Light-responsive self-assembly of a cationic azobenzene surfactant at high concentration

Blayo, Camille; Kelly, Elaine; Houston, Judith E.; Khunti, Nikul; Cowieson, Nathan; Evans, Rachel C.

doi:10.1039/d0sm01512a

Cited by 9 publications

(7 citation statements)

References 42 publications

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“…However, photocleavage in the surfactant is irreversible, limiting their utilization in industrial applications that require reversible properties. Alternatively, photoswitchable units that undergo structural isomerization upon irradiation are promising building blocks for constructing reversible light-responsive materials. − For example, azobenzene moieties have been incorporated into spherical polymer particles that elongate upon exposure to polarized light along the polarization direction. , However, the use of photoswitchable surfactants to tune the shape of BCP particles has never been reported. This is mainly attributed to the difficulty in designing the photoswitchable surfactants that exhibit considerable changes in their amphiphilicity by light irradiation.…”

Section: Introductionmentioning

confidence: 99%

Photoswitchable Surfactant-Driven Reversible Shape- and Color-Changing Block Copolymer Particles

et al. 2021

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Polymer particles that switch their shape and color in response to light are of great interest for the development of programmable smart materials. Herein, we report block copolymer (BCP) particles with reversible shapes and colors activated by irradiation with ultraviolet (UV) and visible lights. This shape transformation of the BCP particles is achieved by a spiropyran-dodecyltrimethylammoium bromide (SP-DTAB) surfactant that changes its amphiphilicity upon photoisomerization. Under UV light (365 nm) irradiation, the hydrophilic ring-opened merocyanine form of the SP-DTAB surfactant affords the formation of spherical, onion-like BCP particles. In contrast, when exposed to visible light, surfactants with the ring-closed form yield prolate or oblate BCP ellipsoids with axially stacked nanostructures. Importantly, the change in BCP particle morphology between spheres and ellipsoids is reversible over multiple UV and visible light irradiation cycles. In addition, the shape-and color-switchable BCP particles are integrated to form a composite hydrogel, demonstrating their potential as high-resolution displays with reversible patterning capabilities.

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Section: Introductionmentioning

confidence: 99%

Photoswitchable Surfactant-Driven Reversible Shape- and Color-Changing Block Copolymer Particles

et al. 2021

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“…These isomers display different molecular geometries, electronic absorption spectra, and dipole moments . Azobenzene motifs have been incorporated into surfactant molecules , and studied for their structure–function–assembly relationships. − Light-induced switching of a photosurfactant’s conformation ,, and properties has emerged as a powerful strategy for tuning the surfactant’s amphiphilicity on demand …”

Section: Introductionmentioning

confidence: 99%

Light Responsiveness and Assembly of Arylazopyrazole-Based Surfactants in Neat and Mixed CTAB Micelles

Tyagi

Greenfield

Jones

et al. 2022

JACS Au

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The self-assembly of an arylazopyrazole-based photosurfactant (PS), based on cetyltrimethylammonium bromide (CTAB), and its mixed micelle formation with CTAB in aqueous solution was investigated by small angle neutron and X-ray scattering (SANS/SAXS) and UV–vis absorption spectroscopy. Upon UV light exposure, PS photoisomerizes from E-PS (trans) to Z-PS (cis), which transforms oblate ellipsoidal micelles into smaller, spherical micelles with larger shell thickness. Doping PS with CTAB resulted in mixed micelle formation at all stoichiometries and conditions investigated; employing selectively deuterated PS, a monotonic variation in scattering length density and dimensions of the micellar core and shell is observed for all contrasts. The concentration- and irradiance-dependence of the E to Z configurational transition was established in both neat and mixed micelles. A liposome dye release assay establishes the enhanced efficacy of photosurfactants at membrane disruption, with E-PS exhibiting a 4-fold and Z-PS a 10-fold increase in fluorescence signal with respect to pure CTAB. Our findings pave the way for external triggering and modulation of the wide range of CTAB-based biomedical and material applications.

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“…Light-responsive LLC dispersions have previously been created through addition of metallic nanoparticles, which induce photothermal phase changes; , however, the toxicity of nanoparticle additions remains a concern . Alternatively, LLCs can be built from amphiphiles, which contain a photoswitchable group. − Of these, azobenzene photosurfactants (AzoPS) have been the most extensively studied . Despite concerns over its potential toxicity, a promising recent work has shown the capability to produce biocompatible azobenzene derivatives .…”

Section: Introductionmentioning

confidence: 99%

“…At higher concentrations, there have been several reports of the self-assembly of AzoPS into higher-order bulk LLC phases using both charged and neutral surfactants; ,,,, however, research has focused on the latter, due to a greater number of hydrogen bonding sites, thought to aid LLC formation . In work by Peng et al , neutral AzoPS molecules, with an oligooxyethylene head and azobenzene-alkyl tail, formed both lamellar and hexagonal LLCs with photoisomerization resulting in a loss of the hexagonal phase. , Houston et al further demonstrated the ability to control LLC phase formation, including lamellar and hexagonal, using the structure, concentration, and temperature in systems of neutral AzoPS, all of which showed loss of LLC order on isomerization …”

Section: Introductionmentioning

confidence: 99%

“…37 As such, AzoPS have been investigated for applications such as: DNA compaction, 38 microfluidics, 39 foam stability, 40 and micellar entrapment and release. 41,42 At higher concentrations, there have been several reports of the self-assembly of AzoPS into higher-order bulk LLC phases using both charged 24 and neutral surfactants; 23,27,28,43,44 however, research has focused on the latter, due to a greater number of hydrogen bonding sites, thought to aid LLC formation. 45 In work by Peng et al, neutral AzoPS molecules, with an oligooxyethylene head and azobenzene-alkyl tail, formed both lamellar and hexagonal LLCs with photoisomerization resulting in a loss of the hexagonal phase.…”

Section: ■ Introductionmentioning

confidence: 99%

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Light-Responsive Molecular Release from Cubosomes Using Swell-Squeeze Lattice Control

et al. 2022

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Stimuli-responsive materials are crucial to advance controlled delivery systems for drugs and catalysts. Lyotropic liquid crystals (LLCs) have well-defined internal structures suitable to entrap small molecules and can be broken up into low-viscosity dispersions, aiding their application as delivery systems. In this work, we demonstrate the first example of light-responsive cubic LLC dispersions, or cubosomes, using photoswitchable amphiphiles to enable external control over the LLC structure and subsequent on-demand release of entrapped guest molecules. Azobenzene photosurfactants (AzoPS), containing a neutral tetraethylene glycol head group and azobenzene-alkyl tail, are combined (from 10−30 wt %) into monoolein-water systems to create LLC phases. Homogenization of the bulk LLC forms dispersions of particles, ∼200 nm in diameter with internal bicontinuous primitive cubic phases, as seen using small-angle X-ray scattering and cryo-transmission electron microscopy. Notably, increasing the AzoPS concentration leads to swelling of the cubic lattice, offering a method to tune the internal nanoscale structure. Upon UV irradiation, AzoPS within the cubosomes isomerizes within seconds, which in turn leads to squeezing of the cubic lattice and a decrease in the lattice parameter. This squeeze mechanism was successfully harnessed to enable phototriggerable release of trapped Nile Red guest molecules from the cubosome structure in minutes. The ability to control the internal structure of LLC dispersions using light, and the dramatic effect this has on the retention of entrapped molecules, suggests that these systems may have huge potential for the next-generation of nanodelivery.

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Light-responsive self-assembly of a cationic azobenzene surfactant at high concentration

Abstract: A cationic azobenzene photosurfactant (AzoTAB) forms self-assembled structures with long-range order and optical anisotropy at high concentrations. These high-concentration mesophases are lost or disrupted with UV irradiation.

Cited by 9 publications

References 42 publications

Photoswitchable Surfactant-Driven Reversible Shape- and Color-Changing Block Copolymer Particles

Photoswitchable Surfactant-Driven Reversible Shape- and Color-Changing Block Copolymer Particles

Light Responsiveness and Assembly of Arylazopyrazole-Based Surfactants in Neat and Mixed CTAB Micelles

Light-Responsive Molecular Release from Cubosomes Using Swell-Squeeze Lattice Control

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