Photo-Isomerization Kinetics of Azobenzene Containing Surfactant Conjugated with Polyelectrolyte

Sharma, Anjali; Bekir, Marek; Lomadze, Nino; Santer, Svetlana

doi:10.3390/molecules26010019

Cited by 16 publications

(14 citation statements)

References 35 publications

(48 reference statements)

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“…We clearly see that for lower intensities (the isomerization-limited region), we have a constant value for the rate of surfactant isomerization. This value is lower than that for the case of bulk ( k = 0.9 × 10 –2 cm 2 (mW s) −1 in blue and 10 –4 cm 2 (mW s) −1 in green light) and can be explained by the formation of the surfactant aggregates within the gel hindering photoisomerization, as in the case of complexes with linear PAA chains …”

Section: Resultsmentioning

confidence: 99%

“…This value is lower than that for the case of bulk (k = 0.9 × 10 −2 cm 2 (mW s) −1 in blue and 10 −4 cm 2 (mW s) −1 in green light) and can be explained by the formation of the surfactant aggregates within the gel hindering photoisomerization, as in the case of complexes with linear PAA chains. 37 To investigate the dynamic exchange of isomer under light exposure as a function of temperature, we irradiate the microgels with blue light (455 nm, I = 2 mW cm −2 ) at different temperatures in the range between 25 and 51 °C (Figure 7a). The rate constant of photoisomerization (calculated using date from Figure 7b and eq 7) of the surfactant as a function of temperature exhibits two regimes before and after ∼32 °C (Figure 7c).…”

Section: ■ Results and Discussionmentioning

confidence: 99%

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Adsorption Kinetics of a Photosensitive Surfactant Inside Microgels

et al. 2021

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Here, we investigate the kinetics of adsorption and desorption of a cationic photosensitive azobenzene-containing surfactant within anionic microgels in the dark and under continuous illumination with light of different wavelengths and show that microgels can serve as a selective absorber of one of the possible isomers of the photosensitive surfactant. The adsorption of the isomer is governed by entropic reasons at which micellization of the surfactant takes place within the microgel matrix composed of cross-linked PNIPAM and anionic poly(acryl acid) chains rendering it photoresponsive. Under irradiation with appropriate wavelength, the surfactant molecules photoisomerize from trans (hydrophobic)- to cis (hydrophilic)-state and the microgel collapses due to diffusion of the cis-isomers out of the particle interior. When the light is switched off, the microgels swell back to the equilibrium size by absorbing the rest of the trans-isomers out of solution with the characteristic time being between a few seconds and hours depending on the amount of the trans-isomers left in the solution. Measuring the kinetics of the microgel size response and knowing the exact isomer composition under light exposure, we calculate the adsorption rate of the trans-isomers. We show that depending on the intensity of the applied light, one can differentiate between two processes, i.e., at low intensities, the kinetics of the size change is mostly dominated by the photoisomerization rate of the surfactant within the interior of the particle, while at larger intensities, the process is limited by the surfactant adsorption/desorption rate. By performing temperature-dependent measurements, we also calculate the activation energy of the adsorption/desorption process.

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Section: Resultsmentioning

confidence: 99%

Section: ■ Results and Discussionmentioning

confidence: 99%

Adsorption Kinetics of a Photosensitive Surfactant Inside Microgels

et al. 2021

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“…It can be supplied by a multitude of easily available light-sources, can be targeted to specific spots and remote-operated with adjustability of wavelength and intensity as additional control parameters. 19,20 Crosslinks play a significant role for controlling the microgel properties, especially their softness. 21,22 So far, mainly covalent crosslinks such as N,N-methylenebis(acrylamide) (BIS) have been used for microgels synthesis.…”

Section: Introductionmentioning

confidence: 99%

Photo- and thermo-responsive microgels with supramolecular crosslinks for wavelength tunability of the volume phase transition temperature

Liang

Lopez

Richtering

et al. 2022

Phys. Chem. Chem. Phys.

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“…It has recently been shown that the photo‐isomerization rate of the surfactant in bulk and at the interface (such as surfaces, polymers, aggregates) differs. [ 47,48 ] Here we expand the analysis of Δ c C to give an estimation of the fluid flow direction and strength for the l ‐LDDO velocity by considering the change in the excess of concentration with the irradiation time as a consequence of isomerization rate, which was especially important for the first few seconds of irradiation till the photo‐stationary state was achieved:

\begin{matrix} \frac{d Δ c_{normalC}}{d t} = \frac{d c_{C, P}}{d t} - \frac{d c_{C, B}}{d t} \end{matrix}

where d c C,P /dt and d c C,B /dt are time‐dependent changes in the cis ‐isomer concentrations at the particle interface and in bulk solution. Inserting rate equations of isomerization at interface, d c C,P /d t , and bulk, d c C,B /d t , [50] one gets:

\begin{matrix} \frac{d c_{C, P}}{d t} = k_{TC,I} \cdot I \cdot c_{T, P} = k_{TC,I} \cdot I \cdot A_{ef f} \cdot θ_{normalT} (c_{normalT, normalB}) \end{matrix}

and d c C,B /dt:

\begin{matrix} \frac{d c_{C, B}}{d t} = k_{TC} \cdot I \cdot c_{T, B} - k_{CT} \cdot I \cdot c_{C, B} \end{matrix}

and finally:

\begin{matrix} \frac{d Δ {normalc}_{normalC}}{d t} \sim I \cdot ([], k_{TC,I} \cdot A_{eff} \cdot θ_{T ...}) \end{matrix}

…”

Section: Methodsmentioning

confidence: 99%

“…It has recently been shown that the photo-isomerization rate of the surfactant in bulk and at the interface (such as surfaces, polymers, aggregates) differs. [47,48] Here we expand the analysis of Δc C to give an estimation of the fluid flow direction and strength for the l-LDDO velocity by considering the change in the excess of concentration with the irradiation time as a consequence of isomerization rate, which was especially important for the first few seconds of irradiation till the photo-stationary state was achieved:…”

Section: Theoretical Backgroundmentioning

confidence: 99%

How to Make a Surface Act as a Micropump

Bekir

Sharma

Umlandt

et al. 2022

Adv Materials Inter

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In this paper, the phenomenon of light‐driven diffusioosmotic (DO) long‐range attractive and repulsive interactions between micro‐sized objects trapped near a solid wall is investigated. The range of the DO flow extends several times the size of microparticles and can be adjusted to point towards or away from the particle by varying irradiation parameters such as intensity or wavelength of light. The “fuel” of the light‐driven DO flow is a photosensitive surfactant which can be photo‐isomerized between trans and cis‐states. The trans‐isomer tends to accumulate at the interface, while the cis‐isomer prefers to stay in solution. In combination with a dissimilar photo‐isomerization rate at the interface and in bulk, this yields a concentration gradient of the isomers around single particles resulting in local light‐driven diffusioosmotic (l‐LDDO) flow. Here, the extended analysis of the l‐LDDO flow as a function of irradiation parameters by introducing time‐dependent development of the concentration excess of isomers near the particle surface is presented. It is also demonstrated that the l‐LDDO can be generated at any solid/liquid interface being more pronounced in the case of strongly absorbing material. This phenomenon has plenty of potential applications since it makes any type of surface act as a micropump.

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Photo-Isomerization Kinetics of Azobenzene Containing Surfactant Conjugated with Polyelectrolyte

Cited by 16 publications

References 35 publications

Adsorption Kinetics of a Photosensitive Surfactant Inside Microgels

Adsorption Kinetics of a Photosensitive Surfactant Inside Microgels

Photo- and thermo-responsive microgels with supramolecular crosslinks for wavelength tunability of the volume phase transition temperature

How to Make a Surface Act as a Micropump

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