Light-directed alignment, surface morphing and related processes: recent trends

Seki, Takahiro

doi:10.1039/c6tc02482c

Cited by 86 publications

(67 citation statements)

References 149 publications

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“…The photon dose for the completion of migration [6,7,[9][10][11][12] becomes approximately 10 3 -fold lower than that for widely reported amorphous polymers [1][2][3] and amorphous molecular materials [13,14]. This can be ascribed to the occurrence of isothermal liquid crystal (LC) to isotropic phase transition in the process of trans-to-cis photoisomerization [6,7,11,[15][16][17]. The film material starts to move from the trans-rich regions to cis-rich ones, which is possibly initiated by the disparities of the viscosity and sharp gradient of surface tension at the boundary regions [6,7,11,15].…”

Section: Introductionmentioning

confidence: 89%

SRG Inscription in Supramolecular Liquid Crystalline Polymer Film: Replacement of Mesogens

et al. 2017

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Abstract:The photoinduced surface relief formation via mass transfer upon irradiation with patterned light has long been a subject of extensive investigation. In azobenzene-containing liquid crystalline materials, UV light irradiation that generates the cis isomer leads to the liquid crystal to isotropic photochemical transition. Due to this phase change, efficiency of the mass transfer to generate a surface relief grating (SRG) becomes markedly greater. We have previously indicated that azobenzene-colored SRG-inscribed film can be bleached by removing a hydrogen-bonded azobenzene mesogen. However, this process largely reduces the height feature of the SRG corrugation. Herein, we propose an extended procedure where a colorless mesogen is filled successively after the removal of the azobenzene side chain. The process involves four stages: (i) SRG inscription in a hydrogen-bonded supramolecular azobenzene material; (ii) crosslinking (insolubilization) of the SRG film; (iii) removal of azobenzene mesogen by rinsing with a solvent, and (iv) stuffing the hollow film with a different mesogen. Although the final stuffing stage was insufficient at the present stage, this work demonstrates the possibility and validity of the strategy of mesogen replacement.

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Section: Introductionmentioning

confidence: 89%

SRG Inscription in Supramolecular Liquid Crystalline Polymer Film: Replacement of Mesogens

et al. 2017

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“…The rod‐like trans Azs are isomerized most effectively when their transition moments are oriented parallel to the electric vector ( E ) of light. In the case of normally incident LPL, this leads to a statistical buildup of Az moieties oriented orthogonal to E , and the concurrent in‐plane alignment of BCP nanostructures . It was shown that the in‐plane alignment of cylinders proceeds through subdomain rotation in a cooperative and synchronized manner .…”

Section: Introductionmentioning

confidence: 99%

3D Orientational Control in Self‐Assembled Thin Films with Sub‐5 nm Features by Light

Nickmans

Bögels

Sánchez‐Somolinos

et al. 2017

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While self‐assembled molecular building blocks could lead to many next‐generation functional organic nanomaterials, control over the thin‐film morphologies to yield monolithic sub‐5 nm patterns with 3D orientational control at macroscopic length scales remains a grand challenge. A series of photoresponsive hybrid oligo(dimethylsiloxane) liquid crystals that form periodic cylindrical nanostructures with periodicities between 3.8 and 5.1 nm is studied. The liquid crystals can be aligned in‐plane by exposure to actinic linearly polarized light and out‐of‐plane by exposure to actinic unpolarized light. The photoalignment is most efficient when performed just under the clearing point of the liquid crystal, at which the cylindrical nanostructures are reoriented within minutes. These results allow the generation of highly ordered sub‐5 nm patterns in thin films at macroscopic length scales, with control over the orientation in a noncontact fashion.

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“…Photochromic liquid‐crystalline (LC) polymers represent a promising type of smart materials with high potential for a large variety of applications in optics and optoelectronics . Among different types of photochromic fragments incorporated in polymer matrices, the azobenzene moieties are the most remarkable chromophores capable of reversible E – Z isomerizing.…”

Section: Introductionmentioning

confidence: 99%

“…Among different types of photochromic fragments incorporated in polymer matrices, the azobenzene moieties are the most remarkable chromophores capable of reversible E – Z isomerizing. Several unique advantages of the azobenzene molecules make them the most popular photochrome, such as high quantum yield of photoisomerization, high fatigue resistance, and extreme change in the shape as well as in dipole moment during isomerization . Photoisomerization of azobenzene fragments in LC media enables to realize isothermal phase transitions .…”

Section: Introductionmentioning

confidence: 99%

Photo-Orientation Phenomena in Photochromic Liquid Crystalline Azobenzene-Containing Polymethacrylates with Different Spacer Length

Bobrovsky

Shibaev

Piryazev

et al. 2017

Macromol. Chem. Phys.

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Synthesis and investigation of the phase behavior and photo‐optical properties of two chiral liquid‐crystalline polymers with azobenzene‐containing side groups having different spacer lengths, 6 and 10 methylene groups (PMAzo‐6 and PMAzo‐10, respectively) are described. Formation of different smectic phases and high‐temperature cholesteric phase is studied by polarizing optical microscope, differential scanning calorimetry, and X‐ray investigations. It is shown that UV‐irradiation induces effective reversible E–Z photoisomerization in polymer solutions and films. Atomic force microscopy (AFM) study reveals substantial changes in the surface topography of the polymer PMAzo‐6 film after UV‐irradiation, whereas PMAzo‐10 surface remains the same. Irradiation by polarized light (457 nm) results in photo‐orientation process in polymer films consequential in significant alignment of the chromophores in direction perpendicular to the polarization plane of the incident light. A significant difference is found in thermal stability of the photoinduced alignment; an annealing of PMAzo‐10 irradiated samples results in a slight decrease of dichroism values (down to 0.57); whereas the dichroism increases up to very high values (0.91) for PMAzo‐6.

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Light-directed alignment, surface morphing and related processes: recent trends

Abstract: The immense potential of light responsive polymer materials toward technological applications in photonics, mechanics and micro-fabrication has been attracting increasing attention from both materials chemists and physicists.

Cited by 86 publications

References 149 publications

SRG Inscription in Supramolecular Liquid Crystalline Polymer Film: Replacement of Mesogens

SRG Inscription in Supramolecular Liquid Crystalline Polymer Film: Replacement of Mesogens

3D Orientational Control in Self‐Assembled Thin Films with Sub‐5 nm Features by Light

Photo-Orientation Phenomena in Photochromic Liquid Crystalline Azobenzene-Containing Polymethacrylates with Different Spacer Length

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