The attachment of low T g poly(n-butyl acrylate) polymers (M n 4100 to 13 100) to naphthopyran photochromic dyes provided large tunable improvements in their photochromic performance in a rigid thermoset host polymer matrix. Both coloration and decoloration speeds were greatly increased, with the critical t 1/2 decoloration times reduced by 50-95% and t 3/4 decoloration times reduced by at least 63% through the use of these polymer conjugates. In addition, the optical density of the colored form of the dye-polymer conjugates rapidly reached a steady state absorption ca. 60-70% greater than the nonpolymer conjugated control dyes. The effect of the geometry of the polymer conjugates was examined, and it was found that mid-placement of the dye on the polymer provided secondary decoloration speed enhancement over end-placement. Thus, conjugation of low T g poly(n-butyl acrylate) not only provides faster coloration and decoloration but also greatly increases optical density with near square-wave characteristics.

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)

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.

We report a method that allows the facile synchronization of multiple photochromic dyes in a rigid polymer lens matrix together with large increases in their switching speeds. This was achieved by simple chromatographic fractionation of dye-poly(dimethylsiloxane) (PDMS) conjugates to provide tunable switching speeds with longer PDMS tails providing faster switching speeds and shorter tails providing slower switching with no effect on the electronic nature of the dyes. This was done for mono end-functional dye-PDMS conjugates (one dye at one end of the PDMS) and new telechelic dye-PDMS conjugates (one dye at each end of a PDMS oligomer) using a wide variety of academic and commercially important spirooxazines and naphthopyrans (chromenes). Telechelic conjugates gave faster fade performance per unit length of PDMS oligomer (greater atom efficiency) while having superior matrix compatibility. Independent photochromic switching of different photochromic dye-PDMS conjugates within the same lens matrix was demonstrated, resulting in the ability to synchronize coloration and decoloration within multidye systems. The utility of the method was shown by the creation of a neutral colored (gray) lens, produced through the combination of three different colored dye-PDMS conjugates having similar independent fade speed kinetics, and showed exceptional fade performance with good hue maintenance compared to the control lens.

The purpose of this study was to create a light responsive nanostructured liquid crystalline matrix using a novel alkylated spiropyran photochromic molecule (spiropyran laurate, SPL) as a light activated drug delivery system. The liquid crystal matrix, prepared from phytantriol, responds reversibly to changes in photoisomerism of SPL on irradiation, switching between the bicontinuous cubic and the reversed hexagonal liquid crystal structures, a change previously shown to dramatically alter drug release rate. In contrast, the non-derivatized spiropyran and spirooxazine photochromic compounds do not sufficiently disrupt the matrix on isomerization to induce the phase change. Thus, novel alkylated spiropyran has the potential to be an effective agent for use in liquid crystalline systems for reversible ‘on-demand’ drug delivery applications.

First report on the sequential, visible light-initiated, single unit monomer insertion (SUMI) of N,N-dimethylacrylamide (DMAm) into the reversible addition fragmentation chain transfer (RAFT) agent, 4-((((2-carboxyethyl)thio)carbonothioyl)thio)-4-cyanopentanoic acid (CTA ), in aqueous solution is provided. The specificity for SUMI over formation of higher oligomers and/or RAFT agent-derived by-products is higher for longer irradiation wavelengths. Red light provides the cleanest product (selective SUMI), showing a linear pseudo-first order kinetic profile to high (>80%) conversion, but also the slowest reaction rate. Blue light provides a relatively rapid reaction, but also gives some by-products (<2%) and the kinetic profile displays a conversion plateau at >65% conversion. Higher specificity with red light is attributed to CTA absorbing at longer wavelengths than the SUMI product, which allows selective excitation of CTA . The use of a higher reaction temperature (65 °C vs ambient) results in a higher reaction rate and a reduction in oligomer formation.

We report a new generic method of reversibly controlling the photochromism of spiropyrans. It was found that the photochromic effect of spiropyrans can be reversibly switched on and off by addition and removal of carbon dioxide (CO(2)) to spiropyran in alcohol solutions containing an amidine (i.e., DBU) that acts as a CO(2) sensitizer. Spiropyrans are not photochromic in the presence of DBU but photochromic when CO(2) is subsequently added to the solution. The CO(2) is readily removed by inert gas bubbling, thus allowing facile activation and deactivation of the photochromic effect. Carbon dioxide, without the presence of the sensitizing amidine, had no effect on photochromism of the spiropyrans. Other photochromic dyes classes such as spirooxazines and chromenes are not affected by this CO(2)/DBU stimulus. As a result, orthogonal activation of mixtures of spirooxazines and spiropyrans was achieved to provide four color states (clear, yellow, green, and blue) by varying the combinations of the stimuli of UV, visible light, CO(2), and CO(2) depleted. This finding now permits the many applications using spiropyrans to be CO(2) responsive.

In this work, we present a polymerized ionic liquid block copolymer (PBCP) film where relevant properties such as ionic conductivity and electrochemical parameters are tailored by using a ternary system comprised of poly(styrene-b-1-((2-acryloyloxy)ethyl)−3-butylimidazolium bis(tri-fluoromethanesulfonyl)imide), LiFSI salt and ethylene carbonate (EC) as a cosolvent. It was found that EC efficiently decreases the glass transition temperature of the ionic block, resulting in an improved ionic conductivity and efficient platting/stripping of lithium. By using an optimal ratio of EC/LiFSI at relatively high LiFSI amount, Li∣Li symmetrical cells at 50 °C show an overpotential as low as 70 mV at 0.1 mA.cm−2 along with a high lithium transport number of 0.56 (tLi+ ). All-solid-state full cells based on lithium iron phosphate cathode paired with a lithium metal anode reveal a rather stable cycling at both 50 °C and 70 °C. A negligible capacity fading is observed up to 30 cycles where a specific capacity as high as 161 mAh.g−1 is achieved with a coulombic efficiency of 99.9%. Thus, this work demonstrates an important pathway for tailoring the properties of solid state polymer electrolytes for emerging and specially designed block copolymer architectures comprising domains that give both excellent ionic conduction along with desirable mechanical properties.