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The development of semiconductor polymers for electronic applications requires tailored synthetic strategies to obtain materials with tunable electronic properties and morphology to enhance their properties. Towards this goal, here is reported the expedient synthesis of a novel class of thiophene-based electrochromic polymers, processable in organic solvents and as nanoparticles (NPs) in water. Their characterization and application in flexible solid-state electrochromic devices (ECDs) are described. All polymers have a repeat unit made of the same linear thienyl–phenyl–thienyl–thienyl fragment. The tuning of the electro-optical properties is achieved by introducing alkyl or alkoxy substituents in thiophene and/or by the presence of either -CH-CH- or -CH2-CH2- linkers connecting the repeat units and acting as conjugation modulators. The ECDs display a bright yellow or red/magenta color in the neutral state and dark blue in the oxidized state. Redox potentials, color contrast, switching time, and stability of the devices are reported, and it is demonstrated that the use of NPs films spray-coated from water instead of cast films from chloroform significantly improves their performance. Density functional theory calculations allow to elucidate the relationship between polymer structure and electrochromic properties and shed light on electronic structure changes upon oxidation, in agreement with spectroelectrochemistry.

We show photorheology in aqueous solutions of weakly entangled wormlike micelles prepared with cetyltrimethylammonium bromide (CTAB), salicylic acid (HSal), and dilute amounts of the photochromic multistate compound trans-2,4,4'-trihydroxychalcone (Ct). Different chemical species of Ct are associated with different colorations and propensities to reside within or outside CTAB micelles. A light-induced transfer between the intra- and intermicellar space is used to alter the mean length of wormlike micelles and hence the rheological properties of the fluid, studied in steady-state shear flow and in dynamic rheological measurements. Light-induced changes of fluid rheology are reversible by a thermal relaxation process, at relaxation rates which depend on pH and which are consistent with photochromic reversion rates measured by UV-vis absorption spectroscopy. Parameterizing viscoelastic rheological states by their effective relaxation time τ(c) and corresponding response modulus G(c), we find the light and dark states of the system to fall onto a characteristic state curve defined by comparable experiments conducted without photosensitive components. These reference experiments were prepared with the same concentration of CTAB, but different concentrations of HSal or sodium salicylate (NaSal), and tested at different temperatures.

We recently reported on the use of caged nucleotides to attain full control of enzymatic polymerization of RNA solely by light. In the absence of light no RNA formation was possible due to the efficient caging by the coumarin moiety; after irradiation, caged ATP was released with quantitative precision and RNA polymerization was resumed. As photolabile protecting group [7-(diethylamino)coumarin-4-yl]methyl] (DEACM) was used due to its high absorbance in the visible region of the spectrum, fast deprotection kinetics and absence of radical intermediates. However, the 7-diethylamino-4-hydroxymethylcoumarin photo-product (DEACM-OH) was shown to inhibit the transcription reaction for concentrations higher than 30 μM [5]. This inhibition has been associated with poor water solubility, which is commonly dealt with via cumbersome chemical modifications of the protecting moiety. To overcome inhibition, we evaluated the use of molecular scavengers to sequester DEACM-OH formed after irradiation. Determination of association constants of coumarin with β-cyclodextrins allowed the assessment of its capability to remove free coumarin molecules from solution. The influence of β-cyclodextrin in transcription reaction was also assessed. Results show that β-cyclodextrin can be successfully used as scavenger as it increases the DEACM-OH threshold concentration for inhibition, amplifying the efficiency of light controlled in vitro transcription.

Selective interaction between Crystal Violet Lactone and Fe 3+ /Fe 2+ in methanol leads to a reversible ionochromic colour change. This interaction can be controlled electrochemically, in order to achieve reversible colour changes with high contrast between colourless and dark blue solutions. The presented system is proposed as an alternative electrochromic solution.

Electrochromic materials are characterized by their colour changes upon applied voltage. Colour can mean many things: a certain kind of light, its effect on the human eye, or the result of this effect in the mind of the viewer. Since the electrochromic materials are developed towards real life applications it is relevant to characterize them with the usual commercial colour standards. A colorimetric study of electrogenerated Prussian blue and electrogenerated polymers based on salen -type complexes of Cu(II), Ni(II) and Pd(II) deposited over transparent flexible electrodes of polyethylene terephthalate coated with indium tin oxide (PET/ITO electrodes) was carried out using the CIELAB coordinates. A cuvette with a designed adapter to allow potentiostatic control was placed on an integrating sphere installed in the sample compartment of a spectrophotometer to run the colorimetric measurements. The colour evolution in situ was measured through the transmittance of the films by potentiostatic control. Chronocoulometry/chronoabsorptometry was used to evaluate maximum coloration efficiencies for the coloration step: 184 (Pd), 161 (Cu) and 83 cm 2 /C (Ni) and for bleaching: 199 (Pd), 212 (Cu) and 173 cm 2 /C (Ni) of the Pd, Cu and Ni polymer films, respectively. The Prussian Blue/Prussian White states over the PET/ITO films were relatively reversible while the reversibility and stability of the polymers based on the metals salen -type complexes depends on the metal, Pd being the most stable.

In this paper we report the encapsulation of the compound 4′,7-dihydroxyflavylium in a water-permeable crosslinked poly(2-hydroxyethyl methacrylate) matrix. The water permeability of the polymer and its transparency allow the use of pH and light stimuli to attain different states on the network defined by the various chemical reactions (multistate/multifunctional system). Unlike in water, in the polymer the compound 4′,7-dihydroxyflavylium encapsulated exhibits a thermal barrier between the cis- and trans-chalcones, a necessary requirement to define a write–read–erase cycle.