Photochromic Polymer Conjugates: The Importance of Macromolecular Architecture in Controlling Switching Speed within a Polymer Matrix

Abstract

Naphthopyran-poly(n-butyl acrylate) conjugates with different geometries were assembled using ATRP. First, within a rigid lens matrix, an investigation of the photochromic behavior of various poly(n-butyl acrylate), p(n-BA), homopolymers showed that midplacement of a single dye moiety, made possible using a Y-branching difunctional photochromic initiator, gave superior fade kinetics per chain length of conjugated polymer compared to end-functionalized homopolymers. Furthermore, having the dye pendant from the chain opposed to directly within the chain was also found to be advantageous. Fading kinetics became faster when chain length was increased, except in the case of linear random copolymers made by copolymerization of n-butyl acrylate with a naphthopyran acrylate. A gradient copolymer made with a nonphotochromic difunctional initiator and a naphthopyran methacrylate displayed superior kinetics. Films consisting of ABA triblock copolymers, incorporating the photochromic in the middle of a soft p(n-BA) section, gave slower switching speeds compared to lens samples, with responses that were highly tunable and dependent on the amount of soft section inhabited by the photochromic moiety. Scheme 2. Atom Transfer Radical Polymerization Synthesis of Naphthopyran-Poly(n-butyl acrylate) Conjugates Displaying Molecular Weights of Purified Samples Tested in Survey (dNbpy = 4,4 0 -Dinonyl-2,2 0 -bipyridine)

Synthesis and characterization of new spiropyran micrometer-sized photochromic fluorescent polymeric particles of narrow size distribution by a swelling process

“…[14] It is also well known from the literature that the rigidity of the host compound has a major influence on the total environment of guest photochromic molecules. More rigid environment are known to retard the photochromic transition, [28,29] or in our case the fluorescence intensity.…”

Inkjet printing and UV-LED curing of photochromic dyes for functional and smart textile applications

“…Whereas, Ercole et al 25 and Malic et al 26 studied the placement of naphthopyran dye in host polymers, Mutoh et al…”

“…The balance (Kern) has 99.96% accuracy when calibrated against a standard weight of 100 mg. The heat ow of samples of about 5.0 mg was measured during a heating and cooling cycle from 25 C to 290 C and back to 25 C with a rate of 10 C min À1 . The released energy DH of the endothermic reaction during melting of the material gives indirect information on the degree of polymer crosslinking at the interface between the PET fabric and the photochromic UVcured ink.…”

“…24,27,28 In particular, the higher the crosslinking density of the ink, the lower the degree of freedom in the matrix and hence the slower the switching reaction of the photochromic dye is. 25,26,29 In this paper, we explore and tune the colour performance of a novel UV-responsive textile using fabrication parameters of an industrially applicable process. Altering the curing intensity of the photochromic ink on the textile during fabrication, inuences the rigidity of the UV-resin, the dye-polymer matrix interaction and hence the degree of freedom of the dye to switch between isomers in the matrix.…”

Preparation and photochromic properties of layer-by-layer self-assembly films and light-responsive micelles based on amphiphilic naphthopyran derivative

“…Two main isomeric open-forms (merocyanines, MC) are produced in the process, which present intense color due to their extended conjugation and quasi-planar structures. Ceasing UV irradiation leads the colored forms to thermally or photochemically return back to the original colorless state and the molecules undergo an important intramolecular rotation in the process [8,9]. The fading speed, that is the change rate of color, plays a crucial role for their practical application.…”