Using light intensity to control reaction kinetics and reversibility in photomechanical crystals

Easley, Connor J.; Tong, Fei; Dong, Xinning; Al‐Kaysi, Rabih O.; Bardeen, Christopher J.

doi:10.1039/d0sc03557b

Cited by 20 publications

(21 citation statements)

References 63 publications

(69 reference statements)

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“…The molecules therefore behave collectively, and there is not enough light to trigger a collective isomerization. This collective behavior at low temperature due to the larger intermolecular interaction has 12/1/2020 been observed experimentally in azobenzene self-assembly monolayers [28] and molecular crystals [6], and has been recently shown in our study on photoactive solids using an Ising spin model [7].…”

Section: Temperature-light Dependent Photo-stationary Statessupporting

confidence: 75%

“…This photomechanical process involves an intrinsic coupling between the mechanics of the solid material and the photochemistry under illumination. Recent studies have revealed that in contrast to photoreactions in solution that undergo a first-order reaction kinetics, photoreactions in solids show a collective behavior through intermolecular interaction [5][6][7][8]. This collective behavior leads to phase transitions in the material, the details of which depend significantly on factors including the exact molecular interaction, elasticity, illumination, external load, temperature, and the energy landscape at various length scales.…”

Section: Introductionmentioning

confidence: 99%

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Photochemical-induced phase transitions in photoactive semicrystalline polymers

2021

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The emergent photoactive materials through photochemistry make it possible to directly convert photon energy to mechanical work. There is much recent work in developing appropriate materials and a promising new system is semi-crystalline polymers of the photoactive molecule azobenzene. We develop a phase field model with two order parameters for the crystal-melt transition and the trans-cis photo-isomerization to understand such materials, and the model describes the rich phenomenology. We find that the photoreaction rate depends sensitively on temperature: at temperatures below the crystal-melt transition temperature, photoreaction is collective, requires a critical light intensity and shows an abrupt first order phase transition manifesting nucleation and growth; at temperatures above the transition temperature, photoreaction is independent and follows first order kinetics. Further, the phase transition depends significantly on the exact forms of spontaneous strain during the crystal-melt and trans-cis transitions. A non-monotonic change of photo-stationary cis ratio with increasing temperature is observed accompanied by a reentrant crystallization of trans below the melting temperature. A pseudo phase diagram is subsequently presented with varying temperature and light intensity along with the resulting actuation strain.These insights can assist the further development of these materials.

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Section: Temperature-light Dependent Photo-stationary Statessupporting

confidence: 75%

Section: Introductionmentioning

confidence: 99%

Photochemical-induced phase transitions in photoactive semicrystalline polymers

2021

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“…The presence of fast and slow components in the photodimerization dynamics has been previously observed 32,39 and attributed to a fast dimerization of the molecules with a favorable orientation (fast initial decay) which then slows down as the exciton search time for a pair of molecules with favorable orientation increases (slower decay, which then levels off at a nonzero value of a 0 ). It is possible that similar considerations are applicable to our case as well, as we observed shortening of the PL lifetimes after the prolonged irradiation (Figure S10a), which indicates that the presence of photodimers induces PL quenching which could lead to kinetics heterogeneity.…”

Section: Thementioning

confidence: 67%

Exciton Polariton-Enhanced Photodimerization of Functionalized Tetracene

et al. 2021

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We explore the photodegradation mechanisms in functionalized tetracene (TIPS-Tc) films and how they are influenced by strong exciton−photon coupling in planar microcavities. We demonstrate that degradation of TIPS-Tc films exposed to air proceeds mainly through an oxygen-mediated pathway, assigned to endoperoxide (EPO) formation, whereas degradation in microcavities proceeds through oxygen-independent photodimerization. The aerobic and anaerobic decay mechanisms were found to differ in rate by more than two orders of magnitude. Both the EPO formation and photodimerization proceeded more efficiently in molecules in configurations favorable for the correlated triplet pair (TT) state formation (precursor to the singlet fission) and their immediate surroundings. For the photodimerization, an alkyne dimer is reported as one of the photoproducts, and its optical properties are presented. Strong coupling of TIPS-Tc to resonant microcavities enhanced the photodimerization quantum yield by a factor of 4.2, with the enhancement robust with respect to cavity detuning.

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“…35 Cracking and destruction is considered a consequence of an inability of a lattice to allow stress to be efficiently released. 36 By contrast, the single-crystals reported here are robust, maintaining the single-crystal character in the wake of both a covalent-bonding forming reaction and release of guests. We attribute the robustness of the single crystals to the discrete, or 0D, nature of the hydrogen-bonded assemblies.…”

Section: ■ Introductionmentioning

confidence: 72%

Phototriggered Guest Release from a Nonporous Organic Crystal: Remarkable Single-Crystal-to-Single-Crystal Transformation of a Binary Cocrystal Solvate to a Ternary Cocrystal

2020

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The development of organic solids for applications in materials science requires a fundamental understanding of how close packing of molecules can affect structure and function. We report here nonporous organic crystals that release entrapped guest molecules upon application of UV light. We show components of binary cocrystal solvates to undergo an intermolecular photoreaction to generate ternary cocrystals that results in release of entrapped solvent molecules. The phototriggered guest release occurs in a single-crystal-to-single-crystal transformation that is in the absence pores and channels in the solid. The cocrystals are composed of a tetratopic hydrogen-bond-acceptor molecule synthesized in the solid state. The UV-light results in [2 + 2] photodimerization of an isocoumarin to generate a ternary cocrystal with cyclobutane molecules that support guest release.

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Using light intensity to control reaction kinetics and reversibility in photomechanical crystals

Abstract: 4-fluoro-9-anthracenecarboxylic acid (4F-9AC) is a thermally reversible (T-type) photomechanical molecular crystal. The photomechanical response is driven by a [4+4] photodimerization reaction, while the photodimer dissociation determines the reset time. In this paper,...

Cited by 20 publications

References 63 publications

Photochemical-induced phase transitions in photoactive semicrystalline polymers

Photochemical-induced phase transitions in photoactive semicrystalline polymers

Exciton Polariton-Enhanced Photodimerization of Functionalized Tetracene

Phototriggered Guest Release from a Nonporous Organic Crystal: Remarkable Single-Crystal-to-Single-Crystal Transformation of a Binary Cocrystal Solvate to a Ternary Cocrystal

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