization kinetics. Our approach is based on trapping emulsified nanodroplets of a hydrophobic solution enclosing the dye into a hydrophilic polymeric matrix. The material is prepared through one single process using commercially available materials, without further modification of the components (the dye and the polymer matrix) nor requiring previous encapsulation steps. The films, which manifest true solution liquid-like and finely tunable photochromic behavior, are also highly transparent, recyclable, scalable, and show enhanced fatigue resistance, making them highly suitable for different smart glass applications.

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